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• type of visualisation (e.g. geographical map, cross section, vertical profile, tephigram)
• parameters specific to that plot type (e.g. geographical area, cross section line, min/max axes values)
• plot position within the page (several plots can share a page)
• how to overlay different data in the same plot (explored in Handling Time in Metview)
• plot decoration (e.g. draw a frame around the plot)

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The Hovmoeller View icon is a computation/plotting specification for Hovmøller diagrams along a specified arbitrary transect line or a rectangular area. The diagram displays a two-dimensional graph with latitude or height as one axis, and time as the other.

Create a new Hovmoeller View icon, Visualise it and drop the t_ts.grib icon into the Display Window. A default diagram derived from a transect line along the Equator is generated. 

Three types of Hovmøller diagrams can be produced:

1.  Area Hovm     - diagram derived from an input rectangular area
2.  Line Hovm      - diagram derived from an input transect line
3.  Vertical Hovm - diagram derived from an input rectangular area and a set of levels.

Experiment with this icon by testing the above types and investigating other input parameters. Please note that type Vertical Hovm requires the following input GRIB data: t_ts_nlevels.grib. Examine and compare this GRIB data with the previous oneFor now, only consider the Area Hovm type and try a different transect line. As previously, you can use a Contouring icon to style the contours of the plotting.

This view requires data at different time steps. Examine the GRIB icons icon to see the fields used for these examplesthis example.

The Thermo View   

The Thermo View icon is a plotting specification for Thermodynamic diagram plots from a suitable GRIB or BUFR data source. In such a diagram, temperature, humidity (represented by the dew point) and wind values are displayed with respect to pressure. Note that only the Tephigram diagram is currently available, although there exist other types of thermodynamic diagrams, such as Skew-T, Emagram and Stuve.

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To customise the curves displayed in this plot, you can apply (or edit it first) icon vdline. The changes will be applied to both lines. The ability to customise each line individually (temperature and dew point) will be is available in a future release of Metview.the Thermo Plotting icon. Try it!

The Wind Plotting icon is the visual definition responsible for specifying how wind vector data is displayed. It controls the plotting of features such as wind arrows and wind flags.     

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t_fc96 = read("/path/to/home/metview/training/day_2/analysis views/t_fc96.grib")
t_fc24 = read("/path/to/home/metview/training/day_2/analysis views/t_fc24.grib")

diff = t_fc96 - t_fc24

pos = mcont(
    legend                         : "on",
    contour_level_selection_type   : "level_list",
    contour_max_level              : 10,
    contour_min_level              : 0.1,
    contour_level_list             : [0.5,1,2,4,10],
    contour_shade                  : "on",
    contour_shade_method           : "area_fill",
    contour_shade_max_level_colour : "red",
    contour_shade_min_level_colour : "orange_yellow",
    contour_shade_colour_direction : "clockwise"
    # <code omitted for brevity>
    )

neg = mcont(
    legend                         : "on",
    contour_level_selection_type   : "level_list",
    contour_max_level              : -0.5,
    contour_min_level              : -10,
    contour_shade_max_level        : -0.1,
    contour_shade_min_level        : -10,
    contour_level_list             : [-10,-4,-2,-1,-0.5],
    contour_shade                  : "on",
    contour_shade_method           : "area_fill",
    contour_shade_max_level_colour : "greenish_yellow",
    contour_shade_min_level_colour : "blue",
    contour_shade_colour_direction : "clockwise"
    # <code omitted for brevity>
    )

xs_europe = mxsectview(
    line : [55,-6,43,16]
    )

plot(xs_europe,diff,neg,pos)

Now run the macro to generate the plot. You can also omit xs_europe from the plot() command; in this case, Metview chooses will use the default view for GRIB data, which is a Geographic View. The data will then be plotted on , giving a map plot.

Finally, Examine the two input GRIB iconsto see how the fields differ in terms of date, time and step.

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Your macro should be 3 lines long (well, 3 commands anyway) - one to read the input GRIB file, one to compute the profile and one to write the result to disk.

Extra Work

Hovmoeller Types

Investigate the different types of Hovmoeller diagrams available. Please note that type Vertical Hovm requires the input GRIB data t_ts_nlevels.grib. Examine this data to see that it contains fields from different vertical levels.

Axis Customisation

Image Added

All of these views allow the ability to customise the rendering of the axes. While the view itself defines the limits and projection parameters for the plot, the axis lines themselves can be customised, for example in terms of colour and title.

Create a new Axis Plotting icon and rename it to H Axis. Edit it to change the colour of the axis and to add an axis title. Repeat the process to create a vertical axis icon.

Edit a Cross Section View icon and drop your icons into the Horizontal Axis and Vertical Axis parameter boxes. Visualise the view to see the results.