A Polar Mars Climate Database built on Mesoscale Simulations Aymeric Spiga 1 & Isaac B. Smith 2 1 Laboratoire de M´ et´ eorologie Dynamique, Universit´ e Pierre et Marie Curie, Paris, France ([email protected]) 2 SouthWest Research Institute, Boulder, Colorado, USA ([email protected]) An interest for Martian geologists and glaciologists Martian polar regions are, meteorogically speaking, very active regions. This activity is evidenced by numer- ous surface morphologic features, from frost streaks to dune fields, which putative inferred direction is roughly compatible with directions obtained by mesoscale mod- els [1]. The varying spectral signatures (H 2 O or CO 2 ) over polar slopes during seasonal retreat have been pos- sibly ascribed to winds too [2]. The occurrence of trough clouds has possibly been linked to the migration of spiral troughs thanks to mesoscale modeling of polar katabatic winds, both over the northern polar cap [3] and the south- ern polar cap [4]. Furthermore, smaller-scale sedimen- tation waves than troughs over the Martian polar caps are thought to be controlled by katabatic winds [5]. The control of surface morphology by winds might even be extended to the paleo-topography revealed by radar im- agery [6]. An interest for Martian climate scientists The inter- est for Martian polar regions is not restricted to surface- atmosphere interactions. Studying the meteorology of the Martian polar regions is a means to address key ques- tions for the Martian climate at all scales. The fact that many flushing storms originate from the Martian polar regions [7] indicates that the mesoscale wind activity in polar regions is likely to play a decisive role [8, 9]. At the same time, the wind variability itself in the polar regions is a matter of active research to disentangle the combined influence of katabatic acceleration [10, 11], sea-breeze circulations caused by the ice-soil contrasts [8], polar transients [9], and, last but not least, the large-scale po- lar vortex [12, 13]. Polar regions also play a key role as a seasonal source/sink for the water annual cycle, where mesoscale transport processes [14] and cloud formation with radiatively-induced effect [15] play a crucial role. As far as the upper troposphere / lower mesosphere is concerned, the polar atmosphere is also prone to a par- ticularly strong mesoscale activity with the frequent oc- currence of gravity waves [16]. Why use mesoscale simulations for polar regions? Mesoscale models are well-suited to get insights into at- mospheric and surface processes in polar regions. Con- trary to global circulations models [GCMs], mesoscale models integrate the atmospheric dynamics at high reso- lution in a specific region of interest on the planet with Figure 1: The retreat of the seasonal CO 2 cap is the primary driver of the variability of the surface wind speeds in spring. Results of a dx = 18 km mesoscale simulation (nested domain in a dx = 54 km mother domain) at Ls = 60, 75, 90 ◦ (northern spring) in the northern polar region. Wind vectors in m s -1 are shown each 3 grid points. Sur- face temperature is contoured. An albedo map of the Martian northern polar region is included in the background to provide context. 6055.pdf Sixth Mars Polar Science Conference (2016)
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A Polar Mars Climate Database built on Mesoscale SimulationsAymeric Spiga1 & Isaac B. Smith21Laboratoire de Meteorologie Dynamique, Universite Pierre et Marie Curie, Paris, France ([email protected])2SouthWest Research Institute, Boulder, Colorado, USA ([email protected])
An interest for Martian geologists and glaciologistsMartian polar regions are, meteorogically speaking, veryactive regions. This activity is evidenced by numer-ous surface morphologic features, from frost streaks todune fields, which putative inferred direction is roughlycompatible with directions obtained by mesoscale mod-els [1]. The varying spectral signatures (H2O or CO2)over polar slopes during seasonal retreat have been pos-sibly ascribed to winds too [2]. The occurrence of troughclouds has possibly been linked to the migration of spiraltroughs thanks to mesoscale modeling of polar katabaticwinds, both over the northern polar cap [3] and the south-ern polar cap [4]. Furthermore, smaller-scale sedimen-tation waves than troughs over the Martian polar capsare thought to be controlled by katabatic winds [5]. Thecontrol of surface morphology by winds might even beextended to the paleo-topography revealed by radar im-agery [6].
An interest for Martian climate scientists The inter-est for Martian polar regions is not restricted to surface-atmosphere interactions. Studying the meteorology ofthe Martian polar regions is a means to address key ques-tions for the Martian climate at all scales. The fact thatmany flushing storms originate from the Martian polarregions [7] indicates that the mesoscale wind activity inpolar regions is likely to play a decisive role [8, 9]. At thesame time, the wind variability itself in the polar regionsis a matter of active research to disentangle the combinedinfluence of katabatic acceleration [10, 11], sea-breezecirculations caused by the ice-soil contrasts [8], polartransients [9], and, last but not least, the large-scale po-lar vortex [12, 13]. Polar regions also play a key role asa seasonal source/sink for the water annual cycle, wheremesoscale transport processes [14] and cloud formationwith radiatively-induced effect [15] play a crucial role.As far as the upper troposphere / lower mesosphere isconcerned, the polar atmosphere is also prone to a par-ticularly strong mesoscale activity with the frequent oc-currence of gravity waves [16].
Why use mesoscale simulations for polar regions?Mesoscale models are well-suited to get insights into at-mospheric and surface processes in polar regions. Con-trary to global circulations models [GCMs], mesoscalemodels integrate the atmospheric dynamics at high reso-lution in a specific region of interest on the planet with
Figure 1: The retreat of the seasonal CO2 cap is the primary driverof the variability of the surface wind speeds in spring. Results ofa dx = 18 km mesoscale simulation (nested domain in a dx = 54 kmmother domain) at Ls = 60, 75, 90◦ (northern spring) in the northernpolar region. Wind vectors in m s−1 are shown each 3 grid points. Sur-face temperature is contoured. An albedo map of the Martian northernpolar region is included in the background to provide context.
