The Radiative Effects of Aerosol Layers on Solar Spectral Flux Measurements Duing ACE-Asia

Maura Rabbette and Peter Pilewskie

The Ames Solar Spectral Flux Radiometer (SSFR) was flown on the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter and acquired over 200,000 upwelling and downwelling irradiance spectra during the Asian-Pacific Regional Aerosol Characterization Experiment (ACE-Asia) deployment (Japan, March/April 2001). Our objective was to perform radiative closure studies on the western Pacific atmosphere for different air mass types. Most of the flights included several horizontal legs above and below various aerosol layers. The analysis is very complicated because of multiple aerosol layers including large dust plumes at higher levels, sea salt at lower levels and intermediate layers of carbon, nitrates and sulfates.

We combined the upwelling and downwelling solar spectral flux with in situ optical depth data to calculate the radiative forcing due to the various aerosol layers. The difference in net flux at two different levels gives the absorption of the intervening layer. This radiative information combined with in situ chemical and particle size information will increase our understanding of how the various types of atmospheric aerosol particles affect the atmospheric energy budget.

Point of Contact: Maura Rabbette, (650) 604-0128,