|Title||IASI PC Compression - Searching for sinal in the residuals|
|Authors||Hultberg, T, August, T, Atkinson, N, Smith, N|
|Event Series/Collection||ECMWF/EUMETSAT NWP-SAF|
|Keywords||EUMETSAT, hyperspectral infrared satellite observations, NWP-SAF, workshop|
Hyper-spectral data, such as IASI L1C radiances, can be seen as a sum of atmospheric signal and random instrument noise. While the spectral correlation in the signal allows for substantial compression, the high entropy of the noise imposes small limits on the maximum possible compression rate. Therefore high compression rates can only be achieved if a large part of the noise can be identified and removed from the spectra before dissemination. Principal component (PC) compression, as used for EUMETSAT's dissemination of compressed IASI spectra, offers a method for doing this. There is a legitimate concern that some amount of genuine atmospheric signal is discarded together with the noise. This happens, in particular, for rare features, not well represented in the training data, and for spectrally narrow features, for which it becomes difficult to distinguish between signal and noise.