Belay Demoz, University of Maryland Baltimore County
Dan DeSlover, University of Wisconsin/CIMSS
Raymond Hoff, University of Maryland Baltimore County
Gary Jedlovec, Global Hydrology Center, Marshall Space Flight Center
Wallace McMillan, University of Maryland Baltimore County
We propose to use the water vapor mixing ratio measurements of the NASA/GSFC Scanning Raman Lidar (SRL) and the University of Maryland Baltimore County (UMBC) Advanced Lidar Experiment (ALEX) for validation of AIRS water vapor retrievals. We will study these retrievals under both clear and cloudy conditions. We will assess the influence of thin cirrus clouds on the AIRS water vapor retrievals and compare the corresponding GOES (Geosynchronous Observational Environmental Satellite) retrievals. In addition, we will compare retrievals of water vapor from co-incident Atmospheric Emitted Radiance Interferometer (AERI) data as well as study the influence of thin cirrus clouds on these measurements. Cirrus particle size retrievals will be compared from both the SRL and AERI measurements.
We are cognizant of the importance of providing accurate, quality-checked measurements of upper tropospheric water vapor mixing ratio during the period of 3 to 5 months after launch (L+3 to L+5). The following workplan addresses this need.
Year 1
1. The SRL will deploy to UMBC in early 2002 for cross-calibration with the ALEX Raman water vapor lidar system at UMBC. After calibration, ALEX will be available to make validation measurements of water vapor during the critical post-launch validation period of L+3 to L+5 from UMBC in addition to the measurements that will be made by the SRL.
2. Whether the SRL is involved in a field campaign or is stationed locally during L+3 to L+5, water vapor measurements will be made co-incident with AIRS overpasses. Radiosonde launches will also be made in coordination with the overpasses.
3. We will expedite the SRL and ALEX analysis in order to deliver quality-checked, calibrated water vapor profile data acquired during AIRS overpasses prior to the end of the L+3 to L+5 validation window.
4. We will study the influence of cirrus clouds on ground-based AERI measurements using existing SRL field measurements. A better understanding of the influence of thin cirrus clouds on ground-based high-resolution interferometer data will permit more rapid development of the forward model for AIRS once similar data are available from AIRS. Several correlative SRL/AERI datasets are available for this study. These include 4 field deployments to the DOE ARM CART site during 1996 2000 as well as the CAMEX-3 deployment to the Bahamas in 1998. We will compare the retrievals of cirrus cloud optical depth made by the SRL and the CART Raman Lidar (CARL). Existing optical depth routines developed by the Department of Energy and others will be used for this comparison.
5. We will study the GOES retrievals for both the past SRL/AERI data described above as well as the measurements to be acquired for AIRS validation.
6. Radiosonde launches will be made from GSFC and/or UMBC in support of this activity.
Year 2
1. Continue study of SRL, AERI, GOES, CARL water vapor and cirrus optical depth measurements in the presence of cirrus clouds.
2. Analyze SRL/AERI data acquired during AIRS overpasses for cirrus cloud optical depth and water vapor products in conjunction with EOS scientists to validate AIRS level 1 radiances. These measurements may be from several geographic locations.
3. Study of the influence of cirrus clouds on AIRS and GOES as AIRS algorithms are adjusted.
4. From the campus of the University of Maryland, Baltimore County, make correlative measurements of water vapor and cirrus clouds with the SRL, BBAERI and ALEX during overpass times of AIRS. Compare with GOES retrievals of water vapor. Water vapor retrievals will be validated under clear and cloudy conditions establishing both cirrus detection threshold of the satellites (over land) and the influence of undetected thin cirrus on water vapor retrievals. Studies will be performed on the shortwave/longwave optical depth ratio of cirrus clouds.
5. Present results at conferences.
Year 3
1. Second deployment of the SRL to UMBC during the winter for measurements of water vapor under both clear and thin cirrus conditions during overpasses of AIRS and GOES. Similar analyses as described in year 2 will be performed.
2. Final analysis of data from the all SRL deployments.
3. Present results at conferences and submit papers for publication.
