Request and download surface pressure timeseries at location

This function return the surface atmospheric pressure timeseries from ERA5 at a queried location.

Usage

geopressure_ts(
  lon,
  lat,
  pressure = NULL,
  end_time = NULL,
  start_time = NULL,
  verbose = TRUE
)

Arguments

lon

Longitude to query (-180° to 180°).

lat

Latitude to query (0° to 90°).

pressure

Pressure list from PAM logger dataset list (optional).

end_time

If pressure is not provided, then end_time define the ending time of the timeserie as POSIXlt.

start_time

If pressure is not provided, then start_time define the starting time of the timeserie as POSIXlt.

verbose

Display (or not) the progress of the query (logical).

Value

A data.frame containing the timeserie of ERA5 pressure (date, pressure) as well as longitude and latitude (different if over water). If pressure is provided, the return data.frame is the same as pressure with altitude and pressure0.

Details

If you supply the pressure (and time) of the geolocator \(P_{gl}\), the function will additionally return the altitude of the geolocator above sea level \(z_{gl}\) using the barometric equation, $$ z_{{gl}}(x)=z_{ERA5}(x) + \frac{T_{ERA5}(x)}{L_b} \left( \frac{P_{gl}}{P_{ERA5}(x)} \right)^{\frac{RL_b}{g M}-1},$$ where \(z_{ERA}\), \(T_{ERA}\) and \(P_{ERA}\) respectively correspond to the ground level elevation, temperature at 2m and ground level pressure of ERA5, \(L_b\) is the standard temperature lapse rate, \(R\) is the universal gas constant, \(g\) is the gravity constant and \(M\) is the molar mass of air. See more information on the GeoPressureAPI documentation.

The timeseries of the response will be on the same as time if supply, otherwise, it will return on a hourly basis between start_time and end_time.

If the location query is over water, the location will be moved to the closest onshore location.

To be able to compare the temporal variation of the retrieved pressure of ERA5 \(P_{ERA}\) to the geolocator pressure \(P_{gl}\), the function also return the ERA pressure normalized with the geolocator mean pressure measurement as pressure0. $$ P_{0}(\boldsymbol{x})[t] = \left( P_{ERA5}(\boldsymbol{x})[t]-P_{gl}[t]\right) - \left( \frac{1}{n}\sum_{i=1}^{n} P_{ERA5}(\boldsymbol{x})[i]-P_{gl}[i] \right).$$

See GeoPressureManual | Probability aggregation for more information on the meaning of this value.

See also

geopressure_ts_path(), GeoPressureManual | Pressure Map ,