Urban areas are sources of many aerosol species which then undergo complex chemical transformation and transport within the urban boundary layer. Interpreting point measurements can be difficult without sufficient information about the dynamical processes contributing to aerosol variability. Doppler lidars are ideally suited to examining both the turbulent structure of the boundary layer and the aerosol structure resulting from turbulent mixing. Results are presented from the second REPARTEE campaign which took place in London, UK during October/November 2007. The aim of the project was to relate aerosol measurements at ground level (within Regent's Park) to measurements at a reference height above the urban canopy (the BT Tower), thereby assessing aerosol transformation and transport within an urban boundary layer. Lidar measurements showed large variability in both boundary layer structure and aerosol loading during the 3 week campaign. Measurements have been compared with eddy covariance flux measurements on the BT Tower. On a few occasions, clear decreases in turbulent mixing at this height during night-time compared to a rooftop reference showed evidence of a residual layer overlying a layer where weak turbulent mixing was still present over the warm urban surface. Such decoupled layers can be linked to differing evolution of aerosol species measured at the two heights. bstract 149844 modified by 134.225.101.157 on 8-8-2008-->