A Doppler Sodar Case Study of Top-Down Convection and Convective Dissipation of Stratus

Abstract

Stratus dissipation over the Swiss Plateau has long been a forecasting problem. A case study of stratus structure and development was conducted during the winter of 1997/98. Measurements were performed with the monostatic Doppler sodar of the Swiss Federal Institute of Technology, Zürich, to supplement conventional observation methods. A pyranometer, a second sodar, and a sonic anemometer were also intermittently available. Sodar echo patterns and vertical velocity data have been investigated with respect to the inversion height, especially during stratus dissipation. Typical cloud-dissipating processes, such as convection, top-down convection, and advection have been discerned. The results show that sodar measurements can supplement other observation methods in a useful way, especially when the data analysis of echo patterns and high-resolution vertical velocities are combined.