0000000000287273
AUTHOR
C. Deutscher
State of mixing, shape factor, number size distribution, and hygroscopic growth of the Saharan anthropogenic and mineral dust aerosol at Tinfou, Morocco
The Saharan Mineral Dust Experiment (SAMUM) was conducted in May and June 2006 in Tinfou, Morocco. A H-TDMA system and a H-DMA-APS system were used to obtain hygroscopic properties of mineral dust particles at 85% RH. Dynamic shape factors of 1.11, 1.19 and 1.25 were determined for the volume equivalent diameters 720, 840 and 960 nm, respectively. During a dust event, the hydrophobic number fraction of 250 and 350 nm particles increased significantly from 30 and 65% to 53 and 75%, respectively, indicating that mineral dust particles can be as small as 200 nm in diameter. Log-normal functions for mineral dust number size distributions were obtained from total particle number size distributio…
Dust mobilization due to density currents in the Atlas region: Observations from the Saharan Mineral Dust Experiment 2006 field campaign
[1] Evaporation of precipitation is a ubiquitous feature of dry and hot desert environments. The resulting cooling often generates density currents with strong turbulent winds along their leading edges, which can mobilize large amounts of dust. Mountains support this process by triggering convection, by downslope acceleration of the cool air, and by fostering the accumulation of fine-grained sediments along their foothills through the action of water. For the Sahara, the world's largest dust source, this mechanism has been little studied because of the lack of sufficiently high resolution observational data. The present study demonstrates the frequent occurrence of density currents along th…
Size distribution, mass concentration, chemical and mineralogical composition and derived optical parameters of the boundary layer aerosol at Tinfou, Morocco, during SAMUM 2006
During the SAMUM 2006 field campaign in southern Morocco, physical and chemical properties of desert aerosols were measured. Mass concentrations ranging from 30 Ã�¼g m-3 for PM2.5 under desert background conditions up to 300,000 Ã�¼g m-3 for total suspended particles (TSP) during moderate dust storms were measured. TSP dust concentrations are correlated with the local wind speed, whereas PM10 and PM2.5 concentrations are determined by advection from distant sources. Size distributions were measured for particles between 20 nm and 500 Ã�¼m diameter (parameterizations are given). Two major regimes of the size spectrum can be distinguished. Smaller than 500 nm particle diameter, the distrib…
In situ measurements of optical properties at Tinfou (Morocco) during the Saharan Mineral Dust Experiment SAMUM 2006
In situ measurements of optical and physical properties of mineral dust were performed at the outskirts of the Saharan Desert in the framework of the Saharan Mineral Dust Experiment part 1 (SAMUM-1). Goals of the field study were to achieve information on the extent and composition of the dust particle size distribution and the optical properties of dust at the ground. For the particle number size distribution, measured with a DMPS/APS, a size dependent dynamic shape factor was considered. The mean refractive index of the particles in this field study is 1.53–4.1 × 10 -3 i at 537 nm wavelength and 1.53–3.1 × 10 -3 i at 637 nm wavelength derived from measurements of scattering and absorption…