Intense Thunderstorms in the Tropics and Subtropics and Their Associated Atmospheric Environment

This study uses the full 16-year TRMM Precipitation Radar observation in conjunction with ERA-Interim Reanalysis to study the relationship between convective intensity and atmospheric environment. Convective intensity is defined by the lightning flash rate measured by TRMM satellite. Intense thunderstorms with flash rate greater than ~0.60 flash/second are found to occur preferentially over some particular subcontinents containing southeast of United States, southeast of South America, Central Africa and Sahel, Ganges Plain and Bangladesh etc. Composite environmental profiles at times and locations of convective features in selected interesting regions show that instability as measured by convective inhibition (CIN) and convective available potential energy (CAPE), and low-level (1-3 km) wind shear have considerable skill in distinguishing environments of intense thunderstorms and weak or non-flash-producing storms. Composite anomalies of each atmospheric field for days when storms occurred are used to investigate the environmental conditions associated with different intensities of storms. Results indicate that intense-thunderstorm environment in different regions share the similar characters: low-level layer of moist airflow moves over the hot arid sub-continent; it is capped by an elevated layer of warm dry air. The low-level restraining inversion or “lid” allow the low-level jet with high moisture content to build up extreme buoyancy and thus enhance the intensity of storm. Quantitative relations between convective intensity and atmospheric predictor variables including 1D, 2D, 3D, etc. are built. Based on these statistical associations, the estimations or reconstructions of geographical distribution of intense thunderstorm are attempted. Low-level wind shear is the best predictor and the general pattern of distribution is well reproduced by this single variable.