The standard deviation and zonal, meridional and 2d length-scales for temperature were computed in both spectral and gridpoint spaces. The computations were performed using the standard NMC statistics for ALADIN-Morocco. The gridpoint derivation of length-scales was done assuming that the local auto-correlation function is flat at the origin. This assumption is based on the fact that the correlation decreases with distance on both sides of the origin and the function is continuous at the origin. No assumption related to the auto-correlation function at the origin was made in the case of spectral derivation of the length-scale. The agreement between the length-scale maps computed in gridpoint and spectral spaces suggests that the assumption of the flat auto-correlation function at the origin, in the case of gridpoint derivation, is good. The comparison between 2d maps of gridpoint and spectral standard deviations show a very good agreement. In the free troposphere, the horizontal variations of standard deviation and length-scale are much influenced by the tropics/mid-latitude contrast, while in the low levels the land/sea contrast has more influence on the horizontal variations of standard deviation and length-scale.
See the report on operations.