| Title: |
Simulating Titan's Atmosphere With the Titan WRF General Circulation Model |
| Authors: |
Newman, C. E.; Richardson, M. I.; Toigo, A. D.; Inada, A. |
| Affiliation: |
AA(California Institute of Technology, MC 150-21, GPS, Caltech, 1200 E. California Boulevard, Pasadena, CA 91125 United States
; claire@gps.caltech.edu), AB(California Institute of Technology, MC 150-21, GPS, Caltech, 1200 E. California Boulevard, Pasadena,
CA 91125 United States ; mir@gps.caltech.edu), AC(Kobe University, Graduate School of Science and Technology, Kobe University,
Rokkodai-cho 1-1, Nada-ku, Kobe, 657-8501 Japan ; toigo@astro.cornell.edu), AD(California Institute of Technology, MC 150-21,
GPS, Caltech, 1200 E. California Boulevard, Pasadena, CA 91125 United States ; inada@gps.caltech.edu)
|
| Journal: |
American Geophysical Union, Fall Meeting 2005, abstract #P43B-05 |
| Publication Date: |
Dec 2005 |
| Origin: |
AGU |
| Keywords: |
0343 Planetary atmospheres (5210, 5405, 5704), 3346 Planetary meteorology (5445, 5739), 5405 Atmospheres (0343, 1060), 6281 Titan |
| Abstract Copyright: |
(c) 2005: American Geophysical Union |
| Bibliographic Code: |
2005AGUFM.P43B..05N |
| Abstract: |
Titan WRF is a new three-dimensional model for the atmosphere of Titan,
and is a globalized, `Titan'-ified version of the Earth-based, mesoscale
`Weather Research and Forecasting' model. Titan WRF thus inherits all of
the desirable features from the original model, including highly
parallelized and accurate code (ideal for the long simulations required
here) and the ability to place high resolution nests within lower
resolution domains (thus study certain areas in high detail without the
expense of running the entire model at this resolution). Unlike the
original mesoscale version of WRF, however, Titan WRF does not require
forcing from a separate model. Our eventual aim is to use Titan WRF to
study the onset and evolution of methane clouds in Titan's atmosphere,
although initially we are concerned with producing and validating the
modeled atmosphere and its seasonal changes, first with a constant haze
distribution (varying with height only) then with advection of
radiatively-active haze within the atmosphere. We will present the first
results for each season of a Titan year, as simulated by Titan WRF (with
a constant haze distribution) following several years during which the
model atmosphere is allowed to `spin up' due to contact and exchange of
angular momentum with the surface. These results will include zonal mean
winds (including a discussion of the amount of equatorial superrotation
produced), temperatures and mass streamfunctions for different seasons.
We will compare these with available observations, then discuss our
future plans.
|
| Title: |
Three-Dimensional Climate Modeling of the Amazonian Environment and Glaciation |
| Authors: |
Richardson, M. I.; Mischna, M. A. |
| Affiliation: |
AA(California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125 United States ; mir@gps.caltech.edu), AB(Jet
Propulsion Laboratory, 4800 Oak Grove Dr, Pasadena, CA 91109 United States ; michael.a.mischna@jpl.nasa.gov)
|
| Journal: |
American Geophysical Union, Fall Meeting 2005, abstract #P34A-07 |
| Publication Date: |
Dec 2005 |
| Origin: |
AGU |
| Keywords: |
4946 Milankovitch theory, 5405 Atmospheres (0343, 1060), 5416 Glaciation, 5462 Polar regions, 6225 Mars |
| Abstract Copyright: |
(c) 2005: American Geophysical Union |
| Bibliographic Code: |
2005AGUFM.P34A..07R |
| Abstract: |
Spacecraft data increasingly suggest that Mars has experienced dramatic
changes in the distribution of surface and subsurface water ice in the
recent past, potentially associated with rather different climate
states. In the limit of high obliquity, this likely corresponds to
tropical water ice sheets, while in the low obliquity limit, it
corresponds to atmospheric collapse. Climate models suggest that such
changes in the planetary environment and water distribution are expected
on the basis of the large change in planetary orbital parameters on time
scales >10{5} yrs. These variations are quazi-cyclical, and so are
expected to have caused ongoing (non-secular) changes in climate
throughout the Amazonian. Indeed, some orbital forcing of climate may be
involved in the episodes of raised and lowered water table in Terra
Meridiani, as inferred from Opportunity observations. It is believed
that superposed on this quazi-cyclical pattern is a signal of net
atmospheric deflation, due primarily to loss to space. The challenge
for climate dynamics is to explain the nature and extent of climate
change through time, with a particular focus on the changing
distribution and stability of water. This presentation will review
developments to date, model sensitivities, and future directions.
