重庆极端高温指标的对比及其与区域性增暖的关系

CLASSIFICATION OF EXTREME HIGH TEMPERATURE INDICES AND THEIR RELATIONSHIP WITH REGIONAL WARMING IN CHONGQING

对重庆市极端高温指标进行了系统分类,即极值、绝对阈值和相对阈值指标,研究了1961—2008年各种极端高温指标自身变化规律及其与区域性增暖的关系,并对比分析了不同指标间的差异。结果表明,由于极端高温指标的定义不同在反映高温上存在一定差异。利用绝对阈值和极值指标能直观地看出极端高温事件的影响强弱,所以利用年极端最高气温、35℃以上高温日数等指标来判别高温影响强弱一直是业务上最常用的方法。相对阈值指标HWDI和WSDI,在定义上受到连续6天的限制,所以在某些高温年份与绝对阈值指标的高温指数差异明显。相对阈值指标(HWDI、WSDI和TX90p)在年内几乎所有季节都可能出现,所以作为年内指标而言,此类指标与年平均气温/最高气温变化的步调更加一致,尤其是TX90p,没有连续定义的限制,它与区域性增暖的关系更为密切。重庆是高温频发区,通过对不同高温指标的对比分析研究,能更好地为业务和科研人员提供参考,同时对极端高温的监测、检测及影响评估具有相当重要的意义。

Based on the daily temperature observations in Chongqing during 1961-2008, systematic classification is carried out to establish indices on extreme high temperature, like extreme value, absolute and relative threshold values, etc, and to investigate variations and indicative difference of these indices and their relationship with regional warming. The results show that there are differences for different indices to indicate extreme temperature. Impact of extreme high temperature can be intuitively described by indices such as annual maximum temperature, number of days with temperature higher than 35 ℃, etc, which are commonly used in operation services as criteria to identify high temperature. However, the indices defined by relative threshold values, HWDI and WSDI, have significant difference from those by absolute threshold values in indicating high temperature events since the HWDI and WSDI are limited by six day succession in their definition. Since these indices （HWDI, WSDI and TX90p） can occur in every season round a year, they are more consistent with variations of annual mean and maximum temperature, in particular for the TX90p which has no limitation for six day succession, and is more correlated with regional warming. Chongqing is a area with high frequency of extreme high temperature. Results from comparative analyses on high temperature indices will provide good reference to those involved in scientific researches and operational services, and at the same time become very important in monitoring, detecting and assessing impacts by extreme high temperature.