Open AccessNucleation in the equatorial free troposphere: Favorable environments during PEM‐Tropics
Author(s) -
Clarke A. D.,
Eisele F.,
Kapustin V. N.,
Moore K.,
Tanner D.,
Mauldin L.,
Litchy M.,
Lienert B.,
Carroll M. A.,
Albercook G.
Publication year - 1999
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/98jd02303
Subject(s) - intertropical convergence zone , troposphere , aerosol , atmospheric sciences , convergence zone , nucleation , environmental science , air mass (solar energy) , sulfuric acid , climatology , geology , meteorology , chemistry , precipitation , physics , boundary layer , thermodynamics , inorganic chemistry
A combination of aerosol and gas phase instrumentation was employed aboard the NASA‐P3B as part of the Pacific Exploratory Mission‐Tropics (PEM‐T) in the eastern equatorial Pacific during August‐October 1996. Recent particle production was found in cloud‐processed air over extended regions aloft (6–8 km). These were clearly associated with clean marine air lofted by deep convection and scavenged of most aerosol mass in the Intertropical Convergence Zone (ITCZ) and in more aged cloud‐scavenged air influenced by a distant continental combustion near the South Pacific Convergence Zone (SPCZ). Recent particle production was evident in regions where sulfuric acid concentrations were about 0.5 to 1 × l0 7 molecules cm −3 , when surface areas were near or below 5 µm 2 cm −3 , and when relative humidity (RH) was elevated over adjacent regions. In regions of recent particle production, the calculated critical sulfuric acid concentrations, based upon classical binary nucleation theory and corrected for in situ conditions near cloud, were generally consistent with nearby observed sulfuric acid concentrations. This indicates that classical binary nucleation theory and natural sources of sulfuric acid can account for nucleation in the near‐cloud environment. Data from six equatorial flights between 20°N and 20°S demonstrate that this process populates extensive regions of the equatorial free troposphere with new particles. Vertical profiles suggest that nucleation, subsidence, and mixing into the MBL can supply the MBL with new aerosol.