热带气旋对1975-2018年暖季中国极端降水气候态、变化趋势及其与温度关系的影响研究

全球变暖背景下我国极端小时降水和极端日降水(EXHP、EXDP)气候态及变化趋势的区域差异明显, 其中热带气旋(TC)的影响尚不明确。利用1975-2018年暖季台站小时降水(P)和热带气旋最佳路径等资料, 采用百分位法定义极端小时降水与极端日降水, 并将总降水(All)客观分为热带气旋降水与非热带气旋(nonTC)降水, 分析热带气旋对中国东部All-P、All-EXHP、All-EXDP的气候态和变化趋势以及极端小时降水随温度变化的影响。主要结论如下: (1) TC-P、TC-EXDP、TC-EXHP占其对应总降水之比均从东南和华南沿海向西北内陆递减, 区域平均而言, TC-P占All-P之比与TC-EXHP占All-EXHP之比均约为11%, 而TC-EXDP占AllEXDP之比为15.8%;(2) 热带气旋和非热带气旋降水变化趋势的空间分布差别较大, 热带气旋对长江流域东部总降水增多的贡献高达49%, 并一定程度上改变了降水趋势的空间分布; (3) TC-EXHP强度与温度的关系在约21℃发生改变, 且截然不同于nonTC-EXHP, 华南、东南沿海TC-EXHP强度随温度的变化率明显低于nonTCEXHP, 造成nonTC-EXHP和All-EXHP随温度变化率不同, 且在东南沿海差异显著。 

IMPACTS OF TROPICAL CYCLONES ON THE CLIMATOLOGY AND TRENDS OF EXTREME PRECIPITATION AND ON THE RELATIONSHIP BETWEEN EXTREME PRECIPITATION AND TEMPERATURE DURING 1975-2018 WARM SEASONS IN CHINA

Under the background of global warming, there are substantial regional variations in the climatology and trends of extreme hourly precipitation (EXHP) and extreme daily precipitation (EXDP) in China. However, the contributions of tropical cyclones (TCs) to such regional variations remain unclear. Using data from hourly rain gauge observations and the TC best track dataset during the 1975-2018 warm seasons, this study defines extreme precipitation at hourly and daily time scales, respectively, employing the 95th percentiles at corresponding time scales. Then, TC precipitation (TC-P) is objectively separated from total precipitation (ALL). The climatology and trends of the EXHP and EXDP as well as the relationship between EXHP and temperature in TC and nonTC cases are compared to unravel the impacts of TC. The main conclusions are as follows. (1) The ratios of TC-P, TC-EXDP and TC-EXHP to their corresponding ALL precipitation decrease rapidly from the coastal areas of Southeast and South China to the inland areas. In terms of regional average, the ratios of TC-P to ALL-P and of TC-EXHP to ALL-EXHP are both about 11%, while the ratio of TC-EXDP to All-EXDP is about 15.8%. (2) The trends of the TC produced precipitation exhibit significantly different spatial distributions from those of the nonTC precipitation. The contribution of TC to the increase of total precipitation in the eastern Yangtze River Basin is up to 49%. The spatial distribution of ALL precipitation trend is changed by TC to some extent. (3) The relationship between TC-EXHP intensity and surface air temperature (T_{2 m}) changes at about 21℃, and substantially differs from that between nonTC-EXHP intensity and T_{2 m}. In the coastal areas of Southeast and South China, the change rate of TC-EXHP intensity with T_{2 m} is significantly lower than that of nonTC-EXHP, resulting in different change rates of the nonTC-EXHP and ALL-EXHP with T_{2 m}. Such differences are statistically significant in the coastal areas of Southeast China.