Research Staff: Peter Pilewskie and Warren Gore

The Radiation Group participated in the third phase of the NASA Earth Science Enterprise project FIRE (First International Satellite Cloud Climatology Project Regional Experiment): An Arctic Cloud Experiment (ACE) conducted during spring of 1998 and the coincident SHEBA (Surface Heat Budget of the Arctic Ocean) campaign. The radiation group deployed Solar Spectral Flux Radiometers on three platforms 1) the NASA ER-2, 2) the University of Washington CV-580, and 3) on the Arctic ice surface. From our observations we have derived the conclusions below.

The measured downwelling spectral flux at 20 km (ER-2) agrees well with model calculations.

At the surface, measured downwelling spectral flux agrees poorly with model calculations. Model input (aerosol model, humidity profile, and surface reflectance) is not well-defined in the Arctic.

Ice-Surface and overlying stratus can be discriminated easily using near-infrared reflectance at wavelengths greater than 700 nm. This finding resolves a difficult remote sensing problem from space.

Thin clouds reduce near infrared (surface) absorption. Thick clouds enhance near-infrared (water vapor) absorption.

Analysis of our data is continuing. We are collaborating with groups from the University of California, Santa Barbara, the University of Washington, Penn State University, and Goddard Space Flight Center to compare spectral radiometric data with theoretical radiative transfer models, and with detailed in situ microphysical measurements to further enhance our understanding of the complex radiative energy budget of the Arctic.

Collaborators: Maura Rabbette, National Research Council Associate; John Pommier, Symtech; Robert Bergstrom, Bay Area Environmental Research Institute

Point of Contact: Peter Pilewskie, (650) 604-0746, ppilewskie@mail.arc.nasa.gov