Moisture changes with increasing summer precipitation in Qilian and Tienshan mountainous areas

The precipitation in the Qilian (QMA) and Tienshan (TMA) mountain areas is one of the main sources of subsurface and surface water in northwestern China (NWC). Based on two datasets, CN05.1 and station-observed daily precipitation, we found that summer precipitation in 1979–2020 exhibited an increasing trend in NWC. The results of rotation empirical orthogonal function (REOF) analysis also separated the increased precipitation patterns in the QMA and TMA from the other REOF modes; the proportion of the precipitation of these areas to the total NWC summer precipitation substantially increased (0.12%⋅year⁻¹ and 0.03%⋅year⁻¹, respectively). According to the moisture budget, the evaporation changes in the QMA and TMA were coherently coupled with precipitation, which suggested the feedback between increasing evaporation and precipitation with the recently warming climate. The precipitation increase was larger than that of evaporation, indicating a net wetting trend in the QMA and TMA. The increase in zonal horizontal and vertical moisture advection terms contributed more to the increased precipitation in the QMA. The increase in meridional moisture advection contributed more to the increased precipitation in the TMA. We concluded comprehensive frameworks of the water vapor transport in climate change in mountain areas in NWC which aimed to contribute to the understanding of arid region hydrology.