Projection of the spatial and temporal variation characteristics of surface air temperature over central Asia in the next 50 years in the Beijing Climate Center Climate System Model V1.1

Based on the CRU(Climatic Research Unit) dataset and the outputs of the historical and 4 representative concentration pathways (RCPs) future projection experiments from the BCC-CSM1.1 (Beijing Climate Center Climate System Model version 1.1) climate model for the IPCC AR5(Intergovernmental Panel on Climate Change: the Fifth Assessment Report), the temporal and spatial distributions of the annual mean surface air temperature over central Asia under the four RCPs during 2011 to 2060 have been studied by using the trend analysis, moving average, and EOF methods. Comparison of the BCC-CSM 1.1 historical experiment outputs with the CRU observed data showed that the BCC-CSM 1.1 model well simulated the significant upward trend, temporal evolution and spatial distribution of the annual mean surface air temperature over central Asia during the past 109 years(1901-2009). The annual mean surface air temperatures regionally averaged over central Asia in the future projection experiments under the 4 RCPs all displayed warming trends in the next 50 years (2011-2060). It also can be noted that the temperature warming rates and the regions with significant increasing temperature rates increase with the increased RCPs. The EOF analysis results showed that the features of the main EOF modes of the annual mean surface air temperature over central Asia from the 4 RCPs experiments arc very similar to their historical patterns. The EOF1 mode and its time coefficients show that the annual mean surface air temperature over central Asia will spatially consistently increase in the next 50 years. The warming rates of the annual mean surface air temperature over central Asia increase with the increased green gas emission, and further analysis showed that a cyclonic (anticyclonic) anomalous circulation at 850 hPa level associated with the EOF1 modes of the projected annual mean near surface air temperature under the 4 RCPs in the next 50 years resulted in the spatially consistent increase in the annual mean near surface air temperature over central Asia. However, the EOF2 modes of the annual mean surface air temperatures from the 4 RCPs future projections all show significant features of inverse phase for the north to the south over central Asia. Corresponding time coefficients have no significant linear trends and show fluctuations within a narrow range.