Denjean C., Caquineau Sandrine, Desboeufs K., Laurent B., Maille M., Rosado M. Q., Vallejo P., Mayol-Bracero O. L., Formenti P. (2015). Long-range transport across the Atlantic in summertime does not enhance the hygroscopicity of African mineral dust. Geophysical Research Letters, 42 (18), p. 7835-7843. ISSN 0094-8276.
Titre du document
Long-range transport across the Atlantic in summertime does not enhance the hygroscopicity of African mineral dust
Denjean C., Caquineau Sandrine, Desboeufs K., Laurent B., Maille M., Rosado M. Q., Vallejo P., Mayol-Bracero O. L., Formenti P.
Source
Geophysical Research Letters, 2015,
42 (18), p. 7835-7843 ISSN 0094-8276
We present the first direct evidence that the hygroscopic properties of super micron (>1 mu m) African dust particles did not change despite undergoing long-range transport across the Atlantic toward the Caribbean. Concurrent measurements of chemical composition show that most of mineral dust was chemically unprocessed and externally mixed. A minor portion of mineral dust was internally mixed with sulfate and chloride (similar to 13-24% by number) or aggregated with sea-salt particles (similar to 3-6%). Only dust particles aggregated with sea salt showed significant hygroscopic growth above 75% relative humidity (RH), resulting in a decrease in extinction mass efficiency by up to a factor 2.2. All other dust particles did not take up significant amounts of water when exposed to up to 94% RH. These results demonstrate that the direct radiative effect of African dust in this region remained independent of RH and an external mixing state could be considered for evaluating the climate effects of dust.
