International audienceGround-based Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements were performed at Tsukuba, Japan (36.1° N, 140.1° E), in November?December 2006. The measured spectra of scattered sunlight are analyzed by DOAS and optimal estimation methods to retrieve the aerosol optical depth (?) and the vertical profile of the aerosol extinction coefficient (?) at 476 nm in the lower troposphere. We characterize these retrieved quantities through comparisons with coincident lidar and sky radiometer measurements. The retrieved ? values for layers of 0?1 and 1?2 km agree with lidar data to within 30% and 60%, respectively, for most cases, including partly cloudy conditions. Results similar to ? at 0?1 km are obtained for the retrieved ? values, demonstrating that MAX-DOAS provides the new, unique aerosol dataset in the lower troposphere