摘要 :
At the Boulder Atmospheric Observatory near Erie, CO, we have established an observational testbed for studies of turbulence and propagation in the intermittent atmospheric surface layer. We have tested and refined scientific hypo...
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At the Boulder Atmospheric Observatory near Erie, CO, we have established an observational testbed for studies of turbulence and propagation in the intermittent atmospheric surface layer. We have tested and refined scientific hypotheses as well as data processing algorithms, with the goal of using optical angle-of-arrival fluctuations along horizontal, near-ground propagation paths for the remote sensing of various characteristics of atmospheric boundary turbulence, such as wind velocities, refractive-index structure parameters, and temporal fluctuations of the vertical temperature gradient.
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摘要 :
Clear-air Doppler radars, also known as clear-air radar windprofilers, have been used for decades to remotely monitor wind velocities in the troposphere, stratosphere, and mesosphere. The traditional assumption is that the Doppler...
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Clear-air Doppler radars, also known as clear-air radar windprofilers, have been used for decades to remotely monitor wind velocities in the troposphere, stratosphere, and mesosphere. The traditional assumption is that the Doppler velocity (the first normalized moment of the Doppler spectrum) is an unbiased measure of the radial wind velocity within the radar's observation volume. Here we show that 'intermittency fluxes,' i.e., covariances of the turbulently fluctuating clear-air radar reflectivity and the turbulently fluctuating radial wind velocity, lead to systematic differences between the Doppler velocity and the (true) radial wind velocity. We use turbulent fields computationally generated by means of a large- eddy simulation to quantify this effect. We show that these biases may amount to several tens of centimeters per second in the atmospheric boundary layer, which is consistent with the biases observed with vertically pointing boundary-layer radar windprofilers.
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摘要 :
The main objective of the project was to study the intermittent atmospheric surface layer on the basis of observations collected with one or two optical telescopes observing an array of test lights and up to twelve sonics placed a...
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The main objective of the project was to study the intermittent atmospheric surface layer on the basis of observations collected with one or two optical telescopes observing an array of test lights and up to twelve sonics placed along a horizontal propagation path of length ca. 200 m. During the reporting period, experimental data collected in June 2010 were analyzed, and a more sophisticated experiment was conducted in June 2011. The analysis of the 2010 data set confirmed that the optical retrievals of (1) temporal fluctuations of path-averaged, vertical temperature gradient fluctuations, (2) path averages of the transverse wind velocity, and (3) path averages of the temperature structure parameter agreed well with the sonic measurements down to time scales of 1 minute or even less.
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摘要 :
The main goals of this project ('Internal consistency of meteorological data obtained with a volume-imaging, multi-receiver radar wind profiler) were (1) to identify as clearly as possible the mathematical relationships between ra...
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The main goals of this project ('Internal consistency of meteorological data obtained with a volume-imaging, multi-receiver radar wind profiler) were (1) to identify as clearly as possible the mathematical relationships between radar wind profiler (RWP) signals and the turbulent atmospheric field in the radar resolution volume; and (2) to develop dynamical and other conservation equations for those properties of the turbulence field that we identify in Part (1). The mathematical relationships between the radar observables and the atmospheric fields have now been formulated in a very general manner. In contrast to all earlier RWP theories, the new theory allows not only the zeroth moment (backscattered power) but also all higher moments (Doppler shift, spectral width, etc.) of the Doppler spectrum to be rigorously expressed in terms of statistics of the velocity and refractive-index fields in the RWP's resolution volume. The theoretical results have been illustrated and enhanced by the analysis of RWP measurements and fine-wire, in-situ turbulence measurements.
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