Application of statistical techniques to study stable isotopes (¹⁸O and ²H) characteristics of precipitation in Iran (Southwest Asia)

Iran is located in semi-arid and arid parts of the world which often faces water shortage crisis. Hence, monitoring precipitation as a crucial part of the water cycle by accurate methods such as stable isotopes techniques has great importance. Various climatic and geographic parameters influence precipitation in Iran which makes the interoperation of stable isotopes signatures in precipitation very complicated. Thus, sampling stations for stable isotopes analyses in Iran have been classified by cluster analysis (CA) to 10 clusters based on their stable isotope characteristics. The results show that the classification of stations by CA has a close correlation with Koppen climatic zones. For instance, the stations in BWh (hot and arid) zone show the most enriched isotopes values as well as high d-excess, and they exist in four clusters. In these stations, the moisture of precipitation is provided from the Persian Gulf, the Arabian and the Red Seas. These stations also deviate from both Global Meteoric Water Line (GMWL) and Eastern Mediterranean Meteoric Water Line (EMMWL) due to intense evaporation effect on precipitation events. However in stations locate in BSk (semi-arid and cold) zone in three clusters, stations mainly plot on the GMWL. These stations show highly depleted stable isotopes signatures as well as high d-excess values. The precipitation over these stations occur by moisture received from the Caspian and the Mediterranean Seas. Stations in two clusters are located in BWk (cold and arid) zone and they show the highest d-excess values and depleted stable isotopes signatures. Finally, in the last cluster, one station exits and located in Dfb (continental and no dry season) zone. This station shows the most depleted stable isotopes signatures.