• Businger, S. and J. A. Businger. 2001. Viscous dissipation of turbulence kinetic energy in storms. J. Atmos. Sci. 58:37933796.

  • Caccia, J-L., F. Bertin, B. Campistron, V. Klaus, Y. Pointin, J. van Baelen, and R. Wilson. 2000. Cut-off low monitoring by the French VHF-ST-radar network during the ESTIME campaign. J. Atmos. Solar-Terr. Phys. 62:639651.

    • Search Google Scholar
    • Export Citation
  • Cornish, C. R. and M. F. Larsen. 1989. Observations of low-frequency gravity waves in the lower stratosphere over Arecibo. J. Atmos. Sci. 46:24282439.

    • Search Google Scholar
    • Export Citation
  • Fukao, S., M. D. Yamanaka, H. Matsumoto, T. Sato, T. Tsuda, and S. Kato. 1989. Wind fluctuations near a cold vortex-tropopause funnel system observed by the MU radar. Pure Appl. Geophys. 130:463479.

    • Search Google Scholar
    • Export Citation
  • Gage, K. S. 1990. Radar observations of the free atmosphere: Structure and dynamics. Radar in Meteorology, D. Atlas, Ed., Amer. Meteor. Soc., 534–565.

    • Search Google Scholar
    • Export Citation
  • Green, J. L., K. S. Gage, and T. E. VanZandt. 1979. Atmospheric measurements by VHF pulsed Doppler radar. IEEE Trans. Geosci. Electron. GE-17:262280.

    • Search Google Scholar
    • Export Citation
  • Hufnagel, R. E. 1974. Variations of atmospheric turbulence. Digest of Technical Papers, Topical Meeting on Optical Propagation through Turbulence, Optical Society of America, Wal-1–Wal-4.

    • Search Google Scholar
    • Export Citation
  • Nastrom, G. D. and F. D. Eaton. 1993. The coupling of gravity waves and turbulence at White Sands, New Mexico, from VHF radar observations. J. Appl. Meteor. 32:8187.

    • Search Google Scholar
    • Export Citation
  • Nastrom, G. D. and F. D. Eaton. 1995. Variations of winds and turbulence seen by the 50-MHz radar at White Sands Missile Range, New Mexico. J. Appl. Meteor. 34:21352148.

    • Search Google Scholar
    • Export Citation
  • Nastrom, G. D. and F. D. Eaton. 1997. Turbulence eddy dissipation rates from radar observations at 5–20 km at White Sands Missile Range, New Mexico. J. Geophys. Res. 102:1949519506.

    • Search Google Scholar
    • Export Citation
  • Nastrom, G. D. and F. D. Eaton. 2001. Persistent layers of enhanced C2 n in the lower stratosphere from VHF radar observations. Radio Sci. 36:137149.

    • Search Google Scholar
    • Export Citation
  • Nastrom, G. D., W. L. Clark, T. E. VanZandt, and J. M. Warnock. 1996. Seasonal and diurnal changes in wind variability from Flatland VHF profiler observations. Contrib. Atmos. Phys. 69:512.

    • Search Google Scholar
    • Export Citation
  • Sato, K. 1990. Vertical wind disturbances in the troposphere and lower stratosphere observed by the MU radar. J. Atmos. Sci. 47:28032817.

    • Search Google Scholar
    • Export Citation
  • Sato, K., D. J. O'Sullivan, and T. J. Dunkerton. 1997. Low-frequency inertia-gravity waves in the stratosphere revealed by three-week continuous observation with the MU radar. Geophys. Res. Lett. 24:17391742.

    • Search Google Scholar
    • Export Citation
  • Thomas, L., T. Pritchard, and I. Astin. 1992. Inertia-gravity waves in the troposphere and lower stratosphere. Ann. Geophys. 10:690697.