|
| Title: |
Orbitally-Driven Change in the Martian Atmosphere |
| Authors: |
Mischna, M. A.; Richardson, M. I.; Newman, C. E.; Toigo, A. D.; Vasavada, A. R.; Inada, A. |
| Affiliation: |
AA(Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109 United States ;
michael.a.mischna@jpl.nasa.gov), AB(California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 United
States ; mir@gps.caltech.edu), AC(California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 United
States ; claire@gps.caltech.edu), AD(Graduate School of Science and Technology, Kobe University, 1-1 Rokkodai-cho, Nada Kobe,
657-8501 Japan ; toigo@astro.cornell.edu), AE(Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove
Dr., Pasadena, CA 91109 United States ; ashwin.r.vasavada@jpl.nasa.gov), AF(California Institute of Technology, 1200 E. California
Blvd., Pasadena, CA 91125 United States ; inada@gps.caltech.edu)
|
| Journal: |
American Geophysical Union, Fall Meeting 2005, abstract #P31B-0202 |
| Publication Date: |
Dec 2005 |
| Origin: |
AGU |
| Keywords: |
0343 Planetary atmospheres (5210, 5405, 5704), 5405 Atmospheres (0343, 1060), 5422 Ices, 5445 Meteorology (3346), 6225 Mars |
| Abstract Copyright: |
(c) 2005: American Geophysical Union |
| Bibliographic Code: |
2005AGUFM.P31B0202M |
| Abstract: |
We consider the impact of orbital cycling (obliquity, eccentricity,
perihelion precession) on the martian atmospheric water cycle through
recent Amazonian history. Changes in obliquity from present-day values
can have a significant effect on the abundance of water vapor in the
martian atmosphere. In addition, the magnitude and distribution of
surface water ice deposits can vary significantly, on timescales
commensurate with the period of obliquity oscillation (100 ky). We have
used results from both the GFDL Mars GCM as well as the Planetary WRF
GCM to examine possible changes in the water cycle induced by these
orbital motions. Preliminary results indicate that if a sublimation lag
develops over extant polar deposits during an extended rise to high
obliquity (105-106 yr), the amount of water vapor released into the
atmosphere will be correspondingly and significantly reduced,
maintained in balance with any ice deposits that developed in the lower
latitudes prior to the ``shutting off'' of the polar ice deposits. Under
these conditions, annual average water abundances at high obliquity may
only be 20-80 prμm, one to two orders of magnitude less than previous
estimates, and only a factor of a few higher than present-day values.
Further, the ``wettest'' periods in recent Mars history may not be
directly correlated with the highest mean obliquity but rather with
brief periods of high obliquity when the mean obliquity was only
slightly higher than present.
|
| Title: |
Simulation of Water Cycle With a Martian Weather Research and Forecast Model |
| Authors: |
Inada, A.; Richardson, M. I.; Mischna, M. A.; Newman, C. E.; Toigo, A. D.; Vasavada, A. R. |
| Affiliation: |
AA(California Institute of Technology, M.S. 150-21 1200 E. California Blvd., Pasadena, CA 91125 United States ; inada@gps.caltech.edu),
AB(California Institute of Technology, M.S. 150-21 1200 E. California Blvd., Pasadena, CA 91125 United States ; mir@gps.caltech.edu),
AC(Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 United States ; mischna@mail.jpl.nasa.gov), AD(California
Institute of Technology, M.S. 150-21 1200 E. California Blvd., Pasadena, CA 91125 United States ; claire@gps.caltech.edu),
AE(Graduate School of Science and Technology, Kobe Univ., 1-1 Nada, Kobe, 657-8501 Japan ; toigo@astro.cornell.edu), AF(Jet
Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 United States ; ashwin_vasavada@yahoo.com)
|
| Journal: |
American Geophysical Union, Fall Meeting 2005, abstract #P21E-08 |
| Publication Date: |
Dec 2005 |
| Origin: |
AGU |
| Keywords: |
5210 Planetary atmospheres, clouds, and hazes (0343), 6225 Mars |
| Abstract Copyright: |
(c) 2005: American Geophysical Union |
| Bibliographic Code: |
2005AGUFM.P21E..08I |
| Abstract: |
The water cycle in the Martian atmosphere is influenced by exchange with
the subsurface, condensation on the surface, mixing between the boundary
layer and the free atmosphere, large-scale horizontal mixing of air
masses and precipitation as water ice particles. We have installed a
water cycle model with microphysics processes into the Martian Weather
Research and Forecast (WRF) model. It treats subsurface water diffusion
and adsorptive / condensational exchange, surface ice formation and
diffusive mixing in the atmosphere. Formed water ice particles in the
atmosphere are transformed by advection, diffusion and sedimentation. We
will present the spatial and diurnal variation of water including
cloud/fog formation.
