Evaluation and projection of extreme events over China under IPCC A1B scenario by MM5V3 model

Based on the regional climate model MM5V3 nesting in one-way mode within the general circulation model ECHAM5, two sets of the 50 km grid spacing simulation for present climate (1978-2000) and future climate (2038-2070) over China are conducted. Results for present extreme climate show that MM5V3 model can simulate reasonably well the spatial and probability distributions of daily maximum / minimum temperature and annual mean heavy and torrential rainy days when compared with observations. But the simulated maximum temperatures biased to cold over most part of China and the minimum temperatures biased to warm in northwestern China and to cold in southern China. Simulated probability distributions move to the lower frequency range for maximum case and significantly higher around the peak of 0 degrees C for minimum case. The heavy and torrential rainy days are overestimated obviously over eastern China and the probability distributions are both larger than observations. Under IPCC AM Scenario, the results for climate change show that there would be increasing amplitudes in maximum id temperature, minimum id temperature, average temperature above 95th percentile of daily maximum temperature climosequence, but decreasing amplitudes in total number of frost days. The total number of hot days and average temperature under 5th percentile of daily minimum temperature climosequence would also increase over most part of China except the Tibetan Plateau and Xinjiang areas. Linear trends of extreme temperature indices would overall increase except the frost-days and average temperature under 5th percentile of daily minimum temperature climosequence. The changes for extreme precipitation indices indicate the regional characteristics. There would be the increasing amplitudes over Yangtze-Huaihe River Basin, southeast China, southwest China as well as decreasing amplitudes over Northeast China, Inner Mongolia areas for all analysis indices (maximum id precipitation, maximum 5d precipitation total, maximum number of consecutive dry days, No. of days with precipitation >= 25 mm/day, simple daily intensity index and total precipitation above 95th percentile of daily precipitation climosequence). The precipitation over southern China would become more "extreme" in future. Meanwhile, the linear trends for extreme precipitation indices would also increase except the maximum number of consecutive dry days.