Spatiotemporal Heterogeneity of Irrigation on Heat Waves across the North China Plain

With climate change, the frequency of heat waves has surged dramatically in the North China Plain (NCP). Irrigation affects the occurrence of heat waves globally, but its dynamics with local climate shifts and varying irrigation levels are not well understood. To delineate the effect of irrigation on heatwave trends and their spatiotemporal heterogeneity in the NCP, we utilize observational data, dividing the period into 1968-1995 and 1996-2015 to distinguish climate variability and irrigation evolution. Spatiotemporal multivariate regression and a window search algorithm are used to quantify and compare the variation in irrigation effects. The results indicate that although the overall influence of irrigation is modest, contributing to a reduction of approximately 10% in heat wave development, significant spatiotemporal heterogeneity is observed. Initially, irrigation mitigated northern and enhanced southern heat waves. Over time, the focus of mitigation expanded southwest, reducing the trend of heat wave frequency by −0.162%/10a. We believe that local moisture conditions can explain these variations, which are visually represented through land-atmosphere coupling strength. Driven by climate mode shifts, overall aridity across the NCP has intensified, particularly in the southwest. The land-atmosphere coupling strength remains strong in the north but reverses in the southwest, leading to spatiotemporal heterogeneity of irrigation effects.