UHF wind profiler observations during a tropical pre-monsoon thunderstorm — A case study

Abstract

This paper describes an investigation of a pre-monsoon thunderstorm that occurred over a tropical station, Pune (18°32′N, 73°51′E), India from observations made using a 404 MHz wind profiler (UHF radar). High resolution profiler data has been used to investigate the time–height variations of vertical velocities, echo power, spectral width and horizontal wind shear in the height range 1.05 km to 8 km on 16 May 2004 during 0800 to 2100 h local time. Rapidly varying vertical velocities (updrafts and downdrafts) and large values of vertical spectral width indicating changes in rain drop size distributions during the period of intense convective activity have been observed. Also, enhanced echo strengths associated with the radar bright band and increased low level wind shears have been noticed. The precipitation echoes dominate the UHF signal with Doppler velocity of hydrometeors reaching as high as 7 m s − 1 . The vertical profile of radar measured horizontal wind direction shows the ‘veering’ of wind indicating the presence of low-level warm air advection. Temporal variations in surface meteorological parameters recorded at the radar site showed changes typical of the various stages of a tropical pre-monsoon thunderstorm with a pressure deficit of about 4 hPa at peak activity. UHF radars/wind profilers provide wind information at high temporal and spatial resolution which is useful to study events of convection in detail.