3. Climate

Iran is characterized by an extremely diversified climate, ranging from extra-arid to per-humid type. The main reasons are (a) vast extension of latitude, (b) stretching mountains and tremendous changes in altitude across the country, and finally (c) the position of the land considering seas and adjacent/far water. In this chapter, the effect of these factors on Iran’s climate is explained, and main climatic parameters including precipitation, temperature, humidity, solar radiation, wind regime, and prevailing winds are classified, and their spatial/temporal distribution maps are presented. The climate-based zoning of Iran according to the modified de Martonne’s classification system shows a rapid decrease from extra-arid toward per-humid in such a way that 64% of the whole country is arid and 20% semi-arid. Hence, Mediterranean to per- humid climate type is limited to 16%. The same study shows the future status of climatic condition during the 2050s and 2080s as becoming drier and warmer. Changes in the percentage of covered areas by different climates and sub-climates are presented quantitatively.