|
| Title: |
THEMIS-VIS Measurements of the Altitude and Velocity of Clouds in the Martian Mesosphere |
| Authors: |
McConnochie, T. H.; Bell, J. F.; Savransky, D.; Wolff, M. J.; Christensen, P. R.; Richardson, M. I.; Titus, T. N. |
| Affiliation: |
AA(Cornell University, Space Sciences Building, Ithaca, NY 14853 United States ; thm9@cornell.edu), AB(Cornell University,
Space Sciences Building, Ithaca, NY 14853 United States ; jfb8@cornell.edu), AC(Cornell University, Space Sciences Building,
Ithaca, NY 14853 United States ; ds264@cornell.edu), AD(Space Science Institude, 4750 Walnut Street Suite 205, Boulder, CO
80301 United States ; wolff@spacescience.org), AE(Arizona State University, Mars Space Flight Facility, Tempe, AZ 85287 United
States ; phil.christensen@asu.edu), AF(Caltech, Div Geological & Planetary Sci MC 150-21, Pasadena, CA 91125 United States
; mir@gps.caltech.edu), AG(USGS, 2255 North Gemini Drive, Flagstaff, AZ 86001 United States ; ttitus@usgs.gov)
|
| Journal: |
American Geophysical Union, Fall Meeting 2005, abstract #P21E-03 |
| Publication Date: |
Dec 2005 |
| Origin: |
AGU |
| Keywords: |
5405 Atmospheres (0343, 1060), 5464 Remote sensing, 5494 Instruments and techniques |
| Abstract Copyright: |
(c) 2005: American Geophysical Union |
| Bibliographic Code: |
2005AGUFM.P21E..03M |
| Abstract: |
Although Mars Odyssey's Thermal Emission Imaging System visible
subsystem (THEMIS-VIS) was not designed or intended for stereo imaging
or cloud tracking, its multiple exposure color-imaging sequence
serendipitously causes a parallax effect that allows the height of
high-altitude clouds to be determined, and has sufficient time delay to
detect the movement of these clouds. As a result, THEMIS-VIS has
acquired exceptionally high resolution (36 or 72 m pixel scale)
nadir-pointed images of martian clouds with altitudes in the 60-80 km
altitude range, and is providing the first direct measurements of wind
speed at these altitudes. We discover high altitude cloud candidates by
noticing a severe misalignment of cloud features between any two bands
of an image which has been map-projected at the altitude of the local
surface. In order to measure altitude and velocity, we reproject the
subframes that make up a THEMIS-VIS image at a series altitudes above
the local surface, shifting the subframes relative to each other to
account for a range of candidate velocities. To select the best fitting
altitude and velocity, we manually inspect the reprojected images to
find an approximate solution, and then maximize the correlation between
the 425 nm band and 540 nm band within a manually selected
high-constrast cloud-dominated region of the image in order to refine
the solution. The precision of this technique is of course inherently
limited by the sharpness of the cloud features. To date we have obtained
two high-altitude velocity measurements, and have identified 50 more
images with high altitude clouds that are likely to yield velocity
measurements. In THEMIS sequence number V06930045, 217 degrees L_s and
47 degrees north latitude, we measure eastward cloud motion of 60 +/-
15 m/s at an altitude of 70 +/- 5 km. In THEMIS sequence number
V10526009, 26 degrees L_s and 0.5 degrees north latitude, we measure
westward cloud motion of 90 +/- 20 m/s at an altitude of 80 +/- 5 km.
|
| Title: |
Planetary WRF: a Multi-Scale, Planetary, Atmospheric Model |
| Authors: |
Toigo, A.; Richardson, M. I.; Newman, C. E. |
| Affiliation: |
AA(Kobe University, Graduate School of Science and Technology Rokkodai-cho 1-1, Nada-ku, Kobe, 657-8501 Japan ; toigo@astro.cornell.edu),
AB(California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 United States ; mir@gps.caltech.edu),
AC(California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 United States ; claire@gps.caltech.edu)
|
| Journal: |
American Geophysical Union, Fall Meeting 2005, abstract #P13A-0140 |
| Publication Date: |
Dec 2005 |
| Origin: |
AGU |
| Keywords: |
3337 Global climate models (1626, 4928), 3346 Planetary meteorology (5445, 5739), 5405 Atmospheres (0343, 1060), 5445 Meteorology (3346), 6225 Mars |
| Abstract Copyright: |
(c) 2005: American Geophysical Union |
| Bibliographic Code: |
2005AGUFM.P13A0140T |
| Abstract: |
The NCAR terrestrial Weather Research and Forecast (WRF) atmospheric
model has been converted into a global, planetary model. Planetary WRF
is the first truly multi-scale numerical model having the ability to run
on scales from meters to global, and with 2-way domain nesting
interactivity. The model is fully compressible, has 3D Coriolis and
curvature treatment and has hydrostatic and non-hydrostatic options. The
model has initially been converted for use on Mars and Titan with future
applications to other planets planned. The dynamical core has been
validated using the standardized forcing and setup described in Held and
Suarez (1994), and comparison of 1D and 3D Martian and 1D Titan versions
with existing models. The conversion process and preliminary results at
a variety of scales including validation will be presented.
|
| Title: |
A New General Circulation Model of Titan's Atmosphere |
| Authors: |
Newman, C. E.; Richardson, M. I.; Toigo, A. D. |
| Affiliation: |
AA(California Institute of Technology), AB(California Institute of Technology), AC(Kobe University) |
| Journal: |
American Astronomical Society, DPS meeting #37, #51.10; Bulletin of the American Astronomical Society, Vol. 37, p.735 |
| Publication Date: |
Aug 2005 |
| Origin: |
AAS |
| Bibliographic Code: |
2005DPS....37.5110N |
| Abstract: |
Some big questions relating to Titan's atmosphere are: How much
equatorial superrotation occurs? What determines the way in which albedo
patterns change over time at different wavelengths? and What determines
the size, frequency and location of the recently observed southern
hemisphere clouds?
To investigate such questions properly requires a three-dimensional
model of Titan's thick atmosphere, which can examine different scenarios
in multi-year simulations. Such simulations are computationally
demanding due to Titan's long radiative and seasonal timescales, as well
as its slow rotation rate, all of which mean a long time is required to
spin up then conduct each run. This demands the use of an efficient,
accurate, and mass- and momentum-conserving model.
