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| Titel |
Probabilistic description of ice-supersaturated layers in low resolution profiles of relative humidity |
| VerfasserIn |
N. C. Dickson, K. M. Gierens, H. L. Rogers, R. L. Jones |
| 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 ; 10, no. 14 ; Nr. 10, no. 14 (2010-07-23), S.6749-6763 |
| Datensatznummer |
250008651
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| Publikation (Nr.) |
 copernicus.org/acp-10-6749-2010.pdf |
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| Zusammenfassung |
The global observation, assimilation and prediction in numerical models of
ice super-saturated (ISS) regions (ISSR) are crucial if the climate impact of
aircraft condensation trails (contrails) is to be fully understood, and if,
for example, contrail formation is to be avoided through aircraft operational
measures. Given their small scales
compared to typical atmospheric model grid sizes, statistical representations
of the spatial scales of ISSR are required, in both horizontal and vertical
dimensions, if global occurrence of ISSR is to be adequately represented in
climate models.
This paper uses radiosonde launches made by the UK Meteorological Office,
from the British Isles, Gibraltar, St. Helena and the Falkland Islands
between January 2002 and December 2006, to investigate the probabilistic
occurrence of ISSR. Each radiosonde profile is divided into 50-
and 100-hPa pressure layers, to emulate the coarse vertical resolution of
some atmospheric models. Then the high resolution observations contained
within each thick pressure layer are used to calculate an average relative
humidity and an ISS fraction for each individual thick pressure layer. These
relative humidity pressure layer descriptions are then linked through a
probability function to produce an s-shaped curve which empirically describes
the ISS fraction in any average relative humidity pressure layer.
Using this empirical understanding of the s-shaped relationship a mathematical
model was developed to represent the ISS fraction within any arbitrary
thick pressure layer. Two models were developed to represent both 50- and 100-hPa
pressure layers with each reconstructing their respective s-shapes within 8–10%
of the empirical curves. These new models can be used, to represent the small scale
structures of ISS events, in modelled data where only low vertical resolution is
available. This will be useful in understanding, and improving the global
distribution, both observed and forecasted, of ice super-saturation. |
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