祁连山北麓牧区植被生长季不同等级降水时空变化特征

Spatio-temporal variations of different grade precipitation in the pastoral area on the northern slope of Qilian Mountains during vegetation growing season

以祁连山北麓肃南县牧区为研究区,选取周边7个气象站1961-2016年的日降水资料,采用气候倾向率、Hurst指数、Mann-Kendall检验和反距离加权插值等方法,对肃南县植被生长季降水的时空变化特征进行研究。结果表明:肃南县植被生长季降水量和降水强度距平百分率趋势显著增加,而降水日数增加趋势不显著;植被生长季降水量和降水强度在1998年发生显著突变,而降水日数无显著突变;植被生长季降水以小雨为主,中雨降水变异系数较大,但近年来趋于稳定上升状态;植被生长季降水日数和降水强度在空间上呈东南多西北少,小雨降水分布与其分布类似,而中雨强度呈南少北多的空间分布差异;小雨对肃南县植被生长季降水量贡献较大,但近年来中雨比小雨增加明显,降水时空分布呈不均衡发展趋势。

Taking the grassland pastoral area of Sunan County on the northern slope of Qilian Mountains as the research area,we selected the daily precipitation data of seven nearby weather stations from 1961 to 2016 to analyze the spatio-temporal variations of different grade precipitation in Sunan County during the vegetation growing season using the climate tendency method,Hurst index method,Mann-Kendall test and inverse distance weighted interpolation. The results show that the anomalous percentages of the quantity and intensity of precipitation in Sunan County during vegetation growing season showed a significant increasing trend,whereas the precipitation days presented an insignificant increase. Significant abrupt changes of the quantity and intensity of precipitation occurred in 1988,but no significant abrupt change of precipitation days occurred. The precipitation was dominated by light rainfall and the variation coefficient of moderate rainfall was large,but it tended to rise steadily in recent years. The spatial distribution of the days and intensity of precipitation decreased from the southeast to the northwest,which was similar to the distribution of light rainfall. To the opposite,the distribution of moderate rainfall decreased from the north to the south. Compared with the contribution of moderate rainfall,light rainfall contributed more to the precipitation;however,the increase of moderate rainfall was more significant than that of light rainfall in recent years,and the spatial and temporal distribution of precipitation showed an unbalanced trend.