Lidar observations of the boundary layer using an aerosol and ozone profiler

Studies of boundary layer structure and dynamics were carried out using aerosol and ozone lidar data from the Convective Storm Initiation Project (CSIP) in Southern England in the summer of 2005.

The mobile aerosol and ozone profiler used was a Differential Absorption Lidar (DIAL) system manufactured by Elight Laser Systems and operated by the Universities’ Facility for Atmospheric Measurement (UFAM) in the UK. Five UV wavelengths were used (266nm, 289nm, 299nm, 316nm and 355nm) at a range from 75m to 5km and an altitude resolution of 75m

The ozone lidar system uses the differential absorption technique. By comparing two wavelengths, one in the absorption band of ozone and one of lower absorption, ozone concentrations can be calculated. This enables the measurement of vertical ozone profiles. The system is unique as it has five wavelengths and thus the accuracy can be improved by using different sets of wavelengths and boundary layer measurements can be obtained.

As ozone does not absorb significantly at 355nm, aerosol profiles were calculated using backscatter data at that wavelength. From the backscatter profiles it was possible to detect the top of the mixing layer as a transition to lower aerosol amounts above the layer, leading to a decrease in backscattered energy. It was also possible to observe other layering phenomena, such as residual layers.

This investigation uses ozone and aerosol both as a tracer and an indicator of boundary layer height. It will be possible to observe and compare layering and entrainment processes in the convective and stable boundary layers in both aerosol and ozone profiles.