Abstract
The flow structure at the intersection between the Rhine and the Seez valleys nearthe Swiss city of Bad Ragaz has been documented by means of wind and pressuremeasurements collected from 9 September to 10 November 1999 during the MesoscaleAlpine Programme (MAP) experiment. To understand better the dynamics of theageostrophic winds that develop in this part of the Rhine valley, some key questionsare answered in this paper including the following: (i) How does air blow at theintersection of the Rhine and Seez valleys? and (ii) what are the dynamical processes(mechanical or thermal) driving the flow circulations in the valleys?
Statistical analysis of the wind and pressure patterns at synoptic scale and at the scaleof the valley shows that five main flow patterns, SE/S, NW/W, NW/N, NW/S, SE/N(wind direction in the Seez valley/wind direction in the Rhine valley) prevail. The SE/S regime is the flow splitting situation. It is mainly driven by a strong pressure gradient across the Alps leading to foehn, even though some nocturnal cases are generated bylocal thermal gradients. The NW/W and NW/N regimes are mechanically forced bythe synoptic pressure gradient (as the flow splitting case). The difference between thetwo regimes is due to the synoptic flow direction [westerly (northerly) synoptic flowfor the NW/W (NW/N) regime], showing that the Rhine valley (particularly from BadRagaz to Lake Constance) is less efficient in channelling the flow than the Seez valley.The NW/S (occurring mainly during nighttime) and SE/N (occurring mainly duringdaytime) regimes are mainly katabatic flows. However, the SE/N regime is also partlyforced at the synoptic scale during the foehn case that occurred between 18 October and 20 October 1999, with a complex layered vertical structure.
This analysis also shows that, contrary to what was observed in a broad section of theupper Rhine valley near Mannheim, very few countercurrents were observed near BadRagaz where the valley width is much smaller.
Similar content being viewed by others
References
Bougeault, P., Binder, P., Buzzi, A., Dirks, R., Houze, R., Kuettner, J., Smith, R. B., Steinacker, R., and Volkert, H.: 2001, 'The MAP Special Observing Period', Bull. Amer. Meteor. Soc. 82, 433–462.
Brinkmann, W. A. R.: 1971, 'What is Foehn?', Weather 26, 230–239.
Dabas, A. M., Drobinski, P., and Flamant, P. H.: 1999, 'Adaptive Filters for Frequency Estimates of Heterodyne Doppler Lidar Returns: Recursive Implementation and Quality Control', J. Atmos. Oceanic Tech. 16, 361–372.
Dabas, A. M., Drobinski, P., and Flamant, P. H.: 2000, 'Velocity Biases of Adaptive Filter Estimates in Heterodyne Doppler Lidar Measurements', J. Atmos. Oceanic Tech. 17, 1189–1202.
Drobinski, P., Brown, R. A., Flamant, P.H., and Pelon, J.: 1998, 'Evidence of Organized Large Eddies by Ground-Based Doppler Lidar, Sonic Anemometer and Sodar', Boundary-Layer Meteorol. 88, 343–361.
Drobinski, P., Dabas, A. M., Delville, P., Flamant, P. H., Pelon, J., and Hardesty, R. M.: 1999, 'Refractive-Index Structure Parameter in the Planetary Boundary Layer: Comparison of Measurements Taken by a 10.6 µm-Coherent Lidar, a 0.9 µm-Scintillometer, and In-Situ Sensors', Appl. Opt. 38, 1648–1656.
Drobinski, P., Dabas, A. M., Haeberli, C., and Flamant, P. H.: 2001, 'On the Small-Scale Dynamics of Flow Splitting in the Rhine Valley during a Shallow Foehn Event', Boundary-Layer Meteorol. 99, 277–296.
Egger, J.: 1990a, 'Thermally Induced Flow in Valleys with Tributaries. Part I: Response to Heating', Meteorol. Atmos. Phys. 42, 113–125.
Egger, J.: 1990b, 'Thermally Induced Flow in Valleys with Tributaries. Part II: Response to Cooling', Meteorol. Atmos. Phys. 42, 127–131.
Egger, J.: 1992, 'Cold Front Propagation in the Loisach Valley: Simulations with a Simple Model', Meteorol. Atmos. Phys. 48, 173–178.
Flamant, C., Drobinski, P., Banta, R. M., Darby, L., Dusek, J., Hardesty, R. M., Nance, L., and Pelon, J.: 2002, 'Gap Flow in an Alpine Valley during a Shallow South Foehn Event: Observations, Numerical Simulations and Hydraulic Analog', Quart. J. Roy. Meteorol. Soc. 128, 1173–1210.
Gross, G. and Wippermann, F.: 1987, 'Channeling and Countercurrent in the Upper Rhine Valley: Numerical Simulations', J. Appl. Meteorol. 26, 1293–1304.
Gutermann, T.: 1970, 'Vergleichende Untersuchungen zur Föhnhäufigkeit im Rheintal zwischen Chur und Bodensee', Veröff. Schweiz. Meteorol. Zentralanstalt 18, 1–64.
Guyon, E., Hulin, J. P., and Petit, L.: 1991, Hydrodynamique physique, Inter Editions, CNRS Editions, Paris.
Hoinka, K. P.: 1980, 'Synoptic-Scale Atmospheric Features and Foehn', Contr. Atmos. Phys. 53, 486–507.
Hoinka, K. P.: 1985, 'Observation of the Airflow over the Alps during a Foehn Event', Quart. J. Roy. Meteorol. Soc. 111, 199–224.
Mass, C. F., Businger, S., Albright, M. D., and Tucker, Z. A.: 1995, 'A Windstorm in the Lee of a Gap in a Coastal Mountain Barrier', Mon. Wea. Rev. 123, 315–331.
Seibert, P.: 1990, 'South Foehn Studies since the ALPEX Experiment', Meteorol. Atmos. Phys. 43, 91–103.
Sprenger, M. and Schär, C.: 2001, 'Rotational Aspects of Stratified Gap Flows and Shallow Foehn', Quart. J. Roy. Meteorol. Soc. 127, 161–188.
Steinacker, R.: 1984, 'Area-Height Distribution of a Valley and its Relation to the Valley Wind', Contr. Atmos. Phys. 57, 64–71.
Wippermann, F.: 1984, 'Air Flow over and in Broad Valleys: Channeling and Counter-Current', Contr. Atmos. Phys. 57, 92–105.
Wippermann, F. and Gross, G.: 1981, 'On the Construction of Orographically InfluencedWind Roses for Given “Distributions of the Large-Scale Wind”', Contr. Atmos. Phys. 54, 492–501.
Zängl, G.: 1999, 'Three-Dimensional Idealized Simulations of the Foehn in the Region of Innsbruck', Contr. Atmos. Phys. 72, 243–266.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Philippe, P., Dabas, A.M., Haeberli, C. et al. Statistical Characterization of the Flow Structure in the Rhine Valley. Boundary-Layer Meteorology 106, 483–505 (2003). https://doi.org/10.1023/A:1021262321679
Issue Date:
DOI: https://doi.org/10.1023/A:1021262321679