CarbonSat: Error Analysis for XCO2 and XCH4 and Secondary Products from Ocean Sunglint Observations
Boesch, Hartmut1; Buchwitz, Michael2; Bovensmann, Heinrich2; Reuter, Max2; Landgraf, Jochen3; Sierk, Bernd4; Loescher, Armin4; Meijer, Yasjka4; Ingmann, Paul4
1University of Leicester, UNITED KINGDOM; 2University of Bremen, GERMANY; 3SRON, NETHERLANDS; 4ESA ESTEC, NETHERLANDS
The ESA Earth Explorer 8 candidate mission CarbonSat aims at determining atmospheric CO2 and CH4 concentrations to better separate biogenic and anthropogenic fluxes with global CO2 and CH4 data and ''imaging'' of strong localised CO2 and CH4 emission. To achieve this goal, CarbonSat will measure reflected sunlight in three shortwave-infrared bands with high spatial resolution and sufficient spatial swath width. To obtain accurate measurements over the ocean CarbonSat will perform ocean sunglint measurements which provide high signal-to-noise for measurements of over ocean surfaces that are otherwise very dark.
Using simulations for a range of geophysical scenarios, we have carried out a characterization of systematic and random errors for the retrieval of the column-averaged dry air mole fraction of CO2 and CH4 from sunglint measurements. As additional secondary products, we have also included surface pressure and aerosol profiles. An error parameterization scheme has been developed to estimate expected biases and random errors as function of key scattering and surface parameters which allow to infer the spatio-temporal distribution of errors over the ocean and to carry out observing system simulation experiments (OSSE) to determine the impact of CarbonSat observations on surface fluxes. A study on error characterization from nadir observations is presented by Buchwitz et al.