Interpolation of winds at 1000 hPa affected by::
- MIR using an intermediate full (regular) Gaussian grid at a resolution corresponding to the target lat-lon resolution for the spectral to grid transformation followed by grid-to-grid interpolation
- MIR using a more accurate truncation of the spectral series corresponding to the target grid resolution to avoid ripples from aliasing effects
HRES T1279
- For transformations to high resolution target grids (0.1x0.1 and 0.125x0.125) for which no spectral truncation occurs
- differences are at most +/-3.5m/s
- differences are smaller than +/-0.5m/s for more than 99% of grid points
- For transformations to lower resolution target grids:
- the maximum and minimum differences are significantly larger.
- differences are smaller than 1 m/s for more than 80% of grid points
- larger differences are due to sub-optimal default truncation of the spectral series used by EMOSLIB:
- EMOSLIB uses truncation=T799 for a 0.25x0.25 target grid compared to the theoretical ideal used by MIR of truncation=T719
- EMOSLIB uses truncation=T319 for a 0.5x0.5 target grid compared to the theoretical ideal used by MIR of truncation=T359
- EMOSLIB uses truncation=T213 for a 1.0x1.0 target grid compared to the theoretical ideal used by MIR of truncation=T179
- Generally, the use of the intermediate grid with MIR produces smoother fields.
The plots show the differences with the contours chosen on a logarithmic scale to enhance the smaller differences. Differences smaller than 0.5% of the field range are not shown. Grid points where the absolute difference is greater than 25% of the maximum absolute difference are indicated with red (EMOSLIB greater than MIR) and blue (EMOSLIB less than MIR) filled circles.
Target resolution | Parameter | Statistics of differences | Histogram of differences | Global | Europe |
---|---|---|---|---|---|
0.1x0.1 | u | Maximum difference = 2.019257 Percentage of points with absolute difference < 0.10 = 91.262% | -2.5 : -2.0 - 0 ( 0.000000%) 0 ( 0.000000%) | ||
v | Maximum difference = 1.914169 Percentage of points with absolute difference < 0.10 = 88.455% | -2.0 : -1.5 - 10 ( 0.000154%) | |||
0.125x0.125 | u | Maximum difference = 2.638397 Percentage of points with absolute difference < 0.10 = 84.039% | -3.5 : -3.0 - 1 ( 0.000024%) 1 ( 0.000024%) | ||
v | Maximum difference = 2.837143 Percentage of points with absolute difference < 0.10 = 79.683% | -3.0 : -2.5 - 1 ( 0.000024%) | |||
0.25x0.25 | u | Maximum difference = 7.823715 Percentage of points with absolute difference < 0.10 = 47.241% | -8.0 : -7.0 - 0 ( 0.000000%) | ||
v | Maximum difference = 9.905029 Percentage of points with absolute difference < 0.10 = 44.908% | -10.0 : -9.0 - 0 ( 0.000000%) | |||
0.5x0.5 | u | Maximum difference = 10.179855 Percentage of points with absolute difference < 0.10 = 28.037% | -11.0 : -10.0 - 0 ( 0.000000%) | ||
v | Maximum difference = 11.994492 Percentage of points with absolute difference < 0.10 = 26.601% | -12.0 : -11.0 - 0 ( 0.000000%) -11.0 : -10.0 - 1 ( 0.000385%) -10.0 : -9.0 - 4 ( 0.001539%) | |||
1.0x1.0 | u | Maximum difference = 12.553375 Percentage of points with absolute difference < 0.10 = 17.397% | -13.0 : -12.0 - 0 ( 0.000000%) | ||
v | Maximum difference = 11.211227 Percentage of points with absolute difference < 0.10 = 16.687% | -16.0 : -15.0 - 1 ( 0.001535%) |