1. Holger Mahlke, Ulrich Corsmeier, Christoph Kottmeier
Driving Processes for Convection Initiation over Complex Terrain: COPS Observations of July 20, 2007, and Respective COSMO-DE Simulations.
Holger Mahlke, Ulrich Corsmeier, Christoph Kottmeier

2. Holger Mahlke, Ulrich Corsmeier, Christoph Kottmeier
Driving Processes for Convection Initiation over Complex Terrain: COPS Observations of July 20, 2007, and Respective COSMO-DE Simulations.
Holger Mahlke, Ulrich Corsmeier, Christoph Kottmeier
With thanks to: Christian Barthlott, Jan Handwerker, Heike Konow, Norbert Kalthoff, Stephen Mobbs, Bernhard Mühr, and the “dropup” teams.

3. Scientific Problem:
COPS overview paper: „The relative importance of forcing mechanisms leading to convection initiation (CI) is neither well understood nor adequately reproduced by weather forecast models.“
Case Study of July, 20, 2007 (IOP 9c): Interaction of convection initiating processes on different scales and respective simulations with the COSMO-DE model (DWD)
Holger Mahlke – Institut für Meteorologie und Klimaforschung: Case Study of

4. Large Scale
Midtropospheric trough over Western Europe and a surface low over eastern France
12:00 UTC
GFS model, 06:00 UTC
Holger Mahlke – Institut für Meteorologie und Klimaforschung: Case Study of

5. A weak cold front was passing the COPS area during the morning
Large Scale
A weak cold front was passing the COPS area during the morning
12:00 UTC
GFS model, 06:00 UTC
Holger Mahlke – Institut für Meteorologie und Klimaforschung: Case Study of

6. Mesoscale convective system (MCS)
A MCS was triggered over eastern France
07:30 UTC
Holger Mahlke – Institut für Meteorologie und Klimaforschung: Case Study of

7. Mesoscale convective system (MCS)
A MCS was triggered over eastern France
The MCS dissipated over the Rhine
valley due to
slight subsidence
decreased solar insolation (nighttime fog + cloudiness of the MCS)
advection of warm air in a lower level during the morning
high values of CIN
10:00 UTC
Holger Mahlke – Institut für Meteorologie und Klimaforschung: Case Study of

8. Observations
Gust front of the MCS passing the Rhine valley and the Black Forest
10:00 UTC
wind vectors and
temperature (colour coded)
Ground station at Hornisgrinde Mountain
Holger Mahlke – Institut für Meteorologie und Klimaforschung: Case Study of

9. Observations
Gust front of the MCS passing the Rhine valley and the Black Forest
Station
UTC
CAPE
[J/kg]
CIN
Calw-Hirsau
10:04
1099 13
Stuttgart
12:00
1212
130
10:00 UTC
wind vectors and
temperature (colour coded)
Holger Mahlke – Institut für Meteorologie und Klimaforschung: Case Study of

10. Observations
Initiation of deep convection over the northern Black Forest Driving processes: gust front and orographic effects
10:05 UTC
Holger Mahlke – Institut für Meteorologie und Klimaforschung: Case Study of

11. a squall line over west Germany and the Benelux countries
Observations
In the east: thermally driven convergence line severe convective systems
a squall line over west Germany and the Benelux countries
11:25 UTC
Holger Mahlke – Institut für Meteorologie und Klimaforschung: Case Study of

12. Model simulations (COSMO-DE 2.8 km, Init: 0 UTC).
no deep convection over the Black Forest and in the east
10:00 UTC
precipitation
11:30 UTC
precipitation
Holger Mahlke – Institut für Meteorologie und Klimaforschung: Case Study of

13. CAPE: band-like structure where in reality CI occurred
Model simulations
CAPE: band-like structure where in reality CI occurred
10:00 UTC
CAPE (ML)
10:00 UTC
spec. humidity (ML)
Holger Mahlke – Institut für Meteorologie und Klimaforschung: Case Study of

14. wind vectors (10 m above ground) and precipitation
Model simulations
wind vectors (10 m above ground) and precipitation
09:00 UTC
10:00 UTC
Holger Mahlke – Institut für Meteorologie und Klimaforschung: Case Study of

15. Comparison: Measurement (left) and model results (right)
Hornisgrinde Mountain
Hornisgrinde Mountain
Holger Mahlke – Institut für Meteorologie und Klimaforschung: Case Study of

16. West to east cross section at latitude of Hornisgrinde mountain
Model simulations
West to east cross section at latitude of Hornisgrinde mountain
Vertical winds
10:00 UTC
specific humidity
10:00 UTC
Holger Mahlke – Institut für Meteorologie und Klimaforschung: Case Study of

17. Summary
COPS IOP 9c – a case with interaction of multiple scale processes
Gust front resulting from the MCS and interaction with orography decisive process for convection initiation over the Black Forest
Comparison between COSMO-DE model and observations:
Large scale features of the development reasonably well predicted
gust front, convergence line poorly simulated
CAPE and moisture convergence simulated roughly at the right location
But model did not capture the initiation of deep convection and subsequent precipitation over the Black Forest and in the east
model simulations did not represent the sub synoptic scale processes adequately that drove the deep convection during this case
Holger Mahlke – Institut für Meteorologie und Klimaforschung: Case Study of

18. Thank you for your attention!
Holger Mahlke – Institut für Meteorologie und Klimaforschung: Case Study of

19. Thank you for your attention!
Holger Mahlke – Institut für Meteorologie und Klimaforschung: Case Study of

20. Thank you for your attention!
Holger Mahlke – Institut für Meteorologie und Klimaforschung: Case Study of

21. Thank you for your attention!
Holger Mahlke – Institut für Meteorologie und Klimaforschung: Case Study of

22.
Holger Mahlke – Institut für Meteorologie und Klimaforschung: Case Study of

23. Comparison: Measurement (black) and model results (red)
Hornisgrinde Mountain
Holger Mahlke – Institut für Meteorologie und Klimaforschung: Case Study of

24. West to east cross section at latitude of Hornisgrinde mountain
Simulations
West to east cross section at latitude of Hornisgrinde mountain
11:00 UTC
11:00 UTC
Holger Mahlke – Institut für Meteorologie und Klimaforschung: Case Study of