'rnl' computes daily net energy flux emitted by the Earth's surface.
Usage
rnl(Tmax,Tmin,sol_rad,vap_pres,extraT,tal)
Arguments
Tmax
Vector of length n containing daily maximum temperature [C].
Tmin
Vector of length n containing daily minumum temperature [C].
sol_rad
Vector of length n of daily solar radiation [MJm-2d-1].
vap_pres
Vector of length n of mean daily vapour pressure [kPa].
extraT
Vector of length n of extraterrestrial solar radiation [MJm-2d-1].
tal
Clear sky transmissivity.
Value
Vector of length n of daily net longwave radiation. [MJm-2d-1]
Details
According to the Stefan-Boltzmann law, the longwave energy emission is proportional to the absolute temperature of the surface raised to the fourth power. This longwave energy is corrected by two factors: humidity ('ea') and cloudiness (estimated based on relation of actual and potential solar radiation. See Allen et al. (1998) for details.
References
Allen, R.G., L.S. Pereira, D. Raes, and M. Smith. 1998. Crop Evapotranspiration: Guidelines for computing crop water requirements. Irrigation and Drainage Paper 56, Food and Agriculture Organization of the United Nations, Rome, pp. 300.
See Also
See 'ea', 'extrat' and 'cst' to calculate necessary input data.