Consider the Penman$-$Monteith approach $($or combination method$)$ for estimation of potential evapotranspiration.

a$.$ Describe why the Penman$-$Monteith technique for estimating potential evapotranspiration weights the net shortwave and longwave radiation by the slope of the saturation vapor pressure vs$.$ temperature curve $(\backslash$Delta $),$ which tends to increase with air temperature.

b$.$ Describe why the Penman$-$Monteith technique for estimating potential evapotranspiration weights the mass transfer effect by the psychrometric constant $(\backslash$gamma $),$ which tends to increase with air pressure.

c$.$ Describe the characteristics of a watershed that control the value of the canopy conductance used for estimating potential evapotranspiration using Penman$-$Monteith theory.

d$.$ For a semi$-$arid watershed, the Penman$-$Monteith equation $($based on canopy conductance of a reference crop$)$ produces an estimate of $1610$ mm yr$-1$ for mean annual reference potential evapotranspiration. The mean annual precipitation for the watershed is $408$ mm yr$-1.$

What would be the value on the PET ratio axis of a Budyko plot for this watershed? Does this value suggest that actual evapotranspiration in this watershed is energy limited or water limited$,$ and why?

Show all work and carry units through all calculations.

e$.$ In the absence of further data about the watershed in part $$d$,$ what is a rough but reasonable estimate of the actual evapotranspiration $($in $[$L T$-1])$ from Budyko theory, and why?

Note that this question can be answered from logic and calculations are not necessarily required.