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| Titel |
Integrating laboratory and field data to quantify the immersion freezing ice nucleation activity of mineral dust particles |
| VerfasserIn |
P. J. DeMott, A. J. Prenni, G. R. McMeeking, R. C. Sullivan, M. D. Petters, Y. Tobo, M. Niemand, O. Möhler, J. R. Snider, Z. Wang, S. M. Kreidenweis |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 1 ; Nr. 15, no. 1 (2015-01-13), S.393-409 |
| Datensatznummer |
250119304
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| Publikation (Nr.) |
 copernicus.org/acp-15-393-2015.pdf |
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| Zusammenfassung |
| Data from both laboratory studies and atmospheric measurements are used to
develop an empirical parameterization for the immersion freezing activity of
natural mineral dust particles. Measurements made with the Colorado State
University (CSU) continuous flow diffusion chamber (CFDC) when processing
mineral dust aerosols at a nominal 105% relative humidity with respect
to water (RHw) are taken as a measure of the immersion freezing
nucleation activity of particles. Ice active frozen fractions vs. temperature
for dusts representative of Saharan and Asian desert sources were consistent
with similar measurements in atmospheric dust plumes for a limited set of
comparisons available. The parameterization developed follows the form of one
suggested previously for atmospheric particles of non-specific composition in
quantifying ice nucleating particle concentrations as functions of
temperature and the total number concentration of particles larger than
0.5 μm diameter. Such an approach does not explicitly account for
surface area and time dependencies for ice nucleation, but sufficiently
encapsulates the activation properties for potential use in regional and
global modeling simulations, and possible application in developing remote
sensing retrievals for ice nucleating particles. A calibration factor is
introduced to account for the apparent underestimate (by approximately 3, on
average) of the immersion freezing fraction of mineral dust particles for CSU
CFDC data processed at an RHw of 105% vs. maximum fractions
active at higher RHw. Instrumental factors that affect activation
behavior vs. RHw in CFDC instruments remain to be fully explored
in future studies. Nevertheless, the use of this calibration factor is
supported by comparison to ice activation data obtained for the same aerosols
from Aerosol Interactions and Dynamics of the Atmosphere (AIDA) expansion
chamber cloud parcel experiments. Further comparison of the new
parameterization, including calibration correction, to predictions of the
immersion freezing surface active site density parameterization for mineral
dust particles, developed separately from AIDA experimental data alone, shows
excellent agreement for data collected in a descent through a Saharan aerosol
layer. These studies support the utility of laboratory measurements to obtain
atmospherically relevant data on the ice nucleation properties of dust and
other particle types, and suggest the suitability of considering all mineral
dust as a single type of ice nucleating particle as a useful first-order
approximation in numerical modeling investigations. |
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