In situ evaluation of spaceborne CALIOP lidar measurements of the upper-ocean particle backscattering coefficient

The spaceborne CALIOP lidar, initially designed for atmospheric measurements, was recently used to retrieve the particulate backscattering coefficient (b bp ) in ocean subsurface layers. However, extensive field evaluation of CALIOP estimates was never conducted due to the scarcity of in situ data. Here, year-round and basin-wide data from Biogeochemical Argo floats (BGC Argo) were used to evaluate CALIOP estimates in the North Atlantic. The high density of BGC Argo float profiles in this region allowed us to test different matchup strategies at different spatio-temporal scales. When averaged over 2° by 2° grid boxes and monthly time resolution, CALIOP data present reasonably good correlation with highly variable float b bp values (correlation r = 0.44, root mean square relative error RMS% = 13.2%), suggesting that seasonal dynamics can be characterized at basin scale.