Xspharm class

class xspharm.xspharm.xspharm(grid_ds, gridtype='regular', rsphere=6371200.0, omega=7.292e-05, legfunc='stored')[source]

Bases: object

Xarray interface to spherical harmonic transforms using pyspharm.

nlat

Number of latitude points.

Type:: int

nlon

Number of longitude points.

Type:: int

fvor

planetary vorticity

Type:: xarray DataArray

s

Spharmt object for spherical harmonic operations.

Type:: Spharmt

truncate()[source]: Truncate a data variable or entire dataset to a specific wavenumber.

exp_taper()[source]: Apply tapering to spherical harmonic coefficients.

uv2sfvp()[source]: Convert zonal and meridional wind components to streamfunction and velocity potential.

uv2vordiv()[source]: Convert zonal and meridional wind components to vorticity and divergence.

uv2absvor()[source]: Convert zonal and meridional wind components to absolute vorticity.

sf2uv()[source]: Convert streamfunction to rotational wind components.

vp2uv()[source]: Convert velocity potential to divergent wind components.

sfvp2uv()[source]: Convert streamfunction and velocity potential to zonal and meridional wind components.

exp_taper(ds_or_var, ntrunc=None, r=2)[source]

Taper (filter) the spherical harmonic coefficients using the equation provided.

Args: - ds_or_var (xr.DataArray or xr.Dataset): Input data. - ntrunc (int): Truncation wavenumber N. - r (float): User-defined parameter.

Returns: xr.DataArray or xr.Dataset: Tapered data.

sf2uv(sf_ds, ntrunc=None)[source]

Computes the rotational wind components via spherical harmonics, given an array containing streamfunction

Inputs: sf_ds streamfunction ntrunc: Truncation limit (triangular truncation) for the spherical harmonic computation.

Returns: u, v: zonal and meridional winds

sfvp2uv(sf_ds, vp_ds, ntrunc=None)[source]

Computes the wind components via spherical harmonics, given streamfunction and velocity potential.

Inputs: sf_ds: streamfunction vp_ds: velocity potential ntrunc: Truncation limit (triangular truncation) for the spherical harmonic computation.

Returns: u, v: zonal and meridional winds

truncate(ds_or_var, ntrunc=None)[source]

Truncate a data variable or entire dataset.

Args: - ds_or_var (xr.DataArray or xr.Dataset): Input data. - ntrunc (int, optional): Truncation wavenumber. Default is None.

Returns: xr.DataArray or xr.Dataset: Truncated data.

uv2absvor(u_ds, v_ds, ntrunc=None)[source]

Computes the absolute vorticity via spherical harmonics, given the u and v wind components

Inputs: u, v: zonal and meridional winds ntrunc: Truncation limit (triangular truncation) for the spherical harmonic computation.

Returns: vor: The absolute vorticity

uv2sfvp(u_ds, v_ds, ntrunc=None)[source]

Streamfunction and velocity potential.

Inputs: u, v: zonal and meridional winds ntrunc: Truncation limit (triangular truncation) for the spherical harmonic computation.

Returns: sf, vp: The streamfunction and velocity potential respectively.

uv2vordiv(u_ds, v_ds, ntrunc=None)[source]

Computes the vorticity and divergence via spherical harmonics, given the u and v wind components

Inputs: u, v: zonal and meridional winds ntrunc: Truncation limit (triangular truncation) for the spherical harmonic computation.

Returns: vor, div : the vorticity and divergence respectively.

vp2uv(vp_ds, ntrunc=None)[source]

Computes the divergent wind components via spherical harmonics, given an array containing velocity potential

Inputs: vp_ds velocity potential. ntrunc: Truncation limit (triangular truncation) for the spherical harmonic computation.

Returns: u, v: zonal and meridional winds