For computing stochastically perturbed parametrization tendency (SPPT) patterns.
To be used as multiplicative noise applied to physical tendencies. SPPT is a parametrization of model error. See ECMWF Tech. Memo. #598 (Palmer et al. 2009).
| Type | Visibility | Attributes | Name | Initial | |||
|---|---|---|---|---|---|---|---|
| real, | public | :: | mu(kx) | = | (/1, 1, 1, 1, 1, 1, 1, 1/) | Array for tapering value of SPPT in the different layers of the atmosphere. A value of 1 means the tendency is not tapered at that level |
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| complex, | private | :: | sppt_spec(mx,nx,kx) | SPPT pattern in spectral space |
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| logical, | private | :: | first | = | .true. | Flag for controlling first-use behaviour |
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| real, | private, | parameter | :: | time_decorr | = | 6.0 | Decorrelation time of SPPT perturbation (in hours) |
| real, | private | :: | phi | = | exp(-(24/real(nsteps))/time_decorr) | Time autocorrelation of spectral AR(1) signals |
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| real, | private, | parameter | :: | len_decorr | = | 500000.0 | Correlation length scale of SPPT perturbation (in metres) |
| real, | private, | parameter | :: | stddev | = | 0.33 | Standard deviation of SPPT perturbation (in grid point space) |
| real, | private | :: | sigma(mx,nx,kx) | Total wavenumber-wise standard deviation of spectral signals |
Generate grid point space SPPT pattern distribution.
The generated grid point pattern
Generates a random number drawn for the specified normal distribution.
| Type | Intent | Optional | Attributes | Name | ||
|---|---|---|---|---|---|---|
| real, | intent(in) | :: | mean | The mean of the distribution to draw from |
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| real, | intent(in) | :: | stdev | The standard deviation of the distribution to draw from |
The generated random number
Seeds RNG from system clock.