青藏高原春季土壤湿度与夏季降水的关系

Relationship between soil moisture in spring and precipitation in summer over the Tibetan Plateau

应用SVD方法对1981—2018年青藏高原春季土壤湿度和高原地区夏季降水进行诊断。结果表明:土壤湿度前两个模态累积协方差百分比达到了61.15%,左右场展开序列的时间相关系数均为0.78,反映两场关系的主要特征。土壤湿度场表现出南北相的一致性,而降水场的一致性较差。第一模态说明青藏高原北部春季土壤湿度较大时,对应高原北部地区和东南部地区夏季降水偏少。第二模态说明高原大部分地区春季土壤湿度较大时,高原北部、中部地区夏季降水偏多,南部夏季降水偏少。从合成500 hPa环流场和可降水量场看,在高原春季土壤湿度偏大的年份,环流形势表现为“-+-”形式,正距平中心位于高原南部和印度北部地区,且有槽存在时,会导致地面降水量增多。

The relationship between soil moisture and precipitation has became a research focus,because soil moisture has the“memory”.Using the data of soil moisture from CPC(Climate Prediction Center)and the SVD(Singular Value Decomposition)method,the influence of soil moisture on summer precipitation in Tibetan Plateau(TP)in spring was discussed.The results showed that the cumulative covariance percentages of the first two modes reached 59.15%,and the time correlation coefficients of the two field expansion sequences were 0.78,reflecting the main characteristics of the two field relations.The soil moisture field shows the consistency of the north and south phases;however,the consistency of the precipitation field was weak.The first mode indicated that when the soil moisture in the northern part of the TP in spring was higher than that of other areas,the precipitation in the northern and southeastern part of the TP in summer was lower than that of other areas.The second mode indicated that when the soil moisture was higher than that of other areas in most areas of the TP in spring,the precipitation in the northern and central parts of the plateau was higher than that of other areas in summer,and the precipitation in the southern part was low.The 500 hPa circulation and precipitable water field match well.When the soil moisture was relatively high in spring,negative anomalies were controlled in the northern part of the TP,and the corresponding high-level precipitation was relatively large.The configuration was conducive to more precipitation in the southwest of the TP.