STANDARDIZED PRECIPITATION INDEX (SPI) IN NORTH LIBYA AND CONNECTION WITH NORTH ATLANTIC OSCILLATION (NAO)
Keywords:precipitation, SPI variability, drought period, wet period, NAO , NAO-
A detailed analysis of the SPI variability was conducted targeting nine north western and northeastern meteorological stations in Libya, which has been followed by another thorough analysis of the relationship between such SPI variability and the North Atlantic Oscillation (NAO). A long term precipitation time series spans over the period (1946-2010) has been used along with NAO index data covering the same period of study. The results of the SPI analysis revealed evident distinguish periods of drought and wet years. Stations from Zwara to Benina have experienced a prolonged spell of drought from the beginning of study period up to early eighties, where since then turned to a clear intensified period of wet years onwards. In an opposite manner, the sites of Shahat and Derna started with wet period up to late seventies and shifted to drought afterwards particularly for Shahat station. Interestingly, the long period of drought illustrated at stations from Zwara through Benina seemed favors the negative phase of NAO (NAO-) whereas wet period is associated with positive phase of NAO (NAO+) with some differences between stations. In contrast, Shahat and Derna have responded negatively to NAO in general although for coastal Derna station, fourteen consecutive wet years from 1992-2005 could be attributed to the late impact of positive NAO in that region. The outcomes of this study could indeed benefit in the proactive management plans for the already at risk sectors e.g. agriculture, water resources including groundwater withdraws and water management during severe drought periods.
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