近极值广义态密度及其在极端温度天气中的应用

The generalized state density of near-extreme and its applications in the study of extreme temperature

为研究近极端温度天气对产生极端温度天气的指示意义,本文基于平均广义态密度的近似形式,构建了近极值广义态密度的参数,并定义了最概然近极值强度和最大平均广义态密度,运用广义态密度研究了1961-2013年间中国近极端温度天气的聚集现象.结果表明,当南京夏季日最高温度达到33.15℃时,下一时刻产生极端高温天气的概率最大,为33.43%.而冬季出现-2.78℃的近极端低温时,出现极端低温的概率最大,为29.83%.从全国范围来看,夏季在西北地区西部、西南及华南地区,当日最高温度达到距离高温阈值1.0~2.6℃的近极端高温时,最有可能出现极端高温天气.冬季,对于西南地区北部和东部以及华南地区西部,当日最低温度高于低温阈值1.2~3.2℃时,应及时给出极端低温天气的预警.

In order to study the indicative significance of near-extreme temperature events to extreme temperature events,this paper is based on the estimation of the approximate expression for mean generalized state density,constructs the parameters in the generalized state density of near-extreme events with the exertion of the maximal and minimum daily temperature records of National Meteorological Information Center from 1961 to 2013over China mainland.In order to further analyze the phenomenon of the crowding of near-extreme temperature events over China quantitatively,the most probable strength of the near-extremes and the maximum mean generalized density of states are defined.The results show that,for Nanjing station in the summer,the maximum probability of near-extreme high temperature events which is 33.15 ℃is 33.43%.In winter,when the minimum daily temperature reaches-2.78 ℃in Nanjing,the maximum probability of extreme low temperature events is 29.83%.From the national perspective,the regional characteristics of the national distribution of the most probable strength of the generalized state density of the near-extremes and the maximum mean generalized density of states in summer and winter are more obvious than in spring and autumn.When the maximal daily temperature reaches the high-temperature threshold about 1.0~2.6 ℃,the extreme high temperature events are most likely to occur at the next moment over the west of northwestern China,southwestern and southern China in summer.In winter,when the minimum daily temperature is higher than the low-temperature threshold about1.2~3.2 ℃,the appropriate extreme low temperature warning signal should be given over the north and east of southwestern China and the west of southern China as soon as possible.