Impact of sea–land thermal contrast along the Silk Road on spring precipitation over Pamirs Plateau

The abundant precipitation over Pamirs Plateau (PP) in spring provides substantial natural and anthropogenic water resources for downstream areas. However, the factors affecting spring precipitation over PP remain unclear. Using statistical analyses and the Weather Research Forecasting (WRF) model simulations, the influence of sea–land thermal contrast along the Silk Road (Mediterranean Sea, Black Sea, Caspian Sea, Red Sea, Persian Gulf, and Turan Plain) on spring precipitation over PP was investigated. The sea–land thermal contrast is defined as sea surface temperature minus land skin temperature over Turan Plain. The spring precipitation over PP was positively correlated with the sea–land thermal contrast along the Silk Road during 1981–2018, but there was a slight difference in March, April, and May. When the sea–land thermal contrast was positive, more moisture was evaporated from the seas into the upper level (700–300 hPa) by the upward movement and transported to PP along the westerlies, which brought more precipitation over PP. When the sea–land thermal contrast was negative, the moisture from the seas transported eastward at the lower level (surface—700 hPa) and part of the moisture was lost by the high terrain along the Silk Road, resulting in less precipitation over PP. Furthermore, the WRF sensitivity simulations corroborated the positive impact of sea–land thermal contrast on the spring precipitation over PP by enhancing the water vapor content along the moisture path arriving at PP and moisture fluxes across PP. Our results emphasize that the spring precipitation over PP is influenced by the sea–land thermal contrast along the pathways of moisture sources.