Wednesday, 5 June 2002: 11:00 AM
Consistency of cloud solar absorption estimates during ARESE II
We examine the quality of solar absorption estimates for three cloudy days of the Atmosphereic Radiation Measurement Enhanced Shortwave Experiment II (ARESE II). The focus is on sampling issues and the feasibility of using narrowband apparent visible absorptances to correct broadband absorptances with previously successful techniques. We show that only one of the three days is characterized by clouds thick and homogeneous enough to overcome the inherent sampling deficiencies (use of a single aircraft) and produce a consistent picture among the various radiometric observations. Our methods to assess the quality of the meausurements also include instrument intercomparisons, correlations between radiometric measurements and cloud liquid water at instances of aircraft overpass above the surface instrument site, cumulative averaging, and analysis of absorptances on a per flight leg basis. Notwithstanding the difficulties in applying corrections for three-dimensional effects, there are strong indications that broadband cloudy sky absorptances are significantly lower for ARESE II compared to ARESE I, with typical two-hour averages reaching approximately 22%.