Aerosol concentration and size distribution measured below, in, and above cloud from the DOE G-1 during VOCALS-REx

L. I. Kleinman, P. H. Daum, Y. N. Lee, E. R. Lewis, A. J. Sedlacek, G. I. Senum, S. R. Springston, J. Wang, J. Hubbe, J. Jayne, Q. Min, S. S. Yum, G. Allen

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Abstract

During the VOCALS Regional Experiment, the DOE G-1 aircraft was used to sample a varying aerosol environment pertinent to properties of stratocumulus clouds over a longitude band extending 800 km west from the Chilean coast at Arica. Trace gas and aerosol measurements are presented as a function of longitude, altitude, and dew point in this study. Spatial distributions are consistent with an upper atmospheric source for O3 and South American coastal sources for marine boundary layer (MBL) CO and aerosol, most of which is acidic sulfate. Pollutant layers in the free troposphere (FT) can be a result of emissions to the north in Peru or long range transport from the west. At a given altitude in the FT (up to 3 km), dew point varies by 40 C with dry air descending from the upper atmospheric and moist air having a boundary layer (BL) contribution. Ascent of BL air to a cold high altitude results in the condensation and precipitation removal of all but a few percent of BL water along with aerosol that served as CCN. Thus, aerosol volume decreases with dew point in the FT. Aerosol size spectra have a bimodal structure in the MBL and an intermediate diameter unimodal distribution in the FT. Comparing cloud droplet number concentration (CDNC) and pre-cloud aerosol (Dp>100 nm) gives a linear relation up to a number concentration of ∼150 cm-3, followed by a less than proportional increase in CDNC at higher aerosol number concentration. A number balance between below cloud aerosol and cloud droplets indicates that ∼25 % of aerosol with Dp>100 nm are interstitial (not activated). A direct comparison of pre-cloud and in-cloud aerosol yields a higher estimate. Artifacts in the measurement of interstitial aerosol due to droplet shatter and evaporation are discussed. Within each of 102 constant altitude cloud transects, CDNC and interstitial aerosol were anti-correlated. An examination of one cloud as a case study shows that the interstitial aerosol appears to have a background, upon which is superimposed a high frequency signal that contains the anti-correlation. The anti-correlation is a possible source of information on particle activation or evaporation.

Original languageEnglish
Pages (from-to)207-223
Number of pages17
JournalAtmospheric Chemistry and Physics
Volume12
Issue number1
DOIs
Publication statusPublished - 2012 Dec 1

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aerosol
cloud droplet
boundary layer
dew point
volcanic cloud
troposphere
air
evaporation
stratocumulus
long range transport
trace gas
droplet
artifact
condensation
aircraft
transect
particle size
spatial distribution
sulfate
pollutant

All Science Journal Classification (ASJC) codes

  • Atmospheric Science

Cite this

Kleinman, L. I., Daum, P. H., Lee, Y. N., Lewis, E. R., Sedlacek, A. J., Senum, G. I., ... Allen, G. (2012). Aerosol concentration and size distribution measured below, in, and above cloud from the DOE G-1 during VOCALS-REx. Atmospheric Chemistry and Physics, 12(1), 207-223. https://doi.org/10.5194/acp-12-207-2012
Kleinman, L. I. ; Daum, P. H. ; Lee, Y. N. ; Lewis, E. R. ; Sedlacek, A. J. ; Senum, G. I. ; Springston, S. R. ; Wang, J. ; Hubbe, J. ; Jayne, J. ; Min, Q. ; Yum, S. S. ; Allen, G. / Aerosol concentration and size distribution measured below, in, and above cloud from the DOE G-1 during VOCALS-REx. In: Atmospheric Chemistry and Physics. 2012 ; Vol. 12, No. 1. pp. 207-223.
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abstract = "During the VOCALS Regional Experiment, the DOE G-1 aircraft was used to sample a varying aerosol environment pertinent to properties of stratocumulus clouds over a longitude band extending 800 km west from the Chilean coast at Arica. Trace gas and aerosol measurements are presented as a function of longitude, altitude, and dew point in this study. Spatial distributions are consistent with an upper atmospheric source for O3 and South American coastal sources for marine boundary layer (MBL) CO and aerosol, most of which is acidic sulfate. Pollutant layers in the free troposphere (FT) can be a result of emissions to the north in Peru or long range transport from the west. At a given altitude in the FT (up to 3 km), dew point varies by 40 C with dry air descending from the upper atmospheric and moist air having a boundary layer (BL) contribution. Ascent of BL air to a cold high altitude results in the condensation and precipitation removal of all but a few percent of BL water along with aerosol that served as CCN. Thus, aerosol volume decreases with dew point in the FT. Aerosol size spectra have a bimodal structure in the MBL and an intermediate diameter unimodal distribution in the FT. Comparing cloud droplet number concentration (CDNC) and pre-cloud aerosol (Dp>100 nm) gives a linear relation up to a number concentration of ∼150 cm-3, followed by a less than proportional increase in CDNC at higher aerosol number concentration. A number balance between below cloud aerosol and cloud droplets indicates that ∼25 {\%} of aerosol with Dp>100 nm are interstitial (not activated). A direct comparison of pre-cloud and in-cloud aerosol yields a higher estimate. Artifacts in the measurement of interstitial aerosol due to droplet shatter and evaporation are discussed. Within each of 102 constant altitude cloud transects, CDNC and interstitial aerosol were anti-correlated. An examination of one cloud as a case study shows that the interstitial aerosol appears to have a background, upon which is superimposed a high frequency signal that contains the anti-correlation. The anti-correlation is a possible source of information on particle activation or evaporation.",
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Kleinman, LI, Daum, PH, Lee, YN, Lewis, ER, Sedlacek, AJ, Senum, GI, Springston, SR, Wang, J, Hubbe, J, Jayne, J, Min, Q, Yum, SS & Allen, G 2012, 'Aerosol concentration and size distribution measured below, in, and above cloud from the DOE G-1 during VOCALS-REx', Atmospheric Chemistry and Physics, vol. 12, no. 1, pp. 207-223. https://doi.org/10.5194/acp-12-207-2012

