基于多源数据的青藏高原夏季降水与水汽输送的联系

The Connection Between the Precipitation and Water Vapor Transport over Qinghai-Tibetan Plateau in Summer Based on the Multiple Datasets

利用国家气象信息中心提供的1979-2014年青藏高原(下称高原)地区(26°N-42°N,75°E-105°E)113个站点的逐月降水资料作为基准降水资料,与另外4套格点降水资料(APHRO、CM AP、GPCP、GPCC)和8套再分析的降水资料(NCEP1、NCEP2、M ERRA、ERA_Interim、ERA20c、20CRv2、JRA55、CFSR)作对比,可得12套再分析资料中,APHRO能够最好地刻画出高原1979-2007年夏季降水的时空分布形态。GPCP次之,能够较好地刻画其1979-2014年的特征。就气候态而言,水汽主要由南边界输入高原,输入大值区是下层;另外水汽同样从西边界和北边界输入高原,主要的输入层分别是中层和下层;而水汽主要是从东边界中层输出。多套资料比较可知,ERA_Interim和MERRA分别能较好地刻画高原本地和其周围地区夏季水汽输送情况。研究高原东南部降水的年际变化和环流的关系,发现在印度半岛和孟加拉湾处有一异常的纬向反气旋,其北边缘加强的水汽输送导致了高原东南部降水的异常增多。

In this study, the monthly precipitation data set at 113 stations during 1979- 2014 over the Qinghai- Tibetan Plateau （QTP） provided by the National Meteorological Information Center, had been compared with 4 gridded precipitation data sets （APHRO, CMAP, GPCP, GPCC） and 8 reanalysis data sets （NCEP1, NCEP2, MERRA, ERA_Interim, ERA20c, 20CRv2, JRA55, CFSR）. Compared with the observation, it was found that the AHPRO and GPCP can capture the spatial and temporal patterns of the summer precipitation over the QTP during 1979- 2007 and 1979- 2014, respectively. For the climatology of water vapor, the southern boundary is the main moisture source over the QTP in summer with the dominant channel in the lower layer. Meanwhile, both the western and northern boundaries are also the moisture input over the QTP, with the main channels in the middle layer and the lower layer, respectively. Furthermore, the water vapor output over the QTP is through the eastern boundary by means of its middle layer. Generally, QTP is a moisture sink in summer, and the moisture is convergent over it, to which moisture advection term makes the greatest contribution, while wind divergence term has a diverse effect. In addition, ERA_Interim and NCEP1 showed better ability to delineate these character- istic, however, MERRA was the worst. By comparing multiple datasets, it was shown that MERRA and ERA_ Interim can better depict the water vapor transport condition over the local QTP and peripheral area, respectively. Exploring relationship between the precipitation variability over the southeastern QTP and the atmospheric circula- tion, we picked out the high and low value years according to precipitation index. By conducting the synthesis a- nalysis on them, it was shown that the moisture from the western boundary was the most sensitive to climate change and the decrease of net income in dry years was greater than the increase of net income in wet years, and ERA_Interim and MERRA can represent the water vapor transport condition at different boundary and levels in dry years and wet years better, respectively. Conducting the synthesis analysis on the integrated water vapor transport, it was revealed that there is a zonally orientated anticyclone anomaly across the Indian subcontinent and the Bay of Bengal, and the strong westwards water vapor transport at its northern edge attributes to the excessive precipitation over the southeastern QTP.