ROMA (ITALPRESS) – A significant episode of air particulate transport is observed from the early morning of yesterday and still in progress at the Ottavio Vittori climate observatory of Monte Cimone, the research station of CNR-ISAC located at 2165 meters of altitude, in the northern Apennines. The measures carried out directly in the atmosphere show, from the early hours of August 27, a strong and rapid increase in the concentration of coarse particles, attributable to Sahariane powders. The transport is evident also to the naked eye if we compare the images of the webcam of the Observatory, taken at the same time in two consecutive days: they show the passage from conditions of good visibility on 26 August to a strongly veiled atmosphere on 27 August, with a marked reduction of visibility.
The episode does not only concern the air immediately in contact with the ground but several kilometers of atmosphere, as the observations made at the Observatory with a remote-sensing tool (Automated-Lidar-Ceilometer, operating within the national ALICENET network). This instrument, able to reveal in real time the distribution with the share of these particles, shows in fact a marked signal of aerosol distributed throughout the day of yesterday, with more intense structures evident between about 2 and 5 km of altitude, descending to the ground especially after the 12 UTC (the 14 local ones). In Monte Cimone, the presence of this thick layer of powders and the increase of coarse particles measured in the air to the surface is consistent with the passage of an air mass containing a significant amount of mineral particulate, that is “sand” Sahariana. The retrotraiettories calculated with the NOAA HYSPLIT model confirm the Saharan origin of the air mass and the Copernicus Atmosphere Monitoring Service (CAMS) forecasts today indicate the presence of an area of high concentration of aerosols and dust on Italy and the Mediterranean. The combination of retrotrajectory, remote sensing observations and situ measurements allows to reconstruct not only the presence of the episode, but also its dynamic 3D air transport. The episode also highlights the quality of air. The PM10 concentration measured at Monte Cimone exceeded the value indicated by the World Health Organization (WHO) as a guide value for the average of 24 hours in the global air quality guidelines, highlighting the intensity of the episode. The presence of mineral powder can therefore contribute importantly to the concentration of PM10, also found in urban areas. The desert particulate matter consists mainly of relatively large particles and, precisely for this reason, can determine particularly marked increases in the coarse fraction of the atmospheric particulate. The concentrations of desert dust also had a significant impact on atmospheric visibility, which was significantly reduced (from 20 km to values around 12 km) with the arrival of the “sand” transported by the Sahara.
The episode observed is an example of the importance of high mountain measures: Monte Cimone is the main Italian station for the study of the composition of the atmosphere at altitude, the only GAW-WMO global station at national and Mediterranean level. The location of the Observatory, at more than 2000 meters of altitude and far from the main local sources of pollution, allows to observe the arrival of air masses from distant regions and to study the transport of aerosols on a regional and continental scale. The combined monitoring of soil particles and aerosols along the atmospheric column allows to distinguish long distance transport episodes from variations in atmospheric composition related to local sources, i.e. pollutants. These observations are also fundamental for understanding the interactions between aerosols, air quality and climate, as atmospheric particles affect both human health and radiative balance and the hydrological cycle of the atmosphere. The measurements of the Ottavio Vittori Observatory will continue in the coming hours to follow the evolution of the episode and verify the duration and characteristics of the dust transport on the area of northern Italy.
– CNR press office photos –
(ITALPRESS).
