Assessing the aridity indices in Northeast Iran: Implications for climate change and agricultural water management.

Abstract

Aridity indices have been widely applied in dividing climate regimes and monitoring drought events. The knowledge of the aridity index and reference evapotranspiration is very important not only for understanding climate change and its effects on ecosystem stability but also for managing agricultural water resources. Therefore, in this work, we studied the spatial-temporal variation and trend of ETo, Tmean, and four aridity indices, such as the De Martonne aridity index, Pinna combinative index, FAO aridity index, and Thornthwaite aridity index, and its climatic attribution in Northeast Iran using the observed climate records from 10 synoptic meteorological stations from 1950 to 2021. The results showed that ETo for Northeast Iran as a whole exhibited an increase at a rate of +9.65 mmyr-1; Tmean showed an increasing trend at the rate of 0.03 ºC year−1 from the beginning of the statistical period of each station until 2021. Also, the AIT, AIDM, AIP, and AIF increased significantly by +0.001, -0.03, -0.01, and -0.001 year-1, respectively. Approximately 100% of stations showed an increasing trend in AIT and AIF, while 50% of stations reached up to a significant increasing level, and about 60% of stations showed an increasing trend in AIDM and AIP, while 70% of stations reached a significantly increasing level, which demonstrated that Northeast Iran was getting drier for the recent 40 years. This analysis of this study enhances the understanding of the relationship between climate change and drought in Northeast Iran, may be helpful for the agricultural irrigation system.