stilt.observations.plume_background#

stilt.observations.plume_background(longitudes, latitudes, values, plume, *, uncertainties=None, side=None, width=0.5, pad=0.1, trim=0.9)[source]#

Return the background from the soundings beside a plume.

The soundings inside plume are enhanced. A box is drawn around them, and the soundings outside the plume within width degrees of the box on each side are the background candidates. The background is their median. Pass only good-quality soundings. Raises when no sounding is inside the plume, since then the overpass did not see it.

Parameters:

  • longitudes (TypeAliasType) – Sounding positions, in degrees.

  • latitudes (TypeAliasType) – Sounding positions, in degrees.

  • values (TypeAliasType) – Sounding values, such as XCH4.

  • plume (Plume | Polygon) – Plume outline, usually from plume_polygon().

  • uncertainties (TypeAliasType | None) – Retrieval uncertainty of each sounding, in the units of values.

  • side (Optional[Literal['north', 'south', 'east', 'west']]) – Use only one side. Choose the upwind side, which the forward particles’ drift shows. None pools all four.

  • width (float) – Width of the band on each side of the box, in degrees.

  • pad (float) – Padding of the box around the in-plume soundings, as a fraction of its size.

  • trim (float | None) – Drop soundings outside the plume above this quantile of their values, to guard against enhanced air the outline missed, as X-STILT does. None keeps them all.

Return type:

PlumeBackground