Relative to $Tcab$

Taking Eq. (30), one may compute the derivative with respect to Tcab:

  $$\frac{1}{Tcal} \frac{\partial Tcal}{\partial T_{cab}} = \frac{(T_{atm} - T_{emi}} {(T_{cab}-T_{emi})*(T_{cab}-T_{emi}-F_{eff}*(T_{cab}-T_{atm})}$$ (43)

or with the numerical values in Eq. (31) about $3.6$ $10^{-3}$ per K.