Evaluation of CMIP5 coupled atmosphere-ocean general circulation models and projection of the Southeast Asian winter monsoon in the 21st century

Abstract

The Southeast Asian (SEA) winter monsoon (December–February) precipitation simulation and the potential future climate changes may bring about under different representative concentration pathways (RCPs) were evaluated using ten coupled atmosphere–ocean general circulation models (AOGCMs) in the fifth phase of the Coupled Model Intercomparison Project (CMIP5). Although all the models simulated the broad features of winter monsoon precipitation spatial patterns, the spread of the bias magnitudes was very large across the AOGCMs. All the models simulated the relationship between the regional rainfall and circulation associated with El Niño-Southern Oscillation (ENSO). However, the strength of the association tended to be weaker in the simulations, ensuing a generally weaker winter monsoon rainfall interannual variability. Three AOGCMs, namely CNRM-CM5, NorESM1-M and IPSL-CM5A-MR, that simulated the most realistic present-day climate, were used for examination of future climate projection based on the RCP 2.5, RCP 4.5 and RCP 8.5 scenarios. The projections showed a gradual increment of SEA winter monsoon rainfall under all the scenarios with the highest changes in the RCP 8.5 scenario. The increment was manifested as a zonal band of positive anomalies located at ∼10°N and ∼5°S, indicating northward and southward expansion of the intertropical convergence belt. Between these bands of increasing rainfall, the equatorial South China Sea (SCS) area was projected to be slightly drier. The projected increase of rainfall appeared to be associated with the prevailing of cyclonic anomalies over the centre SCS, which promote enhance moisture convergence over this region in the warmer climate.