Characterisation of GOME-2 formaldehyde retrieval sensitivity

[摘要] Formaldehyde (CH₂O) is an important tracer of troposphericphotochemistry, whose slant column abundance can be retrieved from satellitemeasurements of solar backscattered UV radiation, using differentialabsorption retrieval techniques. In this work a spectral fitting sensitivityanalysis is conducted on CH₂O slant columns retrieved from the GlobalOzone Monitoring Experiment 2 (GOME-2) instrument. Despite quite differentspectral fitting approaches, the retrieved CH₂O slant columns havegeographic distributions that generally match expected CH₂O sources,though the slant column magnitudes and corresponding uncertainties areparticularly sensitive to the retrieval set-up. The choice of spectralfitting window, polynomial order, I₀ correction, and inclusion of minorabsorbers tend to result in the largest modulations of retrieved slant columnmagnitude and fit quality. However, application of a reference sectorcorrection using observations over the remote Pacific Ocean is shown tolargely homogenise the resulting CH₂O vertical columns obtained withdifferent retrieval settings, thereby largely reducing any systematic errorsources from spectral fitting.

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