%0 Journal Article
%4 sid.inpe.br/plutao/2017/06.21.20.44
%2 sid.inpe.br/plutao/2017/06.21.20.44.38
%@doi 10.5194/acp-2016-1155
%@issn 1680-7367
%F lattes: 5379515759830546 14 BragaRWJAWPVMBAMVMG:2017:AeCoDe
%T Aerosol concentrations determine the height of warm rain and ice initiation in convective clouds over the Amazon basin
%D 2017
%9 journal article
%A Braga, Ramon Campos,
%A Rosenfeld, Daniel,
%A Weigel, Ralf,
%A Jurkat, Tina,
%A Andreae, Meinrat O.,
%A Wendisch, Manfred,
%A Pöschl, Ulrich,
%A Voigt, Christiane,
%A Mahnke, Christoph,
%A Borrmann, Stephan,
%A Albrecht, Rachel I.,
%A Molleker, Sergej,
%A Vila, Daniel Alejandro,
%A Machado, Luiz Augusto Toledo,
%A Grulich, Lucas,
%@affiliation Instituto Nacional de Pesquisas Espaciais (INPE)
%@affiliation The Hebrew University of Jerusalem
%@affiliation Johannes Gutenberg-Universität
%@affiliation Institut für Physik der Atmosphäre
%@affiliation Max Planck Institute for Chemistry
%@affiliation Universität Leipzig
%@affiliation Max Planck Institute for Chemistry
%@affiliation Johannes Gutenberg-Universität
%@affiliation Johannes Gutenberg-Universität
%@affiliation Johannes Gutenberg-Universität
%@affiliation Universidade de São Paulo (USP)
%@affiliation Max Planck Institute for Chemistry
%@affiliation Instituto Nacional de Pesquisas Espaciais (INPE)
%@affiliation Instituto Nacional de Pesquisas Espaciais (INPE)
%@affiliation Johannes Gutenberg-Universität
%@electronicmailaddress ramonbraga87@gmail.com
%@electronicmailaddress
%@electronicmailaddress
%@electronicmailaddress
%@electronicmailaddress
%@electronicmailaddress
%@electronicmailaddress
%@electronicmailaddress
%@electronicmailaddress
%@electronicmailaddress
%@electronicmailaddress
%@electronicmailaddress
%@electronicmailaddress daniel.vila@inpe.br
%@electronicmailaddress luiz.machado@inpe.br
%B Atmospheric Chemistry and Physics Discussion
%V 2017
%P 1-44
%X We have investigated how pollution aerosols affect the height above cloud base of rain and ice hydrometeor initiation and the subsequent vertical evolution of cloud droplet size and number concentrations in growing convective cumulus. For this purpose we used in-situ data of hydrometeor size distributions measured with instruments mounted on HALO (High Altitude and Long Range Research Aircraft) during the ACRIDICON-CHUVA campaign over the Amazon during September 2014. The results show that the height of rain initiation by collision and coalescence processes (Dr, in units of meters above cloud base) is linearly correlated with the number concentration of droplets (Nd in cm-3) nucleated at cloud base (Dr ≈ 5·Nd). When Nd exceeded values of about 1000 cm-3, Dr became greater than 5000 m, and particles of precipitation size were initiated as ice hydrometeors. Therefore, no liquid water raindrops were observed within growing convective cumulus during polluted conditions. Furthermore, also the formation of ice particles took place at higher altitudes in the clouds in polluted conditions, because the resulting smaller cloud droplets froze at colder temperatures compared to the larger drops in the unpolluted cases. The measured vertical profiles of droplet effective radius (re) were close to those estimated by assuming adiabatic conditions (rea), supporting the hypothesis that the entrainment and mixing of air into convective clouds is almost completely inhomogeneous. Secondary nucleation of droplets on aerosol particles from biomass burning and air pollution reduced re below rea, which further inhibited the formation of raindrops and ice particles and resulted in even higher altitudes for rain and ice initiation.
%@language en
%3 braga_aerosol.pdf