Interpolation of temperature at 1000 hPa affected by::
- use by MIR of 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
- use by MIR of using a more accurate truncation of the spectral series corresponding to correspond the target grid resolution to avoid ripples from aliasing effects
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- For transformations to high resolution target grids (0.1x0.1 and 0.125x0.125) for which no spectral truncation occurs
- differences are at most +/-3K
- differences are smaller than +/-1K 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 +/-2K for more than 99% 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 where target grid compared to the theoretical ideal used by MIR is of truncation=T719
- EMOSLIB uses truncation=T319 for a 0.5x0.5 where target grid compared to the theoretical ideal used by MIR is of truncation=T359
- EMOSLIB uses truncation=T213 for a 1.0x1.0 where target grid compared to the theoretical ideal used by MIR is of truncation=T179
- than those produced by MIR.
- 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 0.1% of the field range are not shown. Grid points where the absolute difference is greater than 50% of the maximum absolute difference are indicated with red (EMOSLIB greater than MIR) and blue (EMOSLIB less than MIR) filled circles.
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