For 20 years the biennial symposia organized by the International Society for Acoustic Remote Sensing of the Atmosphere and Oceans and Associated Techniques (ISARS) have been held in different countries The original papers collected in the proceedings of the symposia reflect the development of ideas, equipment, and methods, plus results obtained in the area The spectrum of themes discussed at the symposia is broad More than 60% of the papers were devoted to the role of sodars in atmospheric boundary-layer research This paper presents an overview of the development of sodar technique as elucidated in the proceedings of 11 ISARS symposia Topics include (1) instrumentation, (2) methods of measuring different meteorological quantities and their turbulence characteristics, and (3) validating the methods by comparison of sodar data with in situ measurements

Two decades of progress in SODAR techniques: a review of 11 ISARS proceedings

Simultaneous operation of a sodar system in monostatic and bistatic modes: Preliminary results

Hazardous situations in air pollution can many a times be avoided in case short term local weather forecasting of the boundary layer meteorology becomes available. Amongst the various remote sensing techniques, it has been seen that acoustic remote sensing (SODAR) of the lower atmosphere can be employed to determine and predict the atmospheric boundary layer meteorological parameters. In specific, information can be obtained about thermal stratification, mixing height, low level disturbances, depth of the planetary boundary layer, stability classification, wind velocity, wind variances, turbulence parameters, and diffusion characteristics etc. when SODAR is used in conjunction with surface level measurements of the usual meteorological parameters. In the paper a brief description of the acoustic remote sensing technique and a review of the work done during the last two decades to determine the various air quality related meteorological parameters has been given. The methodology to determine mixing height, stability classification and diffusion and dispersion characteristics using mostly the information from the SODAR echograms has also been described. The SODAR echograms obtained at Delhi for the period May 1977 to April 1982 have been processed and analyzed using pattern recognition to determine these parameters. Doppler SODAR information of wind speed and direction have not been treated for the above purpose. Using the Gaussian dispersion model, pollution concentration downwind of a emission source (in the present case it is a cement factory at Nimbahera, Chittorgarh, India) has also been computed with the help of SODAR determined data. It has been found that measured values with the help of high volume sampler conform to the estimated pollution concentration. A peak in the value of the estimated pollution concentration during the fumigation period has also been seen.

Monitoring air pollution related meteorology using SODAR

Acoustic sounder detection of anabatic/katabatic winds in Abisko, N. Sweden

After a short review of the history of the mini-SODAR, the differences between conventinal SODAR and mini-SODARs are discussed. The background for the interpretation of the turbulent structure parameters are given. In view of existing mini-SODAR systems, some design criteria for portable systems are presented. The limitations in minimum range, vertical resolutions and velocity resolution are discussed. Results from an Arctic boundary-layer experiment, where three monostatic systems are used on a small scale, show the potential of its application. In view of other applications, future developments are presented.

Mobile high-frequency mini-SODAR and its potential for boundary-layer studies : SODAR Monitoring of the atmosphere : recent developments

Detailed spectral analysis of sodar echoes can be utilized to yield information on the structure and vorticity of the wind field within the scattering volume. The analysis is applied to a case of unusually intense turbulence and wind shear recorded at the Capanna Margherita, Monte Rosa, Italy (4559 m.a.s.l.).

Giangiuseppe Mastrantonio

Papers

Characters of the air flow inferred from detailed spectral analysis of acoustic sounder echoes

Sodar retrieval of vertical acceleration, and implications for the determination of temperature and fluxes in the convective boundary layer