Observational aspects of tropical mesoscale convective systems over southeast India

To enhance the knowledge of various physical mechanisms related to the evolution of Tropical Mesoscale Convective Systems (MCSs), detailed analysis has been performed using suite of observations (weather radar, electric field mill, surface weather station, flux tower, microwave radiometer and wind profilers) available at Gadanki (13.5°N/79.2°E), located over southeast India. Analysis suggests that these systems developed in warm, moist environment associated with large scale low level convergence. Significant variations in cloud to ground (CG) lightning activity indicate the storm electrification. Deep (shallow) vertical extents with high (low) reflectivity and cloud liquid water; dominant upward (downward) motion reveals variant distribution in convective (stratiform) portions. Existence of both +CG and –CG flashes in convective regions, dominant –CG in stratiform regions explains the relation between lightning polarity and rain and cloud type. Sharp changes in surface meteorological variables and variations in surface fluxes are noticed in connection to cold pool of the system. Increase (decrease) in temperature, moisture and equivalent potential temperature (θe) within the boundary layer in convective (stratiform) regions associated with latent heat warming (cooling) of air parcel are apparent. Presence of updrafts and downdrafts in convective region and dominant downdrafts in stratiform regions are evident from vertical velocity measurements. Isentropic upgliding (downgliding) illustrate the existence of isentropic ascents (descent) of air parcels in the storm vicinity. Veering (backing) of wind due to warm (cold) and moist (dry) air advections demonstrated the formation of θe ridge in storm environment. Blend of observations provided considerable insight of electrical, microphysical, thermodynamic, dynamic and kinematic features of MCS.