Direct measurement of air and precipitation particle motion by very high frequency Doppler radar

Abstract

Microwave meteorological Doppler radars are the most efficient tool for understanding the dynamical properties of precipitating systems in the troposphere1. However, these radars do not directly observe ambient air motion, but rather the velocity of precipitation particles within a particular region. We have recently completed very high frequency (VHF) Doppler radar at Shigaraki, Japan (34.85° N, 136.10° E) which has enabled the three-dimensional motion of both air and precipitation particles to be observed simultaneously. In particular, it enables vertical air motion as well as precipitation fall speed to be directly observed. Doppler broadening of the precipitation echo reveals features which, when above the melting layer, are characteristic of snowflakes and, when below this layer, are characteristic of raindrops. Sensitive VHF (and, most likely, ultrahigh frequency, UHF) Doppler radars equipped with fast-beam steerability open new possibilities for the investigation of the dynamical properties of precipitation particles in close combination with ambient air motion.