The following paragraphs summarize new deliverables which have been divided into two additional work packages to be added onto the end of the existing contract. Following are tables which break down the contents of each work package and a diagram illustrating the proposed timeline.
The model results incorporated in the database are to be checked and any areas of systematic difference between the two models, such as high-level zonal wind fields, are to be investigated further and explained as far as possible. When observations from Mars Global Surveyor become available during 1998 then these may be used to further verify the models. If these investigations lead to significant changes or improvements to the model then these changes will be incorporated in versions of the model which will be used to compile an improved database at the end of the contract extension period.
[Experiments to be conducted at both LMD and AOPP, LMD to take primary responsibility for report.]
Any updates and improvements to the parameterization schemes supplied as part of the Martian General Circulation Model under the previous contract, which may come to light as a result of model intercomparisons and sensitivity studies conducted under this extension, are to be made available in the model code supplied to ESA and to be used for the improved climate database at the end of the extension period.
[LMD to take primary responsibility.]
In the light of feedback from users of the first version of the Martian Climate Database, improvements will be made where desirable to the access software in terms of speed, memory usage and further options and choices which can be offered to the user. The access software for the first version of the Martian Climate Database can be updated where required during the course of the extension and final improvements will be incorporated in the new version of the climate database at the end of the extension period.
[AOPP to take primary responsibility.]
The variability model, which uses empirical orthogonal functions (EOFs) computed from vertical profiles taken from the model to add large scale variability to the database, will be examined and may be revised. EOFs will be computed from further model simulations in order to improve their statistical significance. The possibility of representing horizontal correlations between variables will be examined and reported on. Improvements will be incorporated in the new version of the climate database.
[AOPP to take primary responsibility.]
The sensitivity of the model results, and therefore the database, to currently uncertain parameters is to be tested by further experiments; for example, runs will be conducted with the Consortium orography dataset which is an alternative to the United States Geological Survey's Digital Topographic Map employed in the initial contract with substantial differences in terrain elevation in some regions.
In 1998 the Mars Global Surveyor Laser Altimeter data should become available which will provide a definitive orographic dataset. If this data can be acquired before the end of the contract extension period, it will be processed and included in the model used to compile the improved climate database at the end of the contract. The new orographic dataset will not only be used for the large-scale orography resolved by the model, but will also be used to re-tune the small-scale orographic and gravity wave drag parameterizations used in the model.
[AOPP to take primary responsibility.]
It is proposed to extend the altitude of the top of the model up to at least 120km, to facilitate re-entry studies and for improved compatibility of our database with MarsGRAM. Since the effects of non-LTE become important in the radiative heating and cooling budget for the atmosphere above the present altitude limit of around 80 km, an additional parametrization will be developed within the model to provide a correction to the radiation scheme at these altitudes to take a first-order account of the effects of non-LTE in both heating and cooling rates. The improved scheme will be validated using available observations and published work on comprehensive calculations of non-LTE heating and cooling rates on Mars, and used in the set of new simulations for incorporation into the database.
[AOPP to take primary responsibility.]
The dust carried by the Martian atmosphere strongly affects the thermal structure through its radiative effects, and, in turn, the atmospheric circulation. In fact, the amount of airborne dust is one of the most variable components of the Martian environment with a strong seasonal cycle, considerable year to year variations and large spatial variations.
In the GCMs that have been used to produce the Martian database, the amount of dust lifted in the atmosphere has been simply prescribed on the basis of the few available observations. Prescribing the dust may sometimes lead to unrealistic results, especially for the periods when the atmosphere is dust-laden. From an engineering point of view, these periods are of particular importance since they correspond to the most extreme conditions for a spacecraft, with strong winds below 50km (dust storms) and a denser atmosphere above (the dust enhances the meridional Hadley circulation, which lead to a strong adiabatic cooling of the upper atmosphere in the summer hemisphere and in the tropics). Also, prescribing the dust hinders the estimation of the interranual variability of the Martian environment, since this variability is also controlled by the dust cycle fluctuations.
To improve knowledge of the dust cycle, and better simulate the related changes in the environmental conditions for the future missions to Mars, it is proposed to incorporate the lifting and transport of the dust in the GCM. In practice this means a parameterizaton of dust lifting by the near surface winds, vertical mixing by the turbulent boundary layer and atmospheric convection, advection by the general circulation and gravitational sedimentation. These changes to the model will be supplied to ESA at the end of the contract and may be used in some extended scenarios which will be designed to compile the improved Martian Climate Database.
[LMD to take primary responsibility.]
A World Wide Web site will be developed and supported for as long as possible at LMD, with much of the material mirrored on a site at AOPP. The sites will be supported until at least December 1999. Material on the site will be made available to be copied at ESTEC as well if required. This site will give direct access to the full Martian Climate Database. The user will be able to select data sets and variables, to specify the season, the time of day, the location and the viewing plane or axis. The results will be returned directly by HTML in GIF format, or may be downloaded by FTP in a variety of data formats (NetCDF, ASCII, ...). The site will also give access to documentation, including the technical notes written for the present ESA contract. Note that, in addition to supporting and illustrating the Climate Database, this WWW site will offer the user an alternative way to access the data, complementary to the MarsGram-like interface, Grads scripts and FORTRAN subroutines to be supplied with the database software under the present contract. The site should contain a suitable statement to the effect that data obtained from it may not be used for profit-making purposes and that there must be a full acknowledgement of the source of the data.
[LMD to take primary responsibility.]
The delivery of the final report, which was a component of WP3 under the original contract, shall be delayed until WP5 under the extended contract.
[LMD to take primary responsibility.]