Numerical Simulation of the Irrigation Effects on Surface Fluxes and Local Climate in Typical Mountain‐Oasis‐Desert Systems in the Central Asia Arid Area

Abstract

In this study, the Weather Research and Forecasting model was coupled with an improved Noah land surface model (WRF‐Noah) where dynamic flood and drip irrigation processes were implemented firstly. We simulated the different irrigation effects on surface water‐heat processes in a typical mountain‐oasis‐desert system in Central Asia for both wet and drought years, respectively, using the modified WRF‐Noah. The modified WRF‐Noah model can dynamically generate amounts of irrigation in agreement with actual values. The statistically significant decrease in the root mean square error and increase in the Pearson correlation coefficient for the 2‐m temperature (T2), relative humidity (RH), latent heat flux (LE), and precipitation suggest that the modified WRF‐Noah model was improved by implementing irrigation processes. During the irrigation season, flood and drip irrigation decreased the average sensible heat flux by −80.69 and −50.50 W/m2 and T2 by 1.09 and 0.82 °C over the irrigated area and increased LE by 88.47 and 66.70 W/m2 and RH by 6.23% and 4.65%, respectively. Throughout the domain, flood irrigation had equivalent or slightly weaker effects on near‐surface temperature and humidity due to the smaller irrigated area. Both flood and drip irrigation increased precipitation throughout the domain, especially in the mountainous area, thereby accelerating the hydrological cycle in the mountain‐oasis‐desert system. The local oasis breeze circulation that plays a role in maintaining the oasis stability is still counteracted by the dominant background circulation even with irrigation processes. Thus, more effort should be exerted to maintain the future sustainability of the oasis.

High Mountains Becoming Wetter While Deserts Getting Drier in Xinjiang, China since the 1980s

“…Other studies have also shown that the use of flood irrigation and drip irrigation in oases in the arid region of Central Asia increases the water vapor in the air and accelerates the hydrological cycle of the whole region. However, due to the existence of local circulation (the role of valley winds), summer precipitation in mountainous areas increased significantly, but there was no obvious trend of wetting in the deserts and oases [33].…”

Impacts of Historical Land Use/Cover Change (1980–2015) on Summer Climate in the Aral Sea Region

“…Finally, since the 1950s, the intensified agriculture activities and widespread use of irrigation have significant impact on the regional water‐heat budget, consumed water measuring about 10,000 m 3 ha −1 in farmland and accordingly increasing the local evapotranspiration, which may induce the nonclosure of the surface energy balance in this region (Zhang et al., 2019). In this study, because of the limitation of observed surface energy fluxes, we only validated the model performance in natural vegetation without irrigation and further verification is needed in irrigation‐intensified oasis in order to improve the model's ability in simulating fluxes (Amri et al., 2014).…”

“…Being one of the driest regions in the world, Central Asia is not only more sensitive to global climate change, but also have been largely affected by regional anthropogenic influence, such as the development of irrigated agricultural (Mirzabaev et al., 2016; Zhang et al., 2019). Especially in Aral Sea region, large irrigation systems were created by the former Soviet Union to divert water from the Amu Darya and Syr Darya rivers in order to promote agriculture production (Lioubimtseva et al., 2005).…”

Analysis of the Impacts of Environmental Factors on Rat Hole Density in the Northern Slope of the Tienshan Mountains with Satellite Remote Sensing Data

“…The northern slope of the Tien Shan Mountains belongs to a typical mountain-oasisdesert (from high land to low land) ecosystem [2,3] in the arid regions of Central Asia. The distribution of flora and fauna is strongly dependent on elevation variation.…”

“…Our objective is to examine the relationship between RHD and ecosystems across elevation gradients and to determine their corresponding mechanisms when RHD and local conditions are influenced by the same environmental factors. This is particularly important to examine within NTXJ because local climate patterns have changed significantly [3], and precipitation in the mid-mountain region has increased due to oasis expansion and increased irrigation [27]. Thus, furthermore, the distribution and intensity of grazing may also be influenced by climate change and vegetation dynamics [28].…”