ALBERT

Description: [1]  Changes in the hydrological cycle being caused by human-induced global warming are triggering variations in observed spatiotemporal distributions of precipitation and temperature extremes, and hence in droughts and floods across China. Evaluation of future climate extremes based on General Circulation Models (GCMs) outputs will be of great importance in scientific management of water resources and agricultural activities. In this study, 5 precipitation extreme and 5 temperature extreme indices are defined. This study analyzes daily precipitation and temperature data for 1960-2005 from 529 stations in China and outputs of GCMs from the Coupled Model Intercomparison Project Phase 3 (CMIP3) and Phase 5 (CMIP5). Downscaling methods, based on QQ-plot and transfer functions, are used to downscale GCMs outputs to the site scale. Performances of GCMs in simulating climate extremes were evaluated using the Taylor diagram. Results showed that: (1) the multimodel CMIP5 ensemble performs the best in simulating observed extreme conditions; (2) precipitation processes are intensifying with increased frequency and intensity across entire China. The southwest China, however, is dominated by lengthening maximum consecutive dry days and also more heavy precipitation extremes; (3) warming processes continue with increasing warm nights, decreasing frost days and lengthening heat waves during the 21 st century; (4) changes in precipitation and temperature extremes exhibit larger changing magnitudes under RCP85 scenario; (5) for the evolution of changes in extremes, in most cases, the spatial pattern keeps the same, even though changing rates vary. In some cases, area with specific changing properties extends or shrinks gradually. The directions of trends may alter during the evolution; and (5) changes under RCP85 become more and more pronounced as time elapses. Under the peak-and-decline RCP26, changes in some cases don't decrease correspondingly during 2070-2099 even though the radiative forcing during 2070-2099 is less than during 2040-2069. The increase of radiative forcing triggers considerable regional variations in consecutive dry days, but causes only slight changes in the areal average in China. The results of this study imply higher flood risk across entire China but intensifying droughts in south China in the 21 st century, and also more heat-related losses in east coasts of China.

Description: [1]  Outputs of 5 Earth System Models (ESMs), including CanESM2, GFDL-ESM2G, MIROC-ESM-CHEM, MPI-ESM-MR, and NorESM1-M under historical and Representative Concentration Pathways (RCPs) from the Coupled Model Intercomparison Project phase 5 (CMIP5) multi-model dataset, as well as daily precipitation from 527 rain gauge stations in China for the period of 1960-2005 are used, employing 8 precipitation indices, to investigate the spatiotemporal variations of precipitation extremes over China for 2071-2100. After the evaluation of the indices by the Mann-Whitney U test and the quantile-quantile plot (Q-Q plot), the Weather Generator Model (WGEN) is used to downscale precipitation extremes. The average of precipitation extremes and values of the 5- and 20-year return periods under RCP26 and RCP85 scenarios are analyzed. Results showed that: (1) WGEN performs satisfactorily in downscaling daily precipitation in China, particularly in wet seasons and also works well in downscaling extreme heavy precipitation indices and consecutive dry days; (2) the risks of meteorological droughts and floods resulting from extreme long-duration precipitation would decrease in southwest China, but the risks of floods due to extreme heavy precipitation would increase. In north and southeast China, the risks of droughts would decrease but floods might occur with higher frequencies; (3) the spatiotemporal variations of averages and values of 5-year return period extreme precipitation would be similar, but those of 20-year return period would be a little different: the 20-year consecutive dry days would decrease faster, and the 20-year values of other indices would increase relatively slower; (5) the spatial patterns of changes in precipitation extremes under RCP26 and RCP85 would be similar, but the changes in RCP85 would be intensifying. Results of this study map the spatiotemporal patterns of precipitation extremes during 2071-2100, providing scientific information for water resources management and the mitigation of the impacts of climate change.