Development of drought monitoring and early warning model by the investigation of dry season properties in the Aegean region

In this study, the properties of dry seasons occurred between 1970 ? 2006 in the Aegean Region are investigated. The relationships among dry seasons, El Nino Southern Oscillation (ENSO) and North Atlantic Oscillation (NAO) are analyzed. The maps of dry phases are developed by Standardized Precipitation Index (SPI) and Palmer Drought Severity Index (PDSI) methods, and the drought variations in the region are surveyed with respect to zone and time. The percent variations of the river flows in the region are also computed and classified into three stages, namely monitoring, warning and emergency.In the drought seasons, the significant relationships between SPI and positive values of winter NAO index are determined, and decrease in Aegean region precipitations are observed in the positive phase of NAO. The increase in total precipitation amount has observed one year before El Nino years, as well as decrease in and after those years. The severe drought periods have experienced in or after the strong El Nino years. It is decided that the ENSO and NAO influence the total annual precipitation amount in the Aegean region.Consequently, drought monitoring and early warning model and also the Drought Management Plans are needed not only to foreknow the droughts but also to decrease the unfavorable impacts of droughts. Therefore, the droughts should be monitored regularly with SPI and PDSI maps, and it should be evaluated with all factors and stakeholders.Keywords:Drought monitoring, El Nino Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), Standardized Precipitation Index (SPI), Palmer Drought Severity Index (PDSI), Aegean region.