Publications

Title:	An initial assessment of the impact of postulated orbit-spin coupling on Mars dust storm variability in fully interactive dust simulations
Authors:	Newman, Claire E.; Lee, Chris; Mischna, Micheal A.; Richardson, Mark I.; Shirley, James H.
Affiliation:	AA(Aeolis Research, Pasadena, CA, United States), AB(University of Toronto, Toronto, Canada), AC(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States)
Journal:	Icarus, Volume 317, p. 649-668.
Publication Date:	Sept 2018
Origin:	ELSEVIER
Keywords:	Atmospheres, dynamics, Mars, atmosphere
Abstract Copyright:	(c) 2018 The Authors
DOI:	https://doi.org/10.1016/j.icarus.2018.07.023
Bibliographic Code:	2019Icar..317..649W
Abstract:	A weak coupling between the rotational and orbital angular momenta of Mars has been postulated to produce a ‘coupling term acceleration’ (CTA) that accelerates the wind field and is asynchronous with the seasonal cycle of solar forcing (Shirley, 2017). This paper presents the first GCM simulations of a fully interactive dust cycle with the CTA included, enabling storm sizes, onset times and locations to be predicted. The inclusion of the CTA greatly augments interannual variability in the occurrence and timing of GDS, with the nature of the storm season strongly linked to the phasing and amplitude of the orbit-spin coupling. This dramatically improves the model's skill at predicting GDS and non-GDS Mars Years (MY) compared to a GCM without CTA forcing. The model is clearly wrong in only 4 out of 22 well-observed storm seasons and is able to capture the general onset time of most observed storms as well as some onset locations. In years when the CTA forcing has large positive amplitudes around perihelion, GDS with onset near perihelion occur due to a net strengthening of the single-cell Hadley circulation at this time, while earlier (or later) GDS are likely produced by more localized constructive interference between the CTA and tidal/topographic flows at a time of peak forcing amplitudes. The latter may be more sensitive to errors in the assumed surface dust availability, which may explain why a late GDS observed in MY 10 is not predicted. Depletion of surface dust in source regions by GDS in prior years may have prevented a GDS from occurring in the real MY 17, when a large GDS is incorrectly predicted. Early GDS are observed but not predicted in two MYs (12 and 25) with large negative CTA forcing amplitudes around perihelion, which may be associated with a lack of water cycle coupling in these simulations. Other missing physical processes, imperfect dust parameterizations or parameter values, the assumption of unlimited surface dust availability, or the wrong CTA strength may account for other mismatches. A GDS is predicted close to perihelion in the current storm season, MY34 (2018), with a smaller GDS predicted later next Mars year, MY35 (2020). The CTA forcing in MY 34 is very similar to that of MY 21, in which a GDS is correctly predicted by the model.

Title:	Age of martian air: Time scales for martian atmospheric transport
Authors:	Waugh, Darryn W.; Toigo, Anthony D.; Guzewich, Scott D.
Affiliation:	AA(Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, Maryland USA), AB(The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland USA), AC(NASA Goddard Spaceflight Center, Greenbelt, Maryland USA)
Journal:	Icarus, Volume 317, p. 148-157.
Publication Date:	August 2018
Origin:	ELSEVIER
Keywords:	Atmospheres, dynamics, Mars, atmosphere
Abstract Copyright:	(c) 2018 Elsevier Inc. All rights reserved.
DOI:	https://doi.org/10.1016/j.icarus.2018.08.002
Bibliographic Code:	2019Icar..317..148W
Abstract:	MarsWRF general circulation model. The spatial distribution and seasonality of the mean age in low- and mid-latitudes broadly follow contours of the mean meridional circulation, with the mean age increasing from 0 at the surface to a maximum of 60–100 sols in the upper atmosphere. Substantially older mean ages (exceeding 300 sols) are found in polar regions, with oldest ages in the lower atmosphere (10–100 Pa), above a near-surface layer with very young ages (around 20 sols). The annual maximum ages occur around the equinoxes, and the age in the polar lower atmosphere decreases during the autumn to winter transition. This autumn-winter decrease in age occurs because of mixing of polar and mid-latitude air when the polar vortex exhibits an annulus of high potential vorticity (PV) with a local minimum near the pole. There is no autumn-winter decrease and old ages persist throughout autumn and winter in simulations with CO2 phase changes disabled, and thus no latent heating, where there is a monopolar vortex (i.e., a monotonic increase in PV from equator to pole) forms. The altitudinal and seasonal variations in the mean age indicates similar variations in the transport of dust into polar regions and the mixing of polar air (with, e.g., low water vapor and high ozone concentrations during winter) into mid-latitudes.

Title:	Dynamical processes of dust lifting in the northern mid-latitude region of Mars during the dust storm season
Authors:	Xiao, Jing; Chow, Kim-Chiu; Chan, Kwing-lam
Affiliation:	AA(Space Science Institute / Lunar and Planetary Science Laboratory, Macau University of Science and Technology, Administration Building, Block A, Avenida Wai Long, Taipa, Macau)
Journal:	Icarus, Volume 317, p. 94-103.
Publication Date:	July 2018
Origin:	ELSEVIER
Keywords:	Atmospheres, dynamics, Mars, atmosphere
Abstract Copyright:	(c) 2018 Elsevier Inc. All rights reserved.
DOI:	https://doi.org/10.1016/j.icarus.2018.07.020
Bibliographic Code:	2019Icar..317..94W
Abstract:	The general circulation model MarsWRF has been used to simulate the regular dust climate on Mars. In particular, the double-peak episodes of dust storm activities during the dust storm season can be captured with the use of an active dust lifting scheme in the model. This study focuses on the dynamical processes of dust lifting in the northern mid-latitude region during these episodic periods. Wavelet analysis to the time series shows that dust lifting activities are associated with three distinct modes of variability. The first is the high frequency signal with a period of 0.5 to 1 sol, which is generally associated with the thermal tide. The second mode has the period about 7 sols, which is generally associated with the mid-latitude planetary waves. The third mode has the period over 50 sols, which is basically the signal of seasonal change in the region. Further analysis on wave numbers suggests that the dust lifting processes are dominated by the mode around wave number three. Results of sensitivity experiments also suggest that topography in the northern mid-latitude region is important to the lifting of dust in the period around 1 sol.

Title:	On the relationship between surface pressure, terrain elevation, and air temperature. Part I: The large diurnal surface pressure range at Gale Crater, Mars and its origin due to lateral hydrostatic adjustment
Authors:	Richardson, Mark I.; Newman, Claire E.
Affiliation:	AA(Aeolis Research, Pasadena, CA, United States)
Journal:	Planetary and Space Science, Volume 164, p. 132-157.
Publication Date:	July 2018
Origin:	ELSEVIER
Keywords:	Atmospheres, dynamics, Mars, atmosphere
Abstract Copyright:	(c) 2018 The Authors
DOI:	https://doi.org/10.1016/j.pss.2018.07.003
Bibliographic Code:	2018PSS..164..132W
Abstract:	The daily variation of surface pressure observed by the Curiosity Rover Environmental Monitoring Station (REMS) is both significantly larger than observed at other landing sites on Mars and larger than simulated for the Curiosity site by global circulation models (GCM). Mesoscale numerical models are able to simulate the large REMS daily pressure range, but only if they possess sufficiently high horizontal resolution (grid spacing <5 km); low resolution (120–500 km) GCM simulations typically generate daily ranges of about half the observed value. The pressure range in low resolution simulations corresponds to the large-scale thermal tides and the augmentation of this range in high resolution models is associable with mesoscale topographic and surface property variations in the Gale Crater region. We show that the augmentation is due to the lateral redistribution of mass required for the surface pressure distribution over topographic relief to remain approximately hydrostatic as the near-surface air temperature varies through the diurnal cycle. The physical origin and nature of this adjustment flow is explored. We provide a means of predicting the daily surface pressure due to lateral hydrostatic adjustment for any location and further show that this range is slightly reduced by the inability of the atmosphere to completely achieve hydrostaticity and by the thermal effects of induced flows.

Title:	The sensitivity of solsticial pauses to atmospheric ice and dust in the MarsWRF General Circulation Model
Authors:	Chris Lee, Mark I. Richardson, Claire E. Newman; Michael A. Mischna
Affiliation:	AA(Department of Physics, University of Toronto, St. George, Toronto, Ontario, M5S 1A7, Canada), AB(Aeolis Research, Pasadena, CA, United States), AC(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA)
Journal:	Icarus, Volume 311, p. 23-34.
Publication Date:	March 2018
Origin:	ELSEVIER
Keywords:	Atmospheres, dynamics, Mars, atmosphere, clouds
Abstract Copyright:	(c) 2018 Elsevier Inc. All rights reserved.
DOI:	https://doi.org/10.1016/j.icarus.2018.03.019
Bibliographic Code:	2018Icar..311..23W
Abstract:	Mars exhibits less atmospheric variability at the solstices than it does during periods nearer the equinoxes. Much of this variability in air temperature and dust activity is attributable to a significant decrease in eastward traveling transient wave amplitudes in the lower atmosphere near the solstice. Pre- vious versions of the Mars Weather Research and Forecasting (MarsWRF) model using only dust radiative forcing have reproduced the nature but not the magnitude of this ‘solsticial pause’ in atmospheric vari- ability. In this paper, we use a version of MarsWRF that includes a fully-interactive dust and water cycle to simulate winter solsticial pauses under a range of dust and water ice conditions. The upgraded model specifically includes a new hybrid binned/two-moment microphysics model that simulates dust, water ice, and cloud condensation nuclei. The scheme tracks mass and number density for the three particle types throughout the atmosphere and allows advection by resolved winds, mixing by unresolved pro- cesses, and sedimentation that depends on particle size and density. Ice and dust particles interact with radiation in the atmosphere using a Mie scattering parameterization that allows for variable particle size and composition. Heterogeneous nucleation and condensation use an adaptive bin size scheme to accu- rately track the particle size during condensation and sublimation processes. All microphysical processes in the model are calculated within the dynamical timesteps using stability-guaranteed implicit calcula- tions with no sub-timestepping. The impact of the addition of water processes to the model was assessed by comparing simulations with only interactive dust (dry simulations) and ones with a fully-interactive dust and water cycle (wet simulations). In dry simulations with dust storms a solsticial pause occurs in the northern winter with a magnitude (or ‘depth’) that depends on the opacity of the southern summer dust storms. In wet simulations that include water ice and dust particles, deep solsticial pauses are found in both winter hemispheres. In all simulations that reproduce the solsticial pause, energy and instabil- ity analysis suggest that a decrease in baroclinic instability and increase in barotropic energy conversion occurs during the solsticial pause. In dry simulations the decrease in baroclinic instability is caused by increased dust opacity leading to increased thermal static stability. In wet simulations, additional opacity from local cap-edge ice clouds reduces the near surface wind shear and further inhibits baroclinic eddy growth. The wet simulations are in better agreement with observations and tend to support results from other models that include ice cloud radiative effects.

