Mapping spectroscopic uncertainties into prospective methane retrieval errors from Sentinel-5 and its precursor

[摘要] Sentinel-5 (S5) and its precursor (S5P) are future Europeansatellite missions aiming at global monitoring of methane(CH₄) column-average dry air mole fractions(XCH₄). The spectrometers to be deployed onboard thesatellites record spectra of sunlight backscattered from the Earth'ssurface and atmosphere. In particular, they exploit CH₄absorption in the shortwave infrared spectral range around1.65 μm (S5 only) and 2.35 μm (both S5 andS5P) wavelength. Given an accuracy goal of better than 2 % forXCH₄ to be delivered on regional scales, assessment andreduction of potential sources of systematic error such asspectroscopic uncertainties is crucial. Here, we investigate howspectroscopic errors propagate into retrieval errors on the globalscale. To this end, absorption spectra of a ground-based Fouriertransform spectrometer (FTS)operating at very high spectralresolution serve as estimate for the quality of the spectroscopicparameters. Feeding the FTS fitting residuals as a perturbation intoa global ensemble of simulated S5- and S5P-like spectra at relativelylow spectral resolution, XCH₄ retrieval errors exceed0.6 % in large parts of the world and show systematic correlationson regional scales, calling for improved spectroscopic parameters.

[学科分类] 几何与拓扑