The Uncertainty Of Projection Of Precipitation Change In The Middle And Lower Reaches Of The Yangtze River Under Global Warming

Based on examining the capabilities of 24 CMIP5 models simulate the 1950-1999 precipitation time series,climatic state average and spatial distribution of summer precipitation in the middle-lower reaches of the Yangtze River(MLRYR),Under the RCPs emission scenarios,the precipitation changes in the MLRYR in the 21st century from 2050 to 2099 are estimated,and the differences in the estimated results under three different emission scenarios are compared.In addition,taking the RCP8.5 high-emission scenario as an example,the summer precipitation changes in the MLRYR under the global warming were analyzed,and the following conclusions as below:the model predicts the MLRYR in the 21st century under different emission scenarios has some differences between the annual and interdecadal changes of precipitation from 2050 to 2099,and the prediction results for the spatial distribution of precipitation are consistent,and the changes in summer precipitation are not obvious.Under the RCP8.5,the multi-modle ensemble(MME)estimates that the summer precipitation in the MLRYR will increase by a small amount.On the one hand,due to global warming,the increase in temperature will cause the atmospheric water vapor content to gradually increase,which is conducive to the increase in precipitation.On the other hand,under the global warming,the South China Sea summer monsoon is weakened.The weakened summer monsoon is not conducive to the increase in precipitation.Under the combined effect of the two,the average summer rainfall forecast in the MLRYR by the MME will not change significantly.However,the prediction result of this model has great uncertainty.The analysis shows that the uncertainty of the model's prediction of precipitation changes mainly comes from the uncertainty of the prediction of large-scale summer monsoon circulation changes.The increase in water vapor has little effect on the uncertainty of precipitation changes.Further research on this source of uncertainty shows that the changes of the precipitation and the EASM circulation in the MLRYR have a strong correlation with the warming amplitudes of the North Atlantic and the Northwest Pacific,with the North Atlantic having a more significant impact.This shows that under the global warming,the warming of the North Atlantic and Northwest Pacific sea surface temperature has a great influence on the prediction results of precipitation changes in the MLRYR;if the uncertainty of the forecast of the North Atlantic and Northwest Pacific sea surface temperature changes can be reduced,Then the prediction of precipitation will be more reliable.