Aerosol concentration and size distribution measured below, in, and above cloud from the DOE G-1 during VOCALS-REx. / Kleinman, L. I.; Daum, P. H.; Lee, Y. N.; Lewis, E. R.; Sedlacek, A. J.; Senum, G. I.; Springston, S. R.; Wang, J.; Hubbe, J.; Jayne, J.; Min, Q.; Yum, S. S.; Allen, G.

In: Atmospheric Chemistry and Physics, Vol. 12, No. 1, 01.12.2012, p. 207-223.

Research output: Contribution to journalArticle

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AU - Kleinman, L. I.

AU - Daum, P. H.

AU - Lee, Y. N.

AU - Lewis, E. R.

AU - Sedlacek, A. J.

AU - Senum, G. I.

AU - Springston, S. R.

AU - Wang, J.

AU - Hubbe, J.

AU - Jayne, J.

AU - Min, Q.

AU - Yum, S. S.

AU - Allen, G.

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N2 - During the VOCALS Regional Experiment, the DOE G-1 aircraft was used to sample a varying aerosol environment pertinent to properties of stratocumulus clouds over a longitude band extending 800 km west from the Chilean coast at Arica. Trace gas and aerosol measurements are presented as a function of longitude, altitude, and dew point in this study. Spatial distributions are consistent with an upper atmospheric source for O3 and South American coastal sources for marine boundary layer (MBL) CO and aerosol, most of which is acidic sulfate. Pollutant layers in the free troposphere (FT) can be a result of emissions to the north in Peru or long range transport from the west. At a given altitude in the FT (up to 3 km), dew point varies by 40 C with dry air descending from the upper atmospheric and moist air having a boundary layer (BL) contribution. Ascent of BL air to a cold high altitude results in the condensation and precipitation removal of all but a few percent of BL water along with aerosol that served as CCN. Thus, aerosol volume decreases with dew point in the FT. Aerosol size spectra have a bimodal structure in the MBL and an intermediate diameter unimodal distribution in the FT. Comparing cloud droplet number concentration (CDNC) and pre-cloud aerosol (Dp>100 nm) gives a linear relation up to a number concentration of ∼150 cm-3, followed by a less than proportional increase in CDNC at higher aerosol number concentration. A number balance between below cloud aerosol and cloud droplets indicates that ∼25 % of aerosol with Dp>100 nm are interstitial (not activated). A direct comparison of pre-cloud and in-cloud aerosol yields a higher estimate. Artifacts in the measurement of interstitial aerosol due to droplet shatter and evaporation are discussed. Within each of 102 constant altitude cloud transects, CDNC and interstitial aerosol were anti-correlated. An examination of one cloud as a case study shows that the interstitial aerosol appears to have a background, upon which is superimposed a high frequency signal that contains the anti-correlation. The anti-correlation is a possible source of information on particle activation or evaporation.

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