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| Titel |
The Microphysics of Cold Fronts measured during DIAMET |
| VerfasserIn |
K. N. Bower, T. W. Choularton, J. Crosier, G. Lloyd, J. R. Dorsey, M. W. Gallagher, P. Connolly, C. Dearden, G. Vaughan |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250064354
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| Zusammenfassung |
| During the autumn and early winter of 2011 a number of combined airborne, radar and
radiosonde studies of frontal systems crossing the UK were undertaken as part of the
DIAbatic influence on Mesoscale structures in ExTratropical storms (or DIAMET ) project.
The main aim of DIAMET is to improve our ability to predict the mesoscale structure of
severe storms over the UK for forecast times ranging from several hours to several days.
Extratropical cyclones are the major cause of damaging weather in north-western Europe,
mainly through the effects of high winds and flooding. Although many such storms are well
forecasted on the synoptic scale, the precise timing, location, and evolution of mesoscale and
convective-scale structures such as the strong winds and intense precipitation within these
cyclones remain uncertain. This project uses the unique measurements of these smaller-scale
structures to guide a programme of research into the dynamics and prediction of
storms.
In this paper we focus on detailed measurements of the microphysics and dynamics of
cold fronts crossing the UK associated with vigorous storm systems during periods with a
very strong zonal jet stream. The FAAM BAe 146 research aircraft was used to drop sondes
into the systems when out to the west of the UK, and to make insitu measurements in the
systems when closer to and over the UK. The aircraft made a number of horizontal passes
over and through the frontal cloud at decreasing levels to make detailed measurements of
the cloud physics (ice and liquid), dynamics and atmospheric aerosol. The aim
was to; measure the cloud microphysics close to cloud top in order to examine the
initiation of the ice phase through heterogeneous (or homogeneous if cold enough)
nucleation; measure at temperature levels around -7oC to study the freezing of water due
to the production of ice by a secondary Ice-particle Production (SIP) mechanism
known as the Hallett-Mossop process; to investigate the properties of the solid
precipitation just above the freezing level; to quantify the diabatic effects of melting
and evaporation below the freezing level. When in range, simultaneous detailed
measurements of the structure of the fronts were also made using the scanning radar
facility at Chilbolton. The observational study was supported by detailed modelling
using a variety of models including the Weather and Research Forecasting (WRF)
model. This presentation focuses on the role of the microphysics and dynamics
in generating zones of intense convergence, and the changes introduced (e.g. as
aerosol properties changed) as the front transitioned from over the ocean to land. |
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