Spatiotemporal analysis of air temperature indices, aridity conditions, and precipitation in Iran

Abstract

Global warming has become a major threat to life on the earth, and recognizing its impacts can de nitely be useful in controlling and mitigating its adverse effects. In this study, time series variations in air temperature indices (frost days, T min , T max , T mean , T minmin , T maxmax , T soil-min ), De Martonne aridity index (I DM ) and total precipitation were investigated using a long-term meteorological data of 31 synoptic stations throughout Iran. The results indicated that more than 94% of the stations had increasing trend in T mean , in which about 70% were signi cant at the 0.05 level. The average increase in T min was calculated approximately 1.7 times higher than T max and also the increase in T minmin was about 2.5 times higher than T maxmax . Our ndings showed that, abrupt changes in T min and T max mostly observed in the 1990s were upward in 87% of all the stations. Increase in annual T mean at a rate of 0.3 ºC per decade and reduction of 5 mm per decade in total annual precipitation led to decrease in the I DM aridity index by 0.35 per decade in Iran. The intensity of air temperature increase was higher in tropical regions than in cold regions. Trend analysis in the partial series before and after a change point showed that the trends in T mean before the change point were negative, but turned to positive afterwards in some stations mostly located in the northwestern cold and mountainous regions of the country. Our results revealed that the climate in Iran, in general, has become warmer and drier in the past 60 years and continuation of the current global warming trend will exacerbate this problem in the future. HighlightsIran has become warmer and drier over the last six decades.Global warming has caused the average annual T min to experience three signi cant abrupt upward changes in their time series at some stations.The time series trend of some indices before the change point was different than their trend afterwards.The east coast of the Caspian Sea has shifted from Mediterranean region to semi-arid region due to climate change.Tropical regions were warmed more intense than cold regions.

Long‐Term Variability and Trends in Snow Depth and Cover Days Throughout Iranian Mountain Ranges

“…In several cases, a combination of both positive and negative trends has been observed (Liu et al, 2021;Nawaz et al, 2019;Sun et al, 2019). Based on a combination of results from the present study and Sadeqi and Kahya (2021), it can be concluded that T min increased faster than T max before 1990 in the Iranian mountain ranges, while T max increased more rapidly than T min afterward. Thus, the DTR experienced a negative trend prior to 1990 and then a positive trend thereafter.…”

“…The increase in surface air temperature in Iran over the last 60 years has been higher than the global average (Sadeqi & Kahya, 2021). It has been reported that the rise in air temperature is expected to be severe in the highlands of the west of the country, which would fundamentally alter the hydrological regime in snow‐dominated basins (Darand, 2020; Irannezhad et al., 2016).…”

“…The country is geographically enclosed by two mountain ranges in the northwest‐west and north‐northeast, exerting significant influence on both the spatial and temporal patterns of surface air temperature and precipitation (Ganji, 1968). This complex topography plays a pivotal role in shaping Iran's climate, which ranges from hyper‐arid conditions in central areas to super‐humid climates along the Caspian Sea shores in the north (Sadeqi & Kahya, 2021). In Iran, precipitation gradually decreases from northwest to southeast, while surface air temperature follows an opposite pattern (Hadi Pour et al., 2020).…”

“…Iran has become drier over the last 60 years (Lashkari et al., 2021; Rahimi et al., 2019; Sadeqi & Kahya, 2021), and suffered from excessive increases in irrigated cultivable lands (Irannezhad et al., 2018; Maghrebi et al., 2020; Mirzaei et al., 2019). These changes in climatic conditions and land use patterns have already raised serious freshwater challenges in this country (Ashraf et al., 2019; Karimi Alavijeh et al., 2021; Noori et al., 2021).…”

Vulnerability and Risk Assessment to Climate Change in Sagar Island, India

“…The consequences of the overpowering erosion process on human activity and the economy are perfectly portrayed along the coasts of any island system [34,[62][63][64][65]. The exposure indices of Tmax, Tmin, and precipitation in the risk analysis have also been used by various workers with similar results [66][67][68]. When examining the vulnerability of the state of Georgia in the United States, Binita et al (2015) discovered that one of the indications of a changing climate is changes in the intensity and frequency of climate extremes.…”