Title:	The cascade from local to global dust storms on Mars: Temporal and spatial thresholds on thermal and dynamical feedback
Authors:	Anthony D. Toigo; Mark I. Richardson; Huiqun Wang; Scott D. Guzewich; Claire E. Newman
Affiliation:	AA(The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland USA), AB(Aeolis Research, Pasadena, CA, United States), AC(Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, Massachusetts 02138, United States) AD(NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA)
Journal:	Icarus, Volume 302, p. 514-536.
Publication Date:	December 2017
Origin:	ELSEVIER
Keywords:	Atmospheres, dynamics, Mars, atmosphere, dust
Abstract Copyright:	(c) 2017 Elsevier Inc. All rights reserved.
DOI:	https://doi.org/10.1016/j.icarus.2017.11.032
Bibliographic Code:	2018Icar..302..514W
Abstract:	We use the MarsWRF general circulation model to examine the temporal and spatial response of the at- mosphere to idealized local and regional dust storm radiative heating. The ability of storms to modify the atmosphere away from the location of dust heating is a likely prerequisite for dynamical feedbacks that aid the growth of storms beyond the local scale, while the ability of storms to modify the atmosphere after the cessation of dust radiative heating is potentially important in preconditioning the atmosphere prior to large scale storms. Experiments were conducted over a range of static, prescribed storm sizes, durations, optical depth strengths, locations, and vertical extents of dust heating. Our results show that for typical sizes (order 10^5 km 2 ) and durations (1–10 sols) of local dust storms, modification of the at- mosphere is less than the typical variability of the unperturbed (storm-free) state. Even if imposed on re- gional storm length scales (order 10^6 km 2 ), a 1-sol duration storm similarly does not significantly modify the background atmosphere. Only when imposed for 10 sols does a regional dust storm create a signifi- cant impact on the background atmosphere, allowing for the possibility of self-induced dynamical storm growth. These results suggest a prototype for how the subjective observational categorization of storms may be related to objective dynamical growth feedbacks that only become available to storms after they achieve a threshold size and duration, or if they grow into an atmosphere preconditioned by a prior large and sustained storm.

Title:	Winds measured by the Rover Environmental Monitoring Station (REMS) during the Mars Science Laboratory (MSL) rover’s Bagnold Dunes Campaign and comparison with numerical modeling using MarsWRF
Authors:	Claire E. Newman; Javier Gómez-Elvira; Mercedes Marin; Sara Navarro; Josefina Torres; Mark I. Richardson; J. Michael Battalio; Scott D. Guzewich; Robert Sullivan; Manuel de la Torre; Ashwin R. Vasavada; Nathan T. Bridges
Affiliation:	AA(Aeolis Research, Pasadena, CA, United States), AB(Centro de Astrobiología (CSIC-INTA), Torrejón de Ardoz, Madrid, Spain), AC(Texas A&M University, College Station, TX 77843, USA), AD(NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA), AE(Cornell University, Ithaca, NY 14853, USA), AF(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA), AG(Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA)
Journal:	Icarus, Volume 291, p. 203-231.
Publication Date:	December 2016
Origin:	ELSEVIER
Keywords:	Atmospheres, dynamics, Mars, atmosphere, dunes
Abstract Copyright:	(c) 2016 Elsevier Inc. All rights reserved.
DOI:	http://dx.doi.org/10.1016/j.icarus.2016.12.016
Bibliographic Code:	2016Icar..291..203W
Abstract:	A high density of REMS wind measurements were collected in three science investigations during MSL’s Bagnold Dunes Campaign, which took place over ∼80 sols around southern winter solstice (Ls ∼90 °) and constituted the first in situ analysis of the environmental conditions, morphology, structure, and composition of an active dune field on Mars. The Wind Characterization Investigation was designed to fully characterize the near-surface wind field just outside the dunes and confirmed the primarily ups- lope/downslope flow expected from theory and modeling of the circulation on the slopes of Aeolis Mons in this season. The basic pattern of winds is ‘upslope’ (from the northwest, heading up Aeolis Mons) during the daytime ( ∼09:0 0–17:0 0 or 18:00) and ‘downslope’ (from the southeast, heading down Aeolis Mons) at night ( ∼20:00 to some time before 08:00). Between these times the wind rotates largely clock- wise, giving generally westerly winds mid-morning and easterly winds in the early evening. The timings of these direction changes are relatively consistent from sol to sol; however, the wind direction and speed at any given time shows considerable intersol variability. This pattern and timing is similar to predictions from the MarsWRF numerical model, run at a resolution of ∼490 m in this region, although the model predicts the upslope winds to have a stronger component from the E than the W, misses a wind speed peak at ∼09:00, and under-predicts the strength of daytime wind speeds by ∼2–4 m/s. The Namib Dune Lee Investigation reveals ‘blocking’ of northerly winds by the dune, leaving primarily a westerly com- ponent to the daytime winds, and also shows a broadening of the 1 Hz wind speed distribution likely associated with lee turbulence. The Namib Dune Side Investigation measured primarily daytime winds at the side of the same dune, in support of aeolian change detection experiments designed to put limits on the saltation threshold, and also appears to show the influence of the dune body on the local flow, though less clearly than in the lee. Using a vertical grid with lower resolution near the surface reduces the relative strength of nighttime winds predicted by MarsWRF and produces a peak in wind speed at ∼09:00, improving the match to the observed diurnal variation of wind speed, albeit with an offset in magnitude. The annual wind field predicted using this grid also provides a far better match to observa- tions of aeolian dune morphology and motion in the Bagnold Dunes. However, the lower overall wind speeds than observed and disagreement with the observed wind direction at ∼09:00 suggest that the problem has not been solved and that alternative boundary layer mixing schemes should be explored which may result in more mixing of momentum down to the near-surface from higher layers. These re- sults demonstrate a strong need for in situ wind data to constrain the setup and assumptions used in numerical models, so that they may be used with more confidence to predict the circulation at other times and locations on Mars.

Title:	The variability, structure and energy conversion of the northern hemisphere traveling waves simulated in a Mars general circulation model
Authors:	Wang, Huiqun; Toigo, Anthony D.
Affiliation:	AA(Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, Massachusetts 02138, United States), AB(Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland 20723, United States)
Journal:	Icarus, Volume 271, p. 207-221.
Publication Date:	Jun 2016
Origin:	ELSEVIER
Keywords:	Atmospheres, dynamics, Mars, atmosphere
Abstract Copyright:	(c) 2016 Elsevier Inc.
DOI:	http://dx.doi.org/10.1016/j.icarus.2016.02.005 http://bit.ly/2bk6MLt
Bibliographic Code:	2016Icar..271..207W
Abstract:	Investigations of the variability, structure and energetics of the m = 1-3 traveling waves in the northern hemisphere of Mars are conducted with the MarsWRF general circulation model. Using a simple, annually repeatable dust scenario, the model reproduces many general characteristics of the observed traveling waves. The simulated m = 1 and m = 3 traveling waves show large differences in terms of their structures and energetics. For each representative wave mode, the geopotential signature maximizes at a higher altitude than the temperature signature, and the wave energetics suggests a mixed baroclinic-barotropic nature. There is a large contrast in wave energetics between the near-surface and higher altitudes, as well as between the lower latitudes and higher latitudes at high altitudes. Both barotropic and baroclinic conversions can act as either sources or sinks of eddy kinetic energy. Band-pass filtered transient eddies exhibit strong zonal variations in eddy kinetic energy and various energy transfer terms. Transient eddies are mainly interacting with the time mean flow. However, there appear to be non-negligible wave-wave interactions associated with wave mode transitions. These interactions include those between traveling waves and thermal tides and those among traveling waves.

