Observational evidence of the cooling effect of agricultural irrigation in Jilin, China.

China features the second largest irrigation area in the world. Several modeling studies on a global scale have shown the irrigation impact in China, but no direct observational evidence has been reported. In this paper, we evaluated the impact of irrigation on temperature in Jilin province, China, using meteorological and satellite observations. The results show that the temperature difference between highly and lightly irrigated sites is statistically significant and highly correlated to the effective irrigation area and crop sown area over the past 53 years. The magnitude of the difference in maximum air temperature was almost twice that of the difference in minimum air temperature. The linear regression coefficient of the time series difference in maximum air temperature was more than three times that of the minimum air temperature. Moreover, both meteorological and satellite observations show that the temperature difference is amplified during drier years. The difference in the magnitude of daytime land surface temperature (LST), between areas with irrigation percentages of more than 50 and less than 50, is as high as 2.7 K during the driest year. Overall, this study may provide evidence that an irrigation cooling effect exists in China. [ABSTRACT FROM AUTHOR]