 |
| Titel |
Implications of the ISOCLOUD campaigns at the AIDA Cloud Chamber for ice growth in cold cirrus |
| VerfasserIn |
Kara Lamb, Benjamin Clouser, Laszlo Sarkozy, Steven Wagner, Volker Ebert, Erik Kerstel, Harald Saathoff, Ottmar Möhler, Elisabeth Moyer |
| Konferenz |
EGU General Assembly 2015
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250110062
|
| Publikation (Nr.) |
 EGU/EGU2015-15244.pdf |
|
|
|
|
|
| Zusammenfassung |
| In-situ water vapor measurements in the upper troposphere and lower stratosphere (UTLS)
have routinely observed anomalous supersaturations on the order of 10-20particles when
temperatures were below 200 K, raising questions about the physics of how ice
forms at cold temperatures in the atmosphere1,2,3,4. The ISOCLOUD campaigns
in 2012-2013 at the AIDA Aerosol and Cloud Chamber sought to investigate ice
growth at cold temperatures by simulating cirrus clouds at temperatures and pressures
characteristic of the upper troposphere. Experiments tested both homogeneous
nucleation of sulfate aerosols and heterogeneous nucleation with various ice nuclei,
including mineral dust and organic aerosols with and without nitric acid coatings.
Optical instruments, both in-situ (TDLAS) and extractive (TDLAS and OFCEAS),
measured ice particle number density, water vapor, total water, and water vapor isotopic
concentrations, with multiple instruments measuring water. In a series of cirrus formation
experiments, we observed no evidence of anomalous saturation vapor pressure
and no evidence of ice growth inhibition at low temperatures for the parameter
space tested during the ISOCLOUD campaigns. That is, we see no evidence for
temperature dependence in the deposition coefficient. In these experiments we determined
the deposition coefficient from bulk parameters of the gas (vapor concentration
and ice number density). The ISOCLOUD experiments were particularly suited to
deposition coefficient measurements since they involved lower pressures and often
lower temperatures than previous similar campaigns, producing lower error bars.5
These results can aid in the interpretation of data from aircraft campaigns in the
UTLS by solidifying our understanding of the microphysics of ice formation at cold
temperatures.
[1] Gao, R. et al., Science, 303, no. 6567, 516-520, (2004). [2] Jensen, E. et
al., Atmos. Chem. Phys., 5, 851-862, (2005). [3] Peter, T. et al., Science, 314, no.
5804, 1399-1402, (2006). [4] Krämer, M. et al., Atmos. Chem. Phys., 9, 3505-3522,
(2009). |
|
|
|
|
|
|