High-Resolution VHF Radar Measurements in the Troposphere with a Vertically Pointing Beam

Abstract

Measurements using the Sounding System (SOUSY) VHF radar in the Harz Mountains, Germany, were carried out in the troposphere and lower stratosphere in the summer of 1996. To study the structure and the dynamics with high temporal and spatial resolution, the beam was pointing continuously in the vertical direction, and a 75-m range resolution was used. Three case studies are analyzed in detail: one within a frontal passage, one during a developing ridge, and one during a thunderstorm. Fine structures in the echo intensity that could not be resolved with the standard resolution of 300 m are observed during the frontal passage and are related to humidity fluctuations. Integrating the high-resolution velocity data with time makes it possible to estimate vertical displacements that are used to indicate vertical transport. The velocities are analyzed harmonically and interpreted as waves with periods of about 6 h and amplitudes of a few centimeters per second. Stable layers evident in the troposphere and lower stratosphere during the approach of a building ridge of anticyclonic flow have slopes with time reminiscent of the latitudinal pattern of the isentropes of the larger-scale flow field. Observations during the thunderstorm reveal strong convective cells with periods of about 10?20 min, associated up- and downdrafts, and a series of persistent stable layers in the troposphere ahead of the thunderstorm.