Impacts of moisture transport through and over the Yarlung Tsangpo Grand Canyon on precipitation in the eastern Tibetan Plateau

Abstract

The Yarlung Tsangpo Grand Canyon (YTGC) acts as a major passage of monsoonal moisture transport from the Bay of Bengal into the Tibetan Plateau (TP). But it remains unclear how moisture transport through and over the YTGC affects the distribution of precipitation in the eastern TP. Based on reanalysis data and two high-resolution WRF simulations (with and without the canyon), this study clarifies the impacts of moisture transport between the lower layer (surface-700 hPa) through the YTGC and the upper layer (700–300 hPa) over the YTGC. The results show that the amount of moisture transport in the lower layer through the YTGC depletes twice more than that in the upper layer, resulting in abundant precipitation in the YTGC. This importance of moisture transport in the lower layer to precipitation of the YTGC is consistent with the significant decrease of precipitation in the mountains along the YTGC after filling the canyon (i.e., blocking moisture transport in the lower layer). However, there is little change in precipitation of the eastern TP (30°-36°N, 88°-103°E) without moisture transport in the lower layer through the YTGC. Therefore, moisture transport in the lower layer through the YTGC is critical to precipitation in the YTGC, while moisture transport in the upper layer over the YTGC is far more important to the formation of precipitation in the eastern TP.