Identification of Atmospheric Fronts over the Ocean with Microwave Measurements of Water Vapor and Rain

Abstract

This Paper describes some basic research techniques and algorithms developed to diagnose fronts in cyclonic storms over the ocean with data from satellite-borne microwave radiometers. The need for this research stems from the limited availability of reliable weather reports over the ocean. In earlier work, we found that a strong gradient in integrated atmospheric water vapor is a good indicator of surface locations of fronts in midlatitude cyclones over the oceans. A second significant indicator of frontal activity is precipitation. Therefore, we have developed methods for flagging strong gradients in integrated atmospheric water vapor and the presence of rain by using data from the Scanning Multichannel Microwave Radiometer (SMMR) on board the polar orbiting Seasal and Nimbus-7 satellites. Examination of 65 frontal systems showed that the water vapor gradient flag correctly identified 86% of the fronts, while the precipitation flagged 91%. The two types of flags emphasize different portions of the cyclone and are therefore complementary. Ultimately, these techniques are intended for operational use with data from the Special Sensor Microwave Imager (SSM/I) which was launched in June 1987 on a satellite in the Defense Meteorological Satellite Program (DMSP). Special Sensor Microwave Imager data can be received in real-time by suitably equipped field stations, but this opportunity is currently restricted to U.S. Naval vessels and other military installations.