Clouds and the Earth's Radiant Energy System Science Team Meeting

--Bruce R. Barkstrom, brb@ceres.larc.nasa.gov ,Co-Principal Investigator
--Gary G. Gibson, g.g.gibson@larc.nasa.gov
NASA Langely Research Center

The 15^th Clouds and the Earth's Radiant Energy System (CERES) Science Team meeting was held at the NASA Langley Research Center (LaRC) in Hampton, VA, April 16-18, 1997. The focus of the meeting was CERES instrument status, data management system status, Release 2 algorithms and issues, and validation plans. The first CERES launch is scheduled for October 31, 1997, on the Tropical Rainfall Measuring Mission (TRMM) spacecraft. The Science Team guides the definition of the CERES instrument and science studies to provide a climate data set suitable for examining the role of clouds in the radiative heat balance of the climate system.

Bruce Wielicki, CERES Co-Principal Investigator, opened the meeting with a program status report. The EOS AM-1 and EOS PM-1 platforms are on schedule. The EOS AM-1 project agreed to perform a space-look orbital maneuver required by CERES and the Moderate-Resolution Imaging Spectroradiometer (MODIS). The National Polar-Orbiting Operational Environmental Satellite System (NPOESS) wants to fly a "CERES Lite" instrument on their 1:30 p.m. platform in 2009 and beyond. The EOS Biennial Review is currently underway with plans to re-compete the EOS-2 missions.

CERES Instrument Status: TRMM and EOS AM-1
Leonard Kopia (LaRC) presented the instrument status report. The CERES Proto-Flight Model (PFM) instrument on the TRMM spacecraft successfully completed thermal vacuum and vibration testing at the spacecraft level. Both the FM1 and FM2 instruments successfully completed Bench Acceptance Tests at the Lockheed-Martin Valley Forge facility, and on March 26, 1997 became the first science instruments to be mechanically integrated on the EOS AM-1 spacecraft. Larry Brumfield (LaRC) reviewed the planned in-orbit checkout and calibration activities, spacecraft yaw maneuvers, and orbit adjust maneuvers. He issued a call for science team requests for special TRMM measurements and outlined procedures for submitting and evaluating requests for operational changes.

Data Systems: EOSDIS, LaRC DAAC, and CERES DMS
As the launch of TRMM approaches, the team placed special emphasis on the readiness of data processing and dissemination systems. In an overview of the EOS Data and Information System (EOSDIS), Bruce Barkstrom (LaRC) noted that the system would likely not be ready by the time of the TRMM launch. The EOSDIS Core System (ECS) Release A is being replaced by a backup processing and distribution system, the Langley TRMM Information System (LaTIS), at the LaRC DAAC for TRMM processing. Also, the Science Working Group for the AM Platform (SWAMP) insisted on an Emergency Backup to cover the first 6 months of AM-1 processing in case of additional EOSDIS delays. Richard McGinnis (LaRC) presented the LaTIS customer requirements, design assumptions, system architecture, and proposed hardware/software.

Jim Kibler (LaRC) presented the CERES Data Management System (DMS) status. Code development, integration, and test activities are all on schedule for TRMM. The CERES Release 2 Data Products Catalog was published to define at-launch products. The catalog is accessible on the Internet from the CERES home page at: asd-www.larc.nasa.gov/ ceres/ASDceres.html. CERES and DAAC teams at Langley and TRMM and EOSDIS teams at the Goddard Space Flight Center (GSFC) conducted the first end-to-end TRMM mission simulation in November 1996. Several anomalies in both the software and the operational procedures were found and corrected as a direct result of the realistic simulation. This simulation demonstrated the successful operation of virtually all elements of the data systems needed to support the CERES launch on TRMM. Near-term plans include:

1) a second TRMM mission-simulation test with live CERES data
2) Release 2 integration and testing on Science Computing Facilities
3) staged deliveries of Release 2 code to the DAAC for LaTIS integration
4) testing LaTIS with a month of simulated CERES data prior to the TRMM launch
5) modification to maintain compatibility with ECS Release B for EOS AM-1 processing

CERES Release 2 Algorithms and Issues
The Release 2.1 CERES Algorithm Theoretical Basis Documents (ATBDs) have been completed for all subsystems and reviewed by the EOS Project Science Office.

