Aerosol processing and CCN formation of an intense Saharan dust plume during the EUCAARI 2008 campaign

Abstract

Abstract. Atmospheric processing and CCN formation of Saharan dust is illustrated through the analysis of an intense Saharan dust event over northern Europe. The analysis of this dust event was realized through the use of different sets of observations and through the use of numerical models. The altitude of the dust plume was assessed using the CALIPSO observations and our model results. The major dust plume was transported over Europe between 2 and 5 km above sea level (a.s.l.). This altitude favored the interaction between the dust plume and the mountain ranges of Europe during its transport. This also led the dust becoming mixed with the European anthropogenic aerosol. The analyses of the simulation show that mineral dust particles accumulated soluble material through internal mixing over the Netherlands (51.97° N; 4.93° E). The value of the CCN0.2/CN ratio obtained over the Netherlands (~50%) is much greater than those observed over the Saharan region. In addition over the Netherlands, the CCN measurement reached 14 000 particles cm−3 at 0.63% supersaturation level on 30 May. Our model results reveal that more than 70% of the CCN concentration observed on 30 May can be explained by the presence of Saharan aged dust. The study reveals that heterogeneous reactions with inorganic salts converted this Saharan mineral dust into compounds that were sufficiently soluble to impact hygroscopic growth and cloud droplet activation over the Netherlands.