Dear all,
I am looking for equations for the adjustment of mid-season stage crop coefficient (Kcmid) and end of late season stage crop coefficient (Kcend) similar to the following equations:
Kcmid = Kcmid (Table 12) + (0.04*(u2-2)-0.004*(Rhmin-45))*(h/3)^0.3
Kcend = Kcend (Table 12) + (0.04*(u2-2)-0.004*(Rhmin-45))*(h/3)^0.3
The equations and Table 12 are located on the following website http://www.fao.org/docrep/X0490E/x0490e0b.htm#calculating%20etc.
The problem is that the previous equations work for a mean daily minimum relative humidity (Rhmin in %) between 20% ≤ RHmin ≤ 80%,. I need to adjust the crop coefficients from table 12 for common reeds so that they would be suitable for a hot and dry climate where monthly mean of daily minimum relative humidity reaches 6.1 %. Can someone direct me to equations suitable for such a low relative humidity or help me out? What would be the error when I use the above equations for a 6.1 % relative humidity?
Many thanks
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