Title:	Variations in Titan's dune orientations as a result of orbital forcing
Authors:	McDonald, George D.; Hayes, Alexander G.; Ewing, Ryan C.; Lora, Juan M.; Newman, Claire E.; Tokano, Tetsuya; Lucas, Antoine; Soto, Alejandro; Chen, Gang
Affiliation:	AA(School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30308, USA), AB(Department of Astronomy, Cornell University, Ithaca, NY 14853, USA), AC(Department of Geology and Geophysics, Texas A&M University, College Station, TX 77840, USA), AD(Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, Los Angeles, CA 90095, USA), AE(Ashima Research, Pasadena, CA 91001, USA), AF(Institut für Geophysik und Meteorologie, Universität zu Köln, 50923 Köln, Germany), AG(AIM CEA-Saclay, Paris VII-Denis Diderot University, Paris 75013, France), AH(Southwest Research Institute, Boulder, CO 80032, USA), AI(Department of Earth and Atmospheric Sciences, Cornell University, Ithaca, NY 14853, USA)
Journal:	Icarus, Volume 270, p. 197-210.
Publication Date:	May 2016
Origin:	ELSEVIER
Keywords:	Titan, Titan, surface, Titan, atmosphere, Atmospheres, dynamics
Abstract Copyright:	(c) 2016 Elsevier Inc.
DOI:	http://dx.doi.org/10.1016/j.icarus.2015.11.036 http://bit.ly/2bk6dBp
Bibliographic Code:	2016Icar..270..197M
Abstract:	Wind-blown dunes are a record of the climatic history in Titan's equatorial region. Through modeling of the climatic conditions associated with Titan's historical orbital configurations (arising from apsidal precessions of Saturn's orbit), we present evidence that the orientations of the dunes are influenced by orbital forcing. Analysis of 3 Titan general circulation models (GCMs) in conjunction with a sediment transport model provides the first direct intercomparison of results from different Titan GCMs. We report variability in the dune orientations predicted for different orbital epochs of up to 70°. Although the response of the GCMs to orbital forcing varies, the orbital influence on the dune orientations is found to be significant across all models. Furthermore, there is near agreement among the two models run with surface topography, with 3 out of the 5 dune fields matching observation for the most recent orbital cycle. Through comparison with observations by Cassini, we find situations in which the observed dune orientations are in best agreement with those modeled for previous orbital configurations or combinations thereof, representing a larger portion of the cycle. We conclude that orbital forcing could be an important factor in governing the present-day dune orientations observed on Titan and should be considered when modeling dune evolution.

Title:	Atmospheric tides in Gale Crater, Mars
Authors:	Guzewich, Scott D.; Newman, C. E.; de la Torre Juárez, M.; Wilson, R. J.; Lemmon, M.; Smith, M. D.; Kahanpää, H.; Harri, A.-M.
Affiliation:	AA(CRESST and Planetary Systems Laboratory, NASA/GSFC, Greenbelt, MD 20771, United States), AB(Ashima Research, Pasadena, CA 91106, United States), AC(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, United States), AD(Geophysical Fluid Dynamics Laboratory, Princeton, NJ 08540, United States), AE(Texas A&M University, College Station, TX 77843, United States), AF(Planetary Systems Laboratory, NASA/GSFC, Greenbelt, MD 20771, United States), AG(Finnish Meteorological Institute, Helsinki, Finland), AH(Finnish Meteorological Institute, Helsinki, Finland)
Journal:	Icarus, Volume 268, p. 37-49.
Publication Date:	Apr 2016
Origin:	ELSEVIER
Keywords:	Mars, atmosphere, Atmospheres, dynamics, Meteorology
Abstract Copyright:	(c) 2016 Elsevier Inc.
DOI:	http://dx.doi.org/10.1016/j.icarus.2015.12.028 http://bit.ly/2boX8dS
Bibliographic Code:	2016Icar..268...37G
Abstract:	Atmospheric tides are the primary source of daily air pressure variation at the surface of Mars. These tides are forced by solar heating of the atmosphere and modulated by the presence of atmospheric dust, topography, and surface albedo and thermal inertia. This results in a complex mix of sun-synchronous and non-sun-synchronous tides propagating both eastward and westward around the planet in periods that are integer fractions of a solar day. The Rover Environmental Monitoring Station on board the Mars Science Laboratory has observed air pressure at a regular cadence for over 1 Mars year and here we analyze and diagnose atmospheric tides in this pressure record. The diurnal tide amplitude varies from 26 to 63 Pa with an average phase of 0424 local true solar time, while the semidiurnal tide amplitude varies from 5 to 20 Pa with an average phase of 0929. We find that both the diurnal and semidiurnal tides in Gale Crater are highly correlated to atmospheric opacity variations at a value of 0.9 and to each other at a value of 0.77, with some key exceptions occurring during regional and local dust storms. We supplement our analysis with MarsWRF general circulation modeling to examine how a local dust storm impacts the diurnal tide in its vicinity. We find that both the diurnal tide amplitude enhancement and regional coverage of notable amplitude enhancement linearly scales with the size of the local dust storm. Our results provide the first long-term record of surface pressure tides near the martian equator.

Title:	Simulating Titan's methane cycle with the TitanWRF General Circulation Model
Authors:	Newman, Claire E.; Richardson, Mark I.; Lian, Yuan; Lee, Christopher
Affiliation:	AA(Aeolis Research, Suite 205, 600 North Rosemead Boulevard, Pasadena, CA 91107, USA), AB(Aeolis Research, Suite 205, 600 North Rosemead Boulevard, Pasadena, CA 91107, USA 0000-0001-9633-4141), AC(Aeolis Research, Suite 205, 600 North Rosemead Boulevard, Pasadena, CA 91107, USA), AD(Aeolis Research, Suite 205, 600 North Rosemead Boulevard, Pasadena, CA 91107, USA)
Journal:	Icarus, Volume 267, p. 106-134.
Publication Date:	Mar 2016
Origin:	ELSEVIER
Keywords:	Titan, Titan, atmosphere, Atmospheres, dynamics, Atmospheres, structure, Meteorology
Abstract Copyright:	(c) 2016 Elsevier Inc.
DOI:	http://dx.doi.org/10.1016/j.icarus.2015.11.028 http://bit.ly/22fPJwT
Bibliographic Code:	2016Icar..267..106N
Abstract:	Observations provide increasing evidence of a methane hydrological cycle on Titan. Earth-based and Cassini-based monitoring has produced data on the seasonal variation in cloud activity and location, with clouds being observed at increasingly low latitudes as Titan moved out of southern summer. Lakes are observed at high latitudes, with far larger lakes and greater areal coverage in the northern hemisphere, where some shorelines extend down as far as 50°N. Rainfall at some point in the past is suggested by the pattern of flow features on the surface at the Huygens landing site, while recent rainfall is suggested by surface change. As with the water cycle on Earth, the methane cycle on Titan is both impacted by tropospheric dynamics and likely able to impact this circulation via feedbacks. Here we use the 3D TitanWRF General Circulation Model (GCM) to simulate Titan's methane cycle. In this initial work we use a simple large-scale condensation scheme with latent heat feedbacks and a finite surface reservoir of methane, and focus on large-scale dynamical interactions between the atmospheric circulation and methane, and how these impact seasonal changes and the long term (steady state) behavior of the methane cycle. We note five major conclusions: (1) Condensation and precipitation in the model is sporadic in nature, with interannual variability in its timing and location, but tends to occur in association with both (a) frequent strong polar upwelling during spring and summer in each hemisphere, and (b) the Inter-Tropical Convergence Zone (ITCZ), a region of increased convergence and upwelling due to the seasonally shifting Hadley cells. (2) An active tropospheric methane cycle affects the stratospheric circulation, slightly weakening the stratospheric superrotation produced. (3) Latent heating feedback strongly influences surface and near-surface temperatures, narrowing the latitudinal range of the ITCZ, and changing the distribution - and generally weakening the strength - of upwelling events. (4) TitanWRF favors low latitude 'cloudiness' around northern spring equinox as the ITCZ moves from south to north across the equator, versus the opposite time of year. (5) TitanWRF produces drying of low and mid latitudes with net transport of surface methane to high latitudes, and shows persistent hemispheric asymmetry in the methane cycle such that the favored pole for surface methane is the one with winter occurring closest to perihelion.

Title:	The impact of surface dust source exhaustion on the martian dust cycle, dust storms and interannual variability, as simulated by the MarsWRF General Circulation Model
Authors:	Newman, Claire E.; Richardson, Mark I.
Affiliation:	AA(Ashima Research, Suite 104, 600 South Lake Avenue, Pasadena, CA 91001, USA), AB(Ashima Research, Suite 104, 600 South Lake Avenue, Pasadena, CA 91001, USA)
Journal:	Icarus, Volume 257, p. 47-87.
Publication Date:	Sep 2015
Origin:	ELSEVIER
Keywords:	Mars, atmosphere, surface, Atmospheres, dynamics, climate
Abstract Copyright:	(c) 2015 Elsevier Inc.
DOI:	http://dx.doi.org/10.1016/j.icarus.2015.03.030 http://bit.ly/2bk6IeS
Bibliographic Code:	2015Icar..257...47N
Abstract:	Observations of albedo on Mars suggest a largely invariant long-term mean surface dust distribution, but also reveal variations on shorter (seasonal to annual) timescales, particularly associated with major dust storms. We study the impact of finite surface dust availability on the dust cycle in the MarsWRF General Circulation Model (GCM), which uses radiatively active dust with parameterized 'dust devil' and wind stress dust lifting to enable the spontaneous production of dust storms, and tracks budgets of dust lifting, deposition, and total surface dust inventory. We seek a self-consistent, long-term 'steady state' dust cycle for present day Mars, consisting of (a) a surface dust distribution that varies from year to year but is constant longer-term and in balance with current dust redistribution processes, and (b) a fixed set of dust lifting parameters that continue to produce major storms for this distribution of surface dust. We relax the GCM's surface dust inventory toward this steady state using an iterative process, in which dust lifting rate parameters are increased as progressively more surface sites are exhausted of dust. Late in the equilibration process, the GCM exhibits quasi-steady state behavior in which few new surface grid points are exhausted during a 60 year period with constant dust lifting parameters. Complex regional-scale dust redistribution occurs on time-scales from less than seasonal to decadal, and the GCM generates regional to global dust storms with many realistic features. These include merging regional storms, cross-equatorial storms, and the timing and location of several storm types, though very early major storms and large amounts of late storm activity are not reproduced. Surface dust availability in key onset and growth source regions appears vital for 'early' major storms, with replenishment of these regions required before another large storm can occur, whereas 'late' major storms appear primarily dependent on atmospheric variability. For the parameter space explored, no simulation achieves a steady state with continuing major storms lasting longer than 60 years when a constant wind stress lifting threshold is used. However, such a long-term steady state is achieved when a variable threshold is introduced, in which the threshold increases as dust is removed. This negative feedback on lifting slows it sufficiently for a balance to be produced between dust removal and re-deposition, even in key source regions for major storms. One concern is that the long-term surface dust distributions produced in these simulations show significant differences to the observed northern hemisphere albedo map, in particular predicting Tharsis and NE Arabia to be relatively dust-free. Although some observed high albedo regions may not have significant mobile dust, others likely have a dust cover several meters thick. The mismatches may reflect deficiencies in the GCM or the iterative process used, or the existence of ancient deep dust deposits formed during a past climate epoch.

