Spatiotemporal patterns of Saharan dust outbreaks in the Mediterranean Basin

Saharan dust outbreaks transport appreciable amounts of mineral particles into the atmosphere of the Mediterranean Basin. Atmospheric particulates have significant impacts on numerous atmospheric, climatic and biogeochemical processes. The recognition of background drivers, spatial and temporal variations of the amount of Saharan dust particles in the Mediterranean can lead to a better understanding of possible past and future environmental effects of atmospheric dust in the region. For this study the daily NASA Total Ozone Mapping Spectrometer's and Ozone Monitoring Instrument's aerosol data (1979-2012) were employed to estimate atmospheric dust amount. Daily geopotential height, wind vector and meridional flow data of the distinguished dust events were obtained from the NCEP/NCAR Reanalysis to compile mean synoptic composite maps. In order to identify the typical dust transportation routes and possible source areas, the backward trajectories were plotted using the NOAA HYSPLIT model. The main period of the dust transportation is from March to end of August, when the thermal convective activity forces the injection of particles to higher atmospheric levels. However, seasonality patterns of the different Mediterranean sub-basins show quite large differences. In western sub-basins, the maxima of Saharan dust outbreaks is in summer, related southwest flow between a southward emanating trough and the northward migrating subtropical high-pressure centre. In the eastern basin, dust storms occur typically in spring, generated by the warm sector winds on foreside of eastward moving Mediterranean and Sharav cyclones. The seasonal distribution of dust events in the central sub-basins shows a bimodal characteristic with a spring and summer peak. (C) 2014 Elsevier B.V. All rights reserved.