Calculates the latent heat flux using the Bowen Method. Positive flux signifies flux away from the surface, negative values signify flux towards the surface. Values above 600 W m-2 and below -600 W m-2 trigger warnings. Output flux values are not smoothed; only the optional denominator cap guards near-zero partition denominators.
Usage
latent_bowen(...)
# Default S3 method
latent_bowen(
t1,
t2,
hum1,
hum2,
z1 = 2,
z2 = 10,
elev,
rad_bal,
soil_flux,
cap = NULL,
...
)
# S3 method for class 'weather_station'
latent_bowen(weather_station, cap = NULL, ...)Arguments
- ...
Additional arguments.
- t1
Temperature at lower height in degrees C.
- t2
Temperature at upper height in degrees C.
- hum1
Relative humidity at lower height in %.
- hum2
Relative humidity at upper height in %.
- z1
Lower height of measurement in m.
- z2
Upper height of measurement in m.
- elev
Elevation above sea level in m.
- rad_bal
Radiation balance in W m-2.
- soil_flux
Soil flux in W m-2.
- cap
A positive denominator guard for near-zero \(1 + B\). Default is NULL.
- weather_station
A weather_station object.
Details
The latent heat flux (\(Q_e\)) using the Bowen method is calculated as: $$Q_e = \frac{R_n - G}{1 + B}$$ where: \(R_n\) is the net radiation, \(G\) is the soil heat flux, and \(B\) is the Bowen ratio.
The implemented Bowen ratio (\(B\)) is calculated from a
potential-temperature gradient and an absolute-humidity gradient:
$$B = \gamma_{code} \cdot \frac{\Delta \theta / \Delta z}{\Delta AH / \Delta z}$$
where:
\(\gamma_{code} = 0.00066 \cdot (1 + 0.000946 \cdot t_1)\)
is the fieldClim empirical implementation coefficient; this documentation
does not assert it as a proven one-to-one replacement for the \(C_a/L_v\)
formulation,
\(\theta\) is potential temperature, and
\(AH\) is absolute humidity.
The inputs t1 and t2 are converted to potential temperature
before the temperature gradient is formed. The inputs hum1 and
hum2 are relative humidity values that are converted internally to
absolute humidity before the humidity gradient is formed.
When \(1 + B\) is close to zero, the latent heat flux can become
unrealistically high. The cap parameter is a numerical safeguard that
replaces near-zero denominators with +/- cap. Exact closure with
sensible_bowen() is guaranteed only for finite uncapped denominators;
capped cases are guarded diagnostic outputs and may not close
rad_bal - soil_flux exactly. Non-finite Bowen ratios or denominators
return NA for affected elements with a warning.