First Doppler weather radar studies of the wintertime meteorology of interior Alaska

Abstract

A weather surveillance radar model 88–D (WSR–88D) was installed on Pedro Dome, a hill approximately 23 km north of Fairbanks, in the late summer of 1993. The radar commenced operation in September 1993. The Fairbanks radar was the first Doppler weather radar installed in Alaska and the farthest north modern weather radar in the world. During the winter of 1993–1994 the Fairbanks radar gave meteorologists their first detailed look at the meteorology of interior Alaska. The area encompassed by the radar's field of view includes complex terrain—both large flatlands and highlands reaching more than 1 km above the valley floor.

This new opportunity yielded some surprises. Foremost among them is the unanticipated complexity and small scale of meteorological processes during the winter in an Arctic region. Sequences of composite reflectivity show a consistent pattern of considerable change over time spans of 10–30 minutes, as well as large variance of reflectivity over distances of 10 km or less. The reflectivity patterns are often composed of banded structures, with small granular areas of higher echo return embedded within. The large-scale bands can be correlated to synoptic scale patterns of wind aloft, while the smaller cellular structures in the bands may be partly attributed to upslope flow over hills. However, some areas of strong radar return appear to have no relation to topography. The high stability of the airmass over Fairbanks most of the winter would appear to rule out convection. Gravity waves at the top of strong temperature inversions are a possible cause. It is presumed that other processes are at work in this scene, and they remain unexplained.