Calculating actual vapour pressure for hourly time step
cal_ActualVapourPressure_for_hourly(Thr, RHhr)
A vector for average hourly actual vapour pressure [kPa].
is average hourly temperature (degrees Celsius).
is average hourly relative humidity [%].
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.