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@Article{BragaRWJAWPVMBAMVMG:2017:FuEvCC,
               author = "Braga, Ramon Campos and Rosenfeld, Daniel and Weigel, Ralf and 
                         Jurkat, Tina and Andreae, Meinrat O. and Wendisch, Manfred and 
                         P{\"o}schl, Ulrich and Voigt, Christiane and Mahnke, Christoph 
                         and Borrmann, Stephan and Albrecht, Rachel I. and Molleker, Sergej 
                         and Vila, Daniel Alejandro and Machado, Luiz Augusto Toledo and 
                         Grulich, Lucas",
          affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and {The Hebrew 
                         University of Jerusalem} and {Johannes Gutenberg-Universit{\"a}t} 
                         and {Deutsches Zentrum f{\"u}r Luft- und Raumfahrt (DLR)} and 
                         {Max Planck Institute for Chemistry} and {Universit{\"a}t 
                         Leipzig} and {Max Planck Institute for Chemistry} and {Johannes 
                         Gutenberg-Universit{\"a}t} and {Johannes 
                         Gutenberg-Universit{\"a}t} and {Johannes 
                         Gutenberg-Universit{\"a}t} and {Universidade de S{\~a}o Paulo 
                         (USP)} and {Max Planck Institute for Chemistry} and {Instituto 
                         Nacional de Pesquisas Espaciais (INPE)} and {Instituto Nacional de 
                         Pesquisas Espaciais (INPE)} and {Johannes 
                         Gutenberg-Universit{\"a}t}",
                title = "Further evidence for CCN aerosol concentrations determining the 
                         height of warm rain and ice initiation in convective clouds over 
                         the Amazon basin",
              journal = "Atmospheric Chemistry and Physics",
                 year = "2017",
               volume = "17",
                pages = "14433--14456",
                month = "Dec.",
             abstract = "We have investigated how 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 aircraft during the ACRIDICONCHUVA 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). Additional cloud processes 
                         associated with Dr , such as GCCN, cloud, and mixing with ambient 
                         air and other processes, produce deviations of \∼ 21 % in 
                         the linear relationship, but it does not mask the clear 
                         relationship between Dr and Nd, which was also found at different 
                         regions around the globe (e.g., Israel and India). When Nd 
                         exceeded values of about 1000 cm\−3 , Dr became greater 
                         than 5000 m, and the first observed precipitation particles were 
                         ice hydrometeors. Therefore, no liquid water raindrops were 
                         observed within growing convective cumulus during polluted 
                         conditions. Furthermore, the formation of ice particles also 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 nearly inhomogeneous. Additional 
                         CCN activation 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.",
                  doi = "10.5194/acp-17-14433-2017",
                  url = "http://dx.doi.org/10.5194/acp-17-14433-2017",
                 issn = "1680-7316 and 1680-7324",
             language = "en",
           targetfile = "braga_further.pdf",
        urlaccessdate = "27 nov. 2020"
}


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