Characteristics of Monsoon Semipermanent Features in Changing Climate: An Environmental Approach

Abstract

The Indian summer monsoon (ISM) spans four months beginning from June to September (JJAS) and produced extensive rainfall over Indian continents. The land-sea heating contrast is one of the major factors facilitating ISM. ISM is managed with the aid of several monsoon semi-permanent features (MSF) which include Pakistan heat low, cross-equatorial low-level jet over the Arabian Sea, and the tropical easterly jet over the Indian Ocean at 200 hPa, Mascarene High, and seasonal anti-cyclone over the Tibet. Any fluctuations in these SMF can strongly modulate Indian Summer Monsoon Rainfall (ISMR). Therefore, it is imperative that the structure and variability of MSF need to be examined in changing climate scenarios to assess its impact on the future monsoon. Further, ISM also experiences internal variability in terms of deficit and surplus years, therefore the impact of MSF on this variability also needs to be examined. The main objective of the study is to examine the variation of rainfall in JJAS over the Indian monsoon core region and the characteristics of SMF for two contrasting monsoon years. Based on the previous study observed that the monsoon core zone has an important role to play in the ISM so for the rainfall study take the monsoon core zone for the study purpose. The 5th generation European Centre for Medium-Range Weather Forecasts (ERA5), India Meteorological Department (IMD) rainfall datasets from 1981-2020, and Coupled Model Intercomparison Project Phase 6 (CMIP6) 2015-2021 for four different SSP scenarios. In addition, to determine the changes in these MSF and their impact on rainfall for ISM. For the calculation of rainfall percentage departure of IMD and ERA5 and CMIP6 dataset following Rajeevan et al. (2010).