Aerosol information content analysis of multi-angle high spectral resolution measurements and its benefit for high accuracy greenhouse gas retrievals

[摘要] New generations of space-borne spectrometers for the retrieval of atmosphericabundances of greenhouse gases require unprecedented accuracies asatmospheric variability of long-lived gases is very low. These instruments,such as GOSAT and OCO-2, typically use a high spectral resolution oxygenchannel (O₂ A-band) in addition to CO₂ and CH₄ channels todiscriminate changes in the photon path-length distribution from actual tracegas amount changes. Inaccurate knowledge of the photon path-lengthdistribution, determined by scatterers in the atmosphere, is the prime sourceof systematic biases in the retrieval. In this paper, we investigate thecombined aerosol and greenhouse gas retrieval using multiple satelliteviewing angles simultaneously. We find that this method, hitherto onlyapplied in multi-angle imagery such as from POLDER or MISR, greatly enhancesthe ability to retrieve aerosol properties by 2–3 degrees of freedom. We findthat the improved capability to retrieve aerosol parameters significantlyreduces interference errors introduced into retrieved CO₂ and CH₄total column averages. Instead of focussing solely on improvements inspectral and spatial resolution, signal-to-noise ratios or samplingfrequency, multiple angles reduce uncertainty in space based greenhouse gasretrievals more effectively and provide a new potential for dedicatedaerosols retrievals.

[学科分类] 几何与拓扑