One such model is the newly developed Planetary Weather Research and
Forecasting model (PWRF), which is based on a pre-existing terrestrial
mesoscale model (WRF). WRF is a highly parallelized and numerically
efficient model, which is also able to place high resolution 'nests'
(with information passing both inwards and outwards) over selected
regions where resolving small-scale features is most necessary. This is
very useful, as increasing the resolution everywhere would slow the
model considerably. PWRF retains these features, but extends to using a
global mother domain (no separate global model required), and has also
been adapted to include a planetary timing system (using areocentric
longitude) and other planetary options (such as radiation schemes).
We will present results from the Titan version of PWRF to demonstrate
how well the model reproduces key aspects of Titan's circulation (e.g.
superrotation, temperature structure). We will describe our plans to
include aerosol transport, and our eventual aim to model the recently
observed (telescopically from Earth, e.g. Griffith et al. Nature 1998,
Brown et al. Nature 2002, and from Cassini, e.g. Porco et al. Nature
2005) methane clouds.
This work is funded by NASA.
|
| Title: |
Simulation of Column Water Processes with a One Dimensional Martian Climate Model |
| Authors: |
Inada, A.; Richardson, M. I.; Mischna, M. A.; Newman, C. E.; Toigo, A. D.; Vasavada, A. R. |
| Affiliation: |
AA(California Institute of Technology), AB(California Institute of Technology), AC(Jet Propulsion Laboratory), AD(California
Institute of Technology), AE(Graduate School of Science and Technology, Kobe Univ.), AF(Jet Propulsion Laboratory)
|
| Journal: |
American Astronomical Society, DPS meeting #37, #33.22; Bulletin of the American Astronomical Society, Vol. 37, p.696 |
| Publication Date: |
Aug 2005 |
| Origin: |
AAS |
| Bibliographic Code: |
2005DPS....37.3322I |
| Abstract: |
The variation of water vapour near the Martian surface will be
influenced by exchange with the subsurface, condensation on the surface
and in the atmosphere, mixing between the boundary layer and the free
atmosphere, and the large-scale horizontal mixing of air masses. In
order to isolate column processes from those of transport, we have
developed a "complete" model of column water cycling based around a
one-dimensional version of the Martian Weather Research and Forecast
(WRF) model. Explicitly treated processes include subsurface water
diffusion and adsorptive/condensational exchange, surface ice formation,
diffusive mixing in the atmosphere, and the microphysics of atmospheric
cloud/fog formation and sedimentation. The formation of surface ices and
clouds/fogs allow for the activation of feedback systems due to their
influence on the radiative heating of the surface and hence the surface
energy balance and temperature. The model is used to assess the
variation of cloud/fog vertical structure and water vapour at likely
Phoenix and MSL landing sites (for which fog and water vapour
measurements, respectively, are planned for collection). The implication
of cloud radiative effects for retrieval of surface thermal properties
will also be discussed.
|
| Title: |
Development of a Martian Sonic Anemometer |
| Authors: |
Dissly, R. W.; Banfield, D. J.; Lasnik, J.; Waters, J. T.; McEwan, I. J.; Richardson, M. I. |
| Affiliation: |
AA(Ball Aerospace), AB(Cornell), AC(Ball Aerospace), AD(Cornell), AE(Caltech), AF(Caltech) |
| Journal: |
American Astronomical Society, DPS meeting #37, #18.05; Bulletin of the American Astronomical Society, Vol. 37, p.650 |
| Publication Date: |
Aug 2005 |
| Origin: |
AAS |
| Bibliographic Code: |
2005DPS....37.1805D |
| Abstract: |
This presentation will describe the progress to-date on the development
of an acoustic anemometer for the in-situ measurement of wind speeds on
Mars, funded by NASA PIDDP. Improved measurements of Martian winds are
needed for several reasons: better prediction and understanding of
global and regional weather, direct measurement of fluxes between
surface/atmosphere of momentum, heat, and trace atmospheric
constituents, characterizing and monitoring boundary layer winds that
influence the safe delivery of spacecraft to/from the Martian surface,
and improved characterization of geologically important aeolian
processes that can pose a hazard to future exploration via dust storms
and dust devils.
Prior attempts to measure surface winds have been limited in capability
and difficult to calibrate. Sonic anemometry, measuring wind speed via
sound pulse travel-time differences, can overcome many of these issues.
Sonic anemometry has several distinct advantages over other methods such
as hot wire techniques: higher sensitivity ( <5 cm/s), higher time
resolution (10-100 Hz), and fewer intrinsic biases for improved
accuracy. Together, these open the possibility of resolving turbulent
boundary layer eddies to directly capture surface-to-atmospheric fluxes
for the first time.
We will describe the results of our development of an acoustic
anemometer using capacitive micro-machined devices, optimized for
acoustic coupling in a low-pressure medium like the Martian atmosphere.
