The research work involves developing algorithms to retrieve the atmospheric boundary layer height from synergetic observations by lidar and microwave radiometer. Atmospheric Boundary-Layer Height (ABLH) is an important parameter for several applications ranging from weather, air-quality and dispersion models, meteorology and avionics. There are several instruments and methods to retrieve the ABLH. However, none of these instruments or methods can measure the development of the ABLH under all atmospheric conditions. For example, aerosol signatures measured by backscatter lidars can be used to determine the ABLH but this approach is reasonable only when the atmosphere is well-mixed. Microwave Radiometer (MWR) derived profiles have low vertical-resolution and cannot resolve fine structures in the boundary-layer, especially, at higher altitudes. We aim to develop a combined algorithm which can provide ABLH estimates through the full diurnal cycle including daytime Mixing Layer (ML), Stable Boundary-Layer (SBL) and transition times.

The daytime Mixing Layer Height (MLH) and the nighttime Stable Boundary-Layer Height (SBLH) are determined by combining their coarse estimates from the MWR measurements with the aerosol backscatter from the lidar. The combination is achieved in the framework of an Extended Kalman Filter (EKF) where the fitting ranges of the EKF are defined by the coarse MWR estimates. The MWR, therefore, plays the role of layer attribution which is especially more pronounced in the multiple aerosol layers and cloudy conditions. For the transition regions only MWR-based estimates are used.

The proposed approach, by exploiting the synergy between the two instruments, enables to detect ABLH with original vertical and temporal resolutions. Test cases combining simulated data as well measured data for a co-located lidar-ceilometer and a MWR are presented.

The simulated data is obtained from the Dutch Atmospheric Large Eddy Simulation (DALES) model for boundary-layer studies. LES provides a virtual laboratory that can be used to investigate the difference in ABLH between aerosol and temperature based estimates without the shortcomings of the instruments, e.g., instrument noise, calibration error and systematic bias.

Doppler wind lidar along with radiosondes (whenever available) are used to assess the quality of the synergetic ABLH estimates. Measurement data from the HD(CP)2 Observational Prototype Experiment (HOPE) campaign at Jülich, Germany is used to test the proposed method.