Studying spatial and temporal changes of aridity in Iran
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ORIGINAL PAPER
Studying spatial and temporal changes of aridity in Iran Hasan Zolfaghari 1 & Jafar Masoompour 1 & Maryam Yeganefar 2 & Mehry Akbary 3
Received: 6 May 2015 / Accepted: 8 February 2016 # Saudi Society for Geosciences 2016
Abstract Optimum use of water in agriculture, drinking, and industry is necessary in arid and semi-arid regions like Iran, which face serious water tensions. Since studying aridity and its trend of changes has a significant role in water resources management and urban planning, this research has investigated spatial and temporal changes and trend of aridity changes in Iran as an arid country. To study the issue, 51 weather stations of Iran which covered a 30-year statistical period (1981–2010) were selected. Climatic variables, namely precipitation, vapor pressure, local pressure, temperature, maximum temperature, and relative humidity and required data to calculate the potential evapotranspiration were extracted from Iran meteorology organization data. In next step by applying Ai, Im, and Iq aridity indices, zoning of the aridity was done after studying the aridity traits and its change. Then the most compatible aridity index was introduced according to the values of correlation between climatic factors of aridity indices and the magnitude of each main climatic area of Iran. Furthermore, in order to recognize aridity changes in Iran
during the selected 30-year period, Mann-Kendal nonparametric test was used. Correlation analysis results showed that 35.4 and 64.6 % of Iran arid areas show more compatibility with Im and Ai, respectively, which means that these indices are more appropriate to study aridity in arid regions of Iran. Also, it was revealed that 5.6 and 94.3 % of Caspian south plain region has more compatibility with Ai and Iq indices, respectively. As a matter of fact, 77.8, 0.75, and 21.4 % of the country area can be studied better by Ai, Iq, and Im, respectively. Also, the results of Mann-Kendal nonparametric test confirmed that aridity is developing in Iran. In other words, 80.4 % of Iran area had increasing trend of aridity during the selected period and in just 19.6 % of the area, aridity trend was not significant or decreasing. Keywords Aridity . Aridity index . Zoning . Trend of aridity changes . Iran
Introduction * Hasan Zolfaghari [email protected] Jafar Masoompour [email protected] Maryam Yeganefar [email protected] Mehry Akbary [email protected]
1
Department of Geography, Razi University, Kermanshah, Iran
2
Razi University, Kermanshah, Iran
3
Faculty of Geographical Sciences, Kharazmi University, Tehran, Iran
Vast areas of Iran and a third of world area have arid condition. These regions face shortages to fulfill water requirements of plants naturally (Rodrigues 2004). Although there are different factors associating with the aridity definitions, the most common of all is the lack of precipitation in comparison with potential evapotranspiration which causes problems for water requirement of plants (Bannayan et al. 2010). Agnew
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