1981—2020 年西藏高原汛期降水量时空变化特征

Temporal and Spatial Variation Characteristics of Flood Season Precipitation in Xizang from 1981 to 2020

基于1981—2020年西藏38个气象站点逐月降水量资料,采用线性倾向估计、相关系数、优势分析以及Mann-Kendall、Cramer等5种突变检验方法,分析近40 a西藏汛期降水量的时空变化特征。结果表明:(1)西藏各站平均汛期降水量总体表现为自东向西递减的分布特征。1991—2020年与1981—2010年的汛期降水量平均值比较,84.2%站点偏多,以改则最为明显。(2)近40 a西藏78.9%站点汛期降水量呈增加趋势(1.2~31.9 mm/10 a),而近30 a(1991—2020年)汛期降水量减少的站点占55.2%,减幅为0.6~42.2 mm/10 a。海拔高度是影响汛期降水量变化趋势的主导因子,3640 m以下地区趋于减少,4000 m以上地区多为增加趋势。(3)近40 a西藏38个站平均汛期降水量以10.2 mm/10 a的速度呈增加趋势,主要表现在5月和7月。西藏汛期降水量表现出1980s明显偏少、1990s偏多、2000s略偏少、2010s正常的年代际变化特征,在2005年前后出现了由多转少的突变,且汛期及各月降水量存在3 a左右的显著周期。

Based on the measured monthly precipitations of 38 meteorological stations in Xizang from 1981 to 2020,the spatial and temporal characteristics of flood season precipitation(P59)in recent 40 years were analyzed by using the linear trend estimation,correlation coefficients,dominance analysis,and five mutation tests such as Mann-Kendall and Cramer.The results show that:(1)The average P59 of each station in Xizang showed a decreasing distribution from east to west.Compared with those in the period of 1981—2020,the average values of 84.2%stations were more in the period of 1991—2020,especially in Gêrzê.(2)The P59 of 78.9%stations increased with a rate of 1.2~31.9 mm·10a−1 over Xizang in the past 40 years,while the P59 of 55.3%stations decreased at a rate of 0.6~42.2 mm·10a−1 in the past 30 years(1991—2020).The altitude was the dominant factor of the change trend of P59,the P59 decreased in area below 3640 m,and increased in area above 4000 m.(3)In recent 40 years,the average P59 of 38 stations increased by a rate of 10.2 mm·10a−1 in Xizang,mainly in May and July.The P59 showed decadal variation with a significant decrease in the 1980s,a significant increase in the 1990s,a slight decrease in the 2000s,and a normal in the 2010s.The P59 showed a sudden climatic change from more to less around 2005.There was a significant period of about 3 a in flood season and monthly precipitation.