Data compression: Regional data user perspective

Numerous topics addressed in the frame of dissemination or assimilation in global models, are also relevant for the dissemination or the assimilation in regional models. Nevertheless, there exist some specificities in the regional models or in the usage. First, regional models generally have a lower model top compared to global models. This implies that PCs which are sensitive to those parts of the atmosphere which are not described in the regional model may not be relevant. Thus, PCs and PC scores to be used in regional models should be trained so that not to have any sensitivity to the upper part of the atmosphere. As the model top varies from one regional model to another, dedicated PC sets should be used for different regional models.

For the time being, the assimilation of PC scores or reconstructed radiances have not been tested in any regional model. At least the monitoring of reconstructed radiances should be done. Another specific need of regional models is a higher horizontal density of information. In the case of IASI, this means that the information from the companion imager AVHRR has to be used and disseminated along with the sounder information. The compression of this additional sub-pixel information should also be addressed.