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Atmospheric radiative effects of an in situ measured Saharan dust plume and the role of large particles

Otto, Sebastian and de Reus, Marian and Trautmann, Thomas and Thomas, Andreas and Wendisch, Manfred and Borrmann, Stephan (2007) Atmospheric radiative effects of an in situ measured Saharan dust plume and the role of large particles. Atmospheric Chemistry and Physics, 7, pp. 4887-4903.

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Official URL: http://www.atmos-chem-phys.net/7/4887/2007/

Abstract

This work will present aerosol size distributions measured in a Saharan dust plume between 0.9 and 12 km altitude during the ACE-2 campaign 1997. The distributions contain a significant fraction of large particles of diameters from 4 to 30 μm. Radiative transfer calculations have been performed using these data as input. Shortwave, longwave as well as total atmospheric radiative effects (AREs) of the dust plume are investigated over ocean and desert within the scope of sensitivity studies considering varied input parameters like solar zenith angle, scaled total dust optical depth, tropospheric standard aerosol profiles and particle complex refractive index. The results indicate that the large particle fraction has a predominant impact on the optical properties of the dust. A single scattering albedo of ω<sub>0</sub>=0.75–0.96 at 550 nm was simulated in the entire dust column as well as 0.76 within the Saharan dust layer at ~4 km altitude indicating enhanced absorption. The measured dust leads to cooling over the ocean but warming over the desert due to differences in their spectral surface albedo and surface temperature. The large particles absorb strongly and they contribute at least 20% to the ARE in the dusty atmosphere. From the measured size distributions modal parameters of a bimodal lognormal column volume size distribution were deduced, resulting in a coarse median diameter of ~9 μm and a column single scattering albedo of 0.78 at 550 nm. A sensitivity study demonstrates that variabilities in the modal parameters can cause completely different AREs and emphasises the warming effect of the large mineral dust particles.

Document Type:Article
Title:Atmospheric radiative effects of an in situ measured Saharan dust plume and the role of large particles
Authors:
AuthorsInstitution or Email of Authors
Otto, SebastianUNSPECIFIED
de Reus, MarianInstitute for Atmospheric Physics, Johannes Gutenberg University Mainz
Trautmann, ThomasUNSPECIFIED
Thomas, AndreasInstitute for Atmospheric Physics, Johannes Gutenberg University Mainz
Wendisch, ManfredInstitute for Atmospheric Physics, Johannes Gutenberg University Mainz
Borrmann, StephanInstitute for Atmospheric Physics, Johannes Gutenberg University Mainz
Date:2007
Journal or Publication Title:Atmospheric Chemistry and Physics
Volume:7
Page Range:pp. 4887-4903
Status:Published
Keywords:radiative transfer calculations, aerosol radiative effect, optical properties of mineral dust particles, Saharan dust
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Space (old)
HGF - Program Themes:W EO - Erdbeobachtung
DLR - Research area:Space
DLR - Program:W EO - Erdbeobachtung
DLR - Research theme (Project):W - Vorhaben Entwicklung von Atmosphärenprozessoren (old)
Location: Oberpfaffenhofen
Institutes and Institutions:Remote Sensing Technology Institute > Atmospheric Processors
Deposited By: Prof.Dr. Thomas Trautmann
Deposited On:09 Jan 2008
Last Modified:12 Dec 2013 20:28

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