18.3
Gravity waves over the Eastern Alps during IOP-10 of MAP: In-situ and remote sensing data compared with a high-resolution simulation
Hans Volkert, DLR Oberpfaffenhofen, Wessling, Germany; and C. Kiemle, J. P. Chaboureau, and E. Richard
In-situ aircraft data acquired during six repetitive flight legs across Großglockner (3797 m), the highest summit in the Hohe Tauern range of the eastern Alps, reveal a coherent, quasi-stationary structure of the mountain wave field generated by the south-westerly cross-Alpine flow. A downward looking laser system operating at 100 Hz provides unique wave-induced signatures in the layered clouds below the crusing altitudes (11.4 and 12.1 km). Three dropsoundings along leg 5 document details of the upper-tropospheric jet and layers of large gradients in potential temperatures at medium levels point to gravity wave breaking induced mixing.
All the measurements are cross-validated with a triple nested, non-hydrostatic simulation (2 km horizontal resolution for the finest grid). Wave cloud signatures in satellite images (Meteosat and NOAA) are used for comparisons (in physical and Fourier space) with the simulated vertical velocity and liquid water fields in regions away from the aircraft track. Altogether the observational evidence and the simulation results provide a firm basis for more systematic modelling studies of the wave patterns generated by the complicated fully three-dimesional terrain features of the eastern Alps.
Finally, references to early German and French mountain wave observations using gliders aid the understanding of the progress made in this field over a period of 60 years.
Figure caption: Juxtaposition of various measurements and the simulation along flight leg 5: Falcon in-situ vertical velocity (top, in m/s; full line: measured; dashed line: simulated); in-situ potential temperature (middle, in K); lidar backscatter (coloured) and wave field in terms of simulated potential temperatures (black/white) below the aircraft track (solid line in 12.1 km) and above the model orography (bottom; abscissa: latitude in degrees N; ordinate: height in km; width of black/white stripes: 2.5 K).
[A note in brackets: as the main organizer of the MAP-meetings 1995 and 2000, which served several hundreds of participants with late deadlines and truely flat rates, I whitness with great regret strangleholds as a much too early deadline, the user hostile submission procedure, and the quite arrogant impudence of AMS to charge $60 from the people who in the end make the event lively and who have to do all this tedious technical work themselves. HV]
Session 18, Mountain Waves: MAP
Friday, 21 June 2002, 9:15 AM-10:45 AM
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