Tuesday, 11 January 2005: 9:30 AM
Role of the Monsoons Variability on the Summer Drought events in the Mediterranean Basin
Drought, defined as “The naturally occurring phenomenon that exists when precipitation has been significantly below normal recorded levels, causing serious hydrological imbalances that adversely affect land resource production systems” is not only confined to arid regions, in fact the Mediterranean Region can be seen in this respect as a zone at desertification risk. In order to evaluate the impact of prolonged summer droughts predicted by climate scenarios in the Mediterranean area, a vulnerability context based on time series analysis of aridity index is created to identify the most sensitive zones (hot spots). The impact of drought on terrestrial systems (natural, agricultural, productivity) is strictly connected to the vulnerability context in which the aridity occurs. In order to analyze the occurrence of droughts in the Mediterranean Region, the aridity index has been analyzed for the period 1961-1990, where the aridity is characterized by a scarcity of rainfall and a loss of humidity due to an excess of evaporation over rainfall. The index adopted in the study gives an evaluation of the hydrologic balance between rainfall and the potential evapotranspiration, analogously to the index adopted by UNCCD to define the sensibility to the desertification. Results can be used to evaluate the impact of possible prolonged droughts in the Mediterranean Region on the basis of a vulnerability context. In this respect, the role of the Asian and the West Africa monsoons on the Mediterranean summer climate is investigated on the basis of multiple gridded data sets. Composite differences of few atmospheric parameters are evaluated in years when the monsoons were stronger and weaker than the climatic average. Results show a link between the monsoon intensity and the summer Mediterranean climate variability. Moreover, the eastern and western basins of the Mediterranean respond differently to the different monsoonal systems. The connection between summer Mediterranean climate and the monsoons is evident when years of strong or weak monsoons are considered.