An Airborne Laser Air Motion Sensing System. Part I: Concept and Preliminary Experiment

Keeler, R. Jeffrey; Serafin, Robert; Schwiesow, R. L.; Lenschow, Donald H.; Vaughan, J. M.; Woodfield, A. A.

doi:10.1175/1520-0426(1987)004<0113:aalams>2.0.co;2

Cited by 28 publications

(13 citation statements)

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“…Airplane measurements could also be considerably enhanced by direct measurements of the Richardson number -i.e., direct measurements of the wind shear and lapse rate -and thus directly relate the mean structure to the turbulence intensity. As pointed out by Keeler et al (1987) and Kristensen and Lenschow (1987), this now seems technically feasible. STABLY STRATIFIED BOUNDARY LAYER OVER THE GREAT PLAINS, I…”

Section: Discussionmentioning

confidence: 99%

The stably stratified boundary layer over the great plains

Lenschow

Zhu

et al. 1988

Boundary-Layer Meteorol

140

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We present airplane measurements of the stably strattied nocturnal boundary layer obtained during the Severe Environmental Storms and Mesoscale Experiment (SESAME) in 1979. The cases presented here were obtained over rolling terrain in central Oklahama, with a mean slope of about 0.003. The results are in general agreement with previous modeling and observational studies for the mean and turbulence structure of the nocturnal boundary layer, with the exception that the eddy diffusivity of heat, and consequently the flux Richardson number are less than expected.

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Section: Discussionmentioning

confidence: 99%

The stably stratified boundary layer over the great plains

Lenschow

Zhu

et al. 1988

Boundary-Layer Meteorol

140

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“…Earlier versions of laser wind sensors operating at 10.6 µm wavelength were designed for use on NCAR aircraft in the 1980s and 1990s, as discussed by Keeler et al (1987), Kristensen and Lenschow (1987) and Mayor et al (1997), but developments in fibre optics now have made a much improved system practical. For the present system, the wavelength used is about 1.56 µm; Spuler et al (2011) estimated that a particle concentration of about 2 cm −3 with a diameter in the range from 0.1 to 3 µm is needed to provide a detectable signal, but the sensitivity has been improved since that early test.…”

Section: The Ncar Laser Air-motion Sensormentioning

confidence: 99%

“…It is not yet clear that this will be a useful measurement because the backscattered return in dense clouds might be dominated by regions closer than the focal point of the system, where airflow distortion could be important. The change in the location of the sample volume of a laser system was recognized by Werner et al (1984), and the possible error in sensed airspeed was discussed by Keeler et al (1987), who recommended modified processing techniques selecting the peak rather than the mean in the Doppler-shifted wavelength spectrum, as used here, for measurements in clouds. Indeed, too low a measurement of airspeed would cause the deduced temperature to be too low, as is the trend in this figure.…”

Section: Using the Lams To Measure Temperaturementioning

confidence: 99%

Calibrating airborne measurements of airspeed, pressure and temperature using a Doppler laser air-motion sensor

et al. 2014

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Abstract.A new laser air-motion sensor measures the true airspeed with a standard uncertainty of less than 0.1 m s −1 and so reduces uncertainty in the measured component of the relative wind along the longitudinal axis of the aircraft to about the same level. The calculated pressure expected from that airspeed at the inlet of a pitot tube then provides a basis for calibrating the measurements of dynamic and static pressure, reducing standard uncertainty in those measurements to less than 0.3 hPa and the precision applicable to steady flight conditions to about 0.1 hPa. These improved measurements of pressure, combined with high-resolution measurements of geometric altitude from the global positioning system, then indicate (via integrations of the hydrostatic equation during climbs and descents) that the offset and uncertainty in temperature measurement for one research aircraft are +0.3 ± 0.3 • C. For airspeed, pressure and temperature, these are significant reductions in uncertainty vs. those obtained from calibrations using standard techniques. Finally, it is shown that although the initial calibration of the measured static and dynamic pressures requires a measured temperature, once calibrated these measured pressures and the measurement of airspeed from the new laser air-motion sensor provide a measurement of temperature that does not depend on any other temperature sensor.

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“…(3) Taking into account Eq. (3) we can obtain the following approximate estimate of Doppler spectrum at the moment 1: W(t, = 5 th J( + )j:(t) e2fT (4) where the bar means averaging over location and scattering amplitudes of scattering particles placed in the probe volume at the moment t.…”

Section: Basic Relationsmentioning

confidence: 99%

“…Let us make the substitution f= (2/X)V (5) in (4). Then the power spectrum W(z', (2/X) V) scaled to the quantity 5d VW(t, (2/X) F) can be considered as probability density of velocity distribution of aerosol particles brought into the probe volume during period [t -t0, t] .…”

Section: Basic Relationsmentioning

confidence: 99%