Impact of atmospheric transport on the evolution of microphysical and optical properties of Saharan dust. Issue 10 (30th May 2013)

• Record Type: Journal Article
• Authors: Ryder, C. L.; Highwood, E. J.; Lai, T. M.; Sodemann, H.; Marsham, J. H.
• Is Part Of: Geophysical research letters. Volume 40:Issue 10(2013:May)
• Page Start: 2433
• Page End: 2438
• Publication Date: 2013-05-30
• Subjects: dust -- aircraft measurements -- transport -- saharan air layer -- deposition -- size distribution; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/grl.50482
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract : [1] Saharan dust affects the climate by altering the radiation balance and by depositing minerals to the Atlantic Ocean. Both are dependent on particle size. We present aircraft measurements comprising 42 profiles of size distribution (0.1–300 µm), representing freshly uplifted dust, regional aged dust, and dust in the Saharan Air Layer (SAL) over the Canary Islands. The mean effective diameter of dust in SAL profiles is 4.5 µm smaller than that in freshly uplifted dust, while the vertical structure changes from a low shallow layer (0–1.5 km) to a well‐mixed deep Saharan dust layer (0–5 km). Size distributions show a loss of 60 to 90% of particles larger than 30 µm 12 h after uplift. The single scattering albedo (SSA) increases from 0.92 to 0.94 to 0.95 between fresh, aged, and SAL profiles: this is enough to alter heating rates by 26%. Some fresh dust close to the surface shows SSA as low as 0.85. Key Points: Airborne vertically resolved measurements of dust size (fresh, aged, Atlantic) Decrease in size with dust age, 60 ‐ 90% of sizes > 30 microns absent after 12 h Change in optical properties and vertical distribution with age and transport