Assessing the climatic effects and feedback mechanisms of large-scale crop irrigation using the improved WRF model

Large-scale crop irrigation (LSCI) plays an important role in regulating regional hydrometeorological processes and influencing climate conditions. This study investigates the climatic effects and underlying mechanisms of LSCI in the Huanghe-Huaihe-Haihe River (HHH) basin during 2001—2022 using the Weather Research and Forecasting (WRF) model coupled with an improved Noah-MP land surface scheme through comparative simulations with and without irrigation. The results show that irrigation significantly modifies surface water and energy balances, leading to a 2.85% increase in evapotranspiration, a 0.19°C reduction in near-surface temperature, and a 5.29 mm increase in precipitation, together with enhanced atmospheric water vapor transport. These changes promote precipitation recycling, with pronounced precipitation enhancement in heavily irrigated eastern regions and downwind areas influenced by monsoon circulation (exceeding 30 mm). Mechanistic analysis indicates that irrigation regulates regional climate through coupled thermodynamic and dynamic processes involving evapotranspiration enhancement, surface energy redistribution, and water vapor flux intensification. Notably, approximately 14.65% of irrigation water is converted into additional precipitation, highlighting a significant land-atmosphere feedback effect in large agricultural basins. This study provides new insights into irrigation climate interactions and offers a scientific basis for understanding land-atmosphere feedback mechanisms and improving regional water resource management.