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GRIB - Forecast Steps with Shared Legend and Title
# (C) Copyright 2017- ECMWF.
#
# This software is licensed under the terms of the Apache Licence Version 2.0
# which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
#
# In applying this licence, ECMWF does not waive the privileges and immunities
# granted to it by virtue of its status as an intergovernmental organisation
# nor does it submit to any jurisdiction.
#
import metview as mv
# getting data
use_mars = False
# getting forecast data from MARS
if use_mars:
g = mv.retrieve(
type="fc",
levtype="sfc",
param=["msl", "10fg6"],
date=20111215,
time=00,
step=[0, "to", 48, "by", 6],
area=[80, -60, 20, 60],
grid=[0.5, 0.5],
)
# reading data from file or getting from data server
else:
filename = "fc_msl_wg_joachim.grib"
if mv.exist(filename):
g = mv.read(filename)
else:
g = mv.gallery.load_dataset(filename)
# read msl and 10m wind gust (max in last 6 hours)
msl = g.select(shortName="msl")
wg = g.select(shortName="10fg6")
# -------------------------------
# define map plots
# -------------------------------
# define contouring for msl
msl_cont = mv.mcont(
contour_line_thickness=2,
contour_line_colour="charcoal",
contour_highlight="off",
contour_highlight_colour="charcoal",
contour_highlight_thickness=4,
contour_level_selection_type="interval",
contour_interval=5,
contour_label_height=0.2,
grib_scaling_of_derived_fields="on",
)
# define contouring for wind gust. The legend is turned off because
# we want to show only a shared legend at the top of the page
wg_cont = mv.mcont(
contour="off",
contour_level_selection_type="level_list",
contour_level_list=[12, 15, 20, 25, 30, 35, 50],
contour_label="off",
contour_shade="on",
contour_shade_colour_method="list",
contour_shade_method="area_fill",
contour_shade_colour_list=[
"RGB(0.5374,0.6855,0.9606)",
"RGB(0.1259,0.5569,0.9878)",
"avocado",
"yellowish_orange",
"red",
"violet",
],
)
# define coastlines
coast = mv.mcoast(
map_coastline_colour="RGB(0.3137,0.3137,0.3137)",
map_coastline_thickness="2",
map_coastline_resolution="medium",
map_coastline_land_shade="on",
map_coastline_land_shade_colour="RGB(0.8314,0.8314,0.8314)",
map_boundaries="on",
map_boundaries_colour="chestnut",
map_grid="off",
map_label="off",
)
# define geo view
view = mv.geoview(area_mode="name", area_name="central_europe", coastlines=coast)
# create a 2x4 plot layout with the defined geoview
pages = mv.mvl_regular_layout(view, 4, 3, 1, 1, [0, 100, 0, 100])
# define title generator for the maps
def make_title(f):
step = mv.grib_get_long(f[0], "step")
vdate = mv.valid_date(f[0])
title = mv.mtext(
text_lines="{} (+{}h)".format(vdate.strftime("%Y-%m-%d %H UTC"), int(step)),
text_font_size=0.4,
)
return title
# ---------------------------------------------
# define positional title at the top
# ---------------------------------------------
# we want to show a shared title at the top of the page. The space is
# is simple not enough above the maps to display this amount of information.
# create an annotation view covering the whole page area (dimensions are in %).
# It is just a placeholder and its only purpose is to hold a custom positional
# mtext object.
title_view = mv.annotationview()
# create the page (dimensions are in %) holding the annotation view. For simplicity
# it covers the whole plot area
title_page = mv.plot_page(top=0, bottom=100, left=0, right=100, view=title_view)
pages.append(title_page)
# create a positional title to be added to the annotation view.
# Note: its coordinates are in cm! x is measured from the left side
# of the parent page (e.i. title_page), while y is measured from the bottom
# of the parent page!
# width of an A4 landscape page in cm
pw = 29.7
bdate = mv.base_date(msl[0])
shared_title = mv.mtext(
text_lines="ECMWF HRES Param: msl/10fg6 Run: {}".format(
bdate.strftime("%Y-%m-%d %H UTC")
),
text_font_size=0.6,
text_mode="positional",
text_box_x_position=3,
text_box_y_position=19.2,
text_box_x_length=20,
text_box_y_length=2,
text_justification="left",
)
# ----------------------------------------------
# define positional shared legend at the top
# ----------------------------------------------
# we do not want to display the legend for each plot (since the space is
# confined) but want to show only one legend atop just below the main page title.
# Since the legend is only generated when data is plotted into a view, we will
# create an "invisible" geo view and properly adjust it so that the legend can
# appear at the desired position.
# create an empty coastlines
empty_coast = mv.mcoast(map_coastline="off", map_grid="off", map_label="off")
# create a geoview
legend_view = mv.geoview(
page_frame="off",
subpage_frame="off",
coastlines=empty_coast,
subpage_x_position=40,
subpage_y_position=65,
subpage_x_length=20,
subpage_y_length=20,
)
# create a page (dimensions are in %) holding the view. It is positioned at the
# top of the A4 superpage
legend_page = mv.plot_page(top=0, bottom=20, left=0, right=100, view=legend_view)
pages.append(legend_page)
# create a field to be plotted into the view. It should only contain missing values,
# since we do not want to generate any result
empty_fld = mv.bitmap(wg[0] * 0, 0)
# define the conturing. It is the same that we defined for wg but the
# legend has to be enabled now!
empty_cont = mv.mcont(**wg_cont, legend="on")
# define an empty title
empty_title = mv.mtext(text_line_count=0)
# define the legend. Note: its coordinates are in cm! x is measured
# from the left side of the parent page (legend_page), while y is measured from
# the bottom of the parent page!
shared_legend = mv.mlegend(
legend_box_mode="positional",
legend_text_font_size=0.4,
legend_box_x_position=3,
legend_box_y_position=1.5,
legend_box_x_length=10,
legend_box_y_length=0.6,
legend_units_text="m/s",
legend_title="on",
legend_title_text="m/s",
legend_title_position="right",
)
# create the final layout
dw = mv.plot_superpage(pages=pages)
# define the output plot file
mv.setoutput(mv.pdf_output(output_name="fc_steps_shared_legend_title"))
# generate plot object
d = [
[dw[i + 3], wg[i], wg_cont, msl[i], msl_cont, make_title(msl[i])] for i in range(9)
]
d.extend([dw[-2], shared_title])
d.extend([dw[-1], empty_fld, empty_cont, shared_legend, empty_title])
# generate plot
mv.plot(d)