Aerosol-cloud drop concentration closure in warm cumulus

William C Conant, T. M. VanReken, T. A. Rissman, V. Varutbangkul, H. H. Jonsson, A. Nenes, J. L. Jimenez, A. E. Delia, R. Bahreini, G. C. Roberts, R. C. Flagan, J. H. Seinfeld

Research output: Contribution to journalArticle

76 Citations (Scopus)

Abstract

Our understanding of the activation of aerosol particles into cloud drops during the formation of warm cumulus clouds presently has a limited observational foundation. Detailed observations of aerosol size and composition, cloud microphysics and dynamics, and atmospheric thermodynamic state were collected in a systematic study of 21 cumulus clouds by the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft during NASA's Cirrus Regional Study of Tropical Anvils and Cirrus Layers-Florida Area Cirrus Experiment (CRYSTAL-FACE). An "aerosol-cloud" closure study was carried out in which a detailed cloud activation parcel model, which predicts cloud drop concentration using observed aerosol concentration, size distribution, cloud updraft velocity, and thermodynamic state, is evaluated against observations. On average, measured droplet concentration in adiabatic cloud regions is within 15% of the predictions. This agreement is corroborated by independent measurements of aerosol activation carried out by two cloud condensation nucleus (CCN) counters on the aircraft. Variations in aerosol concentration, which ranged from 300 to 3300 cm-3, drives large microphysical differences (250-2300 cm-3) observed among continental and maritime clouds in the South Florida region. This is the first known study in which a cloud parcel model is evaluated in a closure study using a constraining set of data collected from a single platform. Likewise, this is the first known study in which relationships among aerosol size distribution, CCN spectrum, and cloud droplet concentration are all found to be consistent with theory within experimental uncertainties much less than 50%. Vertical profiles of cloud microphysical properties (effective radius, droplet concentration, dispersion) clearly demonstrate the boundary layer aerosol's effect on cloud microphysics throughout the lowest 1 km of cloud depth. Onboard measurements of aerosol hygroscopic growth and the organic to sulfate mass ratio are related to CCN properties. These chemical data are used to quantify the range of uncertainty associated with the simplified treatment of aerosol composition assumed in the closure study.

Original languageEnglish (US)
JournalJournal of Geophysical Research: Space Physics
Volume109
Issue number13
DOIs
StatePublished - Jul 16 2004
Externally publishedYes

Fingerprint

volcanic cloud
cumulus
Aerosols
closures
aerosols
aerosol
cloud condensation nucleus
cirrus
condensation nuclei
aerosol composition
cloud microphysics
aircraft
cumulus clouds
droplet
Condensation
Chemical activation
thermodynamics
Aircraft
activation
particle size

Keywords

  • Aerosol
  • CCN
  • Cloud microphysics

ASJC Scopus subject areas

  • Oceanography
  • Astronomy and Astrophysics
  • Atmospheric Science
  • Space and Planetary Science
  • Earth and Planetary Sciences (miscellaneous)
  • Geophysics
  • Geochemistry and Petrology

Cite this

Conant, W. C., VanReken, T. M., Rissman, T. A., Varutbangkul, V., Jonsson, H. H., Nenes, A., ... Seinfeld, J. H. (2004). Aerosol-cloud drop concentration closure in warm cumulus. Journal of Geophysical Research: Space Physics, 109(13). https://doi.org/10.1029/2003JD004324

Aerosol-cloud drop concentration closure in warm cumulus. / Conant, William C; VanReken, T. M.; Rissman, T. A.; Varutbangkul, V.; Jonsson, H. H.; Nenes, A.; Jimenez, J. L.; Delia, A. E.; Bahreini, R.; Roberts, G. C.; Flagan, R. C.; Seinfeld, J. H.

In: Journal of Geophysical Research: Space Physics, Vol. 109, No. 13, 16.07.2004.

Research output: Contribution to journalArticle

Conant, WC, VanReken, TM, Rissman, TA, Varutbangkul, V, Jonsson, HH, Nenes, A, Jimenez, JL, Delia, AE, Bahreini, R, Roberts, GC, Flagan, RC & Seinfeld, JH 2004, 'Aerosol-cloud drop concentration closure in warm cumulus', Journal of Geophysical Research: Space Physics, vol. 109, no. 13. https://doi.org/10.1029/2003JD004324
Conant, William C ; VanReken, T. M. ; Rissman, T. A. ; Varutbangkul, V. ; Jonsson, H. H. ; Nenes, A. ; Jimenez, J. L. ; Delia, A. E. ; Bahreini, R. ; Roberts, G. C. ; Flagan, R. C. ; Seinfeld, J. H. / Aerosol-cloud drop concentration closure in warm cumulus. In: Journal of Geophysical Research: Space Physics. 2004 ; Vol. 109, No. 13.
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