«Until Friday 21 June, very hot air masses of desert origin will reach Italy driven by intense southern winds at medium tropospheric altitudes (between 3,000 and 5,000 metres). This flow, triggered by the presence of a deep depression vortex on the Iberian peninsula, will transport large quantities of Saharan dust towards Italy and central-eastern Europe, giving rise to an intrusion of anomalous proportions. The extension of the phenomenon and the dust concentrations predicted by the dispersion models are, in fact, considered unusual."
This is what Lamma, the environmental monitoring and modeling laboratory that brings together the Tuscany Region and the Cnr, explains. Then between Friday and Saturday «the vortex over Spain will move to France and then move to Eastern Europe. The transit of the disturbance will favor the rotation of the winds in the western quadrants, putting an end to the intrusion of desert dust on Italy and Tuscany".
Lamma also specifies that it is «more correct to speak of "dust" and not of sand. The latter is in fact too heavy and coarse to be transported up to medium tropospheric altitudes by vertical motions and winds. The smallest particles, on the contrary , if inserted into a sufficiently intense flow, they manage to overcome the force of gravity and can travel thousands of kilometers before settling."
Furthermore, Saharan dust is rich in micronutrients which are essential for both plants (phosphorus) and marine photosynthetic organisms (iron) and the months in which there is the greatest frequency of Saharan intrusions on central-northern Italy and the Alpine region are May, June and October.
The episode expected in these days «will be very intense. Tomorrow, Thursday 20th, could be the day of maximum intensity, both at altitude and on the ground. Starting from the 21st the values tend to decrease, although they still remain quite high". Dust, Lamma always explains, "contributes to the increase in PM10 concentrations in the area".
(Unioneonline)
