African Dust Outbreaks Research Articles

Influence of African dust on the levels of atmospheric particulates in the Canary Islands air quality network

Time series of levels of atmospheric particulate matter (TSP and PM10) were studied at 19 air quality monitoring stations in the islands of Tenerife and Gran Canaria (Canary Islands) during the period 1998–2000. After analysing seasonal variations, attention was focused on the detection of high TSP and PM10 events and on the identification of their natural or anthropogenic origins. Back-trajectory analysis and TOMS-NASA aerosol index as well as satellite imagery (SeaWIFS-NASA) were used to identify three types of African dust outbreaks differing in seasonal occurrence, source origin and impact on TSP/PM10 levels. Mean annual and daily TSP and PM10 levels were compared with the forthcoming limit values of the EU Air Quality Directive EC/30/1999, and the results showed that the annual and daily limit values established for 2010 would only be met at rural stations. PM levels at urban background, urban and industrial sites would exceed the 2010 objectives. Only the levels at the urban-background stations would meet the requirements for 2005 despite the fact that the trade winds result in lower levels of atmospheric pollutants in the Canary Islands than in continental environments. The results highlight the role of African dust contributions when implementing the limit values of the EU directive.

The 2nd Aerosol Characterization Experiment (ACE-2): meteorological and chemical context

A review is given of the climatological and actual meteorological conditions in the sub-tropical northeast Atlantic, during June−July 1997, when the 2nd Aerosol Characterization Experiment (ACE-2) took place. Surface pressure maps, trajectory calculations and in-situ measurements show how the outflow of European pollution into the marine boundary layer of this area is determined by the location of the Azores high pressure cell. Observations during ACE-2 and 3 preceding summers show that pollution outbreaks both from the Iberian peninsula and from northern or central Europe can occur during such situations. During ACE-2, an unusually low number of strong North African dust outbreaks were recorded at the free tropospheric station of Izaña (Tenerife, 2360 m asl), although dust was recorded aloft the station.