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| Titel |
Microphysical properties and high ice water content in continental and oceanic mesoscale convective systems and potential implications for commercial aircraft at flight altitude |
| VerfasserIn |
J.-F. Gayet, V. Shcherbakov, L. Bugliaro, A. Protat, J. Delanoë, J. Pelon, A. Garnier |
| 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 ; 14, no. 2 ; Nr. 14, no. 2 (2014-01-27), S.899-912 |
| Datensatznummer |
250118311
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| Publikation (Nr.) |
 copernicus.org/acp-14-899-2014.pdf |
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| Zusammenfassung |
| Two complementary case studies are conducted to
analyse convective system properties in the region where strong cloud-top
lidar backscatter anomalies are observed as reported by Platt et al. (2011).
These anomalies were reported for the first time using in situ microphysical
measurements in an isolated continental convective cloud over Germany during
the CIRCLE2 experiment (Gayet et al., 2012). In this case,
in situ observations quasi-collocated with CALIPSO (Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observation), CloudSat and Meteosat-9/SEVIRI
observations confirm that regions of backscatter anomalies represent the
most active and dense convective cloud parts with likely the strongest core
updrafts and unusually high values of the particle concentration, extinction
and ice water content (IWC), with the occurrence of small ice crystal sizes.
Similar spaceborne observations of a maritime mesoscale
cloud system (MCS) located off the Brazilian
coast between 0° and 3° N latitude on 20 June 2008 are then analysed. Near cloud-top
backscatter anomalies are evidenced in a region which corresponds to the
coldest temperatures with maximum cloud top altitudes derived from
collocated CALIPSO/IIR and Meteosat-9/SEVIRI infrared brightness
temperatures. The interpretation of CALIOP (Cloud Aerosol Lidar
with Orthogonal Polarization) data highlights significant
differences in microphysical properties from those observed in the
continental isolated convective cloud. Indeed, SEVIRI (Spinning Enhanced Visible and
InfraRed Imager) retrievals in the
visible spectrum confirm much smaller ice particles near the top of the isolated
continental convective cloud, i.e. effective radius (Reff) ~ 15 μm
as opposed to
22–27 μm in the whole MCS area. Cloud profiling observations at 94 GHz from CloudSat are then used to describe the
properties of the most active cloud regions at and below cloud top. The
cloud ice-water content and effective radius retrieved with the CloudSat
2B-IWC and DARDAR (raDAR/liDAR) inversion techniques, show that at usual cruise altitudes
of commercial aircraft (FL 350 or ~ 10 700 m level), high IWC
(i.e. up to 2 to 4 g m−3) could be identified according to specific
IWC–Z (Z being the reflectivity factor) relationships. These values correspond to a maximum reflectivity
factor of +18 dBZ (at 94 GHz). Near-top cloud properties also indicate
signatures of microphysical characteristics according to the cloud-stage
evolution as revealed by SEVIRI images to identify the development of new
cells within the MCS cluster. It is argued that the availability of real-time information (on the kilometre-scale) about cloud top IR brightness temperature
decreases with respect to the cloud environment would help identify MCS cloud
areas with potentially high ice water content and small particle sizes
against which onboard meteorological radars may not be able to provide
timely warning. |
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