Dual-wavelength aerosol vertical profile measurements by MAX-DOAS at Tsukuba, Japan
1Frontier Research Center for Global Change, Japan Agency for Marine-Earth Science and Technology, 3173-25 Showa-machi, Kanazawa-ku, Yokohama, Kanagawa 236-0001, Japan
2National Inst. for Environmental Studies, 16-2, Onogawa, Tsukuba, Ibaraki 305-8506, Japan
3Department of Earth Science, Faculty of Sciences, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan
Abstract. We present vertical profiles of the aerosol extinction coefficient retrieved from ground-based Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements at Tsukuba, Japan (36.1° N, 140.1° E), from November 2006 to March 2007. Retrievals utilizing absorption by the oxygen collision complex O4 are first made at two wavelengths, 354 and 476 nm. A robust assessment of the MAX-DOAS aerosol data is made using coincident lidar measurements throughout the period. Agreement between aerosol extinction coefficients measured by MAX-DOAS and the lidar tends to be better at the longer wavelength and at lower altitudes. At 476 nm, the best agreement, to within 30%, is found at altitudes of 0–1 km, confirming results from a literature assessment for a two-month measurement period. These findings are supported by comparisons of the aerosol optical depth by MAX-DOAS and sky radiometer measurements and are further explained by differences in the O4 absorption and the air mass factor profile between 354 and 476 nm. Thus, uncertainty in MAX-DOAS aerosol measurements is well quantified and characterized, providing a basis for quantitative studies using MAX-DOAS measurements.