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"""This script just plots a velocity field. There is not much in it
that is special to surface ocean current coming from AVISO ADT files.
"""
import numpy as np
import cartopy.crs as ccrs
import matplotlib.pyplot as plt
import netCDF4
with netCDF4.Dataset(args.input_file) as f:
if "lon" in f.variables:
lon = "lon"
lat = "lat"
else:
lon = "longitude"
lat = "latitude"
longitude = f[lon][:]
latitude = f[lat][:]
if "time" in f["ugos"].dimensions:
ugos = f["ugos"][0]
vgos = f["vgos"][0]
else:
ugos = f["ugos"][:]
vgos = f["vgos"][:]
if args.window is None:
lon_mask = np.ones(len(longitude), dtype=bool)
lat_mask = np.ones(len(latitude), dtype=bool)
else:
llcrnrlon, llcrnrlat, urcrnrlon, urcrnrlat = args.window
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if urcrnrlon - llcrnrlon > 360:
sys.exit("bad values of urcrnrlon and llcrnrlon")
longitude += np.ceil((llcrnrlon - longitude) / 360) * 360
# (in [llcrnrlon, llcrnrlon + 2 pi[)
lon_mask = longitude <= urcrnrlon
lat_mask = np.logical_and(latitude >= llcrnrlat, latitude <= urcrnrlat)
longitude = longitude[lon_mask]
latitude = latitude[lat_mask]
src_crs = ccrs.PlateCarree()
# Use a conformal projection for quiver:
projection = ccrs.Stereographic(
central_latitude=latitude.mean(), central_longitude=longitude.mean()
)
##projection = ccrs.NorthPolarStereo()
fig = plt.figure()
ax = plt.axes(projection=projection)
if args.undefined:
undef_velocity = np.logical_or(ugos.mask, vgos.mask)
lon_2d, lat_2d = np.meshgrid(longitude, latitude)
ax.plot(
lon_2d[undef_velocity].reshape(-1),
lat_2d[undef_velocity].reshape(-1),
transform=src_crs,
marker="*",
color="violet",
linestyle="None",
)
else:
quiver_return = wind_cartopy.plot(
ax,
longitude,
latitude,
ugos[lat_mask][:, lon_mask],
vgos[lat_mask][:, lon_mask],
scale=args.scale,
scale_units="width",
)
ax.quiverkey(
quiver_return, 0.9, 0.9, 1, r"1 m s$^{-1}$", coordinates="figure"
)
ax.gridlines(draw_labels=True)
ax.coastlines()
if args.save:
fig.savefig(f"plot_velocity.{args.save}")
print(f'Created "plot_velocity.{args.save}".')
else:
plt.show()
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import argparse
parser = argparse.ArgumentParser(
formatter_class=argparse.ArgumentDefaultsHelpFormatter
)
parser.add_argument(
"-s",
"--scale",
default=20,
type=float,
help="scale of arrows for the velocity field",
)
parser.add_argument(
"-w",
"--window",
help="choose a limited plot window",
type=float,
nargs=4,
metavar=("llcrnrlon", "llcrnrlat", "urcrnrlon", "urcrnrlat"),
)
parser.add_argument(
"--save", metavar="format", help="Save file to specified format"
)
parser.add_argument(
"-u",
"--undefined",
action="store_true",
help="plot points where velocity is not defined",
)
parser.add_argument("input_file", help="NetCDF file containing velocity")
args = parser.parse_args()
plot_velocity(args)