Observations of tropical convection events using Indian MST radar: first results

Abstract

Mesoscale convective events, associated with severe weather, play a significant role in troposphere-stratosphere coupling processes. Deep convection occurs very often at tropical latitudes. The convection events result in the transport of energy from the lower troposphere to the upper troposphere and stratosphere, and may also affect global circulation. In the Indian tropical region, meteorological convection events are a common occurrence during the months of May to December. In the present study, very-high-frequency radar located at Gadanki (13.45°N, 79.18°E), a tropical station in India, is used to make observations of winds, turbulence and stable-layer structures, during the passage of convective events over the radar site under different synoptic situations. Radar observations of vertical velocity show enhanced up and down draughts during the passage of convection events. Height and time cross-sections of radar-observed signal-to-noise ratio clearly show distinct regions of enhanced signal intensity, indicating height and time Structures of enhanced atmospheric turbulence associated with the convection. It is also noted that stable-layer structures associated with the tropical tropopause are not well defined during the passage of convection. This suggests 'weakening' of stable-layer structures during the convective activity. The present observations also show enhanced mass flux, both in upward and downward directions, through the tropopause, indicating mass exchange between troposphere and stratosphere during the period of convective activity.