Observations

Functions for column and satellite workflows. They group soundings into overpasses, choose which soundings to run, spread receptors across a pixel, lay out slant lines of sight, and turn a retrieval’s pressure levels into altitudes (Satellite And Column Observations, Slant Columns). They take plain arrays and tables and return the inputs for Receptor objects. Particle weighting, including per-receptor averaging-kernel tables, is in Transforms.

stilt.observations.group_by_overpass	Label each time with the overpass it belongs to.
stilt.observations.select_observations_spatial	Select soundings densely near a site and sparsely across the domain.
stilt.observations.jitter_points	Return (longitude, latitude) points spread over one pixel.
stilt.observations.slant_points	Return (longitude, latitude, altitude) points along a line of sight.
stilt.observations.pressure_altitudes	Return the altitudes above sea level of a retrieval's pressure levels.

Product readers

Each reader returns a table of soundings with the columns listed in Reading Retrieval Products.

stilt.observations.read_tropomi_ch4	Read a TROPOMI (Sentinel-5P) L2 methane file into a table of soundings.
stilt.observations.read_oco2	Read an OCO-2 or OCO-3 L2 Lite XCO2 file into a table of soundings.
stilt.observations.read_tccon	TCCON's public *.public.nc and *.public.qc.nc site files from CaltechDATA are GGG2020 netCDF files, so they are read the same way.
stilt.observations.read_ggg_oof	Read a GGG2020 .oof file into a table of soundings.
stilt.observations.read_ggg_netcdf	Read a GGG2020 netCDF file, private or public, into a table of soundings.

Transport error

The transport error of the modelled enhancement, from wind-perturbed trajectories (Transport Error).

stilt.observations.transport_error	Return the transport-error variance of a modeled enhancement (Lin and Gerbig, 2005).
stilt.observations.TransportError	Transport error of a modeled enhancement, returned by transport_error().

Background

The background mole fraction at a receptor. A field is sampled at the trajectory endpoints and weighted like the footprint (Background).

stilt.observations.background	Return the background mole fraction at a receptor.
stilt.observations.Background	Background at a receptor, returned by background().
stilt.observations.particle_background	Return the field at each particle's endpoint, indexed by indx.
stilt.observations.backgrounds.endpoint_weights	Return each particle's transform weight at its endpoint, indexed by indx.

Plume background

The outline of a forward-run plume over a satellite swath, and the background from the soundings beside it (Plume Background).

stilt.observations.plume_polygon	Return the plume outline from forward-run particle positions at overpass time.
stilt.observations.Plume	Plume outline returned by plume_polygon().
stilt.observations.plume_background	Return the background from the soundings beside a plume.
stilt.observations.PlumeBackground	Background from soundings beside a plume, returned by plume_background().
stilt.observations.plumes.kernel_density	Return the Gaussian kernel density of points on an n by n grid.
stilt.observations.plumes.density_polygon	Return the largest connected region where density >= threshold.

Wind-error statistics

Variograms of analysis-minus-observation winds. Fit them to get the wind-error settings for a transport-error run (Wind Error Statistics).

stilt.observations.variogram	Return the empirical semivariogram of errors over a separation coordinate.
stilt.observations.fit_variogram	Fit an exponential variogram to an empirical one.
stilt.observations.VariogramFit	Exponential variogram σ² (1 − exp(−h / l)), returned by fit_variogram().