Instrument: Robert B. Lee III (LaRC) reported that the Release 2 algorithm was delivered to the DAAC in March 1997. The algorithm is a debugged version of Release 1 with upgraded data handling features for calibration and coastline validation data. Release 2 system architecture has been implemented, and testing and verification are underway.

Clouds and Top-of-Atmosphere (TOA) Fluxes: Bruce Wielicki (LaRC) stated several arguments against merging the CERES/MODIS cloud products. It is unlikely that a single cloud product will be optimal for all users. Cloud validation is being coordinated with the MODIS team. CERES, MODIS, and International Satellite Cloud Climatology Project (ISCCP) product intercomparisons will be performed. MODIS is concentrating on aircraft field experiments, and CERES is focusing on long-term surface site measurements. MODIS Airborne Simulator (MAS) data are useful for validation over ocean backgrounds, but are more difficult to use over land. Issues of consistency in Visible Infrared Scanner (VIRS) and MODIS cloud properties will be addressed by averaging MODIS to VIRS resolution and using only the VIRS channels. Full MODIS capability will be used for EOS AM-1 and EOS PM-1. Polarization and Directionality of EarthÍs Radiances (POLDER) and Multi-Angle Imaging Spectroradiometer (MISR) data will be used to verify consistency of multi-angle optical depth retrievals.

Surface and Atmospheric Radiation Budget (SARB): Thomas P. Charlock (LaRC) reviewed Release 2 improvements for SARB: maximum of two cloud layers per footprint; use of Data Assimilation Office (DAO)-based Meteorology, Ozone, and Aerosol (MOA) data; two-stream Fu-Liou model; updated derivative and sigma tables; and processing nighttime footprints. For SARB, a cloud will be either all liquid or all ice. For each existing cloud layer, given the cloud-top pressure, effective temperature, optical depth, and particle size, the liquid ice water content and the cloud bottom height are determined. The Fu-Liou results will be constrained to match CERES-observed TOA fluxes. David P. Kratz (LaRC) reported that the Li et al. all-sky shortwave (SW), Ramanathan/Inamdar clear-sky longwave (LW), and Gupta et al. all-sky LW TOA-to-surface parameterizations have been completed. He also noted that surface emissivity maps are now being produced for broadband infrared (4.5-100 µm), CERES window (8-12 µm), Fu-Liou infrared intervals, and 3.7 µm.

Temporal Interpolation and Spatial Averaging (TISA): David F. Young (LaRC) reported that TISA algorithms are developed and operating, but several issues must still be considered. Spatial averaging issues include: vertical averaging of clouds, cloud layer averaging, combining data from multiple satellites, spatially averaging rotating azimuth plane (RAP) scanner data, and data ordering and gridding. Temporal interpolation issues include: data gaps greater than 24 hours, augmenting clear-sky interpolation with geostationary data, interpolation of atmospheric fluxes, instantaneous or 3-hour average synoptic maps, mixing crosstrack and RAP data, and using geostationary data to reduce cloud interpolation errors.

Invited Presentations
Leo Donner (GFDL) gave a modellerÍs perspective on using CERES data to evaluate cloud and convective processes in General Circulation Models (GCMs). He addressed current GCM parameterization development issues and the critical need for expanded and improved observational data. CERES data will be used to evaluate 3-D distributions of clouds and radiative fluxes, with special emphasis on the surface radiation budget for issues related to atmospheric absorption and surface temperature control. CERES data are also needed to improve diurnal cycle parameterizations and to examine synoptic evolution of cloud systems.

