EOS Validation Program

Institution: Univ. of Colorado - CIRES
                     NOAA/ARL/SRRB
                     R/E/ARx1
                     325 Broadway
                     Boulder, CO 80303
Phone: (303) 497-6415
FAX: (303) 497-6546
E-mail: augustin@srrb.noaa.gov

John J. DeLuisi

Charles N. Long, Chuck.Long@pnl.gov

June 1999
June 2000
September 2001
Final Report, May 2003

The NOAA/ARL Surface Radiation Research Branch (SRRB) operates a surface radiation budget research (SURFRAD) network across the continental US. Operation of this network includes considerable effort in the yearly calibration and characterization of the radiation instruments, as well as annual rotation and overlap comparisons. With the funding provided by NASA, the data will be reprocessed to include the overlap information, which will improve the continuity/quality of the radiation data for each of the four SURFRAD stations. This data will then be used in cooperative efforts with EOS Validation Scientists to validate satellite surface radiative energy budget retrievals. The SURFRAD data include measurements of upwelling and downwelling shortwave and longwave irradiance, downwelling direct and diffuse shortwave irradiance, and downwelling PAR and UVB irradiance. Standard meteorological measurements of surface pressure, temperature, relative humidity and wind speed and direction are also made. The SURFRAD site data include spectral shortwave irradiance component measurements provided by an MFRSR, which data is then processed to infer aerosol optical depths. And we will be addressing MFRSR absolute calibration issues.

With funding provided by the NASA proposal, each SURFRAD site will be equipped with a Hemispheric Sky Imager recently developed by SRRB. This instrument will be used to infer hemispheric fractional cloud cover amounts and cloud edge-to-area ratio. Again, cooperative efforts will use this data to help validate satellite retrieval of cloud macrophysical properties.

One of the major thrusts of SRRB research involves the study of cloud effects on surface irradiance. Some data analysis techniques developed to aid in this study will provide continuous calculations of clear sky shortwave, PAR and UVB irradiance for each site. These clear sky values are in turn used to quantify the cloud effect by comparison with the actual measurements. In this way, separate validation of both satellite retrieval of clear sky irradiance and cloud forcing become possible. This, combined with the cloud macrophysical measurements, will allow empirical studies of the relationship between cloud effect and cloud amounts and type.

One of the primary obstructions in the validation of satellite retrievals of cloud amount is the difference in view between the satellite and a surface observer. Studies presented at NASA LANGLEY (May, 1997) by Long and Augustine illustrated the necessity of quantifying the relationship between these different views in order for cloud amount validation to become truly possible. As shown during the presentation, time series of narrow FOV instruments such as lidar and cloud radar cannot provide cloud amounts with reasonable consistency and accuracy. We believe that a lidar or cloud radar used in conjunction with a collocated sky imager will provide the tools to help study this view problem. As such, we strongly recommend that at least one SURFRAD site be considered for deployment of the available NASA lidars.

Additional information about SRRB and SURFRAD can be obtained at: http://www.srrb.noaa.gov

Additional information regarding the Hemispheric Sky Imager and the satellite/surface cloud view problem can be found at: http://www.srrb.noaa.gov/~long/current/current.htm