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

Mesoscale convective events, associated with severe weather, play a signifi cant role in troposphere stratosphere coupling processes. Deep convection o ccurs very often at tropical latitudes. The convection events result in the transport of energy from the lower troposphere to the upper troposphere an d stratosphere, and may also affect global circulation. In the Indian tropi cal region, meteorological convection events are a common occurrence during the months of May to December. In the present study, very-high-frequency r adar located at Gadanki (13.45 degreesN, 79.18 degreesE), a tropical statio n in India, is used to make observations of winds, turbulence and stable-la yer 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 enhan ced signal intensity, indicating height and time structures of enhanced atm ospheric turbulence associated with the convection. It is also noted that s table-layer structures associated with the tropical tropopause are not well defined during the passage of convection. This suggests 'weakening' of sta ble-layer structures during the convective activity. The present observatio ns also show enhanced mass flux, both in upward and downward directions, th rough the tropopause, indicating mass exchange between troposphere and stra tosphere during the period of convective activity.