| cal_meanSaturationVapourPressure {simET} | R Documentation |
Calculating mean saturation vapour pressure
Description
Due to the non-linearity of the above equation, the mean saturation vapour pressure for a day, week, decade or month should be computed as the mean between the saturation vapour pressure at the mean daily maximum and minimum air temperatures for that period.
Usage
cal_meanSaturationVapourPressure(Tmax, Tmin)
Arguments
Tmax |
the daily maximum air temperature(degrees Celsius). |
Tmin |
the daily minimum air temperature(degrees Celsius). |
Details
Using mean air temperature instead of daily minimum and maximum temperatures results in lower estimates for the mean saturation vapour pressure. The corresponding vapour pressure deficit (a parameter expressing the evaporating power of the atmosphere) will also be smaller and the result will be some underestimation of the reference crop evapotranspiration. Therefore,the mean sauration vapour pressure should be calculated as the mean between the saturation vapour pressure at both the daily maximum and minimum air temperature.
Value
A vector for mean saturation vapour pressure (es)
References
Allen, R. G., Pereira, L. S., Raes, D., & Smith, M. FAO Irrigation and drainage paper No. 56. Rome: Food and Agriculture Organization of the United Nations, 1998.