土壤湿度年际变化对中国区域极端气候事件模拟的影响研究 Ⅱ.敏感性试验分析

Impact of Interannual Soil Moisture Anomaly on Simulation of Extreme Climate Events in China. Part Ⅱ: Sensitivity Experiment Analysis

利用NCARCAM3.1大气环流模式,设计了有、无土壤湿度年际异常的两组数值试验,探讨了土壤湿度年际异常对极端气候事件模拟的可能影响。结果表明,模式模拟的极端气候事件对土壤湿度异常十分敏感,土壤湿度异常对极端气候指标的多年平均空间分布、年际变率以及年际变化均具有重要影响。当不考虑土壤湿度的年际异常时:(1)模拟的暖夜日数、暖昼日数和热浪持续指数的发生频次在全国范围内均明显减少,而霜冻日数则明显增加。极端降水指标的响应表现出明显的空间差异,极端降水频次在江淮流域明显减小,而极端降水强度则表现为东北减弱、长江流域增强;中雨日数和持续湿期在我国大部分地区减少。(2)极端气温指标的年际变率在我国大部分地区呈减小趋势;而极端降水事件的变化则较为复杂,极端降水频次和极端降水强度的年际变率在长江以南有所增强,而北方地区则有所减弱。中雨日数和持续湿期的年际变率在我国呈现出较为一致的减少趋势。(3)模式对暖夜日数、霜冻日数的年际变化的模拟能力明显下降,并对4个极端降水指标的年际变化的模拟能力在全国多数区域均有不同程度的下降。

Using NCAR Community Atmosphere Model （CAM 3.1）, two numerical experiments are designed to explore the possible influence of the soil moisture anomaly on the simulation of extreme climate events. Results show that the simulated extreme climate events are sensitive to the soil moisture anomaly, and the anomaly has significant impacts on the climatology, interannual variability, and interannual variations of extreme climate events. Without the interannual anomaly of soil moisture included, the simulated Tn95p （warm nights）, Tx95p （warm days）, and HWDI （heat wave duration） significantly decrease in most areas of China, while FD （frost days） increases on the whole. It is also found that the response of the simulated precipitation extremes to the soil moisture anomaly exhibits significant spatial difference. The simulated P95p （the frequency of extreme heavy precipitation） obviously decreases in the Huaihe River basin, and R95p （the intensity of extreme heavy precipitation） also drops in the northeast of China but increases in the Yangtze River valley. Both the simulated R10 （number of days with precipitation greater than 10 mm） and CWD （the consecutive wet days） have experienced an evident drop in most areas of China. In addition, the interannual variability of the temperature extremes has decreased in most areas of China, but the situations of precipitation extremes are much complicated. Both the interannual variability of P95p and R95p decrease in North China and increase over the regions south of the Yangtze River. Throughout the whole country, the interannual variability of R10 and CWD decrease. Results also suggest that the performance of the model in simulating the interannual variations of the extreme climate indices, especially for Tn95p and FD, will become worse when the interannual anomaly of the soil moisture is removed.