我国东南沿海午后短时降水极端峰值强度与湿度和地表气温的关联

CORRELATION BETWEEN EXTREME PEAK INTENSITY OF AFTERNOON SHORT DURATION PRECIPITATION AND HUMIDITY AND SURFACE AIR TEMPERATURE IN SOUTHEAST COAST OF CHINA

利用中国东南沿海地区55个站点的逐时降水、日平均地面温湿场、低空气温露点差及OISST海表温度资料,对午后短时降水的极端峰值强度与湿度和地表气温的关联进行分析。结果表明,东南沿海地区午后短时降水极端峰值强度随气温的变化趋势存在明显变化,日最高气温低于29℃时,峰值强度随气温升高而上升;日最高气温高于29℃时,峰值强度随气温升高而下降。分析水汽条件作用发现,峰值强度在高温条件下随气温的升高而下降的现象与相对湿度变化有关,日最高气温较高时,相对湿度随气温的升高而大幅减小。初步分析可知,当陆地达到较高温度并进一步增温时,附近海域海表温度变化不大,使得洋面水汽含量增加较少。在陆地水汽主要来自于海洋的情况下,伴随陆地的进一步升温,地表相对湿度将减小。

Using hourly rainfall intensity,daily surface temperature and humidity,low-level dew point differences at 55 stations in the southeast coast of China,and sea surface temperature from OISST in the coastal region,this paper analyzes the connection between extreme peak intensity of afternoon short-lived precipitation and humidity as well as surface air temperature.It pointed out that the dependency of extreme peak intensity of afternoon short-lived precipitation on temperature has a significant transition.When daily highest surface temperature is below （above） 29 ℃,peak rainfall intensity shows an ascending （descending） tendency with rising temperature.Having investigated the role of moisture condition in the variation of afternoon short-lived precipitation and temperature,this paper discovered that the descending tendency of peak rainfall intensity with temperature is connected with relative humidity variation.When daily highest temperature becomes high,relative humidity decreases dramatically as temperature increases.Sea surface temperature rarely changes in this further increasing of surface air temperature.Depending on temperature variation,water vapor content at seas could not increase greatly.Therefore,as land water vapor is mainly contributed by adjacent seas,the decline of relative humidity over land would cause further rise in land surface temperature.