Measurement Measurement of Atmospheric Turbulence of Atmospheric Turbulence by Means of Light, Sound, and Radio by Means of Light, Sound, and Radio Waves Waves Andreas Muschinski Andreas Muschinski Dept. of Electrical and Computer Engineering Dept. of Electrical and Computer Engineering University of Massachusetts Amherst University of Massachusetts Amherst Observing the Turbulent Atmosphere: Observing the Turbulent Atmosphere: Sampling Strategies, Technologies, and Applications Sampling Strategies, Technologies, and Applications NCAR, Boulder, CO, 28-31 May 2008 NCAR, Boulder, CO, 28-31 May 2008
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Measurement of Atmospheric Turbulence by Means of Light, Sound, and Radio Waves Andreas Muschinski Dept. of Electrical and Computer Engineering University.
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Measurement Measurement of Atmospheric Turbulenceof Atmospheric Turbulence
by Means of Light, Sound, and Radio Wavesby Means of Light, Sound, and Radio Waves
Andreas MuschinskiAndreas Muschinski
Dept. of Electrical and Computer EngineeringDept. of Electrical and Computer Engineering
University of Massachusetts AmherstUniversity of Massachusetts Amherst
Observing the Turbulent Atmosphere:Observing the Turbulent Atmosphere:
Sampling Strategies, Technologies, and ApplicationsSampling Strategies, Technologies, and Applications
NCAR, Boulder, CO, 28-31 May 2008NCAR, Boulder, CO, 28-31 May 2008
OverviewOverview
IntroductionIntroduction
Wave propagation through turbulence: the basicsWave propagation through turbulence: the basics
Anisotropy in optical surface-layer turbulenceAnisotropy in optical surface-layer turbulence
Vertical-velocity biases observed with radars and sodarsVertical-velocity biases observed with radars and sodars
OutlookOutlook
OverviewOverview
IntroductionIntroduction
Wave propagation through turbulence: the basicsWave propagation through turbulence: the basics
Anisotropy in optical surface-layer turbulenceAnisotropy in optical surface-layer turbulence
Vertical-velocity biases observed with radars and sodarsVertical-velocity biases observed with radars and sodars
OutlookOutlook
Light, sound, and radio waves Light, sound, and radio waves in the optically clear atmospherein the optically clear atmosphere
Do not propagate along straight linesDo not propagate along straight lines
Change their amplitudes, phases, and angles-of-arrival Change their amplitudes, phases, and angles-of-arrival deterministically and randomly in space and timedeterministically and randomly in space and time
Carry information about mean values and fluctuations of wind, Carry information about mean values and fluctuations of wind, temperature, density, pressure, humidity, and refractive index.temperature, density, pressure, humidity, and refractive index.
Describes refraction but not diffractionDescribes refraction but not diffraction
Approximates variances and frequency Approximates variances and frequency spectra of optical angle-of-arrival spectra of optical angle-of-arrival (AOA) fluctuations very well if aperture (AOA) fluctuations very well if aperture diameter is larger than twice the diameter is larger than twice the Fresnel lengthFresnel length
Born approximationBorn approximation
Describes both refraction and diffractionDescribes both refraction and diffraction
Very good approximation for radio-wave Very good approximation for radio-wave backscatter from clear-air refractive-backscatter from clear-air refractive-index perturbationsindex perturbations
Fraunhofer approximation valid if Fraunhofer approximation valid if turbulence is Bragg-isotropicturbulence is Bragg-isotropic
Fresnel approximation (or higher-order Fresnel approximation (or higher-order approximation) necessary if turbulence approximation) necessary if turbulence not Bragg-isotropic of in case of not Bragg-isotropic of in case of scatter from interfacesscatter from interfaces
Turbulence in the inertial range (in a nutshell)Turbulence in the inertial range (in a nutshell)
Upward bias in vertical velocities Upward bias in vertical velocities
observed with a sodar in the lower CBLobserved with a sodar in the lower CBL
Geophysical causesGeophysical causes
of biases in vertical clear-air radar or sodar windsof biases in vertical clear-air radar or sodar winds
Nonzero covariance between local Cn2 and local w (due to gravity Nonzero covariance between local Cn2 and local w (due to gravity waves in the stable free troposphere, Nastrom and VanZandt 1994)waves in the stable free troposphere, Nastrom and VanZandt 1994)
Horizontal advection of asymmetrically corrugated interfaces Horizontal advection of asymmetrically corrugated interfaces (“KHI bias”, Muschinski 1996)(“KHI bias”, Muschinski 1996)
Nonzero covariance between local Cn2 and local w (“intermittency flux” Nonzero covariance between local Cn2 and local w (“intermittency flux” or “reflectivity flux” in the CBL, Muschinski et al., to be published)or “reflectivity flux” in the CBL, Muschinski et al., to be published)
Muschinski, A., 1996: Possible effect of Kelvin-Helmholtz instability on VHF Muschinski, A., 1996: Possible effect of Kelvin-Helmholtz instability on VHF radar observations of the mean vertical wind. radar observations of the mean vertical wind. J. Appl. MeteorJ. Appl. Meteor., ., 3535, 2210-, 2210-2217.2217.
“ “KHI bias”KHI bias”
Muschinski, A., 1996: Possible effect of Kelvin-Helmholtz instability on VHF Muschinski, A., 1996: Possible effect of Kelvin-Helmholtz instability on VHF radar observations of the mean vertical wind. radar observations of the mean vertical wind. J. Appl. MeteorJ. Appl. Meteor., ., 3535, 2210-, 2210-2217.2217.
“ “KHI bias”KHI bias”
Frehlich, R. G., Y. Meillier, M. L. Jensen, and B. Balsley, 2004: A statistical Frehlich, R. G., Y. Meillier, M. L. Jensen, and B. Balsley, 2004: A statistical description of small-scale turbulence in the low-level nocturnal jet. description of small-scale turbulence in the low-level nocturnal jet. J. Atmos. J. Atmos. SciSci., ., 6161, 1079-1085., 1079-1085.
Lognormality of local epsilon and local CT2Lognormality of local epsilon and local CT2
Muschinski, A., Frehlich, and B. Balsley, 2004: Small-scale and large-scale Muschinski, A., Frehlich, and B. Balsley, 2004: Small-scale and large-scale intermittency in the nocturnal boundary layer and the residual layer. intermittency in the nocturnal boundary layer and the residual layer. J. Fluid J. Fluid Mech.Mech., , 515515, 319-351., 319-351.
Joint lognormality of local epsilon and local CT2Joint lognormality of local epsilon and local CT2
Intermittency flux and sodar velocity biasIntermittency flux and sodar velocity bias
Muschinski, A., M. Behn, V. Hohreiter, and Y. Cheon, 2007: Vertical fluxes of Muschinski, A., M. Behn, V. Hohreiter, and Y. Cheon, 2007: Vertical fluxes of
the temperature structure variable […]. Unpublished manuscript.the temperature structure variable […]. Unpublished manuscript.
Upward flux of local CT2 (sodar reflectivity) Upward flux of local CT2 (sodar reflectivity)
in the lower CBL (measured with sonics)in the lower CBL (measured with sonics)
Coulter, R. L., and M. A. Kallistratova, 2004: Two decades of progress in Coulter, R. L., and M. A. Kallistratova, 2004: Two decades of progress in