Johann Christian Doppler and his effect—A brief history

White, D. N.

doi:10.1016/0301-5629(82)90114-4

Cited by 428 publications

(27 citation statements)

References 11 publications

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“…where S air (v − ω Doppler , σ air ) is Gaussian shaped (Gossard, 1994), ω Doppler [m s −1 ] is the Doppler velocity of the ambient air motion defined with motions approaching the radar as positive Doppler motions consistent with the 1842 work by Christian Doppler (White, 1982), and σ air [m s −1 ] represents the spreading of the spectrum. The leading fraction in Eq.…”

Section: Realistic Radarmentioning

confidence: 99%

Raindrop size distribution variability estimated using ensemble statistics

Williams

Gage

2009

Ann. Geophys.

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Abstract. Before radar estimates of the raindrop size distribution (DSD) can be assimilated into numerical weather prediction models, the DSD estimate must also include an uncertainty estimate. Ensemble statistics are based on using the same observations as inputs into several different models with the spread in the outputs providing an uncertainty estimate. In this study, Doppler velocity spectra from collocated vertically pointing profiling radars operating at 50 and 920 MHz were the input data for 42 different DSD retrieval models. The DSD retrieval models were perturbations of seven different DSD models (including exponential and gamma functions), two different inverse modeling methodologies (convolution or deconvolution), and three different cost functions (two spectral and one moment cost functions).Two rain events near Darwin, Australia, were analyzed in this study producing 26 725 independent ensembles of massweighted mean raindrop diameter D m and rain rate R. The mean and the standard deviation (indicated by the symbols x and σ {x}) of D m and R were estimated for each ensemble. For small ranges of D m or R , histograms of σ {D m } and σ {R} were found to be asymmetric, which prevented Gaussian statistics from being used to describe the uncertainties. Therefore, 10, 50, and 90 percentiles of σ {D m } and σ {R} were used to describe the uncertainties for small intervals of D m or R . The smallest D m uncertainty occurred for D m between 0.8 and 1.8 mm with the 90th and 50th percentiles being less than 0.15 and 0.11 mm, which correspond to relative errors of less than 20% and 15%, respectively. The uncertainty increased for smaller and larger D m values. The uncertainty of R increased with R . While the 90th percentile uncertainty approached 0.6 mm h −1 for a 2 mm h −1 rain rate (30% relative error), the median uncertainty was less than 0.15 mm h −1 at the same rain rate (less Correspondence to: C. R. Williams (christopher.williams@colorado.edu) than 8% relative error). This study addresses retrieval error and does not attempt to quantify absolute or representativeness errors.

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Section: Realistic Radarmentioning

confidence: 99%

Raindrop size distribution variability estimated using ensemble statistics

Williams

Gage

2009

Ann. Geophys.

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“…This new physical phenomenon provides a basis for developing photoacoustic Doppler flowmetry, which can potentially be used for detecting fluid flow in optically scattering media and especially low-speed blood flow of relatively deep microcirculation in biological tissue. DOI Laser flowmetry and acoustic flowmetry based on the Doppler effect [1] have become valuable tools for fluid mechanics measurements [2]. More recently, lowcoherence optical Doppler tomography [3] was developed.…”

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confidence: 99%

Photoacoustic Doppler Effect from Flowing Small Light-Absorbing Particles

2007

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From the flow of a suspension of micrometer-scale carbon particles, the photoacoustic Doppler shift is observed. As predicted theoretically, the observed Doppler shift equals half of that in Doppler ultrasound and does not depend on the direction of laser illumination. This new physical phenomenon provides a basis for developing photoacoustic Doppler flowmetry, which can potentially be used for detecting fluid flow in optically scattering media and especially low-speed blood flow of relatively deep microcirculation in biological tissue.

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“…Laser Doppler fluximetry (MoorVMS-LDF2 TM Laser Doppler System, Moor Instruments, United Kingdom), a technique validated in previous clinical studies, was selected for the assessment of perfusion. This technique provides quantifiable results and is a dynamic measure of blood flow, as well as being easy to use and noninvasive [37][38][39][40][41][42][43]. For this trial, approval was obtained from the relevant ethics committee (Devon and Torbay Research Ethics Committee, United Kingdom, Number: 09/H0202/6).…”

Section: Methodsmentioning

confidence: 99%