pysteps.extrapolation.semilagrangian.extrapolate

pysteps.extrapolation.semilagrangian.extrapolate(precip, velocity, num_timesteps, outval=nan, xy_coords=None, **kwargs)

Apply semi-Lagrangian extrapolation to a two-dimensional precipitation field.

Parameters:

precip : array-like

Array of shape (m,n) containing the input precipitation field. All values are required to be finite.

velocity : array-like

Array of shape (2,m,n) containing the x- and y-components of the m*n advection field. All values are required to be finite.

num_timesteps : int

Number of time steps to extrapolate.

outval : float, optional

Optional argument for specifying the value for pixels advected from outside the domain. If outval is set to ‘min’, the value is taken as the minimum value of R. Default : np.nan

xy_coords : ndarray, optional

Array with the coordinates of the grid dimension (2, m, n ).

• xy_coords[0] : x coordinates
• xy_coords[1] : y coordinates

By default, the xy_coords are computed for each extrapolation.

Returns:

out : array or tuple

If return_displacement=False, return a time series extrapolated fields of shape (num_timesteps,m,n). Otherwise, return a tuple containing the extrapolated fields and the total displacement along the advection trajectory.

Other Parameters:  

D_prev : array-like

Optional initial displacement vector field of shape (2,m,n) for the extrapolation. Default : None

n_iter : int

Number of inner iterations in the semi-Lagrangian scheme. Default : 3

inverse : bool

If True, the extrapolation trajectory is computed backward along the flow (default), forward otherwise. Default : True

return_displacement : bool

If True, return the total advection velocity (displacement) between the initial input field and the advected one integrated along the trajectory. Default : False

References

[GZ02] Germann et al (2002)