Local and downwind precipitation has been boosted by evapotranspiration change-induced moisture recycling in the Chinese Loess Plateau

Abstract

The Grain for Green Project in the Chinese Loess Plateau (CLP) has greatly increased vegetation cover and altered land use patterns. However, the effects of evapotranspiration (ET) from different vegetation types on local and downwind precipitation remain unclear. In this study, we employed a moisture tracking model to quantify the contributions of ET-driven moisture recycling to precipitation change for 1990–2019. We found the ET moisture over CLP flows northeastward to contribute to local and downwind precipitation. On average, 21 % of the ET moisture contributed to 14 % of local precipitation. The remaining ET moisture contributed unevenly to downwind precipitation of different regions: 38 % of ET for rest of China, 17 % for other countries, and 24 % for the ocean. The increased ET over the past three decades has greatly contributed to the increases in local precipitation. A 1 mm rise in ET can increase local precipitation by 0.15 mm, among which ∼70 % of the precipitation increase (0.1 mm) is attributed to transpiration. Collectively, a 60-mm increase in ET resulted in a net precipitation increase of 9 mm, accounting for 16 % of the total precipitation increase over the past three decades. The increased ET from grassland and cropland respectively contributed 61 % and 21 % to the increase of local precipitation. We conclude that the increased ET over the past three decades has greatly contributed to the increases in local precipitation, and grassland played a dominant role because of its larger area proportion. This finding has important implications for vegetation restoration and water resource management in the water-limited areas.