Title:	General circulation models of the dynamics of Pluto's volatile transport on the eve of the New Horizons encounter
Authors:	Toigo, Anthony D.; French, Richard G.; Gierasch, Peter J.; Guzewich, Scott D.; Zhu, Xun; Richardson, Mark I.
Affiliation:	AA(Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, United States), AB(Wellesley College, Wellesley, MA 02492, United States), AC(Astronomy Department, Cornell University, Ithaca, NY 14853, United States), AD(NASA Goddard Space Flight Center, Greenbelt, MD 20771, United States), AE(Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, United States), AF(Ashima Research, Pasadena, CA 91106, United States)
Journal:	Icarus, Volume 254, p. 306-323.
Publication Date:	Jul 2015
Origin:	ELSEVIER
Keywords:	Pluto, atmosphere, Atmospheres, dynamics
Abstract Copyright:	(c) 2015 Elsevier Inc.
DOI:	http://dx.doi.org/10.1016/j.icarus.2015.03.034 http://bit.ly/2b2IhC3
Bibliographic Code:	2015Icar..254..306T
Abstract:	Pluto's atmospheric dynamics occupy an interesting regime in which the radiative time constant is quite long, the combined effects of high obliquity and a highly eccentric orbit can produce strong seasonal variations in atmospheric pressure, and the strong coupling between the atmosphere and volatile transport on the surface results in atmospheric flows that are quite sensitive to surface and subsurface properties that at present are poorly constrained by direct observations. In anticipation of the New Horizons encounter with the Pluto system in July 2015, we present a Pluto-specific three-dimensional general circulation model (GCM), PlutoWRF, incorporating the most accurate current radiative transfer models of Pluto's atmosphere, a physically robust treatment of nitrogen volatile transport, and the flexibility to accommodate richly detailed information about the surface and subsurface conditions as new data become available. We solve for a physically self-consistent, equilibrated combination of surface, subsurface, and atmospheric conditions to specify the boundary conditions and initial state values for each GCM run. This is accomplished using two reduced versions of PlutoWRF: a two-dimensional surface volatile exchange model to specify the properties of surface nitrogen ice and the initial atmospheric surface pressure, and a one-dimensional radiative-conductive-convective model that uses the two-dimensional model predictions to determine the corresponding global-mean atmospheric thermal profile. We illustrate the capabilities of PlutoWRF in predicting Pluto's general circulation, thermal state, and volatile transport of nitrogen by calculating the dynamical response of Pluto's atmosphere, based on four different idealized models of Pluto's surface ice distribution from Young (Young, L.A. [2013]. Astrophys. J. 766, L22) and Hansen et al. (Hansen, C.J., Paige, D.A., Young, L.A. [2015]. Icarus 246, 183). Our GCM runs typically span 30 years, from 1985 to 2015, covering the period from the discovery of Pluto's atmosphere to present. For most periods simulated, zonal winds are strongly forced by a gradient wind balance, relaxing in later (recent) years to an angular momentum conservation balance of the seasonal polar cap sublimation flow. Near-surface winds generally follow a sublimation flow from the sunlit polar cap to the polar night cap, with a Coriolis turning of the wind as the air travels from pole to pole. We demonstrate the strong contribution of nitrogen sublimation and deposition to Pluto's atmospheric circulation. As New Horizons data become available, PlutoWRF can be used to construct models of Pluto's atmospheric dynamics and surface wind regimes more constrained by physical observations.

Title:	Martian atmospheric collapse: Idealized GCM studies
Authors:	Soto, Alejandro; Mischna, Michael; Schneider, Tapio; Lee, Christopher; Richardson, Mark
Affiliation:	AA(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA), AB(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA), AC(Department of Earth Sciences, ETH Zurich, Switzerland), AD(Ashima Research, Pasadena, CA 91106, USA), AE(Ashima Research, Pasadena, CA 91106, USA)
Journal:	Icarus, Volume 250, p. 553-569.
Publication Date:	Apr 2015
Origin:	ELSEVIER
Keywords:	Mars, climate, atmosphere, polar caps, Atmospheres, evolution, dynamics
Abstract Copyright:	(c) 2015 Elsevier Inc.
DOI:	http://dx.doi.org/10.1016/j.icarus.2014.11.028 http://bit.ly/1QKB9Hl
Bibliographic Code:	2015Icar..250..553S
Abstract:	Global energy balance models of the martian atmosphere predict that, for a range of total CO2 inventories, the CO2 atmosphere may condense until a state with a permanent polar cap is reached. This process, which is commonly referred to as atmospheric collapse, may limit the time available for physical and chemical weathering. The global energy balance models that predict atmospheric collapse represent the climate using simplified parameterizations for atmospheric processes such as radiative transfer and atmospheric heat transport. However, a more detailed representation of these atmospheric processes is critical when the atmosphere is near a transition, such as the threshold for collapse. Therefore, we use the Mars Weather Research and Forecasting (MarsWRF) general circulation model (GCM) to investigate how the explicit representation of meridional heat transport and more detailed radiative transfer affects the onset of atmospheric collapse. Using MarsWRF, we find that previous energy balance modeling underestimates the range of CO2 inventories for which the atmosphere collapses and that the obliquity of Mars determines the range of CO2 inventories that can collapse. For a much larger range of CO2 inventories than expected, atmospheric heat transport is insufficient to prevent the atmospheric collapse. We show that the condensation of CO2 onto Olympus Mons and adjacent mountains generates a condensation flow. This condensation flow syphons energy that would otherwise be transported poleward, which helps explain the large range of CO2 inventories for which the atmosphere collapses.

Title:	Feasibility Studies on Guidance and Global Path Planning for Wind-Assisted Montgolfière in Titan
Authors:	Fathpour, Nanaz; Blackmore, Lars; Kuwata, Yoshiaki; Assad, Christopher; Wolf, Michael T.; Newman, Claire; Elfes, Alberto; Reh, Kim
Journal:	IEEE Systems Journal, vol. 8, issue 4, pp. 1112-1125
Publication Date:	Dec 2014
Origin:	CROSSREF
DOI:	http://dx.doi.org/10.1109/JSYST.2013.2282700 http://bit.ly/1pnplEY
Bibliographic Code:	2014ISysJ...8.1112F
Abstract:	Not Available

Title:	Threshold for sand mobility on Mars calibrated from seasonal variations of sand flux
Authors:	Ayoub, F.; Avouac, J.-P.; Newman, C. E.; Richardson, M. I.; Lucas, A.; Leprince, S.; Bridges, N. T.
Affiliation:	AA(Division of Geological and Planetary Sciences, California Institute of Technology, 1200 East California Boulevard, MC 100-23, Pasadena, California 91125, USA; fayoub@gps.caltech.edu), AB(), AC(Ashima Research, 600 South Lake Avenue, Suite 104, Pasadena, California 91106, USA), AD(Ashima Research, 600 South Lake Avenue, Suite 104, Pasadena, California 91106, USA), AE(Division of Geological and Planetary Sciences, California Institute of Technology, 1200 East California Boulevard, MC 100-23, Pasadena, California 91125, USA), AF(Division of Geological and Planetary Sciences, California Institute of Technology, 1200 East California Boulevard, MC 100-23, Pasadena, California 91125, USA), AG(Space Department, 200-W230, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, Maryland 20723, USA)
Journal:	Nature Communications, Volume 5, id. 5096 (2014).
Publication Date:	Sep 2014
Origin:	NATURE
Abstract Copyright:	(c) 2014: Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved.
DOI:	http://dx.doi.org/10.1038/ncomms6096 http://bit.ly/24AtjKG
Bibliographic Code:	2014NatCo...5E5096A
Abstract:	Coupling between surface winds and saltation is a fundamental factor governing geological activity and climate on Mars. Saltation of sand is crucial for both erosion of the surface and dust lifting into the atmosphere. Wind tunnel experiments along with measurements from surface meteorology stations and modelling of wind speeds suggest that winds should only rarely move sand on Mars. However, evidence for currently active dune migration has recently accumulated. Crucially, the frequency of sand-moving events and the implied threshold wind stresses for saltation have remained unknown. Here we present detailed measurements of Nili Patera dune field based on High Resolution Imaging Science Experiment images, demonstrating that sand motion occurs daily throughout much of the year and that the resulting sand flux is strongly seasonal. Analysis of the seasonal sand flux variation suggests an effective threshold for sand motion for application to large-scale model wind fields (1-100 km scale) of τs=0.01±0.0015 N m-2.

