Monitoring of mixing layer height was performed during different measurement campaigns in urban and sub-urban area (Hanover, Munich, Budapest, Zurich, Garmisch-Partenkirchen) by the Vaisala ceilometer CT25K and LD40. These are eye-safe commercial lidars and designed originally to detect cloud base heights and vertical visibility for aviation safety purposes. The data interpretation method was presented last year in the paper SPIE 5571-29. Software for routine retrieval of mixing layer height from ceilometer data was developed.
The comparison with mixing layer height retrievals from a SODAR is continued. In the absence of low clouds and precipitation ceilometers can estimate the mixing layer height fairly well. The instruments partly complement each other.
For three dimensional in situ measurements a microlight aircraft equipped with sensors for meteorological parameters and aerosols in different size ranges was used. The microlight, due to its slow horizontal speed, high climb rate and low minimum altitude, serves as very flexible platform for profiling the planetary boundary layer up to about 4500 m a.s.l. on a regional scale. For the measurements of the size distribution of large particles a Grimm aerosol spectrometer type 1.108 with 15 size bins from 0.3 to 20 μm was used, for the small particles > 10 nm a TSI 3010 particle counter. Temperature and dewpoint are measured with a fast chilled mirror (Meteolab, CH). All data are used to evaluate mixing layer height information.