Irrigation effects on humid heat stress under global warming : Focusing on dynamic vegetation feedbacks in a regional climate model

Irrigation exerts contrasting effects on humid heat stress by simultaneously inducing surface cooling and increasing atmospheric humidity through enhanced evapotranspiration, leading to heated debates in heavily irrigated regions such as the North China Plain (NCP). Intensifying or alleviating heat stress due to irrigation may become increasingly important in the context of ongoing global warming. Moreover, irrigation progressively alters vegetation growth, further modifying the local climate and amplifying uncertainties in assessing its overall impact. However, most previous studies have assumed static vegetation or relied on prescribed satellite-based vegetation data, overlooking the two-way feedbacks between irrigation and vegetation. This study adopts recently-improved dynamic crop module that considers the indirect irrigation effect from vegetation, and incorporates it into the Weather Research and Forecasting Model (WRF), to explore the irrigation effects on humid heat stress over the NCP. Using this enhanced model, the EC-Earth3 global projection, which shows a medium level of warming sensitivity among available CMIP6 models, is dynamically downscaled for historical and future periods. The widely used heat stress index, the Wet-Bulb Globe Temperature (WBGT), is then calculated to quantify the combined effects of temperature and humidity changes in response to irrigation amid ongoing global warming. The analysis focuses on understanding the role of dynamic vegetation feedbacks in modulating future humid heat in regions with intense irrigation. Our findings will provide valuable insights into effective irrigation management strategies for thermal risk mitigation. 

[Acknowledgment]

This study was supported by the Research Program for Agricultural Science & Technology Development (Project No. RS-2025-02214912), funded by the National Institute of Agricultural Sciences, Rural Development Administration, Republic of Korea.