Reinhard Beer (beer@atmosmips.jpl.nasa.gov), TES Principal Investigator
Data Analysis Working Group (DAWG)
TES is encouraging the development of three Level 2 retrieval algorithms: a GENLN2-based algorithm at Oxford (specifically for the investigation of troposphere-stratosphere exchange); LBLRTM at Atmospheric and Environmental Research, Inc. (with which the bulk of our sensitivity studies have been made); and SEASCRAPE at JPL (which is our current baseline for the operational algorithm). All three are now sufficiently advanced that we are beginning benchmarking, a process that will continue for some time to come. A major part of the DAWG meeting was given over to reports on these developments by Paul Morris (Oxford), Tony Clough (AER), and Larry Sparks (JPL).
Recent efforts by the JPL and AER groups have focused on efforts to improve computational speed. Work at JPL is centered on timing studies with SEASCRAPE while the AER group is investigating the use of temperature-dependent precalculated absorption cross-sections as a replacement for line-by-line calculations. In initial studies, the AER group achieved forward-model speed enhancements of a factor of 4-5 for the calculation of ozone spectral radiances with negligible loss in calculation accuracy. On the platform utilized, the speed enhancement was I/O limited.
Tony Clough reported initial results for simulated retrieval studies for CO. TES measurements in the thermal region should yield an accurate determination of the total column above the boundary layer as well as integrated amounts with acceptable accuracy for two tropospheric layers. Boundary layer CO measurements can only be reliably obtained from measurements in the reflected solar region where adequate signal-to-noise ratio is a significant issue. Methods for combining the thermal and reflected sunlight measurements in a unified retrieval will be investigated.
The next algorithm validation exercise will be devoted to retrievals of temperature profiles from field measurements and synthetic spectra. Tony Clough voiced concerns about the consistent and significant discrepancies between LBLRTM line-by-line spectral radiance calculations and the U. Wisconsin HIS observations in the 15 µm CO2 region (e.g., the CAMEX dataset). Calculations by Paul Morris using GENLN2 established that the discrepancies are not model dependent. AES spectra may help to resolve whether these differences are due to inadequacies in our understanding of the physics or problems of interpretation of the measured data.
Curtis Rinsland reported on his investigation of sulfate aerosol extinction using data from the Atmospheric Trace Molecules Observed by Spectroscopy (ATMOS) interferometer flown on the Atmospheric Laboratory for Applications and Science (ATLAS-1) shuttle flight in the Spring of 1992, following the June 1991 eruption of Mt. Pinatubo. While the fit is promising, it is clear that the available refractive index data need considerable improvement, especially the temperature-dependence.
Aaron Goldman reported work in progress on generating improved line parameters for HNO3 and O2. Larry Rothman, an invited guest at the DAWG meeting, reported on the updates planned for the 1995 HITRAN database of line strengths and positions. Spectroscopic improvements that would enhance TES capabilities were suggested.
Science Team Meeting
After some welcoming words from our host, Jim Gleason (GSFC), the meeting began with project overviews from Tom Glavich (JPL). TES is now on the CHEM platform (launch Dec. 2002) together with HIRDLS, MLS and a yet-to-be-determined Japanese instrument that will make a powerful atmospheric chemistry payload that addresses many issues at the very heart of Global Climate Change. TES will undergo an Implementation Review at Goddard early in the New Year, our first opportunity to revisit the instrument cost since the original proposal. Substantial changes and descopes of the original system have, of course, occurred in the intervening years, but we have managed to maintain essentially all the science originally proposed.
AES continues its aggressive flight program. Since completion at the end of March 1994, we have undertaken three quite lengthy flight programs on the P-3 and DC-8 aircraft, and an equally busy schedule seems probable for the coming year. Indeed, the brief periods that we have had the instrument back at JPL have seriously constrained our improvement program based on "lessons learned." While the bulk of the flights have been for non-NASA sponsors, we have obtained some excellent data on two western wildfires which we are in the process of analyzing (see below).
Jim Gleason gave an overview of the CHEM platform science. The team expressed concern that the emphasis still seems to be on the stratosphere and that the troposphere is considered to be an "add-on" (and therefore expendable?). While this is explicable in terms of the history of NASA atmospheric science, it is clear that a policy-driven program needs to give much stronger emphasis to the region where a large proportion of Global Climate Change is occurring‹the troposphere. The TES Science Team clearly must do a much better job of making our point than we have to date.
Tom Taylor (the new CHEM Instrument Systems Manager) showed the strawman configuration for the CHEM platform, emphasizing that the selected contractor's version may be different, with the instrument fields-of-view as the only real constraint. He caused some consternation by showing a viewgraph that not only had TES as the major resource user on CHEM (which we are sure is untrue), but also as a driver on AM-2 (where we no longer are)!
Steve Wharton gave the Project Science viewpoint of EOSDIS, observing that the needs of platforms beyond the year 2000 have scarcely been considered. The team noted that we are approaching the time when, without a clear definition of the system for which we are designing our software, our efforts will be seriously impacted. There is also a serious mismatch between the volume of documentation required from us and the resources predicted.
Reinhard Beer reported on three recent meetings: the Baltimore EOS Investigators Working Group (IWG) meeting, the 5th Space Fourier Transform Infrared (FTIR) Workshop, and the 1st ADEOS IWG (both in Japan). At the EOS IWG, the move of TES to CHEM was confirmed. This move has been at the expense of ACRIM, SAGE III, and SOLSTICE. It is being proposed that ACRIM get its own small satellite, and SAGE III has several flights on other platforms planned. Only SOLSTICE appears to be orphaned. Michael King also gave us the welcome news that the barrier between "Science" and "Science Computing Facility" funding has been eliminated (although we must still report them separately). A report has been written on the two meetings in Japan and can be made available to anyone interested.
Following a summary of the DAWG meeting by Curt Rinsland, Tony Clough presented the completion of his ozone retrieval studies. These confirm that the retrieval of tropospheric ozone is feasible from space with reasonable accuracy provided that one does not retrieve too many levels in the troposphere (four seems reasonable).
Helen Worden and Reinhard Beer then showed the progress we are making on the analysis of the wildfire spectra obtained by AES earlier this year. The fires were in northern Oregon and, about two weeks later, in central California near San Luis Obispo. Both were "targets of opportunity" so no ground truth is available. Furthermore, the analysis is proving to be quite difficult because of the extremely inhomogeneous character of a fire - we see a mixture of flame at about 1200 K, smouldering embers at 400 - 500 K and unburned terrain, all overlain by a smoke and gas plume. Spectral modeling, therefore, has to proceed almost independently on each of these elements and an appropriate mix estimated at the end. Nevertheless, we have been reasonably successful in these efforts and can confirm that we observe, besides the expected CO, CO2, and H2O emission, substantial amounts of NH3. We do not, however, see any significant enhancement of N2O, although in situ measurements of controlled burns have reported such enhancements. The results are currently being prepared for publication. Reinhard Beer then reported on our plans to participate in next summer's Southern Oxidants Study (SOS) field campaign in the Nashville area. We will deploy AES on the NASA Wallops C-130 for about two weeks in mid-July.
It was agreed to hold the next Science Team Meeting in California in late May at a TBD location, and the team would like to offer special thanks to Jim Gleason (GSFC) and Bill Bandeen (Hughes STX) for the superb job they did in organizing the meeting.