基于CHIRPS卫星降水的雅砻江流域干湿时空演变分析

雅砻江流域是我国水电开发的重点区域之一，在全球气候变化背景下探究流域干湿时空演变规律有利于合理规划和充分利用水资源，为流域内农业生产活动提供科学指导。基于1981~2017年雅砻江流域内及周边16个气象站月气象数据，采用Penman-Monteith（PM）公式计算各站逐月潜在蒸散量ET0，基于气象站降水校正CHIRPS卫星降水产品，从而获得更高空间分辨率的降水数据，以此计算标准化降水蒸散SPEI指数，采用云模型、Mann-Kendall（MK）趋势检验法分析流域年代际、年、季尺度的干湿时空分布特征与变化趋势。结果表明：（1）对CHIRPS卫星降水产品进行偏差校正不但提高了精度，而且能够获得更高空间分辨率的降水；（2）流域春季呈湿润化趋势，其余时间尺度均呈现干旱化趋势，以冬季干旱化速率最快。年尺度下干湿变化不均匀度的稳定性最差，秋季稳定性相对最好。春、冬两季SPEI空间分布的不均匀度弱于时间分布；（3）同一时间尺度下的流域各级别干湿相对面积近似呈正态分布，流域干湿变化趋势空间分布差异较大；（4）流域各级别干旱与湿润高发区无明显区域分布规律，发生干旱与湿润的最高频率在20%左右，且随着干湿程度的加重，频率变化范围逐渐缩小；（5）不同年代干湿频率差异较为显著，年平均干旱频率变化趋势为减-增-减，湿润频率变化趋势为增-减-减，湿润频率高值区呈现由下游向上游转移的趋势。

Spatial and Temporal Evolution Characteristics of Dry and Wet Conditionin Yalongjiang River Basin Based on the Chirps Satellite Precipitation

The Yalong River Basin is one of the key regions for hydropower development in China. Exploring the temporal and spatial evolution characteristics of dry and wet condition of the basin in the context of global climate change is conducive to rational planning and full use of water resources, providing scientific guidance for agricultural production activities in the basin. Based on the monthly meteorological data of 16 meteorological stations in and around the Yalong River Basin from 1981 to 2017, the potential evapotranspiration ET0 of each station was calculated using the Penman-Monteith (PM) formula. The corrected CHIRPS satellite precipitation products with higher spatial resolution is used to calculate the standardized precipitation evapotranspiration index SPEI. The cloud model and Mann-Kendall (MK) trend test are used to analyze the spatial and temporal distribution characteristics and trends of the inter-decadal, annual and seasonal scales. The results show that: (1) The deviation correction of the CHIRPS satellite precipitation product not only improves the accuracy, but also obtains the precipitation with higher spatial resolution; (2) the spring is humidified in the basin, and the other time scales show a trend of drought. The rate of aridification is the fastest in winter. The stability of the wet and dry variation in the annual scale is the worst, and the stability in autumn is relatively best. The spatial distribution of SPEI in spring and winter is weaker than the time distribution. (3) The relative dry and wet areas of the watershed at the same time scale are approximately normal, and the spatial distribution of dry and wet changes in the basin is quite different; (4) There is no obvious regional distribution pattern in the drought and wetting high-incidence areas of all levels in the basin. The highest frequency of drought and wetting is about 20%, and the frequency change range is gradually reduced with the increase of dryness and wetness; (5) Frequency difference of wet and dry in different ages is more significant. The annual average drought frequency change shows decrease-increase-decrease trend, the wet frequency change shows increase-decrease-decrease trend, and wetting high-incidence areas transferred from downstream to upstream.