Observational Evidence of Increased Afternoon Rainfall Downwind of Irrigated Areas

Irrigation plays a vital role in addressing the growing food demand of an increasing global population. About 70% of worldwide freshwater withdrawals are used for irrigation, and of the ca. 16 million km² of global cropland, about 20% are irrigated. Due to the massive redistribution of water across the land surface and pumping of groundwater resources, irrigation represents one of the most critical and direct human interventions on the coupled water and energy cycles. As irrigated farmland continues to expand, understanding the climate impact of extensive irrigation becomes increasingly important. Yet, the effect on rainfall patterns near irrigated areas remains less clear. Here, we detect a systematic impact of extensive irrigation at the global scale on the location and downwind rainfall amount of afternoon rain. Using two global, high-resolution, sub-daily precipitation datasets, we show that afternoon rain events occur more often 10 km to 50 km downwind and less often upwind of extensively irrigated land. However, we also find that the total amount of heavy afternoon rain downwind of irrigated areas is lower than upwind. Our results provide large-scale observational evidence of the local precipitation dynamics and land-atmosphere interactions surrounding irrigated areas to provide new insights for regional water management and help constrain the representation of these processes in next-generation climate and weather forecasting models.