[摘要] We introduce an alternative method for the retrieval of polarisation inthe ultraviolet by the satellite spectrometer SCIAMACHY. Unlike theoperational polarisation retrieval algorithm, this method does not use thePolarisation Measurement Devices (PMDs) onboard SCIAMACHY, but onlyrequires the reflectance signal. This makes the algorithm more robust andless sensitive to calibration errors caused by either impropercharacterisation of the instrument's response functions (key data) ordegradation of the optical components.
The alternative polarisation retrieval is able to retrieve the full stateof atmospheric polarisation in the wavelength range between 330 and400 nm, which is essentially the wavelength region covered by SCIAMACHY'sPMD 1. This allows a direct comparison with the current operationalproduct.When we compare the alternative polarisation algorithm with theoperational algorithm, we find in some cases agreement, but not in othercases. The alternative algorithm compares well with an analytical model ofthe polarisation of a cloud-free scene. Using the alternative algorithmthe polarisation-sensitive feature in the SCIAMACHY reflectance around350 nm is automatically corrected for.
