Comparison of aerosol backscatter coefficient profiles at 1064 nm from CALIPSO and ground-based ceilometer

This pilot study investigates the direct comparison of backscatter coefficient profiles at 1064 nm which were measured by CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) and by a ground-based ceilometer located at the west coast of Ireland. Data recorded between 2013 to 2016 is used to investigate the challenges and limitations in performing such a comparison. The standard Level 2 CALIOP Aerosol Profile version 4 product is compared to data from a ground-based Jenoptik CHM15K ceilometer. A statistical analysis considering CALIOP overpasses within 100 km from the ceilometer is presented taking into account different along-track averages in CALIOP data (5 km, 15 km, 25 km, 35 km and 100 km) at the closest approach. The mean bias calculated from the correlative measurements between CALIOP and the ground-based ceilometer at Mace Head for cloud-free scenarios shows negative bias for 80% of the cases. The comparison of these results with HYSPLIT shows that air samples with higher or lesser content of marine aerosols produced different biases between the measurements. To our knowledge, this is the first study that investigates the limitations and capabilities in comparing CALIOP and ground-based ceilometer measurements using the 1064 nm wavelength.