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| Titel |
A convergence zone triggering deep convection over complex terrain: COSMO simulations of a case study from COPS |
| VerfasserIn |
Ch. Barthlott, J. W. Schipper, N. Kalthoff, B. Adler, Ch. Kottmeier |
| 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 |
250026849
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| Zusammenfassung |
| A case study of an isolated deep convective cell from the Convective and Orographically
induced Precipitation Study (COPS) is analysed with respect to its representation in the
numerical weather prediction model of the Deutscher Wetterdienst COSMO-DE. The
international field campaign COPS was performed in southwestern Germany and eastern
France in summer 2007 as part of the Priority Programme SPPÂ 1167 of the Deutsche
Forschungsgemeinschaft (DFG). The overall goal of COPS was to advance the quality of
forecasts of orographically-induced convective precipitation by four-dimensional
observations and modeling of its life cycle.
On July 15, deep convection developed in an area east of the Black Forest crest although
convective available potential energy (CAPE) was only moderate and convective inhibition
(CIN) was high. Data analysis revealed that convection was triggered by the superposition of
a synoptically generated eastward moving mesoscale convergence zone and a thermally
induced convergence zone along the mountain crests in the northern Black Forest. More in
the south, radar observations also showed a convergence line hours before a single cell was
initiated. The question if these convergence lines are connected can not be answered by
measurements only.
In the standard configuration (2.8 km grid resolution), COSMO simulations reveal a
near-surface convergence line and the evolution of a line of low clouds northeast
of Freiburg in good agreement with radar and satellite observations. In addition,
model-derived values of CAPE were high (> 2000Â J/kg) accompanied by almost
vanishing CIN. However, no deep convective cell developed out of this line of clouds.
For an improved representation of orographic effects, simulations with 1Â km grid
resolution were performed and compared to the results of the standard configuration.
Although both simulations did not initiate deep convection, the results suggest
hat in a situation with air mass convection without mid-tropospheric forcing, the
simulation of the location and timing of convergence lines in combination with high
values of CAPE and low values of CIN can be used for forecasting deep convection. |
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