Compute windspeed and airspeed on a graph

Reads the NetCDF files downloaded and interpolate the average windspeed experienced by the bird on each possible edge, as well as the corresponding airspeed.

In addition, the graph can be further pruned based on a threshold of airspeed thr_as.

See section 2.2.4 in Nussbaumer (2023b) for more technical details and the GeoPressureManual for an illustration on how to use it.

Usage

graph_add_wind(
  graph,
  pressure,
  rounding_interval = 60,
  interp_spatial_linear = FALSE,
  file = function(stap_id)
    glue::glue("./data/wind/{graph$param$id}/{graph$param$id}_{stap_id}.nc"),
  thr_as = Inf,
  quiet = FALSE
)

Arguments

graph

a GeoPressureR graph object.

pressure

pressure measurement of the associated tag data used to estimate the pressure level (i.e., altitude) of the bird during the flights. This data.frame needs to contain date as POSIXt and value in hPa.

rounding_interval

temporal resolution on which to query the variable (min). Default is to match ERA5 native resolution (1hr).

interp_spatial_linear

logical to interpolate the variable linearly over space, if FALSE takes the nearest neighbour. ERA5 native resolution is 0.25°

file

absolute or relative path of the ERA5 wind data file to be downloaded. Function taking as single argument the stationary period identifier.

thr_as

threshold of airspeed (km/h).

quiet

logical to hide messages about the progress

Value

a graph object with windspeed and airspeed as ws and as respectively.

References

Nussbaumer, Raphaël, Mathieu Gravey, Martins Briedis, Felix Liechti, and Daniel Sheldon. 2023. Reconstructing bird trajectories from pressure and wind data using a highly optimized hidden Markov model. Methods in Ecology and Evolution, 14, 1118–1129 https://doi.org/10.1111/2041-210X.14082.

See also

GeoPressureManual