Influence of Thermodynamic Indices During Severe Convection over Andaman Nicobar and Lakshadweep Islands

The current work is an attempt to study various parameters that influence the occurrence of severe convective activity over two regions, Andaman and Nicobar islands (AND) and Lakshadweep (LAK). k index (KI), total totals index (TTI), Modified K-index (MODKI), Modified total totals index (MODTTI), total precipitable water (TPW), humidity index (HI), deep convective index (DCI), lifted index (LI), convective available potential energy (CAPE) and convective inhibition (CIN) are the parameters used in this analysis. ECMWF Reanalysis 5th Generation (ERA5) and Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA2) reanalysis daily datasets were utilized to study the severe convective activities during 2019. The modified indices of KI and TTI parameters clearly indicated the good chances for occurrence of severe convective systems in monsoon season. The spatial distributions clearly indicated the strong impact of south westerly winds on these islands which lead to the occurrences of high rainfall activity on these islands. The westerly wind values (7 to 9 m/s) are higher over LAK region than AND region (4 to 8 m/s). High sea level pressure (SLP) values help the intensification of south-westerly winds that lead to severe rainfall over islands. The sea surface temperature (SST) values 30 to 30.5 °C were observed over AND and LAK regions. AND region received good rainfall in winter and monsoon season, whereas LAK region receives higher rainfall in monsoon and post-monsoon season. We may infer from this analysis that LAK region has more convection occurrences than AND region. The WRF model prediction was found to be accurate with ERA5 reanalysis data. The WRF model was useful in predicting the severe convective activities prior to their occurrence.