The use of principal component analysis for the assimilation of high‐resolution infrared sounder observations for numerical weather prediction

Methodologies are discussed for the efficient representation of observations from high-resolution infrared sounders for the purposes of assimilation into numerical weather prediction models. The use of principal component analysis is explored and it is noted that, while the available information in the observations is stored efficiently, the non-locality of the Jacobians that arise may cause practical problems in an operational assimilation system. Reconstructing radiance spectra from the principal components appears to be a more realistic approach in the near term. However, initial experiments with reconstructed radiances do not appear to give significant improvements in forecast skill above that already demonstrated with the current use of advanced sounder data. Copyright (C) 2010 Royal Meteorological Society and Crown Copyright.