Spectra

power_spectrum_1d(::AtmosGCMConfigType, var_grid, z, lat, lon, weight)

Calculates the 1D (zonal) power spectra using the fourier transform at each latitude and level from a 3D velocity field. The snapshots of these spectra should be averaged to obtain a time-average. The input velocities must be interpolated to a Gaussian grid.

References

• Aksel WIIN-NIELSEN (1967)
• John N Koshyk , Kevin Hamilton (2001)

Arguments

• var_grid: variable (typically u or v) on a Gausian (lon, lat, z) grid to be transformed
• z: vertical coordinate (height or pressure)
• lat: latitude
• lon: longitude
• mass_weight: for mass-weighted calculations

power_spectrum_2d(::AtmosGCMConfigType, var_grid, mass_weight)

• transform variable on grid to the 2d spectral space using fft on latitude circles

(as for the 1D spectrum) and Legendre polynomials for meridians, and calculate spectra

Arguments

• var_grid: variable (typically u or v) on a Gausian (lon, lat, z) grid to be transformed
• mass_weight: weight for mass-weighted calculations

References

• Ferdinand Baer (1972)

power_spectrum_3d(::AtmosLESConfigType, u, v, w, L, dim, nor)

Calculates the Powerspectrum from the 3D velocity fields u, v, w. Inputs need to be equi-spaced and the domain is assumed to be the same size and have the same number of points in all directions.

Arguments

• L: size domain
• dim: number of points
• nor: normalization factor