1School of Physics and Centre for Climate and Air Pollution Studies, Ryan Institute, National University of Ireland Galway, Galway, Ireland
2Electro-Optical Systems Laboratory, Georgia Tech Research Institute, Georgia Institute of Technology, 225 North Avenue, Atlanta, Georgia 30332, USA
3NILU – Norwegian Institute for Air Research, P.O. Box 100, 2027 Kjeller, Norway
anow at: Federal Office of Meteorology and Climatology, MeteoSwiss, Payerne 1530, Switzerland
bnow at: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 225, North Avenue, Atlanta, Georgia 30332, USA
Received: 17 Dec 2014 – Discussion started: 04 Mar 2015
Abstract. The expedited near-real-time Level 1.5 Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) version 3 products were evaluated against data from the ground-based European Aerosol Research Lidar Network (EARLINET). The statistical framework and results of the three-year evaluation of 48 CALIOP overpasses with ground tracks within a 100 km distance from operating EARLINET stations are presented and include analysis for the following CALIOP classifications of aerosol type: dust, polluted dust, clean marine, clean continental, polluted continental, mixed and/or smoke/biomass burning. For the complete data set comprising both the planetary boundary layer (PBL) and the free troposphere (FT) data, the correlation coefficient (R) was 0.86. When the analysis was conducted separately for the PBL and FT, the correlation coefficients were R = 0.6 and R = 0.85, respectively. From analysis of selected specific cases, it was initially thought that the presence of FT layers, with high attenuated backscatter, led to poor agreement of the PBL backscatter profiles between the CALIOP and EARLINET and prompted a further analysis to filter out such cases; however, removal of these layers did not improve the agreement as R reduced marginally from R = 0.86 to R = 0.84 for the combined PBL and FT analysis, increased marginally from R = 0.6 up to R = 0.65 for the PBL on its own, and decreased marginally from R = 0.85 to R = 0.79 for the FT analysis on its own. This suggests considerable variability, across the data set, in the spatial distribution of the aerosol over spatial scales of 100 km or less around some EARLINET stations rather than influence from elevated FT layers. For specific aerosol types, the correlation coefficient between CALIOP backscatter profiles and the EARLINET data ranged from R = 0.37 for polluted continental aerosol in the PBL to R = 0.57 for dust in the FT.
Revised: 15 Oct 2015 – Accepted: 20 Oct 2015 – Published: 03 Nov 2015
Grigas, T., Hervo, M., Gimmestad, G., Forrister, H., Schneider, P., Preißler, J., Tarrason, L., and O'Dowd, C.: CALIOP near-real-time backscatter products compared to EARLINET data, Atmos. Chem. Phys., 15, 12179-12191, doi:10.5194/acp-15-12179-2015, 2015.