Content
These images are based upon the randomly selected time step 12UTC on 2008-05-03. Two further randomly selected time steps are also available:
The layer is always the one at the lowest altitude because only this is subjected to downscaling.
Fig. 1: Pressure as supplied by the COSMO model: The coarse data.
Downscaled data
Due to the existence of a Schomburg rule for pressure, it can be subjected to full downscaling (fig. 3,5,5.1). Figures 2,4,4.1 deal with results from mere interpolation.
Fig. 2: Pressure after spline interpolation. Fig. 3: Pressure after full downscaling. Fig. 3.1: Detail of figure 3, showing only the area Sauerland.
In cotrast to the merely interpolated field (fig. 2), the fully downscaled temperature field (fig. 3) shows fine scale structures. These have the form of rivers and are thus not numerical fluctuations (fig. 3.1).
Fig. 4: Pressure after spline interpolation and subsequent upscaling back to the coarse grid. Fig. 5: Pressure after full downscaling and subsequent upscaling back to the coarse grid.
Fig. 4.1: Pressure bias after spline interpolation, on the coarse grid. Fig. 5.1: Pressure bias after full downscaling, on the coarse grid. The axis limits have changed.
While the bias after interpolation is evenly distributed above and below 0, the bias after the full downscaling lacks positive values above 0.006 Pa. Still, all values fall short of the usual temperature difference span of about 10^4 Pa. The reasonable interpretation is as numerical fluctuations.