Identifying the changes in winter monsoon characteristics over the Indian subcontinent due to Arabian Sea warming

Abstract

This study investigated the impact of the Arabian Sea (AS) warming in modulating the winter precipitation over the Indian subcontinent and associated dynamical response such as subtropical jet variability using regional climate model, RegCM4.7 of the International Centre for Theoretical Physics (ICTP). In this regard, a control run (RegCTL) is forced by real sea surface temperature (SST), and two sensitivity experiments with uniformly increased SST over AS by 0.45 °C (RegSST45) and 0.90 °C (RegSST90) are performed. The results obtained from a control experiment (RegCTL) are compared with corresponding values from RegSST45 and RegSST90 to assess the warming impact. The model (RegCTL) realistically simulates the circulation features, precipitation, and temperature over the Indian subcontinents in the winter season (November–December-January-February; NDJF) during 2006–2015. It is found that AS warming increases the precipitation over most parts of India during winter. The precipitation response varies with the month (NDJF) and the magnitude of AS warming. In general, precipitation is found to intensify with increasing AS warming over northern India and adjoining south Asian nations like Afghanistan, Pakistan, and some parts of Burma and Nepal. The strengthening of STJ is observed due to AS warming (RegSST45). The strengthening of the subtropical jet (STJ) persists with an intensification of AS warming (RegSST90); however, the magnitude of strengthening is less than RegSST45, which is consistent with the corresponding increase of precipitation over India. Cold wave duration is found to be significantly sensitive to the intensity of AS warming. It is noticed that the AS warming increases the cold wave duration over the northern part of India with major increases over the western Himalayan region.