Raster Plots using Declarative Syntax

The MetPy declarative syntax allows for a simplified interface to creating common meteorological analyses including surface observation plots. This example creates a temperature raster plot, though other potential raster plots include radar.

import xarray as xr

from metpy.cbook import get_test_data
from metpy.plots import MapPanel, PanelContainer, RasterPlot
from metpy.units import units

Import the temperature data from the NARR file.

narr_data = xr.open_dataset(get_test_data('narr_example.nc', as_file_obj=False))

Preview the data:

narr_data

<xarray.Dataset> Size: 21MB
Dimensions:              (time: 1, isobaric: 29, y: 118, x: 292)
Coordinates:
  * time                 (time) datetime64[ns] 8B 1987-04-04T18:00:00
  * isobaric             (isobaric) float64 232B 1e+03 975.0 ... 125.0 100.0
  * y                    (y) float64 944B -3.087e+03 -3.054e+03 ... 678.9 711.4
  * x                    (x) float64 2kB -3.977e+03 -3.945e+03 ... 5.47e+03
Data variables:
    Temperature          (time, isobaric, y, x) float32 4MB ...
    Lambert_Conformal    |S1 1B ...
    lat                  (y, x) float64 276kB ...
    lon                  (y, x) float64 276kB ...
    u_wind               (time, isobaric, y, x) float32 4MB ...
    v_wind               (time, isobaric, y, x) float32 4MB ...
    Geopotential_height  (time, isobaric, y, x) float32 4MB ...
    Specific_humidity    (time, isobaric, y, x) float32 4MB ...
Attributes: (12/14)
    Conventions:              CF-1.0
    Originating_center:       US National Weather Service - NCEP(WMC) (7)
    Originating_subcenter:    The North American Regional Reanalysis (NARR) P...
    Generating_Model:         North American Regional Reanalysis (NARR)
    Product_Type:             Forecast/Uninitialized Analysis/Image Product
    title:                    US National Weather Service - NCEP(WMC) North A...
    ...                       ...
    history:                  Direct read of GRIB-1 into NetCDF-Java 4 API
    CF:feature_type:          GRID
    file_format:              GRIB-1
    location:                 /nomads3_data/raid2/noaaport/merged/narr/198704...
    _CoordinateModelRunDate:  1987-04-04T18:00:00Z
    History:                  Translated to CF-1.0 Conventions by Netcdf-Java...

xarray.Dataset

• Dimensions:
  • time: 1
  • isobaric: 29
  • y: 118
  • x: 292
• Coordinates: (4)
  • time
    (time)
    datetime64[ns]
    1987-04-04T18:00:00

    long_name :

    forecast time

    _CoordinateAxisType :

    Time

    array(['1987-04-04T18:00:00.000000000'], dtype='datetime64[ns]')

  • isobaric
    (isobaric)
    float64
    1e+03 975.0 950.0 ... 125.0 100.0

    long_name :

    Isobaric surface

    units :

    hPa

    positive :

    down

    GRIB_level_type :

    100

    _CoordinateAxisType :

    Pressure

    _CoordinateZisPositive :

    down

    array([1000.,  975.,  950.,  925.,  900.,  875.,  850.,  825.,  800.,  775.,
            750.,  725.,  700.,  650.,  600.,  550.,  500.,  450.,  400.,  350.,
            300.,  275.,  250.,  225.,  200.,  175.,  150.,  125.,  100.])

  • y
    (y)
    float64
    -3.087e+03 -3.054e+03 ... 711.4

    units :

    km

    long_name :

    y coordinate of projection

    standard_name :

    projection_y_coordinate

    grid_spacing :

    32.463 km

    _CoordinateAxisType :

