improver.nowcasting.pysteps_advection module#

Semi-Lagrangian backward advection plugin using pysteps

class PystepsExtrapolate(interval, max_lead_time)[source]#

Wrapper for the pysteps semi-Lagrangian extrapolation method

Reference:: https://pysteps.readthedocs.io/en/latest/generated/ pysteps.extrapolation.semilagrangian.extrapolate.html

__init__(interval, max_lead_time)[source]#

Initialise the plugin

Parameters:

_generate_displacement_array(ucube, vcube)[source]#

Create displacement array of shape (2 x m x n) required by pysteps algorithm

Parameters:

Return type:

ndarray

Returns:

Array of shape (2, m, n) containing the x- and y-components of the m*n displacement field (format required for pysteps extrapolation algorithm)

_generate_forecast_cubes(all_forecasts, attributes_dict)[source]#

Convert forecast arrays into IMPROVER output cubes with re-added orographic enhancement

Parameters:

all_forecasts (ndarray) – Array of 2D forecast fields returned by extrapolation function
attributes_dict (Optional[Dict]) – Dictionary containing information for amending the attributes of the output cube.

Return type:

List[Cube]

Returns:

List of iris.cube.Cube instances containing forecasts at all required lead times, and conforming to the IMPROVER metadata standard.

_get_advectable_precip_rate()[source]#

From the initial cube, generate a precipitation rate array in mm h-1 with orographic enhancement subtracted, as required for advection

_reformat_analysis_cube(attribute_changes)[source]#: Add forecast reference time and forecast period coordinates (if they do not already exist) and nowcast attributes to analysis cube

_set_up_output_cubes(all_forecasts)[source]#

Convert 3D numpy array into list of cubes with correct time metadata. All other metadata are inherited from self.analysis_cube.

Parameters:: all_forecasts (ndarray) – Array of 2D forecast fields returned by extrapolation function
Return type:: CubeList
Returns:: List of extrapolated cubes with correct time coordinates

process(initial_cube, ucube, vcube, orographic_enhancement, attributes_dict=None)[source]#

Extrapolate the initial precipitation field using the velocities provided to the required forecast lead times

Parameters:

initial_cube (Cube) – Cube of precipitation at initial time
ucube (Cube) – x-advection velocities
vcube (Cube) – y-advection velocities
orographic_enhancement (Cube) – Cube containing orographic enhancement fields at all required lead times
attributes_dict (Optional[Dict]) – Dictionary containing information for amending the attributes of the output cube.

Return type:

List[Cube]

Returns:

List of extrapolated iris.cube.Cube instances at the required lead times (including T+0 / analysis time)

improver.nowcasting.pysteps_advection module