Simulating Future Climate Changes over North China with a High Resolution Regional Climate Model

Multi decadal climate change simulations have been performed over China using 20 km horizontal resolution regional climate model (RegCM3) one way nested within a global model (FvGCM/CCM3, here in after called FvGCM) from NCAR/NASA. Two experiments are conducted, one for the period of 1961—1990, the other is for the future climate of 2071—2100 under the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emission Scenarios (SRES) A2 emission scenario. The analysis focuses on the warm half of the year, from April to September. First, simulations of present climate conditions over North China by FvGCM and RegCM3 are compared with observations to assess the model performance. Results show that both models can reproduce the observed spatial patterns of surface air temperature and precipitation. Compared with FvGCM, RegCM3 shows a better performance especially in providing more spatial details of the surface variables. The changes (differences between future and present) of mean temperature and precipitation are analyzed and compared between the two models simulations. Significant warming in the end of 21st century is predicted by both models however their results are different both in spatial distribution and amount. Compared with FvGCM, a greater warming is simulated by RegCM3 in some areas of the northern part while in the southeast and the east of the region RegCM3 indicates the warming is slighter. General increase in mean precipitation is found in FvGCM simulation, in a range of less than 10% to exceeding 30%. While for RegCM3, the simulated precipitation increases in the north of Henan as well as Shandong, but changes little or even decreases in the northern part of the region is simulated. Future changes in extreme heat events simulated by RegCM3 are statistically analyzed using the days with daily maximum temperature no less than 35 ℃(D_T35) and the days with a heat index which includes the humidity factor also no less than 35 ℃(D_HI35). Results show a substantial increase of D_T35 over the whole region and increase of D_HI35over the plain areas. Increase in the maximum number of consecutive dry days (CDD) is also simulated by the model over the region, especially in the north of Hebei Province. According to the classification of UNEP drought index (A_U), there will be significant less humid area and a corresponding increase of dry sub humid and semi arid, indicating the future increase of drought extent in the future over the region.