Title:	Thermal tides during the 2001 Martian global-scale dust storm
Authors:	Guzewich, Scott D.; Wilson, R. John; McConnochie, Timothy H.; Toigo, Anthony D.; Banfield, Donald J.; Smith, Michael D.
Affiliation:	AA(NASA Goddard Spaceflight Center, Greenbelt, Maryland USA), AB(Geophysical Fluid Dynamics Laboratory NOAA, Princeton, New Jersey USA), AC(Department of Astronomy, University of Maryland, College Park, Maryland USA), AD(Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland USA), AE(Center for Radiophysics and Space Research, Cornell University, Ithaca, New York USA), AF(NASA Goddard Spaceflight Center, Greenbelt, Maryland USA)
Journal:	Journal of Geophysical Research: Planets, Volume 119, Issue 3, pp. 506-519
Publication Date:	Mar 2014
Origin:	WILEY
Keywords:	Mars, global dust storm, tides, waves
Abstract Copyright:	©2014. American Geophysical Union. All Rights Reserved.
DOI:	http://dx.doi.org/10.1002/2013JE004502 http://bit.ly/2bk6DaK
Bibliographic Code:	2014JGRE..119..506G
Abstract:	The 2001 (Mars Year 25) global dust storm radically altered the dynamics of the Martian atmosphere. Using observations from the Thermal Emission Spectrometer onboard the Mars Global Surveyor spacecraft and MarsWRF general circulation model simulations, we examine the changes to thermal tides and planetary waves caused by the storm. We find that the extratropical diurnal migrating tide is dramatically enhanced during the storm, particularly in the southern hemisphere, reaching amplitudes of more than 20 K. The tropical diurnal migrating tide is weakened to almost undetectable levels. The diurnal Kelvin waves are also significantly weakened, particularly during the period of global expansion at Ls = 200°-210°. In contrast, the westward propagating diurnal wavenumber 2 tide strengthens to 4-8 K at altitudes above 30 km. The wavenumber 1 stationary wave reaches amplitudes of 10-12 K at 50°-70°N, far larger than is typically seen during this time of year. The phase of this stationary wave and the enhancement of the diurnal wavenumber 2 tide appear to be responses to the high-altitude westward propagating equatorial wavenumber 1 structure in dust mixing ratio observed during the storm in previous works. This work provides a global picture of dust storm wave dynamics that reveals the coupling between the tropics and high-latitude wave responses. We conclude that the zonal distribution of thermotidal forcing from atmospheric aerosol concentration is as important to understanding the atmospheric wave response as the total global mean aerosol optical depth.

Title:	Constraints on Mars' recent equatorial wind regimes from layered deposits and comparison with general circulation model results
Authors:	Sefton-Nash, E.; Teanby, N. A.; Newman, C.; Clancy, R. A.; Richardson, M. I.
Affiliation:	AA(Department of Earth and Space Sciences, University of California Los Angeles, 595 Charles Young Drive East, Los Angeles, CA 90095, USA), AB(School of Earth Sciences, University of Bristol, Queen's Road, Bristol BS8 1RJ, UK), AC(Ashima Research, 600 S. Lake Ave., Suite 104, Pasadena, CA 91106, USA), AD(School of Earth Sciences, University of Bristol, Queen's Road, Bristol BS8 1RJ, UK), AE(Ashima Research, 600 S. Lake Ave., Suite 104, Pasadena, CA 91106, USA)
Journal:	Icarus, Volume 230, p. 81-95.
Publication Date:	Feb 2014
Origin:	ELSEVIER
Abstract Copyright:	(c) 2014 Elsevier Inc.
DOI:	http://dx.doi.org/10.1016/j.icarus.2013.11.014 http://bit.ly/1TQXbh1
Bibliographic Code:	2014Icar..230...81S
Abstract:	Aeolian modification has been a fundamental surface process on Mars throughout the Amazonian. Orientations of aeolian features such as bedforms and yardangs are controlled by the prevailing wind regime during the feature's formation. Therefore, observation of recently formed bedform orientations provides a way to probe Mars' recent wind regime and constrain/test general circulation models (GCMs). We collect statistical distributions of transverse bedform and yardang azimuths at nine sites on Mars, and compare measured feature orientations to those predicted by using vector wind field output from the MarsWRF GCM. We focus on layered deposits because their erodible nature makes them applicable to determination of Mars' modern wind regime. Our methods of mapping from the long-term wind field to predicted feature orientations include consideration of wind stress thresholds for sand movement to occur, sand flux equations, and the direction of maximum gross bedform-normal transport. We find that all methods examined typically agree with each other to within ˜15°, though there are some exceptions using high order wind stress weightings with multi-directional annual wind fields. Generally, use of higher wind stress thresholds produces improved matches to bedform orientations. Comparison of multiple yardang orientations to annually variable wind fields is accomplished by inspection of directional maxima in modelled wind vector frequency distributions. Yardangs match well to model predictions and sub-populations in close proximity to each other are shown to match individual directional maxima in GCM output for a single site, implying that topographic effects may produce very localised unidirectional wind fields unresolved by the GCM.

Title:	Growth and form of the mound in Gale Crater, Mars: Slope wind enhanced erosion and transport
Authors:	Kite, Edwin S.; Lewis, Kevin W.; Lamb, Michael P.; Newman, Claire E.; Richardson, Mark I.
Affiliation:	AA(California Institute of Technology), AB(Princeton University), AC(California Institute of Technology), AE(Ashima Research)
Journal:	Geology, vol. 41, p. 543-546
Publication Date:	May 2013
Origin:	AUTHOR
Bibliographic Code:	2013Geo....41..543K
Abstract:	Ancient sediments provide archives of climate and habitability on Mars. Gale Crater, the landing site for the Mars Science Laboratory (MSL), hosts a 5-km-high sedimentary mound (Mount Sharp/Aeolis Mons). Hypotheses for mound formation include evaporitic, lacustrine, fluviodeltaic, and aeolian processes, but the origin and original extent of Gale’s mound is unknown. Here we show new measurements of sedimentary strata within the mound that indicate ˜3° outward dips oriented radially away from the mound center, inconsistent with the first three hypotheses. Moreover, although mounds are widely considered to be erosional remnants of a once crater-filling unit, we find that the Gale mound’s current form is close to its maximal extent. Instead we propose that the mound’s structure, stratigraphy, and current shape can be explained by growth in place near the center of the crater mediated by wind-topography feedbacks. Our model shows how sediment can initially accrete near the crater center far from crater-wall katabatic winds, until the increasing relief of the resulting mound generates mound-flank slope winds strong enough to erode the mound. The slope wind enhanced erosion and transport (SWEET) hypothesis indicates mound formation dominantly by aeolian deposition with limited organic carbon preservation potential, and a relatively limited role for lacustrine and fluvial activity. Morphodynamic feedbacks between wind and topography are widely applicable to a range of sedimentary and ice mounds across the Martian surface, and possibly other planets.

Title:	The impact of a realistic vertical dust distribution on the simulation of the Martian General Circulation
Authors:	Guzewich, Scott D.; Toigo, Anthony D.; Richardson, Mark I.; Newman, Claire E.; Talaat, Elsayed R.; Waugh, Darryn W.; McConnochie, Timothy H.
Affiliation:	AA(NASA Goddard Spaceflight Center, Greenbelt, Maryland USA), AB(The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland USA), AC(Ashima Research, Pasadena, California USA), AD(Ashima Research, Pasadena, California USA), AE(The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland USA), AF(Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, Maryland USA), AG(Department of Astronomy, University of Maryland, College Park, Maryland USA)
Journal:	Journal of Geophysical Research: Planets, Volume 118, Issue 5, pp. 980-993
Publication Date:	May 2013
Origin:	WILEY
Keywords:	Mars Atmosphere, Dust, GCM Modeling
Abstract Copyright:	©2013. American Geophysical Union. All Rights Reserved.
DOI:	http://dx.doi.org/10.1002/jgre.20084 http://bit.ly/1ncyr61
Bibliographic Code:	2013JGRE..118..980G
Abstract:	Limb-scanning observations with the Mars Climate Sounder and Thermal Emission Spectrometer (TES) have identified discrete layers of enhanced dust opacity well above the boundary layer and a mean vertical structure of dust opacity very different from the expectation of well-mixed dust in the lowest 1-2 scale heights. To assess the impact of this vertical dust opacity profile on atmospheric properties, we developed a TES limb-scan observation-based three-dimensional and time-evolving dust climatology for use in forcing general circulation models (GCMs). We use this to force the MarsWRF GCM and compare with simulations that use a well-mixed (Conrath-ν) vertical dust profile and Mars Climate Database version 4 (MCD) horizontal distribution dust opacity forcing function. We find that simulated temperatures using the TES-derived forcing yield a 1.18 standard deviation closer match to TES temperature retrievals than a MarsWRF simulation using MCD forcing. The climatological forcing yields significant changes to many large-scale features of the simulated atmosphere. Notably the high-latitude westerly jet speeds are 10-20 m/s higher, polar warming collar temperatures are 20-30 K warmer near northern winter solstice and tilted more strongly poleward, the middle and lower atmospheric meridional circulations are partially decoupled, the migrating diurnal tide exhibits destructive interference and is weakened by 50% outside of equinox, and the southern hemisphere wave number 1 stationary wave is strengthened by up to 4 K (45%). We find the vertical dust distribution is an important factor for Martian lower and middle atmospheric thermal structure and circulation that cannot be neglected in analysis and simulation of the Martian atmosphere.

