Impacts of Irrigation and Vegetation Growth on Summer Rainfall in the Taklimakan Desert

Abstract

In recent decades, a greening tendency due to increased vegetation has been noted around the Taklimakan Desert (TD), but the impact of such a change on the local hydrological cycle remains uncertain. Here, we investigate the response of the local hydrological cycle and atmospheric circulation to a green TD in summer using a pair of global climate model (Community Earth System Model version 1.2.1) simulations. With enough irrigation to support vegetation growth in the TD, the modeling suggests first, that significant increases in local precipitation are attributed to enhanced local recycling of water, and second, that there is a corresponding decrease of local surface temperatures. On the other hand, irrigation and vegetation growth in this low-lying desert have negligible impacts on the large-scale circulation and thus the moisture convergence for enhanced precipitation. It is also found that the green TD can only be sustained by a large amount of irrigation water supply since only about one-third of the deployed water can be “recycled” locally. Considering this, devising a way to encapsulate the irrigated water within the desert to ensure more efficient water recycling is key for maintaining a sustainable, greening TD.

摘 要

近几十年来, 塔克拉玛干沙漠 (TD) 由于其周围植被的增加, 出现了绿化的趋势, 但目前这种趋势对当地水循环的影响仍不确定. 这里我们用全球气候模式 (CESM1.2.1) 模拟研究了夏季局地水循环和大气环流对沙漠绿化的响应. 模拟结果表明, 当有足够的灌溉供水维持沙漠中植被生长时, 局地降水量显著增加, 这归因于局地水循环的增强; 其次, 局地地表温度随之降低; 然而, 对低洼的 TD 进行灌溉和植被种植对大尺度环流的影响较小, 所以其对降水以及水汽辐合的影响也较小. 研究还发现, 由于灌溉水的局地再循环率只有大约 1/3, 沙漠绿化的维持需要大量的灌溉. 考虑到这一点, 设计一种能将灌溉水保持在沙漠中的方法以确保更有效的水循环是维持一个可持续的、 绿化的 TD 的关键.