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The O rbiting C arbon O bservatory ( OCO ) Mission Watching The Earth Breathe…Mapping CO 2 From Space. The Use of Spectral Binning in Radiative Transfer: Concepts & Application to Radiant Mick Christi & Zhiming Kuang OCO L2 Breakout Session
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The Orbiting Carbon Observatory (OCO) Mission Watching The Earth Breathe…Mapping CO2 From Space. The Use of Spectral Binning in Radiative Transfer: Concepts & Application to Radiant Mick Christi & Zhiming Kuang OCO L2 Breakout Session March 2006
Brief Overview • Brief review of atmosphere-building in Radiant • Atmospheric layer & block banking concepts • Example of estimated benefit of using these ideas • Implementation of block-banking in Radiant for OCO
Accelerating Radiative Transfer:Layer & Block-Banking Spectral Layer-Binning & Banking → Reduce Number of Individual Layer Buildings Spectral Block-Banking → Reduce Number of “Addings”
O2 A-Band Test Case Table 1. Numbers of operations Table 2. Timing results
Accelerating Radiative Transfer:Spectral Block-Banking #1 #2 Have the entire atmosphere – Don’t do anything. #3 Have upper blocks. Have lower blocks. They meet. Have upper blocks. Have lower blocks. They don’t meet. #4 #5 #6 Have upper blocks. Don’t have lower blocks. Don’t have upper blocks. Have lower blocks. Don’t have anything – Do normal adding.
· · λ · · τabs Layer-Binning • For every layer in the model atmosphere, create a table to bin optical properties (small sample table given at right). • Using the values of optical properties at the center of the appropriate bin for each layer, compute the radiances and analytic derivatives (i.e. compute the “binned radiances” and “binned analytic derivatives”. Scattering optical properties ωo, τs, Pbinned with respect toλ
· · where it is understood that λ · · for a parameter x. Note, for the first derivative above, we have τabs Layer-Binning R = R(λ,τ1,τ2) Simple two-layer atmosphere case: • Using the “binned analytic derivatives”, apply a correction to the “binned radiance” using a truncated Taylor series to obtain the final radiance at the wavelength of interest (sample expression for a simple two-layer case given at right). ·
