Lee Wave Vertical Structure Monitoring Using Height–Time Analysis of VHF ST Radar Vertical Velocity Data

Jean-Luc Caccia Laboratoire de Sondages Electromagnétiques de l’Environnement Terrestre, CNRS, Université de Toulon et du Var, La Garde, France

Search for other papers by Jean-Luc Caccia in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

The strong lee wave event of intensive observation period 3 (14–15 October 1990) of the Pyrenean experiment was studied using a single VHF stratospheric–tropospheric radar installed 35 km downstream from the Pyrenean chain axis. This instrument obtained time series of the air vertical velocity with a time resolution of 4 min 50 s for altitudes ranging from 2250 to 15000 m mean sea level with a 750-m step. Maximum amplitudes of 5–6 m s−1 were measured between 3750 and 5250 m. Temporal variability of the vertical velocity was observed showing that the wave can be nonstationary at timescales on the order of 5–10 min. A classic signal processing technique using the calculation of height–time cross-correlation coefficient in a 2-h moving window was applied to the radar time series and allowed the wave vertical structure to be monitored with a time resolution of 2 h. The lee wave was found to be trapped in a tropospheric duct having an upper limit of 8000 m. The observed wave activity was found to be well developed from 2300 UTC 14 October until 0830 UTC 15 October and slowly decreasing after. This behavior was related to large timescale nonstationarities, that is, changes in the upstream conditions observed every 6 h. All those results obtained from the radar vertical beam data, and interpreted in the frame of the 2D linear theory, were consistent with upstream radiosonde data, numerical simulations by nonhydrostatic models, and measurements made along the chain transect by an aircraft and two constant-level balloons. Thanks to the lee wave horizontal structure obtained by these airborne instruments, it is concluded that the wave activy decrease observed by the radar was mainly due to a progressive shortening of the downstream wave horizontal extent.

Corresponding author address: Dr. Jean-Luc Caccia, Laboratoire de Sondages Electromagnétiques de l’Environment Terrestre, Université de Toulon et du Var, BP132, 83957 La Garde Cedex, France.

caccia@lseet.univ-tln.fr

Abstract

The strong lee wave event of intensive observation period 3 (14–15 October 1990) of the Pyrenean experiment was studied using a single VHF stratospheric–tropospheric radar installed 35 km downstream from the Pyrenean chain axis. This instrument obtained time series of the air vertical velocity with a time resolution of 4 min 50 s for altitudes ranging from 2250 to 15000 m mean sea level with a 750-m step. Maximum amplitudes of 5–6 m s−1 were measured between 3750 and 5250 m. Temporal variability of the vertical velocity was observed showing that the wave can be nonstationary at timescales on the order of 5–10 min. A classic signal processing technique using the calculation of height–time cross-correlation coefficient in a 2-h moving window was applied to the radar time series and allowed the wave vertical structure to be monitored with a time resolution of 2 h. The lee wave was found to be trapped in a tropospheric duct having an upper limit of 8000 m. The observed wave activity was found to be well developed from 2300 UTC 14 October until 0830 UTC 15 October and slowly decreasing after. This behavior was related to large timescale nonstationarities, that is, changes in the upstream conditions observed every 6 h. All those results obtained from the radar vertical beam data, and interpreted in the frame of the 2D linear theory, were consistent with upstream radiosonde data, numerical simulations by nonhydrostatic models, and measurements made along the chain transect by an aircraft and two constant-level balloons. Thanks to the lee wave horizontal structure obtained by these airborne instruments, it is concluded that the wave activy decrease observed by the radar was mainly due to a progressive shortening of the downstream wave horizontal extent.

Corresponding author address: Dr. Jean-Luc Caccia, Laboratoire de Sondages Electromagnétiques de l’Environment Terrestre, Université de Toulon et du Var, BP132, 83957 La Garde Cedex, France.

caccia@lseet.univ-tln.fr

Save
  • Atkinson, B. W., 1981: Meso-Scale Atmospheric Circulations. Academic Press, 495 pp.

