Recent Decline of Irrigation-Induced Cooling Effect Over the North China Plain in Observations and Model Simulations

Abstract

Irrigation over the North China Plain (NCP) has been demonstrated to lower temperature by altering the surface energy budget. During past decades, the concurrence of irrigated area variation and reduced irrigation intensity prompted our investigation into whether there has been a temporal change in irrigation cooling effect over the NCP, which is largely unknown. Using historical observations in 1979–2018, we detect a shift in the cooling effect occurring around 1995, when the expansion of irrigated area was going to slow down and water-conserving irrigation technology was boomingly introduced. After this time, the accelerated process of cooling effect (−0.0045°C year−1) switches to a decelerated one (0.0089°C year−1). Regional climate simulations also show a pronounced slowdown in irrigation-induced cooling with the rate of 0.0081°C year−1. The irrigation-induced cooling is expected to be weaker with the persistent reduction in agricultural water use and contribute to a more rapid warming.