rong-ming hu and randall martin

Rong-Ming Hu and Randall Martin

Inspiring MindsInspiring Minds

Retrieval of Aerosol Single Retrieval of Aerosol Single Scattering Albedo (SSA)Scattering Albedo (SSA)

Determined with radiative transfer calculation as SSA that reproduces Determined with radiative transfer calculation as SSA that reproduces TOMS Aerosol Index when constrained by MODIS aerosol optical TOMS Aerosol Index when constrained by MODIS aerosol optical depth and GEOS-CHEM aerosol vertical profile.depth and GEOS-CHEM aerosol vertical profile.

MODISAOD

GEOS–CHEMAerosol Profile

LIDORT

Calculated Observed (TOMS) AI

TOMSAI

331 nm and 360 nm

Optical depth at 360nmOptical depth at 360nm

1.50

0.01

11.

1.00

0.05

Aerosol profile from GEOS-CHEM Aerosol profile from GEOS-CHEM and validation with ARM dataand validation with ARM data

Southern Great Plains, Lamont, Oklahoma (DOE/ARM site). Results are for 324 profiles from March, 2000 to March, 2003.

Solid: GEOS-CHEM simulations.Asterisk, plus, diamond, triangle andsquare: NOAA/CMDL measurements.

Validation with in situ lidar dataValidation with in situ lidar data(April, 2001)(April, 2001)

Gobi Desert Dust Storm (MODIS).

Solid: GEOS-CHEM simulations.Asterisk: lidar measurements in Cheju island (SNU, South Korea)

Cheju

Aerosol Single Scattering Albedo Aerosol Single Scattering Albedo from retrievalfrom retrieval

Intercomparison with AERONETIntercomparison with AERONET

square: MAM, asterisk: JJA, triangle: SON, plus sign: DJF.

Sensitivity to Aerosol Optical depth Sensitivity to Aerosol Optical depth and surface reflectivityand surface reflectivity

Solid: surface reflectivity=0.05.Dashed: surface reflectivity=0.08.Dotted: surface reflectivity=0.15.

Uncertainty in retrieved Uncertainty in retrieved ωω00

ParameterParameter Input Input UncertaintyUncertainty

Retrieval Retrieval UncertaintyUncertainty

TOMS AITOMS AI ±0.01±0.01 ±± 0.01 0.01

MODIS AODMODIS AOD 20% 20% ±± 0.05 land, 0.05 land, 5% 5% ±± 0.03 ocean 0.03 ocean

±± 0.08 0.08

ÅÅngstrngströöm exponentm exponent ±15 %±15 % ±± 0.11 0.11

Surface reflectivitySurface reflectivity ±0.01±0.01 ±± 0.02 0.02

Refractive indexRefractive index ±0.01±0.01 ±± 0.02 0.02

ProfileProfile ±25 %±25 % ±± 0.05 0.05

CombinedCombined ±± 0.15 0.15

ConclusionConclusion

Low values of aerosol single scattering albedo near 0.8 Low values of aerosol single scattering albedo near 0.8 occur in biomass burning and mineral dust regions.occur in biomass burning and mineral dust regions.

Seasonal variation of single scattering albedo is associated Seasonal variation of single scattering albedo is associated with both mineral dust and biomass burning.with both mineral dust and biomass burning.

Retrieval results present Retrieval results present a high degree of consistency with AERONET measurements; AERONET measurements; the correlation coeffcient, slope

and intercept are 0.75, 0.93 and 0.078 respectively. The dominant terms of retrieval uncertainty are the

Ångström exponent, the aerosol optical depth and aerosol profiles contributing to a total uncertainty of 15 percent.