Spatiotemporal heterogeneity of irrigation on heat waves across the North China plain

Abstract

Irrigation affects the occurrence of heat waves globally, but its dynamics with local climate shifts and varying irrigation levels are not well understood. Utilizing observational data, spatiotemporal multivariate regression, and the window search algorithm, we delineate the effect of irrigation on heat waves in the North China Plain (NCP) before and after 1996. 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 0.232 days/decade. 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.