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If you wish to visualise a very large field (e.g. where a single field contains hundreds of millions of points), Metview may be able to plot it, but it is advised to do certain things to minimise the memory usage.

Set MARS_READANY_BUFFER_SIZE

It Also, it may be necessary to set an environment to increase the size of an internal memory buffer used by the MARS library that Metview uses for some of its GRIB handling. If you see a warning message such as the following:

...

Do this on a command-line before re-starting Metview from the same terminal. Even if Metview can already plot the data, if this warning appears, the handling of the data will be much faster if this env var is set.

Disable the data statistics in the sidebar

...

MCONT,
    LEGEND     = ON,
    CONTOUR    = OFF,
    CONTOUR_MAX_LEVEL = 1.01,
    CONTOUR_SHADE_MAX_LEVEL = 1.01,
    CONTOUR_SHADE = ON,
    CONTOUR_SHADE_TECHNIQUE = CELL_SHADING,
    CONTOUR_SHADE_CELL_RESOLUTION = 50,
    CONTOUR_SHADE_MAX_LEVEL_COLOUR = KELLY_GREEN,
    CONTOUR_SHADE_MIN_LEVEL_COLOUR = 'RGB(0.95,0.97,0.98)',
    CONTOUR_SHADE_COLOUR_DIRECTION = CLOCKWISE

MCONT,
    LEGEND     = ON,
    CONTOUR    = OFF,
    CONTOUR_MIN_LEVEL = 0.0001,
    CONTOUR_SHADE_MIN_LEVEL = 0.0001,
    CONTOUR_SHADE = ON,
    CONTOUR_SHADE_TECHNIQUE = GRID_SHADING,
    CONTOUR_SHADE_MAX_LEVEL_COLOUR = KELLY_GREEN,
    CONTOUR_SHADE_MIN_LEVEL_COLOUR = 'RGB(0.95,0.97,0.98)',
    CONTOUR_SHADE_COLOUR_DIRECTION = CLOCKWISE

Keep an eye on memory usage

Run some kind of process monitor and sort by memory usage. Be ready to 'kill' the uPlot process if it's taking too much memory!

Be careful when plotting to a file

The memory used during an on-screen interactive plot is released when the window is closed. But if you plot to a file (e.g. PNG, PDF, PS) the memory will not be released and you may have to kill the uPlotBatch process in order to release it.