Epochal Changes in the Intrinsic Nature/Dynamics of Flood and Drought During Indian Summer Monsoon

Abstract

The basic and derived meteorological parameters, are important factors that affect the epochal changes of monsoonal drought/flood events which consequently influence the socio‐economic aspects of India. The anomalous tricade departure of parameters namely rainfall, surface pressure, surface temperature, zonal and meridional wind, cloud cover (CC), outgoing longwave radiation, latent heat flux (LHF), sensible heat flux, net incoming shortwave radiation flux and net heat flux (NHF) have been considered between past, and recent tricade respectively drought and flood events. An anomalous decrease (−3 to −2 mm/d) in rainfall over the southern Arabian sea (AS), southern peninsular India and Bay of Bengal during past and recent tricade, on the other side increase (2–2.5 mm/d) in rainfall over the equatorial Indian ocean (EIO) during drought. The drought episode of the recent tricade is showing basin wise significant increase in LHF (20–30 W/m2) and decrease in NHF (−30 to −60 W/m2) from the Somali coast to Indonesian region which is linked with changing oceanic processes linked with the Indian ocean warming. The comparison of past and recent monsoonal flood has shown decrease in the CC over EIO and AS region which supported anomalous highest departure in LHF (12 W/m2) over EIO. A direct association of dry and moist static energy variations have been found to be linked with the surface fluxes during Indian summer monsoon season. Further, epochal differences of vertically integrated moisture flux convergence is consistent with flood/drought rainfall anomaly. Thus, radiative imbalance also plays a secondary role in determining epochal nature of drought/flood variability and its nature.