NASA Ames Solar Spectral Flux Radiometer SSFR

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NASA Ames Solar Spectral Flux Radiometer (SSFR)

• wavelength range
• 300 nm to 1700 nm
• spectral resolution
• 8-12 nm
• simultaneous zenith
• and nadir viewing
• hemispheric FOV
• Accuracy 3 precision 0.5
• Missions FIRE/SHEBA, DOE ARM UAV (1999, 2000,
  2002), PRIDE, SAFARI-2000, ACE-Asia,
  CRYSTAL-FACE, DOE Aerosol IOP

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SSFR Calibration
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Irradiance and Albedo
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SSFR Spectral Albedo
Start
End
300 nm ? 1700 nm
Albedo 0 0.5 1.0
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SSFR Time Series
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Water-leaving radiance MISR Validation

• TOA spectral radiance is integrated contribution
  from the surface and atmospheric.
• MISR uses only the red and near-infrared dark
  water bands for its aerosol retrievals.
• Sea surface reflectance assumed negligible in
  dark bands. Not always negligible in blue-green
  f(?a, depth, polluted water, )

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Water-leaving radiance MISR Validation

• Unless the surface contribution is known
  significant uncertainties retrieved aerosol
  properties
• New algorithm to simultaneously retrieve surface
  reflectance and aerosol properties
  self-consistently - validation needed
• Water-leaving radiance is largest uncertainty for
  low ?a
• Kahn, et al., MISR global aerosol optical depth
  validation based on two years of coincident
  AERONET observations, J. Geophys. Res., in press.
  , 2004.

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Water-leaving Irradiance
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Sea Surface Albedo CF
(Wendisch et al., 2004)
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Water-leaving radiance MISR Validation

• Identify cases
• Extrapolate flight level albedo to sea surface
• J-31 AOD profiles
• RB lidar
• Water-leaving irradiance ? radiance need BRDF

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Forcing Efficiency
21 July 2004
INDOEX Meywerk and Ramanathan, 1999
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Forcing Efficiency Fraction
21 July 2004
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extraterrestrial solar irradiance
state variables P, T, RH
radiative transfer model
SSFR
Cloud Mie theory (?, g) ri, ?i
tables of spectral irradiance
measured spectral irradiance
surface spectral albedo
best fit
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RT Model

• 300 - 1700 nm in 10 nm intervals
• k distribution 16 g points per interval
• 38 layers
• instrument filter function (correlation in g
  space)
• Kurucz solar source function (correlation in g
  space)
• HITRAN with Giver corrections
• DISORT
• spectral surface reflection