Synoptics of dust transportation days from Africa toward Italy and central Europe

Abstract

The mean synoptic situation associated with dust outbreaks from the Sahara into the central Mediterranean was examined on a daily basis for the month of July from 1979 to 1992. Composite patterns of wind, geopotential heights, and temperature for dusty days versus those for all days were analyzed. Dusty days were defined as days with the Total Ozone Mapping Spectrometer Aerosol Index (TOMS‐AI) in the area around the Apennine peninsula (36°N–46°N, 10°E–18°E) equal to or greater than their monthly average plus 1 standard deviation. It was found that the strength and position of two essential features of the circulation patterns, such as the trough emanating southward from the Icelandic low and the eastern cell of the subtropical high, are the governing factors in making suitable flows for the Saharan dust transportation toward Italy. The deep, well‐developed trough near the Atlantic coasts of Europe and Africa, penetrating well to the south, and the strong eastern cell of the subtropical high situated to the northeast from North Africa near the Mediterranean coast, cause strong south‐southwestern flows with the potential to carry dust northward into the Mediterranean. In extreme cases the dust can reach Europe north of the Alps and even northern Europe, reaching the shores of the Baltic. These warm flows, accompanied by high dust load, also cause considerable warming in the central Mediterranean region of the order of 6–8 K at 700 hPa. Alternatively, the weak western trough and the weak eastern subtropical cell cause westerlies, which are inconsistent with the Mediterranean dust intrusions. Analysis of the extreme intrusion cases in July 1988, based on TOMS‐AI data, and several others in July 2001–2003, based on lidar measurements in Rome, demonstrates the synoptic situation that allows the Saharan dust to reach Italy.

Seasonal variability and synoptic characteristics of dust cases over southwestern Saudi Arabia

“…at least one grid point, or one pixel, inside the checking zone that satisfied the corresponding smoothed monthly threshold value). Note that Barkan et al (2005) determined the number of dust days that affected Italy and Central Europe using a threshold value equal to the average plus 1 standard deviation, whereas Prospero et al (2002) used a threshold value, depending on the region, to identify the global dust sources.…”

Novel aerosol analysis approach for characterization of nanoparticulate matter in snow

“…For ice to form in the atmosphere at temperatures warmer than −38°C, airborne particles must be present to initiate heterogeneous ice nucleation, during which ice crystallization starts on a surface. The airborne particles providing their surfaces for initiation of ice crystallization are called ice nuclei (IN) and can be of various sizes and composed of diverse materials (Barkan et al 2005;Xuan et al 2004). Similarly, water droplets rarely form at the conditions found in the atmosphere.…”

Synoptic conditions favouring the occurrence of aerosol episodes over the broader Mediterranean basin

“…Israelevich et al (2003) studied the annual variation of desert dust over the eastern Mediterranean for the warm period of the year and defined its properties, source regions and transport pathways. The synoptic conditions associated with dust transportation towards the central Mediterranean and Europe, based on Aerosol Index (AI) values from the Total Ozone Mapping Spectrometer (TOMS), were analysed by Barkan et al (2005) for the period 1979-1992. Several authors (e.g.…”