Lidar techniques represent the most suitable tool to obtain information on the aerosol vertical distribution and therefore to close this kind of observational gap. Lidar networks are fundamental to study aerosol on large spatial scale and to investigate transport and modification phenomena. These are the motivations why EARLINET, the European Aerosol Research Lidar Network, was established in 2000, as a research program funded by the European Commission in the frame of the 5th framework program. After the end of the project, the network activity continued on the base of a voluntary association. At present, EARLINET consists of 25 lidar stations: 10 single backscatter lidar stations, 8 Raman lidar stations with the UV Raman channel for independent measurements of aerosol extinction and backscatter, and 7 multiwavelength Raman lidar stations (elastic channel at 1064 nm, 532 nm, 355 nm, Raman channels at 532 nm and 355 nm, plus depolarization channel at 532 nm) for the retrieval of aerosol microphysical properties. On March 2006, the EC Project EARLINET-ASOS (Advanced Sustainable Observation System) started on the base of the EARLINET infrastructure. This infrastructure project will enhance the operation of the network. EARLINET data can contribute significantly to the quantification of aerosol concentrations, radiative properties, long-range transport and budget, and prediction of future trends on European and global scale. It can also contribute to improve model treatment on a wide range of scales and to a better exploitation of present and future satellite data.

EARLINET is playing an important role in the validation and in the full exploitation of the CALIPSO mission. EARLINET started correlative measurements for CALIPSO since June 2006. A strategy for correlative measurements has been defined on the base of the analysis of the high resolution ground track data provided by NASA. More than 2000 correlative lidar observations have been performed until now and these measurements are still continuing. Results in terms of comparisons between EARLINET and available CALIPSO products, both level 1 and level 2 data, will be presented. EARLINET will contribute to future satellite missions with lidar onboard such as ADM-Aeolus and EarthCARE. Both these missions will have onboard an High Spectral Resolution Lidar at 355nm able to give independent measurements of aerosol extinction and backscatter coefficient in the UV. The multi-wavelength EARLINET data will be very useful to validate these missions and also to give the conversion factors that allow to integrate the aerosol data at 532nm and 1064nm from CALIPSO with the measurements at 355nm form ADM-Aeolus and EarthCARE.

ACKNOWLEDGMENTS

EARLINET-ASOS is supported by the European Commission under grant RICA-025991. The financial support by the European Space Agency -ESTEC Contract No. 21487/08/NL/HE is gratefully acknowledged.

The authors also thank the German Weather Service for the air mass backtrajectory analysis and the CALIPSO team of the NASA Langley Research Center for the provision of the CALIPSO high resolution ground track data.

CALIPSO data were obtained from the NASA Langley Research Center Atmospheric Science Data Center.