Evaluation of future rainfall over Southeast Asia using the CMIP6 multi-model ensemble

Abstract

A multi-model ensemble from the new Coupled Model Intercomparison Project Phase 6 (CMIP6) models was utilized to determine the future changes in precipitation over Southeast Asia. The changes are computed for the three (3) future time slices (2021–2040, 2041–2060, and 2081–2100) under four (4) different scenarios based on the Shared Socioeconomic Pathways (SSPs): 1-2.6, 2-4.5, 3–7.0, and 5-8.5. Our results indicate that future rainfall in the SEA-averaged region could increase by about 4%, 5%, 6%, and 9% towards the end of the century relative to the present-day average (1995–2014) under SSP1-2.6, 2-4.5, 3–7.0, and 5-8.5, respectively. Among all scenarios, SSP3-7.0 widely shows remarkably dry conditions whereas SSP5-8.5 suggests extremely wet conditions on different time scales. Simulations revealed that large areas of the mainland SEA, the Philippines, and maritime Indonesia would tend to be drier in the near-term (2021–2040) and mid-term (2041–2060) during DJF and MAM but relatively wetter in the mid-term during JJA and SON, in a warmer climate. A clear dissociation of wet and dry areas is expected in the far-term period (2081–2100). The drying (wetting) condition over these regions is caused by a minimal (significant) increase in atmospheric moisture content accommodated with suppressed (enhanced) monsoon flow. Changes in the annual cycle indicate that future monsoon could also experience significant increases in rainfall. Changes in rainfall are also found to be sensitive to global mean temperature. The responses to future rainfall changes per degree Celsius of warming are at the rate of 8.9%, 6.3%, 3.6%, and 2.7% under SSP1-2.6, 2-4.5, 3–7.0, and 5-8.5, respectively.