 |
| Titel |
Aerosol concentration and size distribution measured below, in, and above cloud from the DOE G-1 during VOCALS-REx |
| VerfasserIn |
L. I. Kleinman, P. H. Daum, Y.-N. Lee, E. R. Lewis, A. J. Sedlacek III, G. I. Senum, S. R. Springston, J. Wang, J. Hubbe, J. Jayne, Q. Min, S. S. Yum, G. Allen |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 12, no. 1 ; Nr. 12, no. 1 (2012-01-04), S.207-223 |
| Datensatznummer |
250010430
|
| Publikation (Nr.) |
 copernicus.org/acp-12-207-2012.pdf |
|
|
|
|
|
| Zusammenfassung |
| 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. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|