This development includes transducer characterization tests in a
pressure chamber at Ball Aerospace with Mars-relevant CO2 pressures. We
will also describe experimental results showing that the addition of
water in a low-pressure CO2 atmosphere can significantly increase
acoustic attenuation. Finally we will describe plans for further
optimization of the instrument for future Mars payloads.
|
| Title: |
Surface Dust Redistribution on Mars as Observed by the Mars Global Surveyor |
| Authors: |
Szwast, M. A.; Richardson, M. I.; Vasavada, A. R. |
| Journal: |
36th Annual Lunar and Planetary Science Conference, March 14-18, 2005, in League City, Texas, abstract no.2191 |
| Publication Date: |
Mar 2005 |
| Origin: |
LPI |
| Bibliographic Code: |
2005LPI....36.2191S |
| Abstract: |
A study of MGS TES albedo data set as a proxy for dust cover was
performed focusing around the 2001 global dust storm. We found
widespread surface dust redistribution caused by the storm, and recovery
since implying a multi-year cyclical nature.
|
| Title: |
Does the present-day wind regime explain the location and geomorphology of dunes in the southern highlands of Mars? |
| Authors: |
Fenton, L. K.; Toigo, A. D.; Richardson, M. I. |
| Affiliation: |
AA(Arizona State University, Department of Geology, MS 6305, Tempe, AZ 85287 United States ; lkfenton@asu.edu), AB(Cornell
University, Center for Radiophysics and Space Research, 326 Space Sciences Bldg., Ithaca, NY 14853 United States ; toigo@astro.cornell.edu),
AC(Caltech, Division of Geological and Planetary Sciences, MS 150-21, Pasadena, CA 91125 United States ; mir@gps.caltech.edu)
|
| Journal: |
American Geophysical Union, Fall Meeting 2004, abstract #P22A-05 |
| Publication Date: |
Dec 2004 |
| Origin: |
AGU |
| Keywords: |
5415 Erosion and weathering, 3329 Mesoscale meteorology, 3346 Planetary meteorology (5445, 5739), 3307 Boundary layer processes, 1625 Geomorphology and weathering (1824, 1886) |
| Bibliographic Code: |
2004AGUFM.P22A..05F |
| Abstract: |
Dozens of dunefields are scattered throughout the southern highlands of
Mars, mostly (but not entirely) located in the floors of impact
craters. MOC Narrow Angle images reveal that these dunes are not basic
barchan or transverse in form, but rather that they are a combination of
barchans, reversing, linear, and star dunes, indicating that they were
formed in a multi-directional wind regime. In Noachis Terra, west of
Hellas Planitia, almost all dunefields show three dominant slipface
orientations, indicating formative winds from the SW, SE, and NE.
Different dunefields show these three winds in different proportions,
suggesting that in different areas, different winds have dominated. To
determine how these different winds interact in the present day wind
regime, we ran the Mars MM5 over Noachis Terra. The model runs include
twelve 10-day runs spaced throughout the martian year, with a grid size
of 20 km and a timestep of 10 seconds (physical parameters were saved
once every hour). Winds from the SW blow during winter afternoons,
caused by geostrophic forcing. Because of coverage from the seasonal
polar cap, these winds are more effective in blowing sand at latitudes
poleward of 50° S, roughly consistent with the observed spatial
pattern in dune morphology. Winds from the SE blow during the early to
mid afternoon in the spring, caused by slope winds blowing up and over
the rim of the Hellas basin. These winds should be more common closer to
Hellas Planitia, but they appear in dunes throughout Noachis Terra.
Winds from the NE blow in the evening during summer, and they are
katabatic flows that accelerate into topographic lows, following the
diurnal tide. These winds are strongest equatorward of 50° S, which
is fairly consistent with observed dune morphology. Discrepancies
between the model and observed dune slipfaces can be explain by shifting
physical parameters (i.e., dust loading or obliquity).
|
| Title: |
Surface Dust Redistribution on Mars as Observed by the Viking and Mars Global Surveyor Orbiters |
| Authors: |
Szwast, M.; Richardson, M. I.; Vasavada, A. R.; Wang, H. |
| Affiliation: |
AA(Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Blvd, Pasadena,
CA 91125 United States ; ), AB(Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E.
