"""
==============================
Create a three panel grid plot
==============================

An example which creates a three-panel plot of a gridded NEXRAD radar on a map
with latitude and longitude slices of the reflectivity.  The NCEP
North American regional reanalysis (NARR) pressure is plotted on top of the
grid.

"""
print __doc__

# Author Jonathan J. Helmus
# License: BSD 3 clause

import numpy as np
import matplotlib
import matplotlib.pyplot as plt
from netCDF4 import num2date, date2num, Dataset
import pyart


# read in the NEXRAD data, create the display
fname = '20110520100000_nexrad_grid.nc'
grid = pyart.io.read_grid(fname)
display = pyart.graph.GridMapDisplay(grid)

# create the figure
font = {'size': 16}
matplotlib.rc('font', **font)
fig = plt.figure(figsize=[15, 8])

# panel sizes
map_panel_axes = [0.05, 0.05, .4, .80]
x_cut_panel_axes = [0.55, 0.10, .4, .30]
y_cut_panel_axes = [0.55, 0.50, .4, .30]
colorbar_panel_axes = [0.05, 0.90, .4, .03]

# parameters
level = 5
vmin = -8
vmax = 64
lat = 36.5
lon = -98.5

# panel 1, basemap, radar reflectivity and NARR overlay
ax1 = fig.add_axes(map_panel_axes)
display.plot_basemap()
display.plot_grid('REF', level=level, vmin=vmin, vmax=vmax, title_flag=False,
                  colorbar_flag=False)
display.plot_crosshairs(lon=lon, lat=lat)

# fetch NCEP NARR data
grid_date = num2date(grid.time['data'], grid.time['units'])[0]
y_m_d = grid_date.strftime('%Y%m%d')
y_m = grid_date.strftime('%Y%m')
url = ('http://nomads.ncdc.noaa.gov/dods/NCEP_NARR_DAILY/' + y_m + '/' +
       y_m_d + '/narr-a_221_' + y_m_d + '_0000_000')
# Use a local copy of the online NCEP NARR data, this file can be created with
# the command:
# nccopy http://nomads.ncdc.noaa.gov/dods/NCEP_NARR_DAILY/201105/20110520/narr-a_221_20110520_0000_000?lon,lat,time,prmsl narr-a_221_20110520_0000_000.nc
# comment out the next line to retrieve the data from the OPeNDAP server.
url = 'narr-a_221_20110520_0000_000.nc'
data = Dataset(url)

# extract data at correct time
data_time = data.variables['time']
t_idx = abs(data_time[:] - date2num(grid_date, data_time.units)).argmin()
prmsl = 0.01 * data.variables['prmsl'][t_idx]

# plot the reanalysis on the basemap
lons, lats = np.meshgrid(data.variables['lon'], data.variables['lat'][:])
x, y = display.basemap(lons, lats)
clevs = np.arange(900, 1100., 1.)
display.basemap.contour(x, y, prmsl, clevs, colors='k', linewidths=1.)

# colorbar
cbax = fig.add_axes(colorbar_panel_axes)
display.plot_colorbar(cax=cbax)

# panel 2, longitude slice.
ax2 = fig.add_axes(x_cut_panel_axes)
display.plot_longitude_slice(
    'REF', lon=lon, lat=lat, vmin=vmin, vmax=vmax, title_flag=False,
    colorbar_flag=False, edges=False,
    axislabels=('Distance from SGP CF (km)', 'Height (km)'))

# panel 3, latitude slice
ax3 = fig.add_axes(y_cut_panel_axes)
display.plot_latitude_slice(
    'REF', lon=lon, lat=lat, vmin=vmin, vmax=vmax, title_flag=False,
    colorbar_flag=False, edges=False,
    axislabels=('', 'Height (km)'))

# add a title
slc_height = grid.z['data'][level]
dts = num2date(grid.time['data'], grid.time['units'])
datestr = dts[0].strftime('%H:%M Z on %Y-%m-%d')
title = 'Sliced at ' + str(slc_height) + ' meters at ' + datestr
fig.text(0.5, 0.9, title)
plt.show()
