Assessing the convective available potential energy and convective inhibition derived from ERA5 data over eastern India

Abstract

Convective available potential energy (CAPE) and convective inhibition (CIN) are widely used thermodynamic indicators for diagnosing convective environments and supporting nowcasting of thunderstorm potential. Because reanalysis products provide continuous spatial coverage and long-term consistency, they are increasingly applied for regional assessments of convective instability. However, their reliability depends on how well they reproduce the observed vertical thermodynamic structure. This study evaluates ERA5-derived CAPE and CIN against radiosonde observations for the pre-monsoon season (March-May) over eastern India, during 1987-2016 at Bhubaneswar and Kolkata, and 1994-2016 at Ranchi. The analysis shows that ERA5 CAPE biases are strongly dependent on station, month, and launch time. At 00:00 UTC, ERA5 CAPE is slightly underestimated at Bhubaneswar in March but becomes overestimated in April and May, while Kolkata exhibits consistent CAPE overestimation across March to May; Ranchi shows a significant overestimation at 00:00 UTC, intensifying toward May. At 12:00 UTC, ERA5 CAPE underestimated values in March at Bhubaneswar and Kolkata but shifted to significantly overestimated values in April-May. For CIN, ERA5 consistently overestimates values at 00:00 UTC at all three stations (except for Kolkata in May), while at 12:00 UTC, it is generally overestimated at Bhubaneswar and Ranchi, and it shows a sign change at Kolkata (negative in March, positive in April-May). Correlations between ERA5 and radiosonde CAPE and CIN are weak, suggesting limited skill in reproducing day-to-day variability. Profile diagnostics further indicate that temperature is well represented by ERA5, whereas relative humidity errors (most pronounced at Ranchi) dominate the instability biases.