    • Search Google Scholar
    • Export Citation
  • Tsuda, T., P. T. May, T. Sato, S. Kato, and S. Fukao. 1988. Simultaneous observations of reflection echoes and refractive index gradient in the troposphere and lower stratosphere. Radio Sci. 23:655665.

    • Search Google Scholar
    • Export Citation
  • VanZandt, T. E. and D. C. Fritts. 1989. A theory of enhanced saturation of the gravity wave spectrum due to increases in atmospheric stability. Pure Appl. Geophys. 130:399420.

    • Search Google Scholar
    • Export Citation
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A Case Study of Atmospheric Conditions at 4–19 km over Vandenberg Air Force Base during Passage of a Cyclone

G. D. NastromSt. Cloud State University, St. Cloud, Minnesota

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F. D. EatonAir Force Research Laboratory, Kirtland Air Force Base, New Mexico

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Abstract

Continuous observations from a 50-MHz radar of the vertical profiles of winds, refractivity turbulence structure constant (C2n ), turbulent kinetic energy density (σ2t ) up to two orders of magnitude), and hourly standard deviation of the vertical velocity (σw ) are combined with routine rawinsonde ascents and weather observations to study changes in turbulence intensity over Vandenberg Air Force Base, California, during 21–27 July 2001. Early and late in this period the flow aloft was relatively steady and turbulence intensities in the upper troposphere were very low. For about 36 h around 25 July, the flow at midlevels (about 600–150 hPa) was disturbed by the passage of a cutoff cyclonic circulation center. During the low's passage, C2n and σ2t intensities were enhanced by up to about 15 dB. The enhancements of C2n and σ2t are highly correlated with each other, as well as with the vertical shear of the horizontal wind and synoptic-scale relative vorticity. The increased turbulence intensities apparently are due to in situ processes, such as shear instabilities associated with the low. Brief episodes of enhanced σw, taken as an indicator of enhanced gravity wave activity, are also associated with the low's passage, and they are also apparently due to an in situ process, such as shear instability or geostrophic adjustment. In the lower stratosphere, above 16 km, winds show a periodic oscillation, with a period near the local inertial period and with downward phase progression. There are bursts of enhanced C2n near the lower edge of this oscillation. The oscillation does not appear to be affected by the low's passage.

Corresponding author address: Dr. G. D. Nastrom, Department of Earth and Atmospheric Science, St. Cloud State University, St. Cloud, MN 56301. nastrom@stcloudstate.edu

Abstract

Continuous observations from a 50-MHz radar of the vertical profiles of winds, refractivity turbulence structure constant (C2n ), turbulent kinetic energy density (σ2t ) up to two orders of magnitude), and hourly standard deviation of the vertical velocity (σw ) are combined with routine rawinsonde ascents and weather observations to study changes in turbulence intensity over Vandenberg Air Force Base, California, during 21–27 July 2001. Early and late in this period the flow aloft was relatively steady and turbulence intensities in the upper troposphere were very low. For about 36 h around 25 July, the flow at midlevels (about 600–150 hPa) was disturbed by the passage of a cutoff cyclonic circulation center. During the low's passage, C2n and σ2t intensities were enhanced by up to about 15 dB. The enhancements of C2n and σ2t are highly correlated with each other, as well as with the vertical shear of the horizontal wind and synoptic-scale relative vorticity. The increased turbulence intensities apparently are due to in situ processes, such as shear instabilities associated with the low. Brief episodes of enhanced σw, taken as an indicator of enhanced gravity wave activity, are also associated with the low's passage, and they are also apparently due to an in situ process, such as shear instability or geostrophic adjustment. In the lower stratosphere, above 16 km, winds show a periodic oscillation, with a period near the local inertial period and with downward phase progression. There are bursts of enhanced C2n near the lower edge of this oscillation. The oscillation does not appear to be affected by the low's passage.

Corresponding author address: Dr. G. D. Nastrom, Department of Earth and Atmospheric Science, St. Cloud State University, St. Cloud, MN 56301. nastrom@stcloudstate.edu

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