Test of a Phased Array Sodar by Intercomparison with Tower Data

Abstract

The phased array sodar PA2 recently manufactured by the French REMTECH enterprise was tested using tower data for comparison. Wind speed, wind direction, and the standard deviation of the horizontal wind direction (σ?) were measured continuously using the sodar and the tower instruments. The 10-min mean values were recorded between 60 and 200 m above ground level for a period of two weeks in October 1990 and then compared with each other. Furthermore, the availability of sodar data was investigated as a function of height. The intercomparison comprises a time series and a linear recession and correlation analysis. It shows that the new sodar can estimate the wind data in a reliable manner. The correlation is as good as or even better than that of the previous long-term intercomparisons of the old A0 sodar used at our institute. The root-mean-square difference between the lower and the sodar data is smaller at least for the wind speed and σ ?. The latter is considered an important parameter for the estimation of the atmospheric turbulence. Unfortunately, the acoustic emission of the sodar turned out to be very annoying to the people working nearby. Therefore, two noise protection measures were investigated: 1) operation of the PA2 behind a noise shield and 2) automatic reduction of the power output during daytime. The latter countermeasure proved to be the better one.