近49年那曲市汛期降水变化特征

Variation Characteristics of Precipitation in Flood Season of Nagqu in Recent 49 years

利用那曲市6个气象站1971—2019年汛期(5—9月)逐日、逐月、逐年降水资料,分别采用滑动平均法、累计距平、Mann-Kendall突变检验等方法,研究降水的趋势性及周期性变化。结果表明,近49年来那曲市汛期降水量增幅为14.231 mm/10 a;20世纪70年代初至90年代初汛期降水有弱的增长,90年代末汛期降水量增长较明显,进入21世纪初以后汛期除嘉黎县有较明显的增涨趋势外,其余各站汛期降水量呈减弱趋势;各站点汛期降水的累积距平为负距平,汛期降水呈偏少状态,从累积距平的变化趋势来看历年汛期降水总体呈波动上升的变化态势;根据Mann-Kendall突变检验来看近49年各站点汛期降水呈增长趋势,结合每个站点的累积距平有且只有一次突变,各站点全是降水增多突变;近49年那曲市汛期降水空间分布特征呈由东向西递减,且汛期降水主要集中在每年的7月份;汛期雨日占全年雨日的73.0%,汛期小雨(≥0.1 mm)的雨日占整个汛期雨日的88.0%。

Using the daily,monthly and yearly precipitation data of the 6 weather stations in Nagqu City during the flood season(May-September)from 1971 to 2019,the moving average method,cumulative anomaly,Mann-Kendall mutation test and other methods were used to study the trend and periodic changes of precipitation.The results showed that the precipitation in Nagqu City during the flood season had increased by 14.231 mm/10 a in the past 49 years;there was a weak increase in the precipitation during the flood season from the early 1970 s to the early 1990 s,and the increase in the precipitation during the flood season in the late 1990 s was more obvious;after the beginning of the 21 st century,except for Jiali County,which had a more obvious trend of increase during the flood season,the precipitation at the rest of the stations showed a weakening trend during the flood season.The cumulative anomaly of the precipitation during the flood season at each station was negative,and the precipitation during the flood season is relatively less.From the trend of the cumulative anomaly,the overall precipitation during the flood season has fluctuated and increased over the years;from the change trend of the cumulative anomaly,the overall precipitation in the flood seasons over the years had shown a fluctuating and rising trend.According to the Mann-Kendall mutation test,the precipitation at each station during the flood season had shown an increasing trend in the past 49 years.Combined with the cumulative anomaly at each station,there was only one mutation,and all stations had a sudden increase in precipitation.In the past 49 years,the spatial distribution of precipitation during the flood season in Nagqu City showed a decreasing trend from east to west,and the precipitation during the flood season was mainly concentrated in July each year.Rainy days in the flood season accounted for 73.0%of the annual rainy days,and rainy days with light rain(≥0.1 mm)in the flood season accounted for 88.0%of the rainy days in the entire flood season.