  • Attié, J.-L., 1994: Etude d’un écoulement près d’un relief à partir de moyens aéroportés (Expérience Pyrex). Ph.D. dissertation, Université Paul Sabatier, 154 pp. [Available from Université Paul Sabatier, 118 route de Narbonne, 31062 Toulouse, Cedex, France.].

  • Balsley, B. B., and D. A. Carter, 1989: Mountain waves in the tropical Pacific atmosphere: A comparison of vertical wind fluctuations over Pohnpei and Christmas Island using VHF wind profilers. J. Atmos. Sci.,46, 2698–2715.

  • Bendat, J. S., and A. G. Piersol, 1986: Random Data: Analysis and Measurement Procedures. 2d ed. Wiley and Sons, 566 pp.

  • Benech, B., A. Druilhet, R. Cordesse, B. Dartiguelongue, J. Fournet-Fayard, J.-C. Mesnager, P. Durand, and A. Malaterre, 1987: Un dispositif expérimental utilisant des ballons plafonnants pour l’étude de la couche limite atmosphérique. Adv. Space Res.,7,77–83.

  • ——, and Coauthors, 1994: Observation of lee waves above the Pyrénées (French-Spanish PYREX experiment). Tech. Soaring,18, 7–12.

  • Bougeault, P., A. Jansa, B. Benech, B. Carrissimo, J. Pelon, and E. Richard, 1990: Momentum budget over the Pyrénées: The PYREX experiment. Bull. Amer. Meteor. Soc.,71, 806–818.

  • ——, and Coauthors, 1993: The atmospheric momentum budget over a major mountain range: First results of the PYREX field program. Ann. Geophys.,11, 395–418.

  • Caccia, J. L., B. Benech, and V. Klaus, 1997: Space–time description of nonstationary trapped lee waves using ST radars, aircraft and constant volume balloons during the PYREX experiment. J. Atmos. Sci.,54, 1821–1833.

  • Carter, D. A., B. B. Balsley, W. L. Ecklund, K. S. Gage, A. C. Riddle, R. Garello, and M. Crochet, 1989: Investigations of internal gravity waves using three vertically directed closely spaced wind profilers. J. Geophys. Res.,94, 8633–8642.

  • Chimonas, G., and C. O. Hines, 1986: Doppler ducting of atmospheric gravity waves. J. Geophys. Res.,91, 1219–1230.

  • Corby, G. A., and C. E. Wallington, 1956: Airflow over mountains: The lee wave amplitude. Quart. J. Roy. Meteor. Soc.,82, 266–274.

  • Crochet, M., 1990: Atmospheric profiler radar: Developments and outstanding questions. Meteor. Rundsch.,42, 123–136.

  • ——, F. Cuq, F. M. Ralph, and S. V. Venkateswaran, 1990a: Clear-air radar observations of the great October storm of 1987. Dyn. Atmos. Oceans,14, 443–461.

  • ——, E. Bazile, and G. Rougier, 1990b: Comparison of thermal advection measurements by clear-air radar and radiosonde techniques. Radio Sci.,25, 907–915.

  • Ecklund, W. L., K. S. Gage, B. B. Balsley, R. G. Strauch, and J. L. Green, 1982: Vertical wind variability observed by VHF radar in the lee of the Colorado Rockies. Mon. Wea. Rev.,110,1451–1457.

  • ——, B. B. Balsley, D. A. Carter, A. C. Riddle, M. Crochet, and R. Garello, 1985: Observations of vertical motions in the troposphere and lower stratosphere using three closely spaced ST radars. Radio Sci.,20, 1196–1206.

  • Elkhalfi, A., and B. Carrissimo, 1993: Numerical simulations of a mountain wave observed during “Pyrénées Experiment”: Hydrostatic/non-hydrostatic comparison and time evolution. Beitr. Phys. Atmos.,66, 183–200.

  • Ferrat, S., and M. Crochet, 1994: Methods of detection and estimation errors in ST radar studies. Ann. Geophys.,12, 489–496.

