NEW Paper - Saharan dust in the Mediterranean region

Varga, Gy., Újvári, G., Kovács, J. (2014). Spatiotemporal patterns of Saharan dust outbreaks in the Mediterranean Basin. Aeolian Research 15. pp. 151–160.

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.

Saharan dust addition plays crucial role in the unique Mediterranean terra rossa formation too, where the chemical compounds of soils (e.g. silt sized quartz in limestone or basalt derived soils) can only be explained by some external, aeolian dust accretion as it was identified in Portugal (Jahn et al., 1991), in Spain (Muhs et al., 2010), in Italy (Jackson et al., 1982), in Croatia (Durn et al., 1999), in Greece (MacLeod, 1980), in Turkey (Atalay, 1997) and in Israel (Yaalon and Ganor, 1973; Yaalon, 1997). Small pulses and near-continuous dust addition to soil could affect the whole texture, individual horizons and the fertility by dust-derived nutrients and clay minerals (Simonson, 1995).

Dust activity of Saharan sources has been much more dominant during Pleistocene glacial periods, as it is inferred by the widespread aeolian dust deposits (loess, desert loess, loess-like deposits and marine sediments) of the investigation area with relevant Saharan contribution (Tsoar and Pye, 1987; Cremaschi, 1990; Rózycki, 1991; Hoogakker et al., 2004; Larrasoaña et al., 2008).