  An UV-VIS polarization Lidar has been designed and specified for aerosols
monitoring in the troposphere, showing the ability to precisely address low
particle depolarization ratios, in the range of a few percents. Non-spherical
particle backscattering coefficients as low as 5 {\times} 10-8 m-1.sr-1 have
been measured and the particle depolarization ratio detection limit is 0.6 %.
This achievement is based on a well-designed detector with laser-specified
optical components (polarizers, dichroic beamsplitters) summarized in a
synthetic detector transfer matrix. Hence, systematic biases are drastically
minimized. The detector matrix being diagonal, robust polarization calibration
has been achieved under real atmospheric conditions. This UV-VIS polarization
detector measures particle depolarization ratios over two orders of magnitude,
from 0.6 up to 40 %, which is new, especially in the UV where molecular
scattering is strong. Hence, a calibrated UV polarization-resolved
time-altitude map is proposed for urban and free tropospheric aerosols up to 4
kilometres altitude, which is also new. These sensitive and accurate UV-VIS
polarization-resolved measurements enhance the spatial and time evolution of
non-spherical tropospheric particles, even in urban polluted areas. This study
shows the capability of polarization-resolved laser UV-VIS spectroscopy to
specifically address the light backscattering by spherical and non-spherical
tropospheric aerosols.
