Opposite long-term trends in precipitation during spring and summer over the Pamir Plateau and influential factors

As a vital part of the water tower of Asia, water cycle changes in the Pamir Plateau have significant impacts on the climate of the arid inland regions of Central Asia. Using the high-precision precipitation dataset known as TPHiPr, a significant wetting trend in spring and a drying trend in summer over the Pamir Plateau from 1979 to 2020 is identified in this study. Further analysis reveals that dynamic factors are more important than thermodynamic factors in driving these precipitation trends throughout both seasons. The dynamic factors are closely linked to the anticyclonic trend in spring and the cyclonic trend in summer, both of which are influenced by long-term trends in atmospheric circulation. Furthermore, the warming trend of sea surface temperature (SST) in the North Atlantic (NA) may impact atmospheric circulation over the Pamir Plateau. In spring, the pronounced meridional gradient of potential vorticity over the NA facilitates the northward propagation of the wave train induced by the warm SST along the great circle path, resulting in an anticyclonic trend over the Pamir Plateau. In summer, the wave train excited by the heat source at 60 degrees N propagates eastward along the jet stream, leading to a cyclonic anomaly over the Pamir Plateau. The results were also verified in the Atlantic-pacemaker simulations. Overall, this study highlights the distinct wave trains induced by the NA SST warming trend in spring and summer. These distinct wave trains provide different dynamic conditions contributing to the observed drying and wetting trends over the Pamir Plateau.