Bulk-residual turbulent heat flux workflow — turb_flux_bulk

Adds sensible_bulk and latent_bulk_residual to a weather_station object.

Usage

turb_flux_bulk_residual(weather_station, ...)

Arguments

weather_station: A weather_station object.
...: Further arguments passed to sensible_bulk() and latent_bulk_residual().

Value

The input weather_station object with additional fields sensible_bulk and latent_bulk_residual.

Details

This workflow combines the simple bulk-transfer estimate of sensible heat flux with an energy-balance residual for latent heat flux.

First, sensible heat flux is estimated with:

$$ H_{bulk} = \rho c_p \frac{T_1 - T_2}{r_a} $$

with:

$$ r_a = \frac{\log(z_2 / z_1)}{k \bar{u}} $$

Then latent heat flux is calculated as:

$$ LE_{res} = R_n - G - H_{bulk} $$

The resulting workflow closes the available turbulent energy exactly:

$$ H_{bulk} + LE_{res} = R_n - G $$

under the package sign convention. Here $R_n > 0$ is net radiative input at the surface, $G > 0$ is heat flux into the soil, $H > 0$ is sensible heat flux away from the surface, and $LE > 0$ is latent heat flux away from the surface.

The workflow is intended as a transparent reference and teaching path. It is not a full Monin-Obukhov method and does not apply stability corrections. The latent heat flux is a residual and therefore depends directly on the quality of rad_bal, soil_flux, and the bulk sensible heat estimate.

Required fields in weather_station are:

t1: lower air temperature in degrees C.
t2: upper air temperature in degrees C.
v1: lower wind speed in m s-1.
z1: lower measurement height in m.
z2: upper measurement height in m.
rad_bal: net radiation $R_n$ in W m-2.
soil_flux: soil heat flux $G$ in W m-2.

If v2 is present, it is used together with v1 to compute mean wind speed. If v2 is missing, v1 is used.

Examples

ws <- build_weather_station(
  datetime = as.POSIXct(
    c("2023-06-01 12:00:00", "2023-06-01 12:30:00"),
    tz = "UTC"
  ),
  t1 = c(20, 18),
  t2 = c(18, 19),
  v1 = c(2, 2),
  v2 = c(4, 3),
  z1 = 2,
  z2 = 10,
  rad_bal = c(400, 300),
  soil_flux = c(60, 40),
  elev = 100
)

out <- turb_flux_bulk_residual(ws)
#> Warning: sensible_bulk: there are values above the diagnostic threshold of 600 W m-2.
#> Warning: latent_bulk_residual: there are values above the diagnostic threshold of 600 W m-2.

names(out)
#>  [1] "datetime"             "t1"                   "t2"                  
#>  [4] "v1"                   "v2"                   "z1"                  
#>  [7] "z2"                   "rad_bal"              "soil_flux"           
#> [10] "elev"                 "sensible_bulk"        "latent_bulk_residual"

out_guarded <- turb_flux_bulk_residual(
  ws,
  stability_method = "ri_guard"
)
#> Warning: sensible_bulk: there are values above the diagnostic threshold of 600 W m-2.
#> Warning: sensible_bulk: very stable Richardson cases for some values; returning NA there.
#> Warning: latent_bulk_residual: there are values above the diagnostic threshold of 600 W m-2.

attr(out_guarded$sensible_bulk, "bulk_stability")
#> [1] "unstable"    "very_stable"
attr(out_guarded$sensible_bulk, "bulk_Ri_g")
#> [1] -0.1338652  0.2681879