1997—2017年塔克拉玛干沙漠腹地降水特征

Characteristics of Precipitation at Hinterland of Taklimakan Desert,China

利用塔克拉玛干沙漠腹地塔中气象站1997—2017年逐日和逐时降水资料,分析塔克拉玛干沙漠腹地降水日变化特征、极端强降水特征及其天气背景。结果表明:1997—2017年研究区降水量呈增加趋势、降水日数呈减少趋势,大雨雨量和雨日明显增加,降水呈增强演变。降水多见于6月,最大雨强为8.4 mm·h-1。降水量日变化呈多峰特征,降水量最大值出现在23:00,06:00是降水频次最多时刻。降水强度和降水频次对降水量作用不同,午后至前半夜强度大,频次少;而后半夜至清晨频次多,强度小。降水以短历时降水为主,其中1～3 h的短历时降水对总降水量贡献率高达61.76%。日降水和小时降水的99百分位强度阈值分别为15.3 mm·d-1和6.0 mm·h-1,大于90百分位极端降水量占总降水量贡献率近半。极端强降水天气发生在南疆盆地受北纬40°以南低槽、切变槽或弱的气旋式风场控制地区,南疆盆地提前增湿,民丰850 h Pa比湿接近或超过10 g·kg-1的背景下,降水连续性较差,多中小尺度引发局地短时降水。

With the daily precipitation data of Tazhong Station in the hinterland of Taklimakan Desert from 1997 to2017,the daily variation of precipitation and extremely strong precipitation were analyzed. The results showed that with increasing trend of annual precipitation,the rainy day number was reducing. Especially both the days and volumes of big rainy had obviously increased. The evolvement of rain had enhanced. The rainy days more happened in June,the strongest hourly rain was 8.4 mm which accrued at the end of spring on May 14 th. The diurnal variation of precipitation presented many peaks and troughs. The maximum precipitation appeared near midnight at 23: 00( Beijing Time). The maximum precipitation frequency occurred at 06:00( Beijing Time). The precipitation intensity and frequency played different parts in rain. From afternoon to eve it presented strong precipitation intensity with low precipitation frequency. However,from midnight to day it presented weak precipitation intensity with high precipitation frequency. Short-duration precipitation within 1-3 hours were dominated events in the hinterland of Taklimakan Desert and the contribution rate of short-duration precipitation events within 1-3 hours to total precipitation were up to 61.76%.The threshold of the 99 th percentile for daily rainfall and hourly rainfall were 15.3 mm·d-1 and 6.0 mm·h-1,respectively. Actually,contribution rate of extreme strong rainfall higher more than the threshold of the 90 th percentile was close to half of total precipitation. The extreme strong rainfall events occurred mainly under the 500 hPa circulation background of the south branch through,trough-line and thin cyclonic wind fields which lied at the south of 40°N in the Southern Xinjiang Basin. And the humidity was close or excess to10 g·kg-1 at 850 hPa in the Minfeng which was at the southwest of Taklimakan Desert. The continuous character of precipitation was worse,and there were more short term precipitation at mesoscale and micro scale in local.