stilt.observations.background#

stilt.observations.background(particles, field, *, transforms=(), context=None)[source]#

Background mole fraction at the receptor, from the field at the trajectory endpoints.

Parameters:

  • particles (DataFrame) – The simulation’s particle table (sim.trajectories.data).

  • field (DataArray | Series) – The background field (see particle_background() for its layout), or one value per particle that you sampled yourself, as a Series indexed by indx: for example lair’s CarbonTracker.sample on sim.trajectories.endpoints().

  • transforms (Sequence[Any]) – The footprint’s particle transforms and the context to apply them with (config.transforms and sim.transform_context(name)), so the background is weighted the way the footprint is and adds to its enhancement. For a tower receptor there is nothing to pass.

  • context (Optional[TransformContext]) – The footprint’s particle transforms and the context to apply them with (config.transforms and sim.transform_context(name)), so the background is weighted the way the footprint is and adds to its enhancement. For a tower receptor there is nothing to pass.

Return type:

Background

Notes

Without transforms the value is the plain mean over particles. With pressure weighting the weights sum to the fraction of the column’s air mass the particles cover, (p_sfc - p_top) / p_sfc, the same fraction the enhancement covers; the part of the column above the receptor top is still yours to add from the same field.