Stable Isotopes Anomalies of Storm Event in April 2019 in Southwestern Iran: A Method to Characterize the Origin of the Atmospheric Masses

Abstract

Abstract To determine the source of April 2019 storm event in south-western Iran, stable isotopic technique (2H and 18O) of precipitation were used. The unique event, with a mean of 230 mm/year, i.e. 46% of the annual rainfall over four days, caused large dams on Dez and Karkheh rivers to overflow and a great deal of casualties and financial losses. To determine the characteristics of stable isotopes 2H and 18O of this event, 43 samples of rain water were collected in the area about 41,000 (Km)2 in south-western Iran with altitudes between zero to 2814 m (m.a.s.l). The local meteoric water line (LMWL) was prepared during the storm event and compared with the global, Mediterranean and other parts of Iran as well as neighbouring countries. According to the LMWL equation (δ2H = 6.5996 δ 18O + 7.561) and d-excess (with average 7.85 ‰), the source of precipitation was the integration of the meteoric masses of Mediterranean and Red Sea. There was a low correlation between the altitude increase and the 18O decrease (0.13 per 100 meters), which is a characteristic of this storm event. This isotopic study has proven the impact of Sudanese mass on the occurrence of storm event in south-western Iran for the first time isotopically.