New method for retrieval surface UV albedo from Lidar Surface Returns (LSR) of Aeolus

Here, we report results paving the way toward a new method for retrieving surface albedo at 355 nm from lidar surface returns (LSR) of Aeolus. We found that averaged monthly LSR estimates at 2.5 x 2.5 grid clearly varied depending on the land type with the signal strength descending as follows: snow, arid areas, vegetation, water surfaces. Most importantly, given the difference in the instrumental setup, Aeolus LSR exhibited unexpectedly high agreement with Lambertian Equivalent Reflectance from TROPOMI and GOME-2 with correlation coefficients (r) of ~0.87 at global scales for median estimates at the study period (r = 0.91 for TROPOMI-GOME-2) and regional estimates for 37 selected areas (r > 0.90) where the agreement is driven by land surfaces with lower agreement over water due to inherently different physics of Aeolus LSR. Aeolus LSR showed superior sensitivity to the change of land type from vegetation to arid, compared to GOME-2 or TROPOMI as indicated by the highest negative agreement between Aeolus LSR, compared to GOME-2 or TROPOMI. We anticipate that our results will lay the foundation for the multiyear surface UV albedo climatology during the entire Aeolus lifetime.