6055.pdfSixth Mars Polar Science Conference (2016)
an adapted map projection. Polar mesoscale domains aredefined through stereographic projections, hence devoidof the “pole singularity” present in most GCMs. In ad-dition, high-resolution surface thermophysical properties(albedo, thermal inertia) are used in mesoscale modeling.
A better seasonal coverage for polar mesoscale simu-lations As is detailed in the previous paragraphs, un-derstanding the diurnal, seasonal, and even interannualvariability of temperature, winds, water vapor & clouds,. . . in Martian polar regions is an important step to un-derstanding both surface and atmosphere processes. Ouridea is that, since existing published mesoscale simula-tions focused on a specific season of interest, it is nowtime to attempt a full annual coverage of polar mesoscalesimulations. We performed test mesoscale simulationswith the LMD Martian Mesoscale model [17, 10] overa wide range of seasons to demonstrate the potentialitiesof this concept and offer a first (and quite unprecedentedyet) discussion on the seasonal variability of winds in thenorthern and southern regions of Mars. For instance, forNorth pole, we provide simulations for each 5-10◦ of so-lar longitude (Ls) beginning at northern vernal equinox(Ls 0◦) and ending at northern autumnal equinox (Ls180◦) [18]. Those simulations allow us to explore theMartian polar meteorological variability: we show an ex-ample of wind changes associated with the CO2 cap re-treat in Figure 1.
Building a Polar Mars Climate Database Our pro-posal is to build an online interface to map (and moregenerally extract) the atmospheric predictions from theLMD Martian Mesoscale Model in the Martian po-lar regions, following the example of both the on-line Mars Climate database [http://www-mars.lmd.jussieu.fr/mcd_python], and similar on-line database for terrestrial polar regions [19]. The MarsPolar Conference will be an excellent vector to discusswith the community to determine the most relevant pa-rameters and fields for the various studies undertaken, aswell as to define an infrastructure of the database whichwill optimize the scientific return of the simulations.
References[1] M. Masse, O. Bourgeois, et al. Wide distribution and glacial ori-
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[2] T. Appere, B. Schmitt, et al. Winter and spring evolution of north-ern seasonal deposits on Mars from OMEGA on Mars Express.Journal of Geophysical Research (Planets), 116(E15):5001,2011.
[3] Isaac B. Smith, John W. Holt, et al. The spiral troughs ofmars as cyclic steps. Journal of Geophysical Research: Planets,118(9):1835–1857, 2013.
[4] I. B. Smith, A. Spiga, and J. W. Holt. Aeolian processes as driversof landform evolution at the South Pole of Mars. Geomorphology,240:54–69, 2015.
[5] C. Herny, M. Masse, et al. Sedimentation waves on the MartianNorth Polar Cap: Analogy with megadunes in Antarctica. Earthand Planetary Science Letters, 403:56–66, 2014.
[6] T. C. Brothers, J. W. Holt, and A. Spiga. Planum Boreumbasal unit topography, Mars: Irregularities and insights fromSHARAD. Journal of Geophysical Research (Planets),120:1357–1375, 2015.
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[8] A. D. Toigo, M. I. Richardson, et al. A first look at dust lifting anddust storms near the south pole of Mars with a mesoscale model.Journal of Geophysical Research (Planets), 107:5050–+, 2002.
[9] D. Tyler and J. R. Barnes. A mesoscale model study of summer-time atmospheric circulations in the north polar region of Mars.Journal of Geophysical Research (Planets), 110(E9):6007–+,2005.
[10] A. Spiga, F. Forget, et al. The impact of Martian mesoscale windson surface temperature and on the determination of thermal iner-tia. Icarus, 212:504–519, 2011.
[11] A. Spiga. Elements of comparison between Martian and ter-restrial mesoscale meteorological phenomena: Katabatic windsand boundary layer convection. Planetary and Space Science,59:915–922, 2011.
[12] D. M. Mitchell, L. Montabone, et al. Polar vortices on Earthand Mars: A comparative study of the climatology and variabilityfrom reanalyses. Quarterly Journal of the Royal MeteorologicalSociety, 141:550–562, 2015.
[13] A. D. Toigo, C. Lee, et al. The impact of resolution on the dynam-ics of the martian global atmosphere: Varying resolution studieswith the MarsWRF GCM. Icarus, 221:276–288, 2012.
[14] D. Tyler and J. R. Barnes. Atmospheric mesoscale modelingof water and clouds during northern summer on Mars. Icarus,237:388–414, 2014.
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[16] F. Altieri, A. Spiga, et al. Gravity waves mapped by theOMEGA/MEX instrument through O2 dayglow at 1.27 µm: Dataanalysis and atmospheric modeling. Journal of Geophysical Re-search (Planets), 117(E16):0, 2012.
[17] A. Spiga and F. Forget. A new model to simulate the Mar-tian mesoscale and microscale atmospheric circulation: Valida-tion and first results. Journal of Geophysical Research (Planets),114:E02009, 2009.
[18] I. B. Smith, A. Spiga, et al. Wind at the North Pole of Mars: Com-parisons of Modeling and Observations. In Lunar and PlanetaryScience Conference, volume 47 of Lunar and Planetary ScienceConference, page 1632, 2016.
[19] David H. Bromwich, Keith M. Hines, and Le-Sheng Bai. De-velopment and testing of polar weather research and forecastingmodel: 2. arctic ocean. Journal of Geophysical Research: Atmo-spheres, 114(D8):n/a–n/a, 2009. D08122.
6055.pdfSixth Mars Polar Science Conference (2016)