Investigating Changes in Pan Evaporation Values in Iran, Considering the Autocorrelation Effect

Abstract

Investigating the long-term changes of meteorological parameters in each basin or region serves as the first component of the monitoring system. In this study, the trend of changes in pan evaporation values in Iran's meteorological stations (provincial centers) in the period of 1994-2021 was investigated using the modified Mann-Kendall test by removing the effect of data autocorrelation. The results of the investigation of the trend of changes in pan evaporation values in Iran showed that in 54% of the studied stations, the trend of changes in pan evaporation values is increasing and in 46% it is decreasing. But the average changes in Iran are incremental. Significant increasing and decreasing changes were also observed among the studied stations. The capital of Iran, Tehran, obtained the highest increase in pan evaporation among other studied stations according to the slope of the trend line (Sen’s slope). The highest rate of reduction in annual pan evaporation is related to Ahvaz station in the southwest of Iran. The results of the regional spatial survey also showed that the main decreasing changes in the amount of pan evaporation values are observed in the southern, southwestern and southeastern regions of Iran. The results of the present study show that despite the increase in temperature in most areas, there is a decrease in pan evaporation values in some areas. This reduction of pan evaporation values is important in studies of water resources and meteorology, considering the arid and semi-arid climate of Iran.

Keywords

• aerosol
• climate change
• mann-kendall
• sen’s slope