Title:	Zonal wavenumber three traveling waves in the northern hemisphere of Mars simulated with a general circulation model
Authors:	Wang, Huiqun; Richardson, Mark I.; Toigo, Anthony D.; Newman, Claire E.
Affiliation:	AA(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA), AB(Ashima Research, Pasadena, CA 91101, USA), AC(Applied Physics Laboratory, Johns Hopkins University, Laurel, MD 20723, USA), AD(Ashima Research, Pasadena, CA 91101, USA)
Journal:	Icarus, Volume 223, Issue 2, p. 654-676.
Publication Date:	Apr 2013
Origin:	ELSEVIER
Abstract Copyright:	Elsevier Inc.
DOI:	http://dx.doi.org/10.1016/j.icarus.2013.01.004 http://bit.ly/12XkM2Q
Bibliographic Code:	2013Icar..223..654W
Abstract:	Observations suggest a strong correlation between curvilinear shaped traveling dust storms (observed in wide angle camera images) and eastward traveling zonal wave number m = 3 waves (observed in thermal data) in the northern mid and high latitudes during the fall and winter. Using the MarsWRF General Circulation Model, we have investigated the seasonality, structure and dynamics of the simulated m = 3 traveling waves and tested the hypothesis that traveling dust storms may enhance m = 3 traveling waves under certain conditions.Our standard simulation using a prescribed "MGS dust scenario" can capture the observed major wave modes and strong near surface temperature variations before and after the northern winter solstice. The same seasonal pattern is also shown by the simulated near surface meridional wind, but not by the normalized surface pressure. The simulated eastward traveling 1.4 < T < 10 sol m = 3 waves are confined near the surface in terms of the temperature perturbation, EP flux and eddy available potential energy, and they extend higher in terms of the eddy winds and eddy kinetic energy. The signature of the simulated m = 3 traveling waves is stronger in the near surface meridional wind than in the near surface temperature field.Compared with the standard simulation, our test simulations show that the prescribed m = 3 traveling dust blobs can enhance the simulated m = 3 traveling waves during the pre- and post-solstice periods when traveling dust storms are frequently observed in images, and that they have negligible effect during the northern winter solstice period when traveling dust storms are absent. The enhancement is even greater in our simulation when dust is concentrated closer to the surface. Our simulations also suggest that dust within the 45-75°N band is most effective at enhancing the simulated m = 3 traveling waves.There are multiple factors influencing the strength of the simulated m = 3 traveling waves. Among those, our study suggests that weaker near surface static stability, larger near surface baroclinic parameter, and wave-form dust forcing for latitudinally extended dust storms are favorable. Further study is needed to fully understand the importance of these factors and others.

Title:	Effects of obliquity and water vapor/trace gas greenhouses in the early martian climate
Authors:	Mischna, Michael A.; Baker, Victor; Milliken, Ralph; Richardson, Mark; Lee, Christopher
Affiliation:	AA(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California USA), AB(Department of Planetary Sciences, Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona USA), AC(Department of Geological Sciences, Brown University, Providence, Rhode Island USA), AD(Ashima Research, Pasadena, California USA), AE(Ashima Research, Pasadena, California USA)
Journal:	Journal of Geophysical Research: Planets, Volume 118, Issue 3, pp. 560-576
Publication Date:	Mar 2013
Origin:	WILEY
Keywords:	early Mars, sulfur, volcanism, obliquity, greenhouse effect, MarsWRF
Abstract Copyright:	©2013. American Geophysical Union. All Rights Reserved.
DOI:	http://dx.doi.org/10.1002/jgre.20054 http://bit.ly/1plx6LD
Bibliographic Code:	2013JGRE..118..560M
Abstract:	We explore possible mechanisms for the generation of warm, wet climates on early Mars as a result of greenhouse warming by both water vapor and periodic volcanic trace emissions. The presence of both water vapor (a strong greenhouse gas) and other trace greenhouse gases (such as SO2) in a predominantly CO2 atmosphere may act, under certain conditions, to elevate surface temperatures above the freezing point of liquid water, at least episodically. Variations in obliquity are explored to investigate whether these periodic variations in insolation at Mars can broaden the regions or seasons where warm temperatures can exist. We use the Mars Weather Research and Forecasting general circulation model to perform several simulations of the conditions of the early martian atmosphere containing these gases and find global temperatures to be cooler than the elevated levels suggested by at least one recent study by Johnson et al. (2008). While achieving temperatures above 273 K globally remains challenging, the additional warming by greenhouse gases under certain obliquity states can permit for widespread seasonally warm conditions, which can help to explain the presence of fluvial surface features (e.g., valley networks) and hydrous minerals of post-Noachian age, a period when alternate methods do not convincingly explain the sustainability of liquid water. Furthermore, we find that global warming can be achieved with the presence of a darker surface globally, which is consistent with both widespread exposure of unweathered basaltic bedrock or the presence of a large surface ocean or sea.

Title:	Development of a fast, accurate radiative transfer model for the Martian atmosphere, past and present
Authors:	Mischna, Michael A.; Lee, Christopher; Richardson, Mark
Affiliation:	AA(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA), AB(Ashima Research, Pasadena, California, USA), AC(Ashima Research, Pasadena, California, USA)
Journal:	Journal of Geophysical Research, Volume 117, Issue E10, CiteID E10009
Publication Date:	Oct 2012
Origin:	AGU
Keywords:	Atmospheric Composition and Structure: Planetary atmospheres (5210, 5405, 5704), Planetary Sciences: Astrobiology: Planetary atmospheres, clouds, and hazes (0343), Planetary Sciences: Solid Surface Planets: Atmospheres (0343, 1060)
Abstract Copyright:	(c) 2012: American Geophysical Union
DOI:	http://dx.doi.org/10.1029/2012JE004110 http://bit.ly/W82l7h
Bibliographic Code:	2012JGRE..11710009M
Abstract:	We present details of an approach to creating a k-distribution radiative transfer model (KDM) for use in the Martian atmosphere. Such models preserve the accuracy of more rigorous line-by-line models, but are orders of magnitude faster, and can be effectively implemented in 3-D general circulation models. The approach taken here is sufficiently generalized that it can be employed for atmospheres of any arbitrary composition and mass, and demonstrations are provided for simulated atmospheres with a present-day Martian surface pressure (∼6 mb) and a putative thick early Mars atmosphere (∼500 mb), both with and without atmospheric water vapor. KDM-derived absorption coefficients are placed into a look-up table at a set of gridded points in pressure, temperature and atmospheric composition, and a tri-linear interpolation scheme is used to obtain the coefficients appropriate for the local atmospheric conditions. These coefficients may then be used within any of a variety of commonly used flux solvers to obtain atmospheric heating rates. A series of validation tests are performed with the KDM for both present-day and early Mars atmospheric conditions, and the model is compared against several other widely used radiative transfer schemes, including several used in contemporary general circulation models. These validation results identify weaknesses in some other approaches and demonstrate the efficacy of the KDM, providing a rigorous test of these types of models for use in the Martian atmosphere. A demonstration of results obtained by implementing the KDM in a Mars general circulation model is provided.

Title:	The impact of resolution on the dynamics of the martian global atmosphere: Varying resolution studies with the MarsWRF GCM
Authors:	Toigo, Anthony D.; Lee, Christopher; Newman, Claire E.; Richardson, Mark I.
Affiliation:	AA(The Johns Hopkins University, Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, USA), AB(Ashima Research, Suite 104, 600 South Lake Ave., Pasadena, CA 91106, USA), AC(Ashima Research, Suite 104, 600 South Lake Ave., Pasadena, CA 91106, USA), AD(Ashima Research, Suite 104, 600 South Lake Ave., Pasadena, CA 91106, USA)
Journal:	Icarus, Volume 221, Issue 1, p. 276–288.
Publication Date:	Aug 2012
Origin:	ELSEVIER
Abstract Copyright:	Elsevier Inc.
DOI:	http://dx.doi.org/10.1016/j.icarus.2012.07.020 http://bit.ly/PUT9VM
Bibliographic Code:	2012Icar..218.1043L
Abstract:	We investigate the sensitivity of the circulation and thermal structure of the martian atmosphere to numerical model resolution in a general circulation model (GCM) using the martian implementation (MarsWRF) of the planetWRF atmospheric model. We provide a description of the MarsWRF GCM and use it to study the global atmosphere at horizontal resolutions from 7.5 9 to 0.5 0.5, encompassing the range from standard Mars GCMs to global mesoscale modeling. We find that while most of the gross-scale features of the circulation (the rough location of jets, the qualitative thermal structure, and the major large-scale features of the surface level winds) are insensitive to horizontal resolution over this range, several major features of the circulation are sensitive in detail. The northern winter polar circulation shows the greatest sensitivity, showing a continuous transition from a smooth polar winter jet at low resolution, to a distinct vertically ‘‘split’’ jet as resolution increases. The separation of the lower and middle atmosphere polar jet occurs at roughly 10 Pa, with the split jet structure developing in concert with the intensification of meridional jets at roughly 10 Pa and above 0.1 Pa. These meridional jets appear to represent the separation of lower and middle atmosphere mean overturning circulations (with the former being consistent with the usual concept of the ‘‘Hadley cell’’). Further, the transition in polar jet structure is more sensitive to changes in zonal than meridional horizontal resolution, suggesting that representation of small-scale wave-mean flow interactions is more important than fine-scale representation of the meridional thermal gradient across the polar front. Increasing the horizontal resolution improves the match between the modeled thermal structure and the Mars Climate Sounder retrievals for northern winter high latitudes. While increased horizontal resolution also improves the simulation of the northern high latitudes at equinox, even the lowest model resolution considered here appears to do a good job for the southern winter and southern equinoctial pole (although in detail some discrepancies remain). These results suggest that studies of the northern winter jet (e.g., transient waves and cyclogenesis) will be more sensitive to global model resolution that those of the south (e.g., the confining dynamics of the southern polar vortex relevant to studies of argon transport). For surface winds, the major effect of increased horizontal resolution is in the superposition of circulations forced by local-scale topography upon the large-scale surface wind patterns. While passive predictions of dust lifting are generally insensitive to model horizontal resolution when no lifting threshold is considered, increasing the stress threshold produces significantly more lifting in higher resolution simulations with the generation of finer-scale, higher-stress winds due primarily to better-resolved topography. Considering the positive feedbacks expected for radiatively active dust lifting, we expect this bias to increase when such feedbacks are permitted.

