Diagnosis of a Polar Low Warm Core Utilizing the Advanced Microwave Sounding Unit

Abstract

Data from the Advanced Microwave Sounding Unit (AMSU) are used to examine a polar low that occurred in the Labrador Sea on 17?18 March 2000. During its 40-h lifetime, the polar low was observed three times by AMSU, which captured the formation and subsequent intensification of the storm. The AMSU-A channel-5 (53.6 GHz) brightness temperature field clearly identifies the warm core structure of the polar low, with storm center measurements 2?3 K higher than the background environment. Analysis of these data over time can provide a straightforward and real-time method for tracking storm motion and estimating surface wind speed. The impact of cloud, surface, and moisture variability on the measurements at 53.6 GHz is examined. Although they cannot account for the magnitude of warming, the analysis of additional AMSU frequencies illustrates not only how nonatmospheric temperature effects can subtly influence the structure of the channel-5 brightness temperature field but also how they can provide insight into the polar low and its environment.