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| Titel |
Ice supersaturated regions and cirrostratus observations at northern mid latitudes and the tropics |
| VerfasserIn |
F. J. Immler, H. Vömel, O. Schrems |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250020585
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| Zusammenfassung |
| Cirrostratus (Cs) clouds were observed with the mobile Lidar systems MARL and ComCAL
during field campaigns in the mid latitudes in 2003 (Lindenberg/Germany, 53∘N,
15∘E) and in the tropics in 2004-2006 (Paramaribo/Suriname, 6∘N, 55∘W). The
lidar system MARL and ComCAL are capable of detecting thin cirrus including
extremely thin clouds with optical depth below 10-3. This study is based on lidar
observations and meteorological data obtained from radiosondes as well as the
analysis of the European centre for medium range weather forecast (ECMWF).
Cirrostratus are ubiquitous in the midlatitudes (55% coverage) and even more so
in the tropics (88% coverage). Humidity measurements in the upper troposphere
are difficult to conduct and need careful consideration with respect to systematic
errors. We discuss the reliability of radiosonde data based on the data obtained
during the Lindenberg Upper Air Method Intercomparison (LUAMI) campaign
(Nov 2008) where a number of commercial radiosondes was launched together
with reference instruments including the NOAA crygenic frostpoint hygrometer
(CFH). Relating the humidity profiles obtained from radiosondes to concurrent lidar
observations reveals a close correlation between ice supersaturation and the occurrence of
Cs. This leads us to the conclusion that on synoptic scales ice particles are almost
always present in supersaturated conditions. The ECMWF cloud parametrization
reproduces the observed cirrus clouds consistently and a close correlation between the
ice water path in the model and the measured optical depth of cirrus is observed. |
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