Characterization of anthropogenic methane plumes with the HyperspectralThermal Emission Spectrometer (HyTES): a retrieval method and error analysis

摘要

We introduce a retrieval algorithm to estimate lower tropospheric methane(CH) concentrations from the surface to 1 km with uncertaintyestimates using Hyperspectral Thermal Emission Spectrometer (HyTES) airborneradiance measurements. After resampling, retrievals have a spatialresolution of 6 × 6 m. The total error from a single retrieval isapproximately 20 %, with the uncertainties determined primarily by noiseand spectral interferences from air temperature, surface emissivity, andatmospheric water vapor. We demonstrate retrievals for a HyTES flight lineover storage tanks near Kern River Oil Field (KROF), Kern County, California,and find an extended plume structure in the set of observations withelevated methane concentrations (3.0 ± 0.6 to 6.0 ± 1.2 ppm),well above mean concentrations (1.8 ± 0.4 ppm) observed for this scene.With typically a 20 % estimated uncertainty, plume enhancements with morethan 1 ppm are distinguishable from the background values with itsuncertainty. HyTES retrievals are consistent with simultaneous airborne andground-based in situ CH mole fraction measurements within the reportedaccuracy of approximately 0.2 ppm (or  ∼ 8 %), due toretrieval interferences related to air temperature, emissivity, andHO.