The height of the atmospheric boundary layer (or mixing height) is one of the basic parameters to characterize the structure of the lower atmosphere. Knowledge of this parameter is essential in environmental meteorology, pollutant dispersion and as a scaling parameter for boundary layer variables using similarity theory.

The last comprehensive overview on the status of boundary layer height determination from measurements and models dates from 1997 (e.g., the EURASAP workshop held at Riso National Laboratory). Since then, observational, numerical and theoretical techniques have vastly improved, e.g.,
- new equations have been proposed for MH diagnosis and the impacts of entrainment,
- ceilometers / lidars have been qualified for MH determination,
- new algorithms have been proposed and tested for quasi-operational MH determination from wind profilers, sodars and lidars,
- radiosondes have improved resolution and accuracy thus giving more confidence into MH estimates,
- sensor-synergy studies have been performed and corresponding algorithms have been suggested to match the mixing height estimates from different systems
- Large Eddy simulation have progressed significantly

This joint session aims to provide an overview on current methods, results and open problems in boundary layer height determination, both from models and measurements. Contributions are invited on experimental methods, modelling results (incl. from model outputs), tests of corresponding parameterizations, the role of entrainment, applications of boundary layer height data and climatological studies.