The value of monthly ground reflectance is considered as 0.2 in the standard simulations. This value is resulted from the combination of ground reflectivity of pervious and impervious surfaces and based on equation (1):
\begin{equation} \rho_{\text{GR}}=\rho_{GR\_p}f_{GR\_P}+\rho_{GR_{\text{imp}}}(1-f_{GR\_P})\nonumber \\ \end{equation}
where PGR is  ground reflectance, PGR_P and PGRimp refer to road pervious and impervious fGr_P is road area function. Moreover, the ground reflectance value is affected by ground surfaces cover by snow situation \cite{Clarke_2002}. Since this study is only focused on the cooling season (for shading design purposes), the effect of snow is ignored in the presented calculations. The range of uncertainty in ground reflectance is extracted from Sun et al. \cite{Sun_2013}. According to this study, the range of ground reflectance could vary between 0.05 and 0.45 with a center point of 0.25. This value can be represented through a triangular probability distribution displayed in Fig.4 .