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Title: Analysis of number size distributions of tropical free tropospheric aerosol particles observed at Pico Espejo (4765 m a.s.l.), Venezuela
Authors: Schmeissner, T.Krejci, R.Ström, J.Birmili, W.Wiedensohler, A.Hochschild, G.Gross, J.Hoffmann, P.Calderon, S.
Publishers Version: https://doi.org/10.5194/acp-11-3319-2011
Issue Date: 2011
Published in: Atmospheric Chemistry and Physics, Volume 11, Issue 7, Page 3319-3332
Publisher: München : European Geopyhsical Union
Abstract: The first long-term measurements of aerosol number and size distributions in South-American tropical free troposphere (FT) were performed from March 2007 until March 2009. The measurements took place at the high altitude Atmospheric Research Station Alexander von Humboldt. The station is located on top of the Sierra Nevada mountain ridge at 4765 m a.s.l. nearby the city of Mérida, Venezuela. Aerosol size distribution and number concentration data was obtained with a custom-built Differential Mobility Particle Sizer (DMPS) system and a Condensational Particle Counter (CPC). The analysis of the annual and diurnal variability of the tropical FT aerosol focused mainly on possible links to the atmospheric general circulation in the tropics. Considerable annual and diurnal cycles of the particle number concentration were observed. Highest total particle number concentrations were measured during the dry season (January–March, 519 ± 613 cm−3), lowest during the wet season (July–September, 318 ± 194 cm−3). The more humid FT (relative humidity (RH) range 50–95 %) contained generally higher aerosol particle number concentrations (573 ± 768 cm−3 during dry season, 320 ± 195 cm−3 during wet season) than the dry FT (RH < 50 %, 454 ± 332 cm−3 during dry season, 275 ± 172 cm−3 during wet season), indicating the importance of convection for aerosol distributions in the tropical FT. The diurnal cycle in the variability of the particle number concentration was mainly driven by local orography.
Keywords: aerosol; annual variation; atmospheric general circulation model; concentration (composition); diurnal variation; orographic effect; particle size; size distribution; tropical region; troposphere
DDC: 550
License: CC BY 3.0 Unported
Link to License: https://creativecommons.org/licenses/by/3.0/
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