Elsworth Dutton (NOAA) discussed the Baseline Surface Radiation Network (BSRN) status and future. He noted the principal features of BSRN sites including location criteria, data quality control, World Climate Research Programme (WCRP) organizational support and oversight, uniform measurement specifications, irradiance and atmosphere observations, and uniform archiving. Basic observations include direct and diffuse solar, downward infrared, and basic surface meteorology. There are currently 24 active BSRN field sites around the globe sponsored by 10 different countries.

J. P. Duvel (Laboratoire de Meteorologie Dynamique, France) briefed the team on the POLDER experiment which is being flown aboard Japan's Advanced Earth Observing Satellite (ADEOS) polar orbiting platform launched in 1996. POLDER measures reflected solar radiance and observes a given Earth target pixel under various geometrical, spectral, and polarization conditions. POLDER data provide an opportunity to conduct climate-related research on aerosol cycling, aerosol-cloud-radiation interactions, the Earth radiation budget, ocean primary production, and continental biosphere dynamics.

Working Group Reports
Cloud Working Group: Bruce Wielicki led discussions of Angular Distribution Models (ADMs), smoke retrievals and radiative effects, and MODIS field programs for validation. Yong Xiang Hu (College of William and Mary) constructed theoretical ADMs using both stochastic and plane parallel models. He made a database of broadband radiances as a function of solar and viewing angles, phase, and optical depth for the two models and compared the results. Steve Platnick (GSFC) noted that MAS data are proposed for studies related to the remote sensing of clouds, surfaces, smoke, fires, fog, etc. Options and data availability for post-launch CERES/MODIS validation studies were discussed.

Surface and Atmospheric Radiation Budget (SARB) Working Group: Thomas Charlock led the SARB Working Group in discussions of anomalous SW absorption, smoke effects on surface properties, and meteorological data sources. Bob Cess (State University of New York at Stony Brook) presented theoretical results and ARM Enhanced Shortwave Experiment (ARESE) data taken on clear and cloudy days to show that excess SW absorption occurs only on cloudy days. In a discussion of the spectral dependence of excess absorption, Cess explained that it occurred at most visible and near-IR wavelengths, but not at 0.5 µm. Sundar Christopher (S. Dakota School of Mines & Technology) showed the effect of smoke from biomass burning on surface insolation, and the smoke radiative forcing of the climate system. He also demonstrated a new algorithm for detecting biomass burning events from imager data. Shi-Keng Yang (NOAA) presented a new ozone product called SMBOA (Stratospheric Monitoring-groupÍs Blended Ozone Analysis), which is an analysis/assimilation product based on Solar Backscatter UltraViolet (SBUV/2) data. This may be the best ozone product for CERES MOA use because it provides ozone mixing ratios at many more levels. Man-Li Wu (GSFC) discussed problems affecting the meteorological fields of the Goddard Earth Observing System (GEOS)-1 GCM and the steps being taken to remedy those problems.

In a joint meeting of the SARB and Cloud Working groups, Charlock presented full-day, global Pathfinder results from the SARB constrainment algorithm. ADM errors were also discussed, particularly the possibility of large Earth Radiation Budget Experiment ADM errors over large-optical-depth convective regions in the tropics. Wielicki concluded that global statistics of all output products should be closely examined.

Time Interpolation and Spatial Averaging (TISA) Working Group: David Young led discussions of algorithm changes, code development, validation plans, and ongoing temporal and spatial averaging studies. All TISA subsystems are on-target for delivery to meet TRMM schedules. Takmeng Wong (LaRC) showed initial validation results for the CERES-algorithm-derived monthly average products. Martial Haeffelin (Virginia Tech) used CAGEX (CERES/ARM/Global Energy and Water Cycle Experiment, GEWEX) data to evaluate temporal sampling errors in atmospheric and surface fluxes. Dave Doelling (AS&M) presented results of CERES spatial sampling studies. Steven Dewitte (Belgium) presented a spherical wavelet transform technique for radiation budget data compression.

Investigator Presentation Highlights
Bryan Baum (LaRC): Reviewed the goals, data products, and access information for the CERES Pathfinder. He presented a new algorithm for detecting overlapped cloud pixels based on the relationship between reflectance and brightness temperature.

