Decreasing potential evaporation trends in China from 1956 to 2005: Accelerated in regions with significant agricultural influence?

Abstract

The potential evaporation trends in stations in China with varying agricultural influences from 1956 to 2005 were evaluated. The decreasing trends in potential evaporation are accelerated for stations in regions with significant agricultural influences. A total of 244 stations, whose cultivated land area ratio within a 5 km radius is larger than 50%, are categorized as having significant agricultural influence and designated as agricultural stations, whereas 195 stations, whose sum of cultivated, residential, industrial, and traffic land area ratio within a 5 km radius is smaller than 30%, are categorized as having little anthropogenic influence and designated as natural stations. The decreasing trends in potential evaporation are more significant in agricultural stations with a more significant decrease in the aerodynamic term in the arid/semi-arid region and a more significant decrease in the radiation term in the humid region. In the arid/semi-arid region, the significant decrease in potential evaporation in the agricultural stations is attributed to the significant decrease in wind speed, significant increase in relative humidity, and smaller increase in air temperature compared with those in the natural stations. In the semi-humid and humid regions, the more significant decrease in potential evaporation in the agricultural stations is attributed to the significant decrease in solar radiation and wind speed compared with those in the natural stations. According to the analysis of the complementary relationship between actual and potential evaporation, the decrease in potential evaporation is accelerated in the agricultural stations with a more significant increase in water availability induced by irrigation in the arid/semi-arid region and a more significant decrease in solar radiation in the humid region.