Climate of Iran according to Köppen-Geiger, Feddema, and UNEP climate classifications

This study introduces the climate of Iran determined according to Köppen-Geiger, Feddema, and UNPEP climate classifications, computed with a high-resolution ground-based gridded dataset for the 1985–2017 period. Ten Köppen-Geiger climate types were found for Iran, from which climate types “Bwh,” “Bsk,” “Csa,” “Bsh,” and “Bwk” cumulatively account for more than 98% of the territory. Likewise, fourteen Feddema’s climate types were determined for Iran when only a combination of moisture and thermal factors were used for the classification, but a set of 24 climate types were identified when annual and seasonal characteristics were also incorporated in an exhaustive Feddema’s climate classification. From these 24 climate types, “dry cool with extreme seasonal temperature,” “semiarid hot with extreme seasonal temperature,” “semiarid warm with extreme seasonal temperature,” “semiarid torrid with extreme seasonal temperature,” and “dry warm with extreme seasonal temperature” cover 24.55%, 15.32%, 14.92%, 14.40%, and 8.90% of Iran, respectively. These main climate types collectively cover more than 87% of Iran. Similarly, UNEP’s climate types “arid,” “semi-arid,” “humid,” and “sub-humid” characterized more than 98% of Iran. A few other vertically stratified climate types appeared over the highlands of Iran as a result of changes in elevation and slope aspects of the mountains. The spatial distribution of the climate types in all created climate classification maps reflects the general pattern of the topographical features of Iran, including the Alborz and Zagros mountain ranges. The combined effect of topography and vicinity to the Caspian Sea also creates very distinct climate types in northern Iran. The climate maps of the three used methods reflect the joint effects of topography, latitudinal variation, and land/sea surface contrast on the climate of Iran, which are jointly responsible for creating the diverse climate types of the country. A pairwise comparison made between the three classifications showed a satisfactory agreement between the three schemes in representing the main climate types of Iran.