    GeoY

    array([-3.086806e+03, -3.054343e+03, -3.021880e+03, -2.989417e+03,
           -2.956954e+03, -2.924491e+03, -2.892028e+03, -2.859565e+03,
           -2.827102e+03, -2.794639e+03, -2.762176e+03, -2.729713e+03,
           -2.697250e+03, -2.664787e+03, -2.632324e+03, -2.599861e+03,
           -2.567398e+03, -2.534935e+03, -2.502472e+03, -2.470009e+03,
           -2.437546e+03, -2.405083e+03, -2.372620e+03, -2.340157e+03,
           -2.307694e+03, -2.275231e+03, -2.242768e+03, -2.210305e+03,
           -2.177842e+03, -2.145379e+03, -2.112916e+03, -2.080453e+03,
           -2.047990e+03, -2.015527e+03, -1.983064e+03, -1.950601e+03,
           -1.918138e+03, -1.885675e+03, -1.853212e+03, -1.820749e+03,
           -1.788286e+03, -1.755823e+03, -1.723360e+03, -1.690897e+03,
           -1.658434e+03, -1.625971e+03, -1.593508e+03, -1.561045e+03,
           -1.528582e+03, -1.496119e+03, -1.463656e+03, -1.431193e+03,
           -1.398730e+03, -1.366267e+03, -1.333804e+03, -1.301341e+03,
           -1.268878e+03, -1.236415e+03, -1.203952e+03, -1.171489e+03,
           -1.139026e+03, -1.106563e+03, -1.074100e+03, -1.041637e+03,
           -1.009174e+03, -9.767106e+02, -9.442476e+02, -9.117846e+02,
           -8.793216e+02, -8.468586e+02, -8.143956e+02, -7.819326e+02,
           -7.494696e+02, -7.170066e+02, -6.845436e+02, -6.520806e+02,
           -6.196176e+02, -5.871546e+02, -5.546916e+02, -5.222286e+02,
           -4.897656e+02, -4.573026e+02, -4.248396e+02, -3.923766e+02,
           -3.599136e+02, -3.274506e+02, -2.949876e+02, -2.625246e+02,
           -2.300616e+02, -1.975986e+02, -1.651356e+02, -1.326726e+02,
           -1.002096e+02, -6.774665e+01, -3.528365e+01, -2.820646e+00,
            2.964235e+01,  6.210535e+01,  9.456835e+01,  1.270314e+02,
            1.594944e+02,  1.919574e+02,  2.244204e+02,  2.568834e+02,
            2.893464e+02,  3.218094e+02,  3.542724e+02,  3.867354e+02,
            4.191984e+02,  4.516614e+02,  4.841244e+02,  5.165874e+02,
            5.490504e+02,  5.815134e+02,  6.139764e+02,  6.464394e+02,
            6.789024e+02,  7.113654e+02])

  • x
    (x)
    float64
    -3.977e+03 -3.945e+03 ... 5.47e+03

    units :

    km

    long_name :

    x coordinate of projection

    standard_name :

    projection_x_coordinate

    grid_spacing :

    32.463 km

    _CoordinateAxisType :

    GeoX

    array([-3977.054864, -3944.591864, -3912.128864, ...,  5404.752136,
            5437.215136,  5469.678136])

• Data variables: (8)
  • Temperature
    (time, isobaric, y, x)
    float32
    ...

    units :

    K

    long_name :

    Temperature @ isobaric

    grid_mapping :

    Lambert_Conformal

    GRIB_param_name :

    Temperature

    GRIB_param_short_name :

    TMP

    GRIB_center_id :

    7

    GRIB_table_id :

    131

    GRIB_param_number :

    11

    GRIB_param_id :

    [ 1 7 131 11]

    GRIB_product_definition_type :

    Initialized analysis product

    GRIB_level_type :

    100

    GRIB_VectorComponentFlag :

    gridRelative

    [999224 values with dtype=float32]

  • Lambert_Conformal
    ()
    |S1
    ...

    grid_mapping_name :

    lambert_conformal_conic

    standard_parallel :

    50.0

    longitude_of_central_meridian :

    -107.0

    latitude_of_projection_origin :

    50.0

    earth_shape :

    spherical

    earth_radius :

    6367470.21484375

    GRIB_param_Dx :

    32463.0

    GRIB_param_Dy :

    32463.0

    GRIB_param_GDSkey :

    55295

    GRIB_param_La1 :

