The long-term precipitation trend over the Tibetan Plateau (TP) was studied using a high spatiotemporal resolution precipitation dataset. It was found that the warm season (May–Sept.) precipitation over TP increased significantly during 1981–2015 (grid-mean: 0.9 mm/a), which was most significant in the northeastern, central, and western TP. The geopotential height field of 500 hPa over TP was divided into 9 circulation patterns (T1–T9) by using the obliquely rotated Principal Components in the T-mode (PCT) method, in which T2 and T4 were the dominant circulation patterns (DT) for the increase of precipitation. The geopotential height field of DT was low over the west but high over the east. DT dominated the increase of precipitation was reflected in the increase of precipitation days and daily precipitation. The increase in the number of DTs led to increased precipitation in the central and western TP. Another dominant mechanism was the optimization of precipitation conditions: T2 was dominated by the optimization of dynamic conditions driven by the larger gradient of geopotential height, and T4 was dominated by the optimization of thermal conditions driven by more water vapor.

利用最新的高时空分辨率融合降水数据集, 研究青藏高原的长期降水变化趋势。结果表明, 在1981—2015年的暖季(5—9月), 青藏高原降水量显著增加(格点平均趋势为0.9 mm/a), 其东北部、中部和西部最为显著。采用 T 模态倾斜旋转主成分分析法(PCT), 将青藏高原 500 hPa位势高度场分为9个典型环流型, 发现第2和第4环流型(T2和T4)是暖季降水量增加的主导环流型(DT)。DT位势高度场为西低东高的“槽脊对峙”分布, 青藏高原暖季降水量增加体现在DT主导降水日数和日均降水量的共同增加。除DT环流型数量的增加导致青藏高原中西部降水增加外, 降水增加机制还包括降水条件的优化, 即T2以“槽脊对峙”加强为驱动的动力条件优化为主导, T4以“水汽滞增”加强为驱动的热力条件优化为主导。