Study of Relation between ENSO Phenomenon and Drought Occurrence in Iran

The role of ENSO ocean- atmosphere phenomena in occurrence of country drought was studied based on 30 synoptic stations in a time span from station construction to 2010. For assessment of ENSO role some indices, including SOI, MEI, NINO1, NINO3.4, NINO3, NINO4, NOI, TNI and PNA were used as independent variabales and SPI as dependent variable to determine drought occurrence. The results of the Pearson correlation analysis expressed the relationship between ENSO climatic indices and the SPI. The maximum correlation belonged to SOI with 43.33 %. The correlation values of MEI, NINO 3.4, NINO 4, NOI, NINO 1, TNI and PNA were in the next ranks, respectively. Mereover, drought correlation with SOI in parts of the west and North West of the country were more than other areas. Comparison of drought occurrence number in El Nino as warm phase of ENSO and La Nina as cold phase of ENSO showed that the droughts number in the La Niña phase was more than the El Nino, which confirmed that the El Nino phase led to reduce the country drought.