Bob Cess (State University of New York at Stony Brook): Examined the role of clouds in the relation between surface downward LW and outgoing LW radiation. Results suggest that a new LW TOA-to-surface parameterization might be feasible.

Tom Charlock (LaRC): Compared SW results from the Fu-Liou code with ARM measurements. Results from CAGEX Version 2 indicate the Fu-Liou code significantly overestimates clear-sky surface insolation measurements. Evidence exists for enhanced SW absorption by clouds.

Dominique Crommelynck and Steven Dewitte (Royal Meteorological Institute of Belgium): Presented an overview of determining radiation budget parameters from geostationary and polar measurements. Discussed the application of the Space Absolute Radiometric Reference (SARR) to adjust solar measurements since 1978 to the same reference.

Jennifer Francis (Rutgers University): Presented a method for detecting nighttime polar clouds that combines wavelengths with different cloud absorption characteristics to detect clouds over snow, determine cloud phase, and estimate thickness of thin clouds.

Laura Fowler (representing Dave Randall, Colorado State University): Simulated the orbital coverage of the Geoscience Laser Altimeter System (GLAS) and Pathfinder Instrument for Cloud and AeroSol Spaceborne Observations (PICASSO) satellites in the Colorado State University (CSU) GCM. The approach is to sample the hourly GCM cloud/radiation gridded fields using the satellite sampling (near-simultaneous observations of GLAS or PICASSO with EOS) and then compare it with the truth field, which includes all samples.

Qingyuan Han (representing Ron Welch, S. Dakota School of Mines & Technology): Examined the relationship between liquid water path (LWP) and droplet size used in GCMs with a near-global data set. Presented an improved smoke retrieval algorithm and showed how combining the smoke mask with the CERES cloud mask could improve retrievals.

Anand Inamdar (representing V. Ramanathan, Scripps): Analyzed global-scale water vapor radiative feedback. Derived the greenhouse effect for oceans and land separately and combined, and examined the annual cycles of the atmospheric greenhouse effect, surface temperature, and total precipitable water. Inferred the water vapor sensitivity factor from the annual cycle. CERES will provide additional insights into the role of continuum, water vapor feedback, and lapse rate effects.

Robert Kandel (Laboratoire de Meteorologie Dynamique, France): Gave an overview of the year of Scanner for Radiation Budget (ScaRaB) data with regard to the effects of restricted time sampling.

Bing Lin (Hampton University): Developed a microwave cloud retrieval method to detect water clouds beneath upper-level ice clouds.

Norman Loeb (representing Jim Coakley, Oregon State University): Examined the influence of cloud-top structure on the view-angle dependence of reflectances from overcast cloud layers.

Pat Minnis (LaRC): Examined the use of narrowband geostationary data as a surrogate for broadband data with applications for time interpolation of the CERES data and the use of geostationary data for estimating broadband flux fields.

Larry Stowe (NOAA): Presented the status of two-channel algorithm development for aerosol retrievals. Derived aerosol products using Advanced Very High Resolution Radiometer (AVHRR) 0.63- and 0.83-µm channels. Discussed the 5-µm leak in the VIRS 1.6-µm channel.

Shi-Keng Yang (NOAA): Showed diagnostic results of an experimental SW code in the National Centers for Environmental Prediction global forecast model.

CERES Educational Outreach
Lin Chambers (LaRC) briefed the team on the CERES S'COOL (Students' Cloud Observations On-Line) Project. Schools observe and report clouds at the time of CERES instrument overpass, compare their observations to CERES cloud retrievals, and provide feedback on up versus down-looking results. The program has already been tested locally, and is expected to expand to national, international, and global scales within the next year. The S'COOL internet interface is: asd-www.larc.nasa.gov/SCOOL/

Science Team Logistics
The next CERES Science Team meeting is scheduled for September 16-18, 1997, at Oregon State University in Corvallis, Oregon. Major topics will include readiness of all systems for the TRMM launch on October 31, and subsequent processing and validation of CERES and VIRS data.