Polar Low Structure over the Northern Gulf of Alaska Based on Research Aircraft Observations

Abstract

During the 1987 Alaska Storms Program, a polar low that developed over the northern Gulf of Alaska was investigated during two flights by a WP-3D research aircraft on successive days. Analyse based on data obtained from omega dropwindsondes during the first flight showed the small (?300 km) horizontal scale of the vortex The vortex center was characterized by suppressed cloudiness on both days and was decidedly warmer at low levels than its surroundings. The vorticity associated with the polar low was largest new the surface and decreased rapidly with height on the first day, with only a very weak circulation evident by 700 mb. Coldest 500-mb temperatures and lowest static stabilities were found directly above the surface low. On the second day the vortex was more intense at midtropospheric levels than on the previous day, and convective clouds extended to higher levels.