California Blvd, Pasadena, CA 91125 United States ; ), AC(Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109
United States ; ), AD(Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California
Blvd, Pasadena, CA 91125 United States ; Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 United States
; )
|
| Journal: |
American Geophysical Union, Fall Meeting 2004, abstract #P22A-04 |
| Publication Date: |
Dec 2004 |
| Origin: |
AGU |
| Keywords: |
5415 Erosion and weathering, 5445 Meteorology (3346), 5462 Polar regions, 5470 Surface materials and properties, 6225 Mars |
| Bibliographic Code: |
2004AGUFM.P22A..04S |
| Abstract: |
The global redistribution of dust by the atmosphere is geologically and
climatologically important. Dust deposition and removal at the surface
represents ongoing sedimentary geology: a vestige of aeolian processes
responsible for the concentration of vast dustsheets and potentially for
ancient layered units at various locations on Mars. The varying amount
of dust on the surface has also long been hypothesized as a factor in
determining whether regional or global dust storms occur in a given
year. Indeed, the atmosphere has a very short, sub-seasonal time-scale
(or memory) and as such, any inter-annual variability in the climate
system that is not simply ascribable to stochastic processes, must
involve changing conditions on the surface. An excellent, multi-year
dataset is provided by the combined Viking and Mars Global Surveyor
(MGS) orbiter albedo and thermal observations, from the Infrared Thermal
Mapper (IRTM) and Thermal Emission Spectrometer (TES), and from the MGS
Mars Orbiter Camera Wide Angle imager (MOC-WA). This dataset allows
investigation into the degree to which surface dust deposits on Mars
really change: over decadal time scales, over the course of the annual
cycle, and as a result of global and regional dust storms. The MGS
mapping orbit data set extends over almost 3 Martian years at the time
of writing, while the Viking data set provides a much less complete
sampling of three northern summers/autumns and one southern
summer/autumn. These data sets include three global dust storms (two
for Viking and one for MGS) and smaller regional storms (one in the
first TES mapping year and two in the third). We have examined the
Viking IRTM, MGS TES, and MGS MOCWA data sets to determine what types of
changes in dust coverage have occurred. Viking-to-MGS changes in albedo
are highlighted by the drastic modification of a large, low albedo (low
dust) feature to the east of Utopia Planitia. Year-to-year changes
within the Viking and MGS records are dominanted by the effects of
global dust storms. The 2001 storm observed by MGS is the best
documented. We found a number of regions that changed significantly
after the 2001 global dust storm. Areas with noticeable changes include
the brightening of Syrtis Major, Hellas Planitia, and the region east of
Hellas Planitia, and the darkening of Tharsis. Solis Planum, a region
known to have participated as a secondary source for the 2001 storm
became darker following the storm, while an area directly to the east of
Solis became brighter. The majority of these changes are visible in
both TES maps and MOC wide-angle images. These changes have been slowly
relaxing back towards pre-storm conditions since the end of the storm.
Similar albedo changes in these same regions were found associated with
the global storms observed by the Viking IRTM. This suggests that the
very limited number of dust storms observed by spacecraft have tended to
produce the same kinds of changes in surface dust coverage. The origin
of the long-term changes in Utopia are not understood.
|
| Title: |
The Long-Term Evolution of Transient Liquid Water on Mars |
| Authors: |
Mischna, M. A.; Richardson, M. I. |
| Affiliation: |
AA(Jet Propulsion Laboratory, 4800 Oak Grove Drive M/S 183-401, Pasadena, CA 91109 United States ; michael.a.mischna@jpl.nasa.gov),
AB(California Institute of Technology, 1200 E. California Blvd. M/S 150-21, Pasadena, CA 91125 United States ; mir@gps.caltech.edu)
|
| Journal: |
American Geophysical Union, Fall Meeting 2004, abstract #P13A-0977 |
| Publication Date: |
Dec 2004 |
| Origin: |
AGU |
| Keywords: |
5409 Atmospheres: structure and dynamics, 5445 Meteorology (3346), 5450 Orbital and rotational dynamics, 3344 Paleoclimatology, 3319 General circulation |
| Bibliographic Code: |
2004AGUFM.P13A0977M |
| Abstract: |
Liquid water is not currently stable on the surface of Mars but
transient liquid water, generated by the melting of ice, may occur if
surface temperatures are between the melting and boiling points and the
surface pressure exceeds the triple point. Such conditions can be met on
Mars with current-day surface pressures and obliquity due to the large
diurnal range of surface temperatures, yielding the potential for
liquid water. A general circulation model is used to undertake an
initial exploration of the variation of this ``liquid water potential''
(LWP) for different obliquities and over a range of increased
atmospheric CO2 abundances representing progressively earlier
phases of Martian geological history. At higher obliquities and
slightly higher surface pressures (<50 mb) possible in the relatively
recent past (<108 yr), the LWP conditions are met over a
very large fraction of the planet. However, as the surface pressure is
increased above about 50--100 mb, the increased atmospheric heat
capacity and greenhouse effect reduce the diurnal surface temperature
range, resulting in daytime temperatures rarely exceeding the melting
point. This reduction of peak daytime temperatures below the melting
point greatly reduces the possibility of even transient liquid water.
The modeling presented here does not extend to a state of stable liquid
water for early Mars---how Mars may have yielded a ``warm, wet'' early
climate is currently an open research question. However, if Mars had
an early ``warm, wet'' stage, then the potential for liquid water on
Mars has not decreased monotonically from that state to the present day,
as the atmosphere was lost. Instead, a distinct minimum in LWP will
have occurred during the extended period for which pressures were in the
middle range of about 0.1 and 1 bar. These results suggest that the
current climate and recent paleoclimate may be more conducive for liquid
water than paleoclimate states corresponding to much thicker
atmospheres. The existence of this ``dead zone'' for liquid water,
likely extending over a large fraction of Martian history has direct and
restrictive implications for chemical weathering and life. The
fundamental conclusion of this study is insensitive to invocation of
brines and to more detailed treatment of atmospheric radiative
processes.
