@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 = "20 abr. 2024"
}