pysteps.noise.motion.initialize_bps¶

pysteps.noise.motion.initialize_bps(V, pixelsperkm, timestep, p_par=None, p_perp=None, randstate=None, seed=None)¶

Initialize the motion field perturbator described in [BPS06]. For simplicity, the bias adjustment procedure described there has not been implemented. The perturbator generates a field whose magnitude increases with respect to lead time.

Parameters:

V : array_like: Array of shape (2,m,n) containing the x- and y-components of the m*n motion field to perturb.
p_par : tuple: Tuple containing the parameters a,b and c for the standard deviation of the perturbations in the direction parallel to the motion vectors. The standard deviations are modeled by the function f_par(t) = a*t**b+c, where t is lead time. The default values are taken from [BPS06].
p_perp : tuple: Tuple containing the parameters a,b and c for the standard deviation of the perturbations in the direction perpendicular to the motion vectors. The standard deviations are modeled by the function f_par(t) = a*t**b+c, where t is lead time. The default values are taken from [BPS06].
pixelsperkm : float: Spatial resolution of the motion field (pixels/kilometer).
timestep : float: Time step for the motion vectors (minutes).
randstate : mtrand.RandomState: Optional random generator to use. If set to None, use numpy.random.
seed : int: Optional seed number for the random generator.

Returns:

out : dict: A dictionary containing the perturbator that can be supplied to generate_motion_perturbations_bps.