Determination of Wind Direction on Mars through Lee Wave Analysis

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Determination of Wind Direction on Mars through
Lee Wave Analysis
Bob Haberle, Sara Acevedo, Stasia McGehee
Space Science Division, MS 245-3, NASA Ames
Research Center, Moffet Field, CA 94035
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Determination of Wind Direction on Mars through
Lee Wave Analysis

• MGCM - The Mars Global Circulation Modeling Group

http//www-mgcm.arc.nasa.gov/MGCM

• Bob Haberle, Principal Investigator, NASA
• Sara Acevedo,Research Assistant, SETI Institute
• Stasia McGehee, Data Analyst
• Intern, De Anza College, stasia_at_eversmile.com /
  smcgehee_at_mail.arc.nasa.gov
• Internship Duties Contributions
• Gather atmospheric data by analyzing photos
  organize images into an easily accessible
  database maintain website.
• Importance of work Observed data can be
  compared to the Global Circulation Model, a
  computer simulation of Mars atmosphere.

The Mars Global Circulation Modeling Group (MGCM)
is in the Planetary Systems Branch of the Space
Science Division at NASA. MGCM contributes to
mission designs and procedures by providing
forecasts of the behavior of the Mars
atmosphere. MGCM Goals to understand the
nature of the general circulation of Mars
atmosphere, how that circulation is driven, and
how it affects long-term climate.
Image From Mars Today by Howard Houben of the
Mars Global Circulation Group. The updated
poster depicts current conditions on Mars
http//humbabe.arc.nasa.gov.
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Mars GCM - Global Circulation Model

• The accuracy of the model can be determined by
  comparing its predictions to actual observations
  of Mars.
• We can look at high-resolution photographs of
  clouds to determine present wind directions on
  Mars.
• Mars Orbiter Camera (MOC) is carried around Mars
  in a polar orbit by Mars Global Surveyor (MGS)
  and is continually imaging the entire planets
  surface every day.

Mars has an atmosphere with general circulation
patterns similar to Earths. The Mars Global
Circulation Model is a computer simulation used
to predict wind speed and direction at specific
locations over time.
Image depicting Hadley cell on Mars
http//www.adlerplanetarium.org/learn/planets/mars
/circulation.ssi
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Organizing the Data
A database of 150,000 publicly available Mars
Observer Camera (MOC) images exists at
www.msss.com.

• Lists of URLs linked to MOC images are compiled,
  and organized by regions of interest.
• There are 4 major regions of interest the
  volcano region, the storm track region, selected
  craters, and the North Pole.

Annotated MOLA Map produced by Sara Acevedo. A
MOLA map (Mars Orbiter Laser Altimeter) is a
complete topographical map of Mars.
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Analyzing Images
Vectors representing wind direction are
determined visually from MOC images. Wind
direction is calculated as b, the angle of the
wind direction vector off North (red).

• Lee waves are bands of clouds that occur downwind
  of a topographical feature such as a crater.
• As clouds of ice vapor pass over a crater, they
  oscillate up and down. At the higher elevations,
  the water vapor freezes into ice crystals,
  forming parallel bands, perpendicular to the wind
  direction.

Image Sara E. Acevedo James Schaeffer, Mars
GCM Workshop 6/1/04.
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Calculations
Conclusions

• The latitude and longitude of lee waves and
  craters in the MOC images are measured using ISIS
  (Integrated Software for Imagers and
  Spectrometers, US Geological Survey). From this
  data, wind directions are calculated.
• The observed winds are then compared to the wind
  directions predicted by the Mars Global
  Circulation Model for that time and location.

This image shows that most observed measurements
(black arrows) fall within the predicted range of
the GCM at 1 to 15 km altitude (orange wedges).
Image Sara E. Acevedo James Schaeffer, Mars
GCM Workshop 6/1/04.
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Further Research

• Algorithms will be developed to estimated wind
  speed. Lee wave altitude may be determined by
  measuring cloud shadows.
• The current focus is on craters. Other areas
  known to have a high frequency of lee waves will
  be studied next. This includes the storm track
  region, the volcano region, and the North Pole.
• Other Aeolian features, such as yardangs, the
  eroded rock formations to the left, may tell us
  about ancient long-term wind patterns.

Yardang picture http//www.msss.com/mars_images/m
oc/2004/07/13/