Subject: TGCM / MGCM coupling

From: Jim Murphy <[email-masked]>
Date: Mon, 10 May 1999 10:17:15 -0600 (MDT)

TO:  Ben Foster (NCAR) and Jim Schaeffer (NASA Ames)
FROM:  Jim Murphy (NMSU)
  RE:  interactive coupling of the Mars TGCM and MGCM
DATE:  11 May, 1999

   Hello Ben and Jim,

  I am incredibly delinquent in getting this message out and I apologize
to you both and to Steve Bougher.

  Our ongoing effort at coupling Steve's Thermospheric Mars GCM (TGCM) and
the NASA Ames Mars GCM (MGCM) requires the expertise that you each possess
with your respective codes. To date, our coupling efforts have been
'offline'.  In this mode, time and zonal mean fields (geopotential and
temperature of a given pressure surface) and time-of-sol geopotential
variations (thermal tidal variations)  have been obtained from the MGCM
for some specified time interval (10 sols), and these values have been
used as a lower boundary condition to drive the TGCM.   These experiments
have been illuminating.  However, as became apparent during the
aerobraking process for the Mars Global Surveyor spacecraft, which dipped
down to ~110 km altitude within the atmosphere, there is an incredible
amount of structure in the atmospheric fields at these heights 
(pressures), much of which is not captured by our to-date simple model
coupling.

   Therefore we have undertaken, and are being funded by NASA's Planetary
Atmospheres Program, to improve the sophistication of the coupling between
the TGCM and MGCM.   This new coupling is envisioned to be fully
interactive, whereby fields of importance (geopotential, temperature,
wind, and possibly others) are passed both upward and downward across the
interface (pressure) level at which the models are joined.  Thus far, this
level has been the 0.32 microbar level (~70 km above the surface).

    In order to move this process along, we would like the two of you to
spend a day or two together to brainstorm the most effective route to
follow to develop this interactive coupling.  The two of you can talk with
each other and decide where you would like this get-together to take
place, and when.  Sooner would be preferable, but my tardiness in getting
this message out to you puts me in no position to force this issue.

    Currently, the MGCM is undergoing a number of upgrades / improvements,
including possibly the inroduction of a new horizontal grid-structure.
However, the general framework of the model will remain the same (I think
this is true, Jim...am I mistaken?), thus I do not believe that this
get-together needs to wait for these improvements to be completed.   Steve
and I can certainly provide some input prior to your meeting, but I'm sure
the most progress will be accomplished when you all can sit down and talk
models.

    Below I list the contact info for both Jim and Ben.  I hope you can
get in touch with each other this week and set up a time to get
together.

    If you have any questions, please let me know ([email-masked];
505-646-5333) and I'll get an answer to you quickly, or will have Steve do
so if it is better answered by him.

    I'm looking forward to getting a coupled model developed, and hope you
are also.

    Best Regards,

      Jim Murphy

  CONTACTS:

Ben Foster
National Center for Atmospheric Research
High Altitude Observatory
Boulder, CO 80307-3000
(303)-497-1595
[email-masked]

Jim Schaeffer
NASA Ames Research Center
MS 245-3
Moffett Field, CA 94035-1000
[email-masked]
(650) 604-6078

____________________________________
Jim Murphy
Assistant Professor
Department of Astronomy
New Mexico State University
[email-masked]
(505) 646-5333    FAX (505) 646-1602