Static 2D current field

from datetime import datetime, timedelta
import numpy as np

from opendrift.readers.reader_constant_2d import Reader
from opendrift.models.oceandrift import OceanDrift

Constructing a static, rotating ocean current field,

lon, lat = np.meshgrid(np.linspace(2,6,30), np.linspace(59,62,30))
lon0 = 4
lat0 = 60.5
u = -(lat-lat0)/np.sqrt((lon-lon0)**2 + (lat-lat0)**2)
v = (lon-lon0)/np.sqrt((lon-lon0)**2 + (lat-lat0)**2)
lon = np.linspace(0,5,30)
lat = np.linspace(59,62,30)

r = Reader(x=lon, y=lat, proj4='+proj=latlong',
           array_dict = {'x_sea_water_velocity': u, 'y_sea_water_velocity': v})

o = OceanDrift(loglevel=20)
o.set_config('environment:fallback:land_binary_mask', 0)
o.add_reader(r)
o.seed_elements(lon=3, lat=60.5, number=1000, radius=30000, time=datetime.now())
o.run(duration=timedelta(hours=72))
o.animation(fast=True)

14:10:46 INFO    opendrift:569: OpenDriftSimulation initialised (version 1.14.3 / v1.14.3-25-gcd89af5)
14:10:46 INFO    opendrift.models.basemodel.environment:206: Adding a global landmask from GSHHG
14:10:50 INFO    opendrift.models.basemodel.environment:229: Fallback values will be used for the following variables which have no readers:
14:10:50 INFO    opendrift.models.basemodel.environment:232:    sea_surface_height: 0.000000
14:10:50 INFO    opendrift.models.basemodel.environment:232:    x_wind: 0.000000
14:10:50 INFO    opendrift.models.basemodel.environment:232:    y_wind: 0.000000
14:10:50 INFO    opendrift.models.basemodel.environment:232:    upward_sea_water_velocity: 0.000000
14:10:50 INFO    opendrift.models.basemodel.environment:232:    ocean_vertical_diffusivity: 0.000000
14:10:50 INFO    opendrift.models.basemodel.environment:232:    sea_surface_wave_significant_height: 0.000000
14:10:50 INFO    opendrift.models.basemodel.environment:232:    sea_surface_wave_stokes_drift_x_velocity: 0.000000
14:10:50 INFO    opendrift.models.basemodel.environment:232:    sea_surface_wave_stokes_drift_y_velocity: 0.000000
14:10:50 INFO    opendrift.models.basemodel.environment:232:    ocean_mixed_layer_thickness: 50.000000
14:10:50 INFO    opendrift.models.basemodel.environment:232:    sea_floor_depth_below_sea_level: 10000.000000
14:10:50 INFO    opendrift:1779: Skipping environment variable ocean_vertical_diffusivity because of condition ['drift:vertical_mixing', 'is', False]
14:10:50 INFO    opendrift:1779: Skipping environment variable ocean_mixed_layer_thickness because of condition ['drift:vertical_mixing', 'is', False]
14:10:50 INFO    opendrift:1790: Storing previous values of element property lon because of condition (('general:coastline_action', 'in', ['stranding', 'previous']), 'or', ('general:seafloor_action', 'in', ['previous']))
14:10:50 INFO    opendrift:1790: Storing previous values of element property lat because of condition (('general:coastline_action', 'in', ['stranding', 'previous']), 'or', ('general:seafloor_action', 'in', ['previous']))
14:10:50 INFO    opendrift:1798: Storing previous values of environment variable sea_surface_height because of condition ['drift:vertical_advection', 'is', True]
14:10:50 INFO    opendrift:945: Using existing reader for land_binary_mask to move elements to ocean
14:10:50 INFO    opendrift:975: All points are in ocean
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14:10:52 WARNING opendrift:2445: Plotting fast. This will make your plots less accurate.
14:10:53 INFO    opendrift:4613: Saving animation to /root/project/docs/source/gallery/animations/example_static_2d_current_0.gif...
14:11:39 INFO    opendrift:3054: Time to make animation: 0:00:47.385147