Climatological Analysis in Identification of Pre-monsoon Convective Potential Zones over Eastern and North-Eastern States of India During the Last Four Decades

This study investigates the climatological variability and trends of thermodynamic parameters in four eastern and north-eastern Indian states Odisha, Bihar, Jharkhand, and Assam, during the pre-monsoon season (March–May) from 1980 to 2020 using high-horizontal resolution (0.25° × 0.25°) European Centre for Medium-Range Weathe (ECMWF) reanalysis (ERA-5) and hourly time interval data. For this purpose, the Mann–Kendall test has been implemented to analyse the spatial patterns of inter-annual variability and trends in convective available potential energy (CAPE), convective inhibition (CIN), CAPE/CIN ratio, and K-index to identify convective potential zones for the occurrence of thunderstorms. The climatological trend analysis of parameters reveals significant spatial variation in convective potential over the study region. The southeastern area of Odisha showed high atmospheric instability, with low CIN, higher CAPE ranging from 2000 to 3500 J kg⁻¹, and high values of CAPE/CIN ratios associated with the minimal spatial pattern of interannual variability, indicating a higher convective potential zone for the occurrence of thunderstorms. The analysis reveals that eastern Bihar and southeastern Jharkhand are noted to be convective potential zones. Results have shown that southwestern Assam is a significant convective, potentially active zone during the last two decades. Significant increases in dew point temperature, which represent greater availability of moisture and air temperature trends, were observed over these regions, aligning with the trends of the convective indices, signifying the convective potential of these regions. In alignment with the climatological analysis, higher occurrences of thunderstorms over southwestern Assam since 2000 are based on India Meteorological Department (IMD) reports.