Trends in pan evaporation and climate variables in Iran

Fatemeh Soroush, Farshad Fathian*, Farideh Sadat Hasheminasab Khabisi, Ercan Kahya

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)


Contrary to expectations that global warming will be accompanied by an increase in terrestrial evaporation, pan evaporation (PE) has decreased in several parts of the world during the last decades. This opposing relationship is known as the pan evaporation paradox phenomenon that can be affected by climate change. For this purpose, this study identifies spatial and temporal trends in PE and its associated climate variables (Cvars) in Iran at seasonal and annual time scales. Hence, PE and Cvars data from 68 meteorological stations distributed over Iran during the period 1987–2016 were selected. The analyses of the temporal and spatial trends in PE, Cvars, and relationships among them were examined using the statistical techniques to identify the causes of PE trends. Results indicated that stations located in the subtropical region (latitude below 32°), which is mostly located in the southern half of Iran, showed significant negative PE trends (about 20–30% of stations) in spite of an increasing trend in temperatures indicating the “pan paradox” phenomenon. However, stations with significant positive PE trends (about 40% of stations), which are mostly located in the northern half of Iran, are placed at latitudes above 32°. Trend analysis of other Cvars indicated significant increases in temperatures, sunshine duration, and wind speed in more than half of the stations on all time scales. In addition, minimum, maximum, and mean temperatures, and sunshine duration were the most dominant variables affecting PE in annual, spring, autumn, and summer, respectively, in Iran.

Original languageEnglish
Pages (from-to)407-432
Number of pages26
JournalTheoretical and Applied Climatology
Issue number1-2
Publication statusPublished - 1 Oct 2020

Bibliographical note

Publisher Copyright:
© 2020, Springer-Verlag GmbH Austria, part of Springer Nature.


The authors would like to acknowledge the Vali-e-Asr University of Rafsanjan for providing the data used in the paper. The authors wish to thank the editor and two anonymous reviewers for their fruitful comments that helped us improve the quality of the paper.

FundersFunder number
Vali-e-Asr University of Rafsanjan


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