The dynamical influence of energy fluxes in modulating variability of the Indian summer monsoon

Abstract

The surface heat fluxes have a significant role in shaping the Indian summer monsoon (ISM) dynamics. The present study investigates the climatological tricadal and decadal variability of surface energy fluxes viz., net shortwave radiation flux, latent heat flux (LHF) and net heat flux (NHF) during ISM season. For that purpose, a long-term (1961–2020) reanalysis data sets derived from the European Centre for Medium-Range Weather Forecasts fifth-generation (ERA5) and National Center for Environmental Prediction-National Centre for Atmospheric Research reanalysis (NCEP-NCAR) has been considered. Significant regional differences and changing patterns have been observed in the distribution of energy fluxes over southern peninsular India, Arabian Sea (AS), Bay of Bengal (BoB), Equatorial Indian Ocean (EIO), and Southern Indian Ocean. The BoB and AS emerge as vital moisture sources, directly contributing to the monsoon rainfall over eastern, central and western India, respectively. A significant positive change in LHF is observed over AS (9W/m2) and EIO (12W/m2) regions, whereas over the BoB region, a negative departure of −8 W/m2 has been persistent in the recent tricade. These changes correspond to the significant negative anomalous patterns of NHF, i.e., −11 W/m2 over AS and −18 W/m2 over EIO, alongside the highest increase in NHF value over the BoB regions (20 W/m2). The pronounced tricadal phase shift of surface fluxes over AS, EIO, and BoB is identified as a contributing factor influencing ISM rainfall. © 2025 Elsevier Ltd