Simultaneous horizontal and vertical acoustic sounding of the atmospheric boundary layer

Some preliminary results from a series of experiments of simultaneous horizontal and vertical acoustic sounding of the atmosphere are described and discussed. The novel horizontal configuration offers some potential for investigating thermal plume motion and characteristics within the boundary layer. It could also be of use in assessing the importance of excess attenuation in quantitative acoustic sounding. © 1979 D. Reidel Publishing Co

Some aspects of the construction and use of atmospheric acoustic sounders

Acoustic sounder design and performance parameters are described. Various atmospheric features as recorded by the acoustic sounder, including thermal plumes, inversions and waves, are presented and their interpretation given. The use of the acoustic sounder to monitor the height of low level layer cloud and the depth of radiation fog is discussed as well as the detection and tracking of plumes of methane gas. © 1980, The Institution of Electronic and Radio Engineers. All rights reserved

A quantitative comparison of horizontal and vertical acoustic sounding with in-situ measurements

In this paper, we present some results on an experiment to test the accuracy and utility of a horizontally-aimed acoustic sounder. A high-frequency, high-resolution mini-sounder was mounted on the mast of the Boulder Atmospheric Observatory aimed in the cross-wind direction. Measurements of CT2, wind velocity and temperature and velocity variances were obtained under both stable and unstable conditions. These measurements were found to be in agreement with the equivalent values obtained, where appropriate, by the tower-fixed instrumentation and a vertically-pointed sounder, confirming the accuracy of the horizontal sounder. In addition, some information into the horizontal structure of plumes and gravity waves was obtained along with evidence of lack of excess attenuation at least for lengths within the unambiguous range of mini-sounders. © 1985 D. Reidel Publishing Company

Measurement of boundary layer structure parameter profiles by acoustic sounding and comparison with direct measurements

Acoustic sounder derived profiles of the atmospheric velocity and temperature structure parameters, Cv2 and CT2, are presented. the former is obtained using a novel bistatic acoustic sounder comprising a fan beam transmitter and a vertically directed receiver. Simultaneous profiles of the temperature structure parameter are obtained using a conventional monostatic sounder. Time histories of these quantities at two heights in the boundary layer are given and are compared with in‐situ measurements. the results indicate significant anisotropy in the temperature field at scales greater than a few metres and emphasize the care required when comparing directly measured and acoustically estimated turbulence quantities. the significance of anisotropy in the assessment of excess attenuation is also discussed. Copyright © 1981 Royal Meteorological Societ

Quantitative low-level acoustic sounding and comparison with direct measurements

In this paper, measurements of the first 150 m of the atmospheric boundary layer obtained by a high-frequency acoustic mini-sounder are compared with measurements obtained by a full complement of instruments including sonic anemometers mounted on the Boulder Atmospheric Observatory tower. The acoustic mini-sounder, starting as low as 6 m from the ground, measures in the monostatic mode the profiles of the vertical wind speed, w, and of the temperature structure parameter, CT2 with enhanced height resolution of the order of 1 m and time resolution of the order of 30 s. The results of the comparison show that the high-frequency mini-sounder is an effective atmospheric boundary-layer profiler that is also portable and relatively inexpensive. Measurements of the spectrum of CT2 are presented that provide information on the local isotropy of the temperature field. Statistics of the variability of CT2 in both stable and unstable conditions are also given. The sounder's capabilities are further demonstrated by some detailed observations of the structure and time evolution of a thermal plume root at noon and of a nocturnal, stably stratified layer in which a dynamic instability develops. The plume starts at a height of less than 5 m, possesses substantial internal structure, and includes vertical velocities in excess of 2 m s-1. © 1983 D. Reidel Publishing Company

Quantitative interpretation of acoustic echoes from the planetary boundary layer

Recent advances in the quantitative application of acoustic sounders to studies of the atmospheric boundary layer are described. Precise measurement of the echo strength is shown to provide a means of estimating the structure parameters for wind velocity and temperature. Extraction of the Doppler shift provides a method for obtaining information on the mean airflow and small-scale fluctuations in wind velocity. © 1980, The Institution of Electronic and Radio Engineers. All rights reserved