# This file is part of OpenDrift.
#
# OpenDrift is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, version 2
#
# OpenDrift is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with OpenDrift. If not, see <https://www.gnu.org/licenses/>.
#
# Copyright 2015, Knut-Frode Dagestad, MET Norway
from datetime import datetime, timedelta
import numpy as np
import pyproj
from opendrift.readers.basereader import BaseReader, ContinuousReader
[docs]
class Reader(BaseReader, ContinuousReader):
"""Analytical current field with double gyre"""
def __init__(self, initial_time=datetime(2000,1,1,0,0),
epsilon=0.1, omega=0.628, A=0.25,
proj4='+proj=stere +lat_0=0 +lon_0=0 +lat_ts=0 ' +
'+units=m +a=6.371e+06 +e=0 +no_defs'):
self.fileName = 'double_gyre'
self.name = 'double_gyre'
self.proj4 = proj4
self.proj = pyproj.Proj(proj4)
self.xmin = 0.
self.xmax = 2.
self.ymin = 0.
self.ymax = 1.
self.A = A
self.epsilon=epsilon
self.omega=omega
self.initial_time = initial_time
self.start_time = None
self.end_time = None
self.time_step = None
self.variables = ['x_sea_water_velocity',
'y_sea_water_velocity']
# Run constructor of parent Reader class
super(Reader, self).__init__()
[docs]
def get_variables(self, requestedVariables, time=None,
x=None, y=None, z=None):
requestedVariables, time, x, y, z, outside = self.check_arguments(
requestedVariables, time, x, y, z)
variables = {}
# Construct double gyre current field
# https://shaddenlab.berkeley.edu/uploads/LCS-tutorial/examples.html
t = (time-self.initial_time).total_seconds()
a = self.epsilon*np.sin(self.omega*t)
b = 1-2*self.epsilon*np.sin(self.omega*t)
f = a*x*x + b*x
dfdx = 2*a*x + b
variables['x_sea_water_velocity'] = -np.pi*self.A*np.sin(np.pi*f)*np.cos(np.pi*y)
variables['y_sea_water_velocity'] = np.pi*self.A*np.cos(np.pi*f)*np.sin(np.pi*y)*dfdx
variables['land_binary_mask'] = np.zeros(x.shape)
variables['time'] = time
variables['x'] = x
variables['y'] = y
return variables