|
| Title: |
Variation of Non-Condensables in the Martian Atmosphere |
| Authors: |
Xiao, J.; Richardson, M. I. |
| Affiliation: |
AA(Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Blvd., Pasadena,
CA 91125 United States ; jiafang@gps.caltech.edu), AB(Division of Geological and Planetary Sciences, California Institute
of Technology, 1200 E. California Blvd., Pasadena, CA 91125 United States ; mir@gps.caltech.edu)
|
| Journal: |
American Geophysical Union, Fall Meeting 2004, abstract #P11A-0962 |
| Publication Date: |
Dec 2004 |
| Origin: |
AGU |
| Keywords: |
5405 Atmospheres: composition and chemistry, 5409 Atmospheres: structure and dynamics, 5462 Polar regions, 6225 Mars, 3319 General circulation |
| Bibliographic Code: |
2004AGUFM.P11A0962X |
| Abstract: |
The Martian atmosphere is dominated by CO{_2}, but a small fraction is
made up of non-condensables, predominantly Ar and N{_2}. These
non-condensables make up about 4.7% of the atmosphere, but this fraction
is likely not constant over the seasonal cycle or spatially. The reason
for this is that the major gas, CO{_2} condenses in the autumn pole and
sublimes at the spring pole, concentrating and diluting, respectively,
the non-condensable mass-mixing ratio. The purpose of this study has
been to examine the seasonal cycle of non-condensables with a Martian
General Circulation Model (GCM) to provide a basis of comparison with
data becoming available from the Mars Odyssey spacecraft, and to provide
insight into the evolving non-condensable distributions. The model
includes a full seasonal cycle of CO{_2} and atmospheric dust.
|
| Title: |
Hydrodynamic Escape from Hydrogen Rich Atmospheres |
| Authors: |
Parkinson, C. D.; Richardson, M. I.; Hill, D. J. |
| Affiliation: |
AA(California Institute of Technology), AB(California Institute of Technology), AC(California Institute of Technology) |
| Journal: |
American Astronomical Society, DPS meeting #36, #40.07; Bulletin of the American Astronomical Society, Vol. 36, p.1167 |
| Publication Date: |
Nov 2004 |
| Origin: |
AAS |
| Abstract Copyright: |
(c) 2000: American Astronomical Society |
| Bibliographic Code: |
2004DPS....36.4007P |
| Abstract: |
Atmospheric loss processes have played a major role in the evolution and
habitability of the terrestrial planet atmospheres in our solar system.
The hydrogen escape rate to space is the key parameter that controls the
composition of the primitive terrestrial atmosphere, including its
possible methane concentration. Most models of the early atmosphere
assume that hydrogen escapes at the diffusion-limited rate (Walker,
1977), but this need not necessarily have been true. A CO2-
or CH4-rich primitive atmosphere may have been relatively
cool in its upper regions, and the escape may therefore have been
limited by energy considerations rather than by diffusion. Resolving
questions of hydrogen escape for these cases requires solving a set of
hydrodynamic equations for conservation of mass, momentum, and energy.
Hydrodynamic escape may also be important for Close-in Extrasolar Gas
Giants (CEGPs) such as HD209458b, which has recently been observed to be
losing hydrogen by the Hubble Space Telescope (Vidal-Madjar et al.,
2003; 2004). Although planetary hydrodynamic escape models have been
created in the past (Watson et al., 1981; Kasting and Pollack, 1983;
Chassefiere, 1996), the problems were solved by integrating the coupled,
time independent mass, momentum, and energy equations for the escaping
gas from the homopause out to infinity. Solving the one-dimensional,
steady state approximation becomes problematic at the distance where the
outflow becomes supersonic. A new technique has been developed for the
treatment of hydrodynamic loss processes from planetary atmospheres that
overcomes the instabilities inherent in modelling transonic conditions
by solving the coupled, time dependent mass, momentum, and energy
equations, instead of integrating time independent equations.
We validate a preliminary model of hydrodynamic escape against simple,
idealized cases (viz., steady state and isothermal conditions) showing
that a robust solution obtains and then compare to existing cases in the
literature as cited above. The general tools developed here are applied
to the problems of hydrodynamic escape on the early Earth and close-in
extrasolar gas giant planets and results from these analyses are shown.
|
| Title: |
The Martian Atmosphere, Climate, and General Circulation Models |
| Authors: |
Richardson, M. I. |
| Affiliation: |
AA(California Institute of Technology, MC 150-21, 1200 E. California Blvd., Pasadena, CA 91125 United States ; mir@gps.caltech.edu) |
| Journal: |
American Geophysical Union, Spring Meeting 2004, abstract #SA51B-03 |
| Publication Date: |
May 2004 |
| Origin: |
AGU |
| Keywords: |
0343 Planetary atmospheres (5405, 5407, 5409, 5704, 5705, 5707), 3367 Theoretical modeling, 5409 Atmospheres: structure and dynamics, 5445 Meteorology (3346), 6225 Mars |
| Bibliographic Code: |
2004AGUSMSA51B..03R |
| Abstract: |
Our understanding of the Martian atmosphere, and the embodiment of this
understanding in GCM models, sits part way between that of the Earth's
atmosphere and that of the other planets in the solar system. Compared
to the Earth, it is incomplete even as it applies to certain basic,
elementary components and it is studied by a very limited community.
