The synergistic use of the measurements carried out using active and passive techniques represent a powerful
solution to fully exploit the capabilities of each remote sensing techniques and to contemporarily overrun its main
limitations. The ground-based facility operational at the CNR-IMAA for the study of the atmosphere is an optimal site
where testing possible synergies between active and passive techniques for improving the profiling capabilities of
atmospheric key variables, such as aerosol, water vapor and clouds.
The combination of the measurements provided by a lidar and a passive sensor is a particularly promising
approach because it puts together the high-resolution measurements obtained using a lidar and the operational
capabilities typical of passive sensors. In particular, the combination of the Raman lidar and sunphotometry
measurements allows to describe the aerosol optical and microphysical properties, supporting the lidar retrievals during
daytime and in presence of thick clouds. Moreover, the use of Raman lidar and microwave measurements, integrated
using an approach based on the Kalman filter, is an optimal way to provide high-resolution measurements of the
tropospheric water vapor in nearly all weather conditions. A strong improvement in the supercooled liquid water
retrieval, obtained through the inversion of the microwave brightness temperature, is also achievable using the cloud
base height information retrieved using the lidar backscattering ratio profile to constrain the microwave retrieval.