Aerosol-Cloud-Radiation Interactions in the Arctic

University Of Utah, Salt Lake City UT

Investigators

Abstract

This grant supports an investigation of the way arctic haze interacts with low-level clouds to affect longwave and shortwave radiative fluxes at the ground. It is based on analysis of data from two observational sites near Barrow, Alaska. One is the NOAA Climate Monitoring and Diagnostics Laboratory (CMDL), which measures aerosol concentrations near the ground; the other is the DOE Atmospheric Radiation Measurement (ARM) site, which monitors cloud and atmospheric radiative properties with ground-based remote sensing equipment. New and existing algorithms will be used for inferring cloud microstructure, the net radiative flux, and the presence of precipitation from the observations. From the long records available, it will be possible to study the annual and interannual variability of these quantities. Concentrations of cloud condensation nuclei (CCN) will be estimated from measurements at the ground of aerosol concentration and scattered solar radiation. This requires information about the cloud droplet size distribution, which will be based on archival data from the University of Washington LEADEX experiment conducted in the Arctic in the spring of 1998 and from other field experiments. The project will evaluate the hypothesis that pollution-induced arctic haze causes stratus clouds to have smaller but more drops, leading to a higher infrared emissivity and increased longwave surface heating in the arctic winter and early spring. In addition, it will provide new information on the composition of wintertime arctic clouds, about which little is known. The results will lead to improved treatment of the radiative properties of clouds in climate models.