EOS Validation Program

August 2001

We propose to use the observational capabilities of the University of Utah Facility for Atmospheric Remote Sensing (FARS) to perform validation of the satellite-derived cloud and aerosol properties. We will collect observations of cloud and aerosol characteristics during satellite overpasses at FARS and the ARM sites, use these data to infer cloud macroscale and microphysical properties, compile this information into a format useful to EOS scientists and deliver the data in a timely fashion.

Additional Information: The capabilities of Facility for Atmospheric Remote Sensing (FARS) and the ARM sites are nearly ideal for use in validation of the EOS-derived cloud and radiation parameters using surface-based remote sensing data. The particular combination of active and passive sensors will allow for a direct intercomparison of derived parameters, and, when combined with in situ data will enable a thorough validation of many algorithms. The CERES ATBD Subsystem 4.0 (Wielicki et al., 1996) states that "The most fruitful validation is not simply the comparisons of end results, but rather the validation of underlying assumptions. The successes and failures of these assumptions lead to critical new results and methods". This statement summarizes concisely the approach we will take to this project. Our goal is to use the surface observations at FARS and the ARM sites to derive a suite of validation products tailored for efficient use by the EOS science teams. We look forward to an active collaboration with the EOS team members to make our products as useful as possible. Our objective is to sequentially examine the assumptions underlying the surface and satellite retrievals with the ultimate goal being the convergence of the end results.

To this end, we will operate the FARS site in clear and cloudy conditions for periods bracketing satellite overpasses of interest (approximately 15 overpasses each month). The length of operation in each situation will be determined on a case by case basis but will in general consist of 1-3 hour periods. The overpasses we will support (high and low angle, day or night) will be determined in consultation with the EOS team scientists. In cloudy conditions, the full suite of FARS instrumentation will be operated. In clear conditions, the radiometric instrumentation and ruby lidar will be operated to map the vertical properties of aerosol layers (King et al., 1978; Harrison et al., 1994; Kato et al., 1997). Additionally, we will perform one extended observing period each quarter where we will collect data for at least 12 hours centered on an overpass so as to characterize a representative cloud system. We will, in close collaboration with EOS team members, develop standard deliverable products from both the FARS and DOE ARM data streams that will be delivered in a timely fashion to any designated archive and posted on the world wide web. At a minimum the deliverable products will include the raw data time sections, the derived macroscale cloud properties, derived microphysical and radiative cloud properties from all pertinent algorithms, and the measured and derived radiometric fluxes calculated using the derived macroscale, microphysical and radiative properties as input.