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Verification Using GOSAT Measurements

Verification Using GOSAT Measurements. Jochen Landgraf and Andre Galli. Does the lower spectral resolution enhance the sensitivity to spectroscopic errors ?. GOSAT spectral resolution: 0.24 cm -1 CarbonSat reduced spectral resolution. Reduce Spectral Resolution. Back: native GOSAT

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Verification Using GOSAT Measurements

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  1. Verification Using GOSAT Measurements Jochen Landgraf and Andre Galli

  2. Does the lower spectral resolution enhance the sensitivity to spectroscopic errors ? • GOSAT spectral resolution: 0.24 cm-1 • CarbonSat reduced spectral resolution

  3. Reduce Spectral Resolution Back: native GOSAT Red: Gaussian FWHM 1.0 cm-1 Blue: truncated, FWHM 1.2 cm-1 Additional convolution with Gaussian with a resulting FWHM of 0.5 cm-1, 1.0 cm-1, CarbonSat, settings sampling ratio 2.5

  4. Noise Model SWIR-1a spectrum black: native GOSAT red: reduced to CarbonSat resolution GOSAT shot noise model is used to weight measurements in the inversion Convolution approach: Noise on the measurement is the original GOSAT noise after convolution The measurement noise is not consistent with the proposed CarbonSat performance (higher SNR). The study only consider the effect of reduced spectral resolution of GOSAT measurements.

  5. TCCON Colocations-CO2 Time Series Analysis is based on validation with FTS measurements at six TCCON sites: Park Falls, Lamont, Orleans, Bialystok, Darwin, Wollongong Park Falls black crosses: TCCON black plus: native GOSAT Red: CarbonSat resolution

  6. TCCON Colocations-CH4 Time Series Park Falls black crosses: TCCON black plus: native GOSAT Red: CarbonSat resolution

  7. Summary of TCCON validation GOSAT native CarbonSat scatter interstational bias mean bias Performance characterized by bias (median of the relative difference), scatter (standard deviation of the relative difference).

  8. Correlations … of retrieval difference with SZA, water vapour column and aerosol size for CO2 and CH4.

  9. CO2 correlation with aerosol size

  10. Degradation for single retrieval windows Park Falls data set Consider change in bias and scatter when spectra resolution is reduced in the single for windows: O2A scattering properties SWIR-1a CO2 absorption SWIR-1b CH4 absorption SWRI-2 strong CO2 absorption / scattering properties Consider relative change, i.e.:

  11. Degradation for single retrieval windows Δσ [1] Δb [1]

  12. Degradation for single retrieval windows Δσ [1] Δb [1]

  13. Main Conclusions • CO2retrieval: the increase of scatter from 0.66% to 1.01% • CH4 retrieval: the scatter increases from 0.86% to 1.02%, and the average bias drops from -0.28% to -0.78%. • The limited parameter range of retrieved aerosol size indicates that CarbonSat resolution spectra do not allow to retrieve the same number of independent scattering parameters as for native GOSAT resolution. • The retrieval accuracy is dominated by the spectral range where the absorption bands of the target molecule are situated. We investigated the effect of reduced spectral resolution of GOSAT measurements When degrading spectral resolution to CarbonSat spectral resolution, we observe: CarbonSat has an improved SNR which may compensate the loss of information because of reduced spectral resolution.

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