Simulating the Climatic Effects of Irrigation Over China by Using the WRF‐Noah Model System With Mosaic Approach

Abstract

Investigation on the climatic effects of irrigation is of great significance to fully understand the impact of water management on the Earth's environment and hydrological cycle. To comprehensively explore the effects of irrigation across different climatic regions over China, we propose a novel combined irrigation scheme (including dynamic and fixed irrigation schemes) into the Weather Research and Forecasting (WRF)‐Noah‐mosaic model. Two experiments (with and without irrigation) are designed to simulate the impacts of irrigation over China on regional climate. As irrigation increases the latent heat flux but decreases the sensible heat flux and surface temperature, and the magnitudes of corresponding change are highly dependent on the irrigation amounts and irrigation fraction, the evaporative cooling effects significantly reduce the warm bias over extensive irrigation area during crop growing seasons. Meanwhile, irrigation increases soil moisture during both irrigated and non‐irrigated seasons. Compared with the dynamic irrigation scheme, the fixed irrigation scheme results in relatively higher subsurface runoffs due to the continuous infiltration. In addition, the irrigation‐induced changes on precipitation during spring (March–May) are weaker than that during summer (June–August). The opposed effects of irrigation cooling and wetting on generating convective precipitation, and the irrigation‐induced changes in large‐scale circulation jointly give rise to the heterogeneous changes of precipitation. Besides, the subgrid‐scale irrigation scheme can capture the climatic effects of irrigation in some grids where the dominant land use types are not cropland, indicating that in mesoscale simulation, climate model coupled with subgrid‐scale irrigation scheme may improve climate variables trends attribution studies.

Reforestation in Southern China Enhances the Convective Afternoon Rainfall During the Post-flood Season

“…For example, Zhong et al (2017) highlighted that urban heat islands in the Yangtze River Delta urban cluster can increase extreme summer rainfall through enhanced afternoon convergence and updrafts. Liu et al (2021a) revealed that the cooling and wetting effects of irrigation exerted opposite impacts on convective precipitation over China. To better assess the climate effects of realistic LUCCs, the effects of vegetation changes, urbanization and land management changes (e.g., irrigation) on regional climate need to be considered and quantified simultaneously in future studies.…”

A review on irrigation parameterizations in Earth system models

“…The dataset further includes spatial information about multi-cropping agricultural land as well as irrigation calendars. MIRCA2000 has been used in multiple studies, e.g., Leng et al (2017), Cheng et al (2021), andLiu et al (2021). For the continental United States, two other datasets of irrigated areas are available at higher resolution, namely (i) Ozdogan and Gutman (2008) at ∼500 meters resolution and (ii) the Irrigated Agriculture Dataset (MIrAD-US) developed by Pervez and Brown (2010) and Brown and Pervez (2014) at 250 meters.…”

“…The latter approach is expressed as the number of consecutive hours h I , and is used to localize the irrigation procedure in time (e.g., Leng et al, 2013;Valmassoi et al, 2020a). Examples of different start hours and length are 06 local and 4 h (e.g., Ozdogan et al, 2009;Leng et al, 2013;Yang et al, 2016), 08 (Liu et al, 2021) or 09 (Evans and Zaitchik, 2008;Wu et al, 2018) local time and for 2 h and 30 min, respectively, or a sensitivity to these parameters by Valmassoi et al (2020a). The irrigation duration period is usually employed to equally partition the calculated water over all the consecutive hours, transforming the quantity to a rate (mm s −1 ), for example.…”

“…where θ i has to be calculated only for the liquid water content to already account for the plant-available water. The maximum function is used in Leng et al (2013), but not by e.g., Decker et al (2017), Wu et al (2018), andLiu et al (2021). This implies that Leng et al (2013) does not allow for a surplus in one layer to reduce the deficit in another.…”

Interplay Between Urbanization and Irrigation on Summer Climate in the Huang‐Huai‐Hai Plain, China

“…Climate change influences grain production as the atmospheric conditions and water supply alter, which makes the climatic research regarding 3HP greatly significant. Understanding the specific environmental impact of urbanization and irrigation is of great significance to fully understanding the regional climate response to the land use policy and water management (G. Liu et al., 2020).…”