Mars Analysis Correction Data Assimilation (MACDA): MGS/TES v1.0 dataset

MACDA is a publicly-available dataset containing three martian years of data assimilated into the UK/LMD Mars GCM.

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More details and the data itself are available on the British Atmospheric Data Centre (BADC) website. MACDA is a collaboration between the University of Oxford and the Open University in the UK.

Dataset overview

MACDA contains basic gridded atmospheric and surface variables for the planet Mars over three martian years, produced by assimilating data from spacecraft observations.

Each file in the dataset spans 30 martian mean solar days (sols) during the science mapping phase of NASA's Mars Global Surveyor (MGS) spacecraft, between May 1999 and August 2004. The dataset is produced by the re-analysis of Thermal Emission Spectrometer (TES) retrievals of nadir thermal profiles and total dust opacities, using the MACDA scheme in a Mars global circulation model (MGCM). The MGCM used is the UK spectral version of the model developed by the Laboratoire de Météorologie Dynamique in Paris.

Observations

The Thermal Emission Spectrometer (TES, Christensen et al., 2001) on board NASA's Mars Global Surveyor (MGS) has produced an extensive atmospheric data set during its scientific mapping phase between 1999 and 2004. Nadir thermal profiles for the atmosphere below about 40 km altitude and total dust opacities have been retrieved from TES spectra among other products (Smith et al., 2004).

Assimilation

Assimilated transient surface pressure in Mars' southern hemisphere during Mars year 25, just before the onset of the planet-encircling dust storm.TES retrievals of temperature and total (i.e. column-integrated) dust opacities were assimilated into the Mars global circulation model that is in use at the University of Oxford and at The Open University in the UK (UK-LMD-MGCM). The analyses cover almost three complete martian seasonal cycles, from 141 degrees solar longitude in martian year (MY) 24 through 82 degrees solar longitude in MY 27.

The assimilation scheme makes use of a sequential procedure known as the Analysis Correction scheme (Lorenc et al., 1991), a form of successive corrections method which has proved simple and robust under martian conditions, even during the less-than-ideal MGS aerobraking period (Lewis et al., 2007).

The UK-LMD-MGCM uses a spectral dynamical core and a shared Martian physics package that was largely developed by the Laboratoire de Meteorologie Dynamique at the Universite' Pierre et Marie Curie in Paris (France).

The MGS/TES MACDA dataset v1.0 was built with a version of the UK-LMD-MGCM mainly described in Forget et al. (1999). Montabone et al. (2006) and Lewis et al. (2007) detail the current MACDA set-up.

Limitations

One limitation of TES is that only a reduced number of limb profiles are available, so these are not used in the current MGS/TES MACDA dataset. Our re-analysis of TES retrievals, therefore, does not include observations of temperature above about 40 km altitude, nor vertical information on dust opacity.

In the current version of the downloadable dataset we did not use the capacity of the MGCM to lift, transport and sediment the martian dust. The vertical distribution of dust opacity is, therefore, analytically prescribed in the model using the so-called "Conrath distribution", which assumes a mixing ratio of dust exponentially decreasing with altitude.

Values of total dust opacity where no information from TES can be assimilated (mainly during the polar nights and the planet-encircling dust storm in martian year 25) are also prescribed in the model. The column-integrated dust opacity variable is provided in the dataset also at those times and locations where there is no information from TES dust opacity observations.

Variables included

The dataset includes the following atmospheric and surface variables on a longitude, latitude, vertical sigma levels grid (72x36x25 grid points). Variables are provided every 2 martian hours (1 Mars hour = 1.0275 Earth hours).

  • Solar longitude (degrees)
  • Martian year
  • Amount of deposited carbon dioxide (kg m-2)
  • Surface pressure (Pa)
  • Surface temperature (K)
  • Column-integrated visible dust optical thickness at 610 Pa level (dust opacity)
  • Atmospheric temperature (K)
  • Zonal wind (m s-1)
  • Meridional wind (m s-1)

Data availability and file format

The dataset is available from the British Atmospheric Data Centre (BADC) website.

Data are freely available to all registered BADC users, subject to due credit being given to the data provider.

The data themselves are held in CF-NetCDF format. The dataset is divided into 63 mainly CF-compliant NetCDF files (note that the variable 'Martian year' included in the dataset is not a standard CF variable). Each file includes data covering 30 martian mean solar days (sols). The name of each file is formed using the approximate solar longitude and martian year of the first and last available sols. The header of each NetCDF file contains detailed information about the included variables, the spatial and temporal grid, as well as general information about the dataset.

Citation

Please cite the dataset as

University of Oxford and The Open University. [Montabone, L.; Lewis, S. R.; Read, P. L.]. Mars Analysis Correction Data Assimilation (MACDA): MGS/TES v1.0, [Internet]. NCAS British Atmospheric Data Centre, 29 November 2011, doi:10.5285/78114093-E2BD-4601-8AE5-3551E62AEF2B.

There will be new versions of the dataset available in the future. People interested in the most recent version are encouraged to contact the authors (below) to know the status of the work in progress.

Contacts

Luca Montabone montabone [at] atm.ox.ac.uk University of Oxford (UK) and Université Pierre et Marie Curie (Paris; France)
Stephen R. Lewis s.r.lewis [at] open.ac.uk The Open University (UK)
Peter L. Read read [at] atm.ox.ac.uk University of Oxford (UK)