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Aerosols in the tropical and subtropical UT/LS: in-situ measurements of submicron particle abundance and volatility

Borrmann, Stephan and Kunkel, Daniel and Weigel, Ralf and Minikin, Andreas and Deshler, Terry and Wilson, J. C. and Curtius, Joachim and Shur, G. and Belyaev, D. and Law, K. S. and Cairo, F. (2010) Aerosols in the tropical and subtropical UT/LS: in-situ measurements of submicron particle abundance and volatility. Atmospheric Chemistry and Physics, 10, pp. 5573-5592. DOI: 10.5194/acp-10-5573-2010.

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Official URL: http://www.atmos-chem-phys.net/10/5573/2010/acp-10-5573-2010.html

Abstract

Processes occurring in the tropical upper troposphere and lower stratosphere (UT/LS) are of importance for the global climate, for the stratospheric dynamics and air chemistry, and they influence the global distribution of water vapour, trace gases and aerosols. The mechanisms underlying cloud formation and variability in the UT/LS are of scientific concern as these still are not adequately described and quantified by numerical models. Part of the reasons for this is the scarcity of detailed in-situ measurements in particular from the Tropical Transition Layer (TTL) within the UT/LS. In this contribution we provide measurements of particle number densities and the amounts of non-volatile particles in the submicron size range present in the UT/LS over Southern Brazil, West Africa, and Northern Australia. The data were collected in-situ on board of the Russian high altitude research aircraft M-55 "Geophysica" using the specialised COPAS (COndensation PArticle counting System) instrument during the TROCCINOX (Araçatuba, Brazil, February 2005), the SCOUT-O3 (Darwin, Australia, December 2005), and SCOUT-AMMA (Ouagadougou, Burkina Faso, August 2006) campaigns. The vertical profiles obtained are compared to those from previous measurements from the NASA DC-8 and NASA WB-57F over Costa Rica and other tropical locations between 1999 and 2007. The number density of the submicron particles as function of altitude was found to be remarkably constant (even back to 1987) over the tropical UT/LS altitude band such that a parameterisation suitable for models can be extracted from the measurements. At altitudes corresponding to potential temperatures above 430 K a slight increase of the number densities from 2005/2006 results from the data in comparison to the 1987 to 2007 measurements. The origins of this increase are unknown. By contrast the data from Northern hemispheric mid latitudes do not exhibit such an increase between 1999 and 2006. Vertical profiles of the non-volatile fraction of the submicron particles were also measured by a COPAS channel and are presented here. The resulting profiles of the non-volatile number density fraction show a pronounced maximum of 50% in the tropical TTL over Australia and West Africa. Below and above this fraction is much lower attaining values of 10% and smaller. In the lower stratosphere the fine particles mostly consist of sulphuric acid which is reflected in the low numbers of non-volatile residues measured by COPAS. Without detailed chemical composition measurements the reason for the increase of non-volatile particle fractions cannot yet be given. The long distance transfer flights to Brazil, Australia and West-Africa were executed during a time window of 17 months within a period of relative volcanic quiescence. Thus the data measured during these transfers represent a "snapshot picture" documenting the status of a significant part of the global UT/LS aerosol (with sizes below 1 μm) at low concentration levels 15 years after the last major (i.e., the 1991 Mount Pinatubo) eruption. The corresponding latitudinal distributions of the measured particle number densities are also presented in this paper in order to provide input on the UT/LS background aerosol for modelling purposes.

Document Type:Article
Title:Aerosols in the tropical and subtropical UT/LS: in-situ measurements of submicron particle abundance and volatility
Authors:
AuthorsInstitution or Email of Authors
Borrmann, StephanMPI für Chemie, Mainz
Kunkel, DanielMPI für Chemie, Mainz
Weigel, RalfUniv. Mainz
Minikin, AndreasDLR
Deshler, TerryUniv. of Wyoming, USA
Wilson, J. C.Denver Univ., Denver, CO, USA
Curtius, JoachimUniv. Frankfurt
Shur, G.Central Aerological Observ., Dolgoprudny, Moskow Region, R
Belyaev, D.MDB-Myasishchev Design Bureau, Moscow Region, R
Law, K. S.Univ. Paris VI, Paris, F
Cairo, F.CNR, Roma, I
Date:2010
Journal or Publication Title:Atmospheric Chemistry and Physics
Refereed publication:Yes
In Open Access:Yes
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:10
DOI:10.5194/acp-10-5573-2010
Page Range:pp. 5573-5592
Status:Published
Keywords:aerosol, UT/LS, TROCCINOX, AMMA
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:ATM and Operation
DLR - Research area:Aeronautics
DLR - Program:L AO - Air Traffic Management and Operation
DLR - Research theme (Project):L - Climate, Weather and Environment
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics > Atmospheric Trace Species
Deposited By: Dr.rer.nat. Andreas Minikin
Deposited On:12 Jul 2010 11:41
Last Modified:12 Dec 2013 20:59

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