Compared to the other planets in the solar system, most elements of the
circulation are understood in outline, the data sets are vast and rich,
and a number of well-staffed, competing modeling groups exist. Given
this ``middle sibling'' status of Martian atmospheric science, an
obvious issue arises as to whom it should be compared: Is the paucity of
our understanding compared to the Earth motivation for redoubled
efforts, or advanced state of knowledge cause to refocus on other
planetary bodies? In this presentation, I will review the components
of the Martian circulation and the progress that has been made in their
understanding through the synthesis of data with GCMs. I will also
review the aspects of Martian climate that uniquely influence the
atmosphere. These include the lofting of dust by large-scale winds and
thermal convection, resulting in a permanent (if varying) dust haze that
significantly increases atmospheric temperatures, and occasionally
leading to the generation of global dust storms. The spontaneous
generation of such storms in a GCM has only very recently been
accomplished. The condensation of the major atmospheric constituent
(CO2) onto the surface to form massive seasonal ice caps in
the frigid polar winter also generates a significant climate signal and
a pole-to-pole condensation flow. Finally, Mars possesses an active
water cycle with the development of clouds, formation of seasonal water
ice deposits, and storage of water in the near-sub surface as
adsorbate. The water cycle is fundamentally driven by exchange with a
residual water ice cap at the northern (and not the southern) pole. Such
asymmetries abound in the Martian atmosphere and climate system - some
are tied to the planetary eccentricity and some to the difference in
topographic elevation of the two hemispheres. Many significant
questions remain open regarding how these climate system elements
interoperate and how they might have changed the face of Mars as
forcing, due to abundance of greenhouse gases or the pattern of
insolation associated with particular obliquity or orbital parameter
values, have changed.
|
| Title: |
Interpreting Martian Paleoclimate with a Mars General Circulation Model |
| Authors: |
Richardson, M. I.; Mischna, M. A.; Basu, S.; Fenton, L. K.; Wilson, R. J. |
| Journal: |
35th Lunar and Planetary Science Conference, March 15-19, 2004, League City, Texas, abstract no.2100 |
| Publication Date: |
Mar 2004 |
| Origin: |
LPI |
| Bibliographic Code: |
2004LPI....35.2100R |
| Abstract: |
We review the capabilities and studies undertaken with the Geophysical
Fluid Dynamics Laboratory (GFDL) Mars GCM.
|
| Title: |
Enhanced Water-Equivalent Hydrogen on the Western Flanks of the Tharsis Montes and Olympus Mons: Remnant Subsurface Ice or
Hydrate Minerals?
|
| Authors: |
Elphic, R. C.; Feldman, W. C.; Prettyman, T. H.; Tokar, R. L.; Lanza, N.; Lawrence, D. J.; Head, J. W., III; Mischna, M. A.; Richardson, M. I. |
| Journal: |
35th Lunar and Planetary Science Conference, March 15-19, 2004, League City, Texas, abstract no.2011 |
| Publication Date: |
Mar 2004 |
| Origin: |
LPI |
| Bibliographic Code: |
2004LPI....35.2011E |
| Abstract: |
Enhanced water-equivalent hydrogen (2 8 wt%) is found in and around the
Tharsis Montes and Olympus Mons, especially on the western flanks. This
is where glacial landforms are found, and where GCMs hint at past ice
accumulations.
|
| Title: |
Explaining the Mid-Latitude Ice Deposits with a General Circulation Model |
| Authors: |
Mischna, M. A.; Richardson, M. I.; Wilson, R. J.; Zent, A. |
| Journal: |
35th Lunar and Planetary Science Conference, March 15-19, 2004, League City, Texas, abstract no.1861 |
| Publication Date: |
Mar 2004 |
| Origin: |
LPI |
| Bibliographic Code: |
2004LPI....35.1861M |
| Abstract: |
We look at the formation of the mid- and low-latitude subsurface water
deposits using the GFDL Mars GCM with an active regolith. Results
suggest such deposits are a combination of diffusively placed water and
surface ice deposits while at high obliquity.
|
| Title: |
Dynamics and structure of the Mars atmosphere: The post-Viking perspective |
| Authors: |
Zurek, R. W.; Murphy, J.; Kass, D.; Richardson, M. I.; Rafkin, S.; Malin, M.; Cantor, B.; Keating, G.; Smith, M. |
| Journal: |
35th COSPAR Scientific Assembly. Held 18 - 25 July 2004, in Paris, France., p.4291 |
| Publication Date: |
n/a 2004 |
| Origin: |
ADS |
| Bibliographic Code: |
2004cosp...35.4291Z |
| Abstract: |
Past summaries of knowledge about the dynamics of the Mars atmosphere
were based on Mariner 9 and Viking data and on then state-of-the-art
general circulation models. Since then, Mars Pathfinder and the two Mars
Exploration Rovers have provided new in situ entry data, and a suite of
Mars spacecraft have provided in situ measurements during aerobraking
and new remote sensing observations from orbit. Mars Express has joined
the ongoing Mars Global Surveyor and the 2001 Mars Odyssey spacecraft in
orbit around Mars, and the Mars Reconnaissance Orbiter is preparing for
launch in 2005. Entry data and measurements from orbit are providing the
data needed to test our understanding and our advanced modeling of Mars
atmospheric processes. Analyses of these data have provided both
confirmation of some earlier expectations and new perspectives on
atmospheric dynamics. These will be reviewed in this talk, which will
touch on the roles of synoptic-scale weather events and of mesoscale
circulations, the connections between lower and upper atmosphere, and
the nature of seasonal and interannual variations.
|
