对我国极端高温事件阈值的探讨

Threshold Values on Extreme High Temperature Events in China

利用我国1951-2008年逐日最高气温资料集,进行缺测资料的恢复整理,得到较完整的1961—2008年224站逐日最高气温资料集。在此基础上,采用两种基于正态分布的传统阈值计算的方法(方法1,方法2)和该文提出的基于实际样本频率分布的阈值计算方法(方法3),对我国高温阈值的确定进行比较研究。结果表明:该文提出根据最高气温的实际样本频率分布作为实际概率分布的近似,较传统求极端气候事件阈值方法效果更好,能够比较接近日常使用极端气候事件阈值,亦有较好的稳定性。另外,根据计算结果,除西南地区、青海、东北地区大部和内蒙古外,我国大部分地区最高气温极端气候事件的阈值均超过35℃,即在我国日常人们使用的35℃高温阈值作为夏季高温极端事件标准是合理的。

The threshold values are very important to define the indices of extreme climate events. Usually, the 90 percentile threshold value is used as the threshold values of extreme high temperature events, while the specific methods of categorization and calculation lead to different threshold values. In order to find the most suitable method, the quality controlled and homogenized daily maximum temperature data in China for the period of 1951--2008 are checked, and some missing data are reconstructed. Analysis is conducted using a new data for 1961--2008 in 224 selected stations. The preliminary analysis shows that the daily da ta series of most stations are not fit for normal distribution as generally believed. Based on the analysis above, the comparison for the threshold values falling into the percentiles of the extreme events of maximum temperature is accomplished using three different methods （including two traditional methods of cal culating threshold values based on the assumed normal distribution and a new method by which the thresh- old values are calculated based on the sample probability distribution）. The results show that the evaluation of the threshold values on the method using the real sample fre quency distribution to simulate the probability distribution （the new method） has got the best results than using the other traditional threshold values calculating methods. Based on the comparisons, the threshold values of extreme events of maximum temperature in China have been developed with the 30-year sample climate phase. The following inspection shows the threshold values can reflect the real threshold values on the maximum temperature in daily use, and they are more stable and representative. In addition, the dis- tribution charts of the threshold values developed by the different methods are drawn, and it＇s found that except for in Southwest and Northeast China, Qinghai, Inner Mongolia, the threshold values of extreme high temperature events for most part of China are all above sing the threshold 35 °C as the standard of high temperature 35 °C, which proves that it is reasonable of u disasters.