  • Fritts, D. C., and L. Yuan, 1989: An analysis of gravity wave ducting in the atmosphere: Eckart’s resonances in thermal and Doppler ducts. J. Geophys. Res.,94, 18455–18466.

  • Gage, K. S., and B. B. Balsley, 1978: Doppler radar probing of the clear atmosphere. Bull. Amer. Meteor. Soc.,59, 1074–1093.

  • ——, and J. L. Green, 1978: Evidence for specular reflection from monostatic VHF radar observations of the stratosphere. Radio Sci.,13, 991–1001.

  • Larsen, M. F., and J. Röttger, 1982: VHF and UHF Doppler radars as tools for synoptic research. Bull. Amer. Meteor. Soc.,63,996–1008.

  • MacAfee, J. R., K. S. Gage, and R. G. Strauch, 1994: Examples of vertical velocity comparison from collocated VHF and UHF profilers. Radio Sci.,29, 879–880.

  • ——, ——, and ——, 1995: Vertical velocity at Platteville, Colorado: An intercomparison of simultaneous measurements by the VHF and UHF profilers. Radio Sci.,30, 1027–1042.

  • Masson, V., and P. Bougeault, 1996: Non-hydrostatic 3D simulations of real mountain flows observed during the PYREX experiment. Seventh Conf. on Mesoscale Processes, Reading, UK, Amer. Meteor. Soc., 307–309.

  • Nance, L., and D. Durran, 1997: A modeling study of nonstationary trapped mountain lee waves. Part I: Mean flow variability. J. Atmos. Sci.,54, 2275–2291.

  • ——, and ——, 1998: A modeling study of nonstationary trapped mountain lee waves. Part II: Nonlinearity. J. Atmos. Sci.,55,1429–1445.

  • Ralph, F. M., M. Crochet, and V. Venkateswaran, 1992a: A study of mountain lee waves using clear-air radar. Quart. J. Roy. Meteor. Soc.,118, 597–627.

  • ——, P. J. Neiman, L. S. Fedor, and B. L. Weber, 1992b: Nonstationary trapped lee waves: Wind profiler, RASS, and satellite observations. Sixth Conf. on Mountain Meteorology, Portland, OR, Amer. Meteor. Soc., 68–75.

  • ——, M. Crochet, and V. Venkateswaran, 1993: Observations of a mesoscale ducted gravity wave. J. Atmos. Sci.,50, 3277–3291.

  • ——, P. J. Neiman, T. L. Keller, D. Levinson, and L. Fedor, 1997: Observations, simulations, and analysis of nonstationary trapped lee waves. J. Atmos. Sci.,54, 1308–1333.

  • Roddier, F., 1978: Distributions et Transformation de Fourier. McGraw-Hill, 323 pp.

  • Röttger, J., and C. H. Liu, 1978: Partial reflection and scattering of VHF radar signals from the clear air atmosphere. Geophys. Res. Lett.,5, 357–360.

  • Sato, K., 1990: Vertical wind disturbances in the troposphere and lower stratosphere observed by the MU radar. J. Atmos. Sci.,47, 2803–2817.

  • Satomura, T., and P. Bougeault, 1994: Numerical simulation of lee wave event over the Pyrenees. J. Meteor. Soc. Japan,72, 173–195.

  • Scorer, R. S., 1949: Theory of waves in the lee of mountains. Quart. J. Roy. Meteor. Soc.,75, 41–56.

  • Tannhauser, D. S., and J.-L. Attié, 1995: Linear analysis of the wave field during a lee wave event of the PYREX campaign. Meteor. Z.,4, 203–208.

  • Yamamoto, M., T. Sato, P. T. May, T. Tsuda, S. Fukao, and S. Kato, 1988: Estimation error of spectral parameters of MST radars obtained by least squares fitting method and its lower bound. Radio Sci.,23, 1013–1021.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 248 96 2
PDF Downloads 46 11 0