Large-scale atmospheric circulations impacts on eastern Mediterranean region

A group of earlier investigations has identified eastern Mediterranean region in which hydrometeorological surface parameters (i.e. precipitation and streamflow) appear to have consistent relationships with some large-scale atmospheric circulations such as the North Atlantic Oscillation (NAO) and El Nino–Southern Oscillation (ENSO). Discussing physical mechanism related to the circulation, in this paper, the impacts of the NAO and ENSO on the hydrology of eastern Mediterranean countries, focusing on Turkey and Iran, are documented from a general perspective. The findings in terms of NAO and ENSO signals for the eastern Mediterranean region differ from one location to another. The articled highlights comprise: For Turkey; i. The results of some lag correlations also indicated a considerable prediction potential for precipitation and streamflow variables. Correlation analysis revealed less sensitive characteristics of Turkish temperature patterns against the NAO. ii. The relation between the NAO index and streamflow PC1 scores (representing a basic streamflow anomaly pattern in the entire Turkey) was determined highly significant for annual average and various seasonal averages. iii. For western Anatolia, the April–July wet period during El Nino events is the season when the teleconnection is strong and consistent. For eastern Anatolia, the February–June wet period during El Nino events is found to be the signal season having high rates of coherence and consistency. For Iran; i. Aridity index series compiled from Khorasan province in northeast of Iran revealed significant correlations between the NAO and NINO-3.4. ii. The NAO index alone could not be a predictor of the local climate in the Zagros Mountains, Iran. Similar to droughts, the wet winter seasons were not in association with the NAO in the same area. In southwest Iran, the October– December NAO season was influenced most by the NAO in both dry and wet spells. iii. The extreme and severe droughts in the western and north western Iran were observed mostly during the warm phase of ENSO. iv. The annual and seasonal water volume of the largest Iranian river, Karoon, has a significant correlation with ENSO indices. v. The ENSO–rainfall relationship was found to be important for rainfallprediction at western margin of the Caspian Sea.