Radar Measurements of Turbulent Eddy Dissipation Rate in the Troposphere: A Comparison of Techniques

Cohn, Stephen A.

doi:10.1175/1520-0426(1995)012<0085:rmoted>2.0.co;2

Cited by 117 publications

(98 citation statements)

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“…2. These two methods are extensively compared (Cohn, 1995) and a reasonably good agreement has been found between the two methods. However, primarily two non-turbulent effects, beam broadening and shear broadening, contaminate the observed spectral width.…”

Section: Introductionmentioning

confidence: 85%

Seasonal variation of vertical eddy diffusivity in the troposphere, lower stratosphere and mesosphere over a tropical station

et al. 2001

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Abstract. Long-term VHF radar (53 MHz with 3 • beamwidth) observations at Gadanki (13.5 • N, 79.2 • E), India, during the period from September 1995 to August 1999 are used to study monthly, seasonal and annual medians of vertical eddy diffusivity, K in the troposphere, lower stratosphere and mesosphere. First, the spectral width contribution due to non-turbulent effects has been removed for further analysis and the monthly, seasonal medians of K are calculated. The monthly median of K in the troposphere shows maximum and minimum in June-July and November-December, respectively. In general, large values of K are seen up to 10 km and then decrease with height. Larger values of K are observed during monsoon and post-monsoon than in winter and summer. In general, the maximum and minimum values of the annual median of K (in logarithmic values) in the troposphere are found to be 0.25 and −1.3 m 2 s −1 respectively. In the mesosphere, the monthly median of K shows maximum and minimum during June-July and November-December, respectively, similar to the lower atmosphere. The value of K in the mesosphere becomes larger and it increases with height up to 75 km and again decreases above that height.The maximum values are seen during the summer, followed by equinoxes and a minimum during the winter. In general, the maximum and minimum values of K (in logarithmic values) are found to be 0.7 and 0.3 m 2 s −1 , respectively, in the mesosphere. A comparison of Doppler spectral parameters in different beam directions shows anisotropy in both signalto-noise ratio (SNR) and spectral widths in the mesosphere, whereas it shows isotropy in SNR and anisotropy in the spectral widths in troposphere and lower stratosphere.

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Section: Introductionmentioning

confidence: 85%

Seasonal variation of vertical eddy diffusivity in the troposphere, lower stratosphere and mesosphere over a tropical station

et al. 2001

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“…In-situ turbulence measurements have been used for many years to study the turbulent structure of the CBL (e.g., Lenschow and Kristensen 1985). However, remote sensing techniques such as lidar and radar systems have reached the resolution and accuracy to enable profiles of turbulent variables to be measured through the lower troposphere (e.g., Kropfli 1986;Eberhard et al 1989;Angevine et al 1993;Cohn 1995;Frehlich and Cornman 2002;Hogan et al 2009). The major advantage in the application of these remote sensing techniques lies in the simultaneous investigation of turbulence properties from the surface layer to and through the entrainment zone.…”

Section: Introductionmentioning

confidence: 99%

Can Water Vapour Raman Lidar Resolve Profiles of Turbulent Variables in the Convective Boundary Layer?

Wulfmeyer

Pal

Turner

et al. 2010

Boundary-Layer Meteorol

111

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High-resolution water vapour measurements made by the Atmospheric Radiation Measurement (ARM) Raman lidar operated at the Southern Great Plains Climate Research Facility site near Lamont, Oklahoma, U.S.A. are presented. Using a 2-h measurement period for the convective boundary layer (CBL) on 13 September 2005, with temporal and spatial resolutions of 10 s and 75 m, respectively, spectral and autocovariance analyses of water vapour mixing ratio time series are performed. It is demonstrated that the major part of the inertial subrange was detected and that the integral scale was significantly larger than the time resolution. Consequently, the major part of the turbulent fluctuations was resolved. Different methods to retrieve noise error profiles yield consistent results and compare well with noise profiles estimated using Poisson statistics of the Raman lidar signals. Integral scale, mixing-ratio variance, skewness, and kurtosis profiles were determined including error bars with respect to statistical and sampling errors. The integral scale ranges between 70 and 130 s at the top of the CBL. Within the CBL, up to the third order, noise errors are significantly smaller than sampling errors and the absolute values of turbulent variables, respectively. The mixing-ratio variance profile rises monotonically from ≈0.07 to ≈3.7 g 2 kg −2 in the entrainment zone. The skewness is nearly zero up to 0.6 z/z i , becomes −1 around 0.7-0.8 z/z i , crosses zero at about 0.95 z/z i , and reaches about 1.7 at 1.1 z/z i (here, z is the height and z i is the CBL depth). The noise errors are too large to derive fourth-order moments with sufficient accuracy. Consequently, to the best of our knowledge, the ARM Raman lidar is the first water vapour Raman lidar with demonstrated capability to retrieve profiles of turbulent variables up to the third order during daytime throughout the atmospheric CBL.

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“…of results obtained by both power and width methods using a common data set has been done by Cohn [1995] using the Millstone Hill UHF radar and by Delage et al [this issue] using the high-resolution UHF PROUST radar. However, as will be shown in more detail in the next section, some assumptions on the flux Richardson number, or the Prandtl number, are made in these procedures and introduce significant uncertainties in the final results because these parameters are up to now poorly known and may vary with time within turbulent layers, as stressed by Mcintyre [1989], or Mourn [1990].…”

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confidence: 99%

Energy dissipation rates, eddy diffusivity, and the Prandtl number: An in situ experimental approach and its consequences on radar estimate of turbulent parameters

Bertin¹,

Barat²,

Wilson³

1997

Radio Science

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Abstract. Different methods have been proposed to derive the energy dissipation rate and eddy diffusion coefficients from ST radar measurements. However, their validity is still questionable because they implicitly assume that the Prandtl number is always equal to one, an assumption which is not verified. An experimental approach to this question, using balloon-borne experiment results, is proposed in this paper in order to test the validity/invalidity of the methods generally used. In situ observations show that the potential temperature gradient is more efficiently (and probably more rapidly) eroded by the turbulent activity than the wind shear.

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Radar Measurements of Turbulent Eddy Dissipation Rate in the Troposphere: A Comparison of Techniques

Cited by 117 publications

References 0 publications

Seasonal variation of vertical eddy diffusivity in the troposphere, lower stratosphere and mesosphere over a tropical station

Seasonal variation of vertical eddy diffusivity in the troposphere, lower stratosphere and mesosphere over a tropical station

Can Water Vapour Raman Lidar Resolve Profiles of Turbulent Variables in the Convective Boundary Layer?

Energy dissipation rates, eddy diffusivity, and the Prandtl number: An in situ experimental approach and its consequences on radar estimate of turbulent parameters

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