Abstract :
Sodar measurements have been used to estimate the mixing height for about 20 yr, nevertheless the issue is still the subject of controversial discussion. The paper attempts to critically examine the methods and results of mixing height determination from sodar data that have been reported in the literature. The theoretical base, the methods suggested, the automatization of algorithms, and the intercomparison of sodar-based mixing height values with data from independent measurements and models are briefly discussed. An assessment is given of sodar capabilities in comparison with other profiling techniques. It is concluded that sodar data may be used to derive reliable mixing height information in many situations which are of special relevance for environmental monitoring, namely in stagnant weather situations with low mixing height values between about 50 and 500–1000 m, depending on the type of the sodar. However, the algorithms available up to now for their automatic evaluation appear not yet reliable enough to be recommended for operational purposes, and a control of the output by a trained analyst is advisable. Simultaneous operation of sodars and other remote sensing systems (lidar, wind profiler) is shown to be a promising way to overcome the range limitations of sodars and to allow continuous mixing height estimation throughout the complete diurnal cycle.
