A comprehensive boundary layer measurement program has been set up at the Meteorological Observatory Lindenberg (MOL) of the German Meteorological Service (DWD) over the last five years. The measurements are aimed at the investigation of atmosphere - land surface interaction processes over a heterogeneous landscape. Moreover, boundary layer data form an integral part of the "Lindenberg Column", a reference data set created operationally at MOL in order to characterize the vertical structure of the whole troposphere with high vertical and temporal resolution.

The experimental boundary layer facilities comprise, i.a., a boundary layer field site (equipped with a 99m tower, various mesurement complexes for the determination of air ~, soil ~ and radiation parameters, a sodar / RASS) and a network of up to seven micrometeorological stations operated over different surfaces in an area of about 20km * 20km around the MOL site. In addition to a great variety of standard meteorological sensors, these facilities have been equipped with instruments for the operational determination of heat and momentum fluxes continuously throughout the year (profile mast, ultrasonic anemometer-thermometers, laser scintillometer). The operational determination of the latent heat flux based on direct humidity fluctuation measurements, however, is a much more challenging task and has been performed during field experiments only in the past.

Current activities are directed towards the integration of different fast-response hygrometers in the existing micrometeorological measurement systems at MOL. In connection with this, a number of problems have to be solved which partially originate from contradictions between operational requirements and sensor characteristics. These inlude unattended operation vs. extensive maintenance requirements, high sampling rates vs. limited data transmission capacities, sensor intelligence vs. decentralized, heterogeneous infrastructure, data pre-processing vs. raw data analysis. Other issues of importance are the monitoring of long-term stability, sensor re-calibration, application of data correction algorithms, automatic error detection, data and command transmission.

The presentation will report on the status, experiences and problems related to the integration of different humidity fluctuations sensors in the operational boundary-layer measurement program at MOL including sensor calibration and sensor intercomparison results.