Aerosol Properties Computed from Aircraft-Based Observations During the ACE-Asia Campaign: 2. A Case Study of Lidar Ratio Closure

Figures & data

FIG. 1 (left) Vertical profile of aerosol extinction at different wavelengths, derived from sunphotometer measurements on April 17 (Schmid et al. 2003). (middle) Vertical profiles of the lidar ratio derived from sunphotometer/lidar measurements (implied lidar ratio) (Schmid et al. 2003), and the lidar ratios calculated from the retrieved and in-situ measured size distributions. The error bars in the lidar ratios modeled from the measured size distributions are due to uncertainties in size distributions and real part of refractive index. (right) The lidar ratio modeled profiles which correspond to single scattering albedo values of 0.88 and 0.98 in the boundary layer, 0.88 and 0.94 in the pollution layer, and 0.92 and 0.96 in the dust layer.

TABLE 1 Uncertainties in in-situ measured aerosol size distributions (Wang et al. 2002) (note that these uncertainties do not include uncertainties associated with adjustment to ambient RH)

Particle	Uncertainty in	Uncertainty in
diameter	particle size	concentration
range	measurements	measurements
Dp < 0.5 μm	±5%	±10%
0.5 μm < Dp < 5000 nm	±10%	±20%
Dp > 5000 nm	±10%	±50%

FIG. 2 (top) Comparison of size distribution retrieved from the sunphotometer-derived aerosol layer optical thickness spectrum, with the layer-averaged in-situ measured size distribution in the pollution layer (Kuzmanoski et al. 2006). (bottom) Corresponding extinction and backscattering contribution functions R.

FIG. 3 (top) Comparison of size distribution retrieved from the sunphotometer-derived layer aerosol optical thickness spectrum, with the layer-averaged in-situ measured size distribution in the dust layer (Kuzmanoski et al. 2006). (botto m) Corresponding extinction and backscattering contribution functions.

TABLE 2 Aerosol size-dependent refractive indices based on aerosol chemical analysis (Wang et al. 2002), in three layers observed in the vertical profile of April 17, and average lidar ratio values calculated from retrieved and measured size distributions.

	Refractive index		Modeled lidar ratio (sr)
Aerosol layer	Real part	Imaginary part	Retrieved SD	Measured SD
Dust layer	1.51–1.56	0–0.003	11.9 (6.1–24.8)*	10.4 (6.0–21.9)*
Pollution layer	1.40–1.54	0.0003–0.046	39.5 (22.1–50.6)*	48.1 (22.4–61.2)*
Boundary layer	1.53–1.54	0	14.1 (7.3–28.2)*	17.3 (7.6–17.2)*

TABLE 3 Uncertainties in calculated lidar ratios in three observed layers in the aerosol profile observed on April 17, 2001

	Retrieved size distributions			Measured size distributions
Sources of errors	Boundary layer	Pollution layer	Dust layer	Boundary layer	Pollution layer	Dust layer
Aerosol size	(−15.2%, +0.7%)	(−15.2%, +0.7%)	(−15.2%, +0.7%)	(−13.6%, +15.9%)	(−11.0%, +12.4%)	(−6.2%, +11.2%)
distribution
Refractive index	(−46.0%, +53.0%)	(−15.1%, +28.2%)	(−45.9%, +107.8%)	(−41.6%, +49.2%)	(−25.8%, +24.3%)	(−42.0%, +109.9%)
(real part) ± 5%
Refractive index	(+12.5%, +84.7%)	(−24.2%, −38.5%)	(−5.1%, +11.2%)	(+12.1%, +88.1%)	(−29.1%, −45.5%,)	(−5.1%, +11.2%)
(imaginary part)*

FIG. 4 Comparison of size distributions, derived using LUT and constrained linear inversion methods from the sunphotometer-derived extinction and corresponding extinction spectra at the altitude h = 0.63 km.

Schmid , B. , Hegg , D. A. , Wang , J. , Bates , D. , Redemann , J. , Russell , P. B. , Livingston , J. M. , Jonsson , H. H. , Welton , E. J. , Seinfeld , J. H. , Flagan , R. C. , Covert , D. S. , Dubovik , O. and Jefferson , A. 2003 . Column Closure Studies of Lower Tropospheric Aerosol and Water Vapor During ACE-Asia Using Airborne Sun Photometer and Airborne in Situ and Ship-Based Lidar Measurements . J. Geophys. Res. , 108 ( D23 ) : 8656 doi:10.1029/2002JD003361

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Wang , J. , Flagan , R. C. , Seinfeld , J. H. , Jonsson , H. H. , Collins , D. R. , Russell , P. B. , Schmid , B. , Redemann , J. , Livingston , J. M. , Gao , S. , Hegg , D. A. , Wetton , E. J. and Bates , D. 2002 . Clear-Column Radiative Closure During ACE-Asia: Comparison of Multiwavelength Extinction Derived from Particle Size and Composition with Results from Sun Photometry . J. Geophys. Res , 107 ( D23 ) : 4688 doi:10.1029/2002JD002465

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Kuzmanoski , M. , Box , M. A. , Box , G. P. , Schmid , B. , Wang , J. , Russell , P. B. , Jonsson , H. H. and Seinfeld , J. H. 2006 . Aerosol Properties Computed from Aircraft-based Observations During the ACE-Asia Campaign: 1. Aerosol Size Distributions Retrieved from Optical Thickness Measurements . Aerosol Science and Technology , (in press)

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