Characteristics of spectral energetics during excess and deficient rainfall years in India

Abstract

Significant spatial and temporal deviations from the seasonal mean precipitation, such as severe droughts (deficient rainfall) and floods (excess rainfall), have a major influence on India. The non-linear energy interactions between the various scale atmospheric systems are important as they play a crucial role in the Indian summer monsoon variability. Since studies have yet to look at the whole energy budget of the southwest monsoon, it is necessary to accurately capture these energy exchanges to represent the monsoon circulation better. In this study, we found the exact nature of complex non-linear energy interactions of synoptic-scale mainly low-pressure systems (LPSs) and Intraseasonal Oscillation (lSO) 30-60 day scale with other scales, including the seasonal mean, Indian Ocean Dipole (IOD), and El Niño–Southern Oscillation (ENSO) using the in-scale and out of scale energetics. These energy interactions are calculated in the frequency domain for the Indian monsoon region using the ECMWF ERA-5 data for 72 years (1950-2021) during the monsoon season (JJAS). Since the seasonal mean kinetic energy is highly correlated with the seasonal mean rainfall, we explored how these energy exchanges vary during excess and deficient rainfall years. We also found that the ISO and synoptic scale systems influence the interannual variability of the Indian Summer Monsoon mainly through the interactions with the mean flow. In addition, the monsoon mean flow and most energy exchanges show a significant relationship at the upper level (200 hPa) and lower level (850 hPa) atmosphere.