陕甘宁三河源区1971—2017年极端降水时空变化分析

Spatiotemporal variation analysis of extreme precipitation in the Three River Source Area of the Shaanxi-Gansu-Ningxia Contiguous Region from 1971 to 2017

为了揭示陕甘宁三河源区极端降水时空分布及其变化规律,利用1971—2017年逐日降水、气温数据,辅以气候趋势系数、小波相干分析等方法分析三河源地区极端降水时空变化特征,并探究极端降水指数与厄尔尼诺南方涛动(ENSO)的关联关系。结果表明:1971—2017年,陕甘宁三河源地区极端降水有明显增多的趋势;在空间分布上受地理位置和地形的影响,总体呈现“南高北低”的分布格局,空间差异显著。研究区内极端降水指数变化增减不一,大部地区极端降水量增多,弱降水日数减少,强降水日数增多,降水强度增大,降水趋于极端化。极端降水指数与多元ENSO指数(MEI)呈显著负相关关系,存在3~5 a及9~12 a时间尺度的显著共振周期。

Combined with the climate tendency analysis and wavelet coherence analysis,the daily precipitation and temperature data from 1971 to 2017 were used to reveal the spatiotemporal variations of extreme precipitation in the Three River Source Area of the Shaanxi-Gansu-Ningxia Contiguous Region and explore the relationship between extreme precipitation and the El Nio-Southern Oscillation(ENSO)activities.The results show that there was a significant increase in extreme precipitation in the Three River Source Area from 1971 to 2017.Precipitation in this region has an apparent spatial pattern with higher values in the south and lower values in the north,showing the apparent impacts of geography and topography.Changes in the extreme precipitation indices in this area are mixed.In most areas,the amount of extreme precipitation,number of heavy precipitation days,and precipitation intensity increase over the study period,while the number of low precipitation days decreases over time,indicating that precipitation in this region tends to become more extreme.There were significant negative correlations between the extreme precipitation indices and the multivariate ENSO index(MEI),and the periods of maximum coherences between extreme precipitation indices and MEI are 3-5 a and 9-12 a.