Title:	Winds and tides of Ligeia Mare, with application to the drift of the proposed time TiME (Titan Mare Explorer) capsule
Authors:	Lorenz, Ralph D.; Tokano, Tetsuya; Newman, Claire E.
Affiliation:	AA(JHU Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, USA), AB(Institut für Geophysik und Meteorologie, Universität zu Köln, Albertus-Magnus-Platz, 50923 Köln, Germany), AC(Ashima Research, 600 S. Lake Avenue Suite 104, Pasadena, CA 91106, USA)
Journal:	Planetary and Space Science, Volume 60, Issue 1, p. 72-85.
Publication Date:	Jan 2012
Origin:	ELSEVIER
Abstract Copyright:	(c) 2012 Elsevier Ltd
DOI:	http://dx.doi.org/10.1016/j.pss.2010.12.009 http://bit.ly/1TQXbh1
Bibliographic Code:	2012P&SS...60...72L
Abstract:	We use two independent General Circulation Models (GCMs) to estimate surface winds at Titan’s Ligeia Mare (78° N, 250° W), motivated by a proposed mission to land a floating capsule in this ∼500 km hydrocarbon sea. The models agree on the overall magnitude (∼0.5-1 m/s) and seasonal variation (strongest in summer) of windspeeds, but details of seasonal and diurnal variation of windspeed and direction differ somewhat, with the role of surface exchanges being more significant than that of gravitational tides in the atmosphere. We also investigate the tidal dynamics in the sea using a numerical ocean dynamics model: assuming a rigid lithosphere, the tidal amplitude is up to ∼0.8 m. Tidal currents are overall proportional to the reciprocal of depth-with an assumed central depth of 300 m, the characteristic tidal currents are ∼1 cm/s, with notable motions being a slosh between Ligeia’s eastern and western lobes, and a clockwise flow pattern. We find that a capsule will drift at approximately one tenth of the windspeed, unless measures are adopted to augment the drag areas above or below the waterline. Thus motion of a floating capsule is dominated by the wind, and is likely to be several km per Earth day, a rate that will be readily measured from Earth by radio navigation methods. In some instances, the wind vector rotates diurnally such that the drift trajectory is epicyclic.

Title:	Demonstration of ensemble data assimilation for Mars using DART, MarsWRF, and radiance observations from MGS TES
Authors:	Lee, C.; Lawson, W. G.; Richardson, M. I.; Anderson, J. L.; Collins, N.; Hoar, T.; Mischna, M.
Affiliation:	AA(Ashima Research, Pasadena, California, USA); AB(Point Carbon, Washington, D. C., USA); AC(Ashima Research, Pasadena, California, USA); AD(Institute for Mathematics Applied to Geosciences, National Center for Atmospheric Research, Boulder, Colorado, USA); AE(Institute for Mathematics Applied to Geosciences, National Center for Atmospheric Research, Boulder, Colorado, USA); AF(Institute for Mathematics Applied to Geosciences, National Center for Atmospheric Research, Boulder, Colorado, USA); AG(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA)
Journal:	Journal of Geophysical Research, Volume 116, Issue E11, CiteID E11011
Publication Date:	Nov 2011
Origin:	AGU
Keywords:	Global Change: Global climate models (3337, 4928), Informatics: Community modeling frameworks, Informatics: Data assimilation, integration and fusion, Mathematical Geophysics: Numerical approximations and analysis (4260), Planetary Sciences: Solar System Objects: Mars
Abstract Copyright:	(c) 2011: American Geophysical Union
DOI:	http://dx.doi.org/10.1029/2011JE003815 http://bit.ly/Yknr7L
Bibliographic Code:	2011JGRE..11611011L
Abstract:	We describe a global atmospheric data assimilation scheme that has been adapted for use with a Martian General Circulation Model (GCM), with the ultimate goal of creating globally and temporally interpolated “reanalysis” data sets from planetary atmospheric observations. The system uses the Data Assimilation Research Testbed (DART) software to apply an Ensemble Kalman Filter (EnKF) to the MarsWRF GCM. Specific application to Mars also required the development of a radiance forward model for near-nadir Thermal Emission Spectrometer (TES) observations. Preliminary results from an assimilation of 40 sols of TES radiance data, taken around Ls = 150° (August 1999, Mars Year 24), are provided. 1.3 million TES observations are ingested and used to improve the state prediction by the GCM, with bias and error reductions obtained throughout the state vector. Results from the assimilation suggest steepening of the latitudinal and vertical thermal gradients with concurrent strengthening of the mid-latitude zonal jets, and a slower recession of the southern polar ice edge than predicted by the unaided GCM. Limitations of the prescribed dust model are highlighted by the presence of an atmospheric radiance bias. Preliminary results suggest the prescribed dust vertical profile might not be suitable for all seasons, in accordance with more recent observations of the vertical distribution of dust by the Mars Climate Sounder.

Title:	Stratospheric superrotation in the TitanWRF model
Authors:	Newman, Claire E.; Lee, Christopher; Lian, Yuan; Richardson, Mark I.; Toigo, Anthony D.
Affiliation:	AA(Ashima Research, Suite 104, 600 South Lake Avenue, Pasadena, CA 91106, USA), AB(Ashima Research, Suite 104, 600 South Lake Avenue, Pasadena, CA 91106, USA), AC(Ashima Research, Suite 104, 600 South Lake Avenue, Pasadena, CA 91106, USA), AD(Ashima Research, Suite 104, 600 South Lake Avenue, Pasadena, CA 91106, USA), AE(The Johns Hopkins University, Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, USA)
Journal:	Icarus, Volume 213, Issue 2, p. 636-654.
Publication Date:	Jun 2011
Origin:	ELSEVIER
Abstract Copyright:	Elsevier Inc.
DOI:	http://dx.doi.org/10.1016/j.icarus.2011.03.025 http://bit.ly/TZAPqA
Bibliographic Code:	2011Icar..213..636N
Abstract:	TitanWRF general circulation model simulations performed without sub-grid-scale horizontal diffusion of momentum produce roughly the observed amount of superrotation in Titan's stratosphere. We compare these results to Cassini-Huygens measurements of Titan's winds and temperatures, and predict temperature and winds at future seasons. We use angular momentum and transformed Eulerian mean diagnostics to show that equatorial superrotation is generated during episodic angular momentum 'transfer events' during model spin-up, and maintained by similar (yet shorter) events once the model has reached steady state. We then use wave and barotropic instability analysis to suggest that these transfer events are produced by barotropic waves, generated at low latitudes then propagating poleward through a critical layer, thus accelerating low latitudes while decelerating the mid-to-high latitude jet in the late fall through early spring hemisphere. Finally, we identify the dominant waves responsible for the transfers of angular momentum close to northern winter solstice during spin-up and at steady state. Problems with our simulations include peak latitudinal temperature gradients and zonal winds occurring ˜60 km lower than observed by Cassini CIRS, and no reduction in zonal wind speed around 80 km, as was observed by Huygens. While the latter may have been due to transient effects (e.g. gravity waves), the former suggests that our low (˜420 km) model top is adversely affecting the circulation near the jet peak, and/or that we require active haze transport in order to correctly model heating rates and thus the circulation. Future work will include running the model with a higher top, and including advection of a haze particle size distribution.

Title:	Atmospheric modeling of Mars methane surface releases
Authors:	Mischna, Michael A.; Allen, Mark; Richardson, Mark I.; Newman, Claire E.; Toigo, Anthony D.
Affiliation:	AA(Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., M/S 183-401, Pasadena, CA 91109, USA), AB(Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., M/S 183-401, Pasadena, CA 91109, USA; Also, Division of Geological and Planetary Sciences, California Institute of Technology, MC 150-21, 1200 E. California Blvd. Pasadena, CA 91125, USA), AC(Division of Geological and Planetary Sciences, California Institute of Technology, MC 150-21, 1200 E. California Blvd. Pasadena, CA 91125, USA; Present address: Ashima Research, 600 S. Lake Ave, Suite 303, Pasadena, CA 91106, USA), AD(Division of Geological and Planetary Sciences, California Institute of Technology, MC 150-21, 1200 E. California Blvd. Pasadena, CA 91125, USA; Present address: Ashima Research, 600 S. Lake Ave, Suite 303, Pasadena, CA 91106, USA), AE(Cornell University, Department of Astronomy, Ithaca, NY 14853, USA; Present address: The Johns Hopkins University, Applied Physics Laboratory, 11100 Johns Hopkins Rd., Laurel, MD 20723, USA)
Journal:	Planetary and Space Science, Volume 59, Issue 2-3, p. 227-237.
Publication Date:	Feb 2011
Origin:	ELSEVIER
Abstract Copyright:	Elsevier Ltd
DOI:	http://dx.doi.org/10.1016/j.pss.2010.07.005 http://bit.ly/WsimoA
Bibliographic Code:	2011P&SS...59..227M
Abstract:	We utilize the MarsWRF general circulation model (GCM) to address the behavior of gas plumes in the Martian atmosphere, with the specific goal of characterizing the source of the recently identified methane detection in the Martian atmosphere. These observations have been interpreted as the release of methane from localized surface sources with spatial and temporal variabilities. Due to the limited temporal coverage of ground-based observations, we use a GCM to simulate the development of passive atmospheric plumes over relevant timescales. The observations can be reproduced best if the release occurred just before the time of observation—no more than 1-2 sols earlier—and if this release were nearly instantaneous rather than a slow, steady emission. Furthermore, it requires a source region spanning a broad latitudinal range rather than a point emission. While the accuracy of our conclusions about this specific methane release scenario is limited by the uncertainties inherent in GCM simulations of the Martian atmosphere, our findings regarding generalized plume behavior are robust, and illustrate the potential power of numerical modeling for constraining plume source conditions.

