Hydrological drought in the west of Iran and possible association with large-scale atmospheric circulation patterns

Drought is a slow-onset, creeping natural hazard which is an inevitable part of normal climate fluctuation especially in arid and semiarid regions, and its variability can be explained in terms of large-scale atmospheric circulation patterns. Standardized streamflow index (SSFI) was utilized to characterize hydrological drought in the west of Iran for the hydrological years of 1969-1970 to 2008-2009. The linkage of atmospheric circulation patterns (ENSO, NAO) to hydrological drought was also used to reveal relations of climate variability affecting hydrological drought. River discharges exhibited negative anomalies during the warm phase of ENSO (El Nino) which caused the extreme and severe droughts in the study area, being strongest during the hydrological years of 2007-2008 and 2008-2009. The analysis also indicated the teleconnection impact of ENSO on the hydrological drought severity in the first half of the hydrological year especially between November and March. Moreover, the concurrent and lag correlations revealed a weak relationship between the SSFI drought severity and the NAO index. Copyright (c) 2012 John Wiley & Sons, Ltd.