    1.0

    GRIB_param_Latin1 :

    50.0

    GRIB_param_Latin2 :

    50.0

    GRIB_param_Lo1 :

    -145.5

    GRIB_param_LoV :

    -107.0

    GRIB_param_NpProj :

    true

    GRIB_param_Nx :

    349

    GRIB_param_Ny :

    277

    GRIB_param_ProjFlag :

    0

    GRIB_param_ResCompFlag :

    8

    GRIB_param_SpLat :

    0.0

    GRIB_param_SpLon :

    0.0

    GRIB_param_VectorComponentFlag :

    gridRelative

    GRIB_param_Winds :

    Relative

    GRIB_param_grid_name :

    Lambert_Conformal

    GRIB_param_grid_radius_spherical_earth :

    6367.47

    GRIB_param_grid_shape :

    spherical

    GRIB_param_grid_shape_code :

    0

    GRIB_param_grid_type :

    3

    GRIB_param_grid_units :

    m

    GRIB_param_scanning_mode :

    64

    _CoordinateTransformType :

    Projection

    _CoordinateAxisTypes :

    GeoX GeoY

    [1 values with dtype=|S1]

  • lat
    (y, x)
    float64
    ...

    units :

    degrees_north

    long_name :

    latitude coordinate

    standard_name :

    latitude

    _CoordinateAxisType :

    Lat

    [34456 values with dtype=float64]

  • lon
    (y, x)
    float64
    ...

    units :

    degrees_east

    long_name :

    longitude coordinate

    standard_name :

    longitude

    _CoordinateAxisType :

    Lon

    [34456 values with dtype=float64]

  • u_wind
    (time, isobaric, y, x)
    float32
    ...

    units :

    m/s

    long_name :

    u_wind @ isobaric

    grid_mapping :

    Lambert_Conformal

    GRIB_param_name :

    u_wind

    GRIB_param_short_name :

    UGRD

    GRIB_center_id :

    7

    GRIB_table_id :

    131

    GRIB_param_number :

    33

    GRIB_param_id :

    [ 1 7 131 33]

    GRIB_product_definition_type :

    Initialized analysis product

    GRIB_level_type :

    100

    GRIB_VectorComponentFlag :

    gridRelative

    [999224 values with dtype=float32]

  • v_wind
    (time, isobaric, y, x)
    float32
    ...

    units :

    m/s

    long_name :

    v_wind @ isobaric

    grid_mapping :

    Lambert_Conformal

    GRIB_param_name :

    v_wind

    GRIB_param_short_name :

    VGRD

    GRIB_center_id :

    7

    GRIB_table_id :

    131

    GRIB_param_number :

    34

    GRIB_param_id :

    [ 1 7 131 34]

    GRIB_product_definition_type :

    Initialized analysis product

    GRIB_level_type :

    100

    GRIB_VectorComponentFlag :

    gridRelative

    [999224 values with dtype=float32]

  • Geopotential_height
    (time, isobaric, y, x)
    float32
    ...

    units :

    gpm

    long_name :

    Geopotential_height @ isobaric

    grid_mapping :

    Lambert_Conformal

    GRIB_param_name :

    Geopotential_height

    GRIB_param_short_name :

    HGT

    GRIB_center_id :

    7

    GRIB_table_id :

    131

    GRIB_param_number :

    7

    GRIB_param_id :

    [ 1 7 131 7]

    GRIB_product_definition_type :

    Initialized analysis product

    GRIB_level_type :

    100

    GRIB_VectorComponentFlag :

    gridRelative

    [999224 values with dtype=float32]

  • Specific_humidity
    (time, isobaric, y, x)
    float32
    ...

    units :

    kg/kg

    long_name :

    Specific_humidity @ isobaric

    grid_mapping :

    Lambert_Conformal

    GRIB_param_name :

    Specific_humidity

    GRIB_param_short_name :

    SPFH

    GRIB_center_id :

    7

    GRIB_table_id :

    131

    GRIB_param_number :

    51

    GRIB_param_id :

    [ 1 7 131 51]