Title:	On the mystery of the perennial carbon dioxide cap at the south pole of Mars
Authors:	Guo, Xin; Richardson, Mark Ian; Soto, Alejandro; Toigo, Anthony
Affiliation:	AA(Planetary Science, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AB(Ashima Research, Pasadena, California, USA); AC(Planetary Science, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AD(Center for Radiophysics and Space Research, Cornell University, Ithaca, New York, USA)
Journal:	Journal of Geophysical Research, Volume 115, Issue E4, CiteID E04005
Publication Date:	Apr 2010
Origin:	AGU
Keywords:	Atmospheric Composition and Structure: Planetary atmospheres (5210, 5405, 5704), Planetary Sciences: Solar System Objects: Mars, Planetary Sciences: Solid Surface Planets: Polar regions, Planetary Sciences: Solid Surface Planets: Atmospheres (0343, 1060), Planetary Sciences: Solid Surface Planets: Ices
DOI:	http://dx.doi.org/10.1029/2009JE003382 http://bit.ly/Tha6XP
Bibliographic Code:	2010JGRE..11504005G
Abstract:	A perennial ice cap has long been observed near the south pole of Mars. The surface of this cap is predominantly composed of carbon dioxide ice. The retention of a CO2 ice cap results from the surface energy balance of the latent heat, solar radiation, surface emission, subsurface conduction, and atmospheric sensible heat. While models conventionally treat surface CO2 ice using constant ice albedos and emissivities, such an approach fails to predict the existence of a perennial cap. Here we explore the role of the insolation-dependent ice albedo, which agrees well with Viking, Mars Global Surveyor, and Mars Express albedo observations. Using a simple parameterization within a general circulation model, in which the albedo of CO2 ice responds linearly to the incident solar insolation, we are able to predict the existence of a perennial CO2 cap at the observed latitude and only in the southern hemisphere. Further experiments with different total CO2 inventories, planetary obliquities, and surface boundary conditions suggest that the location of the residual cap may exchange hemispheres favoring the pole with the highest peak insolation.

Title:	Fitting the Viking lander surface pressure cycle with a Mars General Circulation Model
Authors:	Guo, Xin; Lawson, W. Gregory; Richardson, Mark I.; Toigo, Anthony
Affiliation:	AA(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AB(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AC(Ashima Research, Pasadena, California, USA); AD(Center for Radiophysics and Space Research, Cornell University, Ithaca, New York, USA)
Journal:	Journal of Geophysical Research, Volume 114, Issue E7, CiteID E07006
Publication Date:	Jul 2009
Origin:	AGU
Keywords:	Atmospheric Composition and Structure: Planetary atmospheres (5210, 5405, 5704), Planetary Sciences: Solar System Objects: Mars, Planetary Sciences: Solid Surface Planets: Polar regions, Planetary Sciences: Solid Surface Planets: Atmospheres (0343, 1060), Planetary Sciences: Solid Surface Planets: Ices
DOI:	http://dx.doi.org/10.1029/2008JE003302 http://bit.ly/V2IEgh
Bibliographic Code:	2009JGRE..11407006G
Abstract:	We present a systematic attempt to fit the Viking lander surface pressure cycle using a Mars General Circulation Model, MarsWRF. Following the earlier study by Wood and Paige (1992) using a one-dimensional model, high-precision fitting was achieved by tuning five time-independent parameters: the albedo and emissivity of the seasonal caps of the two hemispheres and the total CO2 inventory in the atmosphere frost system. We used a linear iterative method to derive the best fit parameters: albedo of the northern cap = 0.795, emissivity of the northern cap = 0.485, albedo of the southern cap = 0.461, emissivity of the southern cap = 0.785, and total CO2 mass = 2.83 × 1016 kg. If these parameters are used in MarsWRF, the smoothed surface pressure residual at the VL1 site is always smaller than several Pascal through a year. As in other similar studies, the best fit parameters do not match well with the current estimation of the seasonal cap radiative properties, suggesting that important physics contributing to the energy balance not explicitly included in MarsWRF have been effectively aliased into the derived parameters. One such effect is likely the variation of thermal conductivity with depth in the regolith due to the presence of water ice. Including such a parameterization in the fitting process improves the reasonableness of the best fit cap properties, mostly improving the emissivities. The conductivities required in the north to provide the best fit are higher than those required in the south. A completely physically reasonable set of fit parameters could still not be attained. Like all prior published GCM simulations, none of the cases considered are capable of predicting a residual southern CO2 cap.

Title:	Sulfur-induced greenhouse warming on early Mars
Authors:	Johnson, Sarah Stewart; Mischna, Michael A.; Grove, Timothy L.; Zuber, Maria T.
Affiliation:	AA(Department of Earth, Atmospheric and Planetary Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA), AB(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA), AC(Department of Earth, Atmospheric and Planetary Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA), AD(Department of Earth, Atmospheric and Planetary Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA)
Journal:	Journal of Geophysical Research, Volume 113, Issue E8, CiteID E08005
Publication Date:	Aug 2008
Origin:	AGU
Keywords:	Planetary Sciences: Solar System Objects: Mars, Planetary Sciences: Solid Surface Planets: Atmospheres (0343, 1060), Biogeosciences: Sulfur cycling, Atmospheric Processes: Climate change and variability (1616, 1635, 3309, 4215, 4513)
DOI:	http://dx.doi.org/10.1029/2007JE002962 http://bit.ly/RiwrZq
Bibliographic Code:	2008JGRE..11308005J
Abstract:	Mineralogical, geological, geophysical, and isotopic data recently returned from Mars suggest that the delivery of sulfur gases to the atmosphere may have played a significant role in the planet's early evolution. Using the Gusev Crater basalt composition and a batch melting model, we obtain a high sulfur solubility, approximately 1400 ppm, in Martian mantle melts. We proceed to explore different scenarios for the pulsed degassing of sulfur volatiles associated with the emplacement of near-surface dikes during the late Noachian or early Hesperian, when surface pressures are thought to be substantially higher than present. We investigate background Martian atmospheres of 50 and 500 mbar CO2 with varying abundances of H2O and sulfur volatiles (H2S and SO2 mixing ratios of 10-3 to 10-6). Results suggest that these sulfur volatile influxes, alone, could have been responsible for greenhouse warming up to 25 K above that caused by CO2. Including additional water vapor feedback, this process could have raised the early surface temperature above the freezing point for brines and possibly allowed transient liquid water on the Martian surface. Each temperature rise was likely to have been short-lived, however, due to brief residence times for sulfur volatiles in an optically thin atmosphere.

Title:	Two aerodynamic roughness maps derived from Mars Orbiter Laser Altimeter (MOLA) data and their effects on boundary layer properties in a Mars general circulation model (GCM)
Authors:	Heavens, N. G.; Richardson, M. I.; Toigo, A. D.
Affiliation:	AA(Division of the Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AB(Division of the Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AC(Center for Radiophysics and Space Research, Cornell University, Ithaca, New York, USA)
Journal:	Journal of Geophysical Research, Volume 113, Issue E2, CiteID E02014
Publication Date:	Feb 2008
Origin:	AGU
Keywords:	Planetary Sciences: Solar System Objects: Mars, Planetary Sciences: Solid Surface Planets: Atmospheres (0343, 1060), Planetary Sciences: Solid Surface Planets: Surface materials and properties, Atmospheric Processes: Boundary layer processes, Atmospheric Processes: Global climate models (1626, 4928)
Abstract Copyright:	(c) 2008: American Geophysical Union
DOI:	http://dx.doi.org/10.1029/2007JE002991 http://bit.ly/UXryQt
Bibliographic Code:	2008JGRE..11302014H
Abstract:	Mechanical (forced convective) and free convective turbulent heat and momentum transfer in the lower atmosphere of a terrestrial planet has some dependence on the roughness characteristics of the surface, often quantified in terms of a single roughness parameter which is then used to calculate the coefficients that govern heat and momentum transport between the surface and the boundary layer. We take two different approaches for deriving this aerodynamic roughness parameter for Martian surfaces using data from the Mars Orbiter Laser Altimeter. We then use these two different roughness maps to force the boundary layer in a Mars general circulation model, primarily investigating differences in temperatures and the pressure cycle between the two simulations. While the pressure cycle does not vary significantly, spring and summer high-latitude temperatures are somewhat sensitive to the input roughness conditions. Daytime temperatures may vary up to 10 K seasonally, though zonally and annually averaged daytime temperatures vary only by ~1 K. Our results can be explained by the dominance of mechanical over convective turbulent heat transfer processes on Mars. These simulations, however, use a prescribed atmospheric dust distribution and thus only provide a minimum estimate of the uncertainty in boundary layer temperatures because of this plausible range of aerodynamic roughness parameters. Since surface roughness determines the threshold wind velocity for dust lifting we anticipate a much larger effect of the aerodynamic roughness parameter on temperatures when the dust distribution is allowed to vary according to predicted lifting and transport.

Title:	PlanetWRF: A General Purpose, Local to Global Numerical Model for Planetary Atmospheric and Climate Dynamics
Authors:	Richardson, M. I.; Toigo, A. D; Newman, C. E.
Journal:	Journal of Geophysical Research, Volume 112, Issue E9, CiteID E09001
Publication Date:	Sep 2007
DOI:	http://dx.doi.org/10.1029/2006JE002825 http://bit.ly/TmLSvq
Abstract:	A new planetary atmospheric numerical model, “planetWRF,” has been developed by modifying the Weather Research and Forecasting (WRF) model. The model has generalized map projection, multiscale, and nesting capabilities, blurring the distinction between global and mesoscale models and enabling investigation of coupling between processes on all scales, including global. The model can also be run in one, two, or three dimensions. The conversion of the dynamical core for global application by altering the map projection grid and the boundary conditions as well as conversion of the physics parameterizations and constants for planetary application are described. Validation of the global dynamical core through use of standard forcing scenarios is presented. Example results from a series of simulations for Mars, Titan, and Venus are shown to demonstrate that the model performs well for a variety of planets and operating modes (microscale, mesoscale, and global scale).