rnl {sirad}

Net longwave radiation

Description

'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.

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.

Value

Vector of length n of daily net longwave radiation. [MJm-2d-1]

Author(s)

Jedrzej S. Bojanowski

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.

Examples

rnl(Tmax=25.1,Tmin=19.1,sol_rad=14.5,vap_pres=2.1,extraT=23.5,tal=0.8)