    GRIB_product_definition_type :

    Initialized analysis product

    GRIB_level_type :

    100

    GRIB_VectorComponentFlag :

    gridRelative

    [999224 values with dtype=float32]

• Indexes: (4)
  • time
    PandasIndex

    PandasIndex(DatetimeIndex(['1987-04-04 18:00:00'], dtype='datetime64[ns]', name='time', freq=None))

  • isobaric
    PandasIndex

    PandasIndex(Index([1000.0,  975.0,  950.0,  925.0,  900.0,  875.0,  850.0,  825.0,  800.0,
            775.0,  750.0,  725.0,  700.0,  650.0,  600.0,  550.0,  500.0,  450.0,
            400.0,  350.0,  300.0,  275.0,  250.0,  225.0,  200.0,  175.0,  150.0,
            125.0,  100.0],
          dtype='float64', name='isobaric'))

  • y
    PandasIndex

    PandasIndex(Index([-3086.8056464496035, -3054.3426464496033, -3021.8796464496036,
           -2989.4166464496034,  -2956.953646449603, -2924.4906464496034,
           -2892.0276464496037, -2859.5646464496035, -2827.1016464496033,
           -2794.6386464496036,
           ...
            419.19835355039686,   451.6613535503966,  484.12435355039634,
              516.587353550397,   549.0503535503967,   581.5133535503965,
             613.9763535503971,   646.4393535503968,   678.9023535503966,
             711.3653535503963],
          dtype='float64', name='y', length=118))

  • x
    PandasIndex

    PandasIndex(Index([ -3977.054863757302, -3944.5918637573022, -3912.1288637573025,
           -3879.6658637573023,  -3847.202863757302, -3814.7398637573024,
            -3782.276863757302,  -3749.813863757302, -3717.3508637573022,
           -3684.8878637573025,
           ...
             5177.511136242698,   5209.974136242698,   5242.437136242697,
             5274.900136242699,   5307.363136242699,   5339.826136242698,
             5372.289136242698,   5404.752136242698,   5437.215136242698,
             5469.678136242697],
          dtype='float64', name='x', length=292))

• Attributes: (14)

  Conventions :

  CF-1.0

  Originating_center :

  US National Weather Service - NCEP(WMC) (7)

  Originating_subcenter :

  The North American Regional Reanalysis (NARR) Project (15)

  Generating_Model :

  North American Regional Reanalysis (NARR)

  Product_Type :

  Forecast/Uninitialized Analysis/Image Product

  title :

  US National Weather Service - NCEP(WMC) North American Regional Reanalysis (NARR) Forecast/Uninitialized Analysis/Image Product

  institution :

  Center US National Weather Service - NCEP(WMC) (7) Subcenter The North American Regional Reanalysis (NARR) Project (15)

  source :

  Forecast/Uninitialized Analysis/Image Product

  history :

  Direct read of GRIB-1 into NetCDF-Java 4 API

  CF:feature_type :

  GRID

  file_format :

  GRIB-1

  location :

  /nomads3_data/raid2/noaaport/merged/narr/198704/19870404/narr-a_221_19870404_1800_000.grb

  _CoordinateModelRunDate :

  1987-04-04T18:00:00Z

  History :

  Translated to CF-1.0 Conventions by Netcdf-Java CDM (NetcdfCFWriter) Original Dataset = narr-a/198704/19870404/narr-a_221_19870404_1800_000.grb; Translation Date = Fri Jun 16 13:26:21 EDT 2017

Create the ‘RasterPlot’ object and provide it with the NARR data. Specify the level to be plotted, and use the Data variables column to specify the data field to be plotted.

raster = RasterPlot()
raster.data = narr_data
raster.field = 'Temperature'
raster.level = 700 * units.hPa

Add the plot to a Map Panel and Panel Container.

panel = MapPanel()
panel.area = 'us'
panel.projection = 'lcc'
panel.layers = ['coastline']
panel.plots = [raster]

pc = PanelContainer()
pc.size = (8, 8)
pc.panels = [panel]
pc.draw()

pc.show()