陕北黄土高原地区极端降水事件时空分布特征

ANALYSIS OF EXTREME PRECIPITATION IN LOESS PLATEAU AREA OF NORTHERN SHAANXI PROVINCE

以陕西省北部6个气象站点1959-2011年逐日降水数据为基础,采用百分比方法确定各站点极端降水阈值,选取极端降水量、极端降水频率、极端降水强度、暴雨量、暴雨日数、大雨量和大雨日数,分析陕北黄土高原地区极端降水事件时空变化特征,结果表明:(1)极端降水经历近30年的持续减少后,近10多年增加较快,各极端降水指数空间上均呈自东南向西北的递减趋势。(2)极端降水量2000~2011年最大,极端降水阈值和极端降水量自东南向西北递减分布。(3)极端降水频率以2000~2011年最大,极端降水强度变化趋势不明显。空间分布上极端降水频率以绥德最高,榆林最低;极端降水强度以洛川最高,横山最低。(4)暴雨量和暴雨日数均以2000~2011年最高,空间分布呈自东而西递减,分别形成以绥德和延安、横山和吴起为中心的高值和低值区域。大雨量和大雨日数以1959~1969年最高。空间分布上呈自南而北的递减趋势,均形成以洛川和横山为中心的高值和低值区域。

Spatial and temporal change of extreme precipitation has been analyzed by extreme rainfall,frequency of extreme precipitation,intensity of extreme precipitation,rainstorm and its frequency,heavy rain and its frequency,through thresholds calculated by the methods of percent on the basis of daily precipitation data in the 6meteorological stations located in Loess Plateau area,the northern of Shaanxi province. Results show:( 1) extreme precipitation increased fast in the last 10 years after decreased nearly 30 years reflected by the statistical results in decades of Loess Plateau area in northern Shaanxi,and all the index of extreme precipitation has shown decreased tendency from southeast to northwest in spatial.( 2) Extreme rainfall was the largest in the year from2000 to 2011,and thresholds of extreme precipitation and extreme rainfall decreased from southeast to northwest in spatial.( 3) Frequency of extreme precipitation was the largest in the year from 2000 to 2011 while the tendency of intensity of extreme precipitation was not obviously. In the spatial distribution,frequency of extreme precipitation was largest in Suide,while smallest in Yulin,and intensity of extreme precipitation was largest in Luochuan while smallest in Hengshan.( 4) Precipitation and frequency of rainstorm were the largest in the year from2000 to 2011,and had the similar spatial distribution,which shown decreased from east to west. Precipitation of rainstorm had high value area nearby Suide while lowvalue area nearby Yan'an,and frequency of rainstorm had high value area nearby Hengshan while lowvalue area nearby Wuqi in spatial. Precipitation and frequency of heavy rain were the largest in the year from 1959 to 1969,and decreased from south to north in spatial,which two index had showthe high value area nearby Luochuan while lowvalue area nearby Hengshan.