## 3 Methodology
### Developing GLOPEM Model and CEVSA Model : GLOPEM-CEVSA Model
NDVI\({}_{\text{i,max}}\) and NDVI\({}_{\text{i,min}}\) correspond to the maximum and minimum values of the vegetation types of NDVI, respectively, and correspond to a certain type of vegetation NDVI of 5% and 95% of the underside of percentile, respectively; the same situation applies to SR\({}_{\text{i,min}}\) and SR\({}_{\text{i,max}}\). Among them, i represents different vegetation types, such us evergreen coniferous forest, evergreen broadleaved forest, deciduous coniferous forest, deciduous broad-leaved forest, shrub, grassland, farmland, urban-land, and bareland. Figure 2: The framework of the GLOPEM-CEVSA model. fPAR\({}_{\text{min}}\) and fPAR\({}_{\text{max}}\) are unrelated to vegetation types. fPAR\({}_{\text{min}}\) value is 0.001, and fPAR\({}_{\text{max}}\) value is 0.95. Combined with the data of Chongqing, the maximum and the minimum of NDVI and SR for different vegetation types are calculated. The data involved in these calculations have been normalized and harmonized to the same spatial scale and coordinate system. LUE is the product of potential maximum light use efficiency and is also the key link in the GLOPEM-CEVSA model. We estimated LUE using critical environmental factors known to impact stomatal conductance, according to Equation (20):  
\[\text{LUE}=\text{PLUE}\cdot\text{S(Ta)}\cdot\text{S(VPD)}\cdot\text{S(SWC)} \cdot\text{S(PAR)}\cdot\text{S(CO}_{2}) \tag{20}\]  
where PLUE is the potential maximum light utilization, and the model is based on the actual situation in Chongqing. The PLUE is estimated by different types of vegetation (Table 3), and the value is based on the simulation results of BIOME-BGG model by [PERSON] [31] and the actual situation in the southwest region. S(Ta), S(VPD), S(SWC), S(PAR) and S(CO\({}_{2}\)), respectively, represent the effects of air temperature (Ta), vapor pressure (VPD), soil moisture (SWC), solar radiation (PAR) and carbon dioxide (CO\({}_{2}\)) on stomatal conductance of vegetation. The temperature effect (T) can be divided into two factors. \begin{table}
\begin{tabular}{c c} \hline
**Conception** & **Meaning Explanation** \\ \hline NPP & Net primary productivity (gC/m\({}^{2}\)a) \\ PAR & Photosynthetically active radiation (MJ/m\({}^{2}\)a) \\ fPAR & Photosynthetically active radiation \\ LUE & Actual light use efficiency \\ PLUE & Potential maximum light use efficiency \\ Ra & Autotrophic respiration \\ S(PAR) & Radiation stress \\ S(T) & Temperature stress \\ S(SWC) & Soil water stress \\ S(VPD) & Vapor stress \\ S(CO\({}_{2}\)) & Carbon dioxide stress \\ EET & The actual evapotranspiration \\ PET & The potential evapotranspiration \\ Tem & Temperature (\({}^{\circ}\)C) \\ PPT & Precipitation (mm) \\ WSP & Wind speed \\ RH & Air relative humidity \\ Sunhit & Sunshine hours (h) \\ LAT & Latitude \\ ELV & Altitude \\ SLP & Slope \\ ASP & Aspect \\ \hline \end{tabular}
\end{table} 
Table 2: The key conceptions and parameters in the framework of model. \begin{table}
\begin{tabular}{c c} \hline
**LUCC** & **PLUE** \\ \hline evergreen coniferous forest & 1.008 \\ evergreen broadleaved forest & 1.259 \\ deciduous coniferous forest & 1.103 \\ deciduous broad-leaved forest & 1.004 \\ shrub & 0.888 \\ grassland & 0.608 \\ farmland & 0.604 \\ urban-land & 0.542 \\ bareland & 0.542 \\ \hline \end{tabular}
\end{table} 
Table 3: The PLUE of different LUCC. \[\mathrm{S(Ta)}=\mathrm{T_{a1}}\times\mathrm{T_{a2}} \tag{21}\] \[\mathrm{T_{a1}}=0.8+0.02\times\mathrm{T_{opt}}-0.0005\times\left( \mathrm{T_{opt}}\right)^{2}\] (22) \[\mathrm{T_{a2}}=1.184/\left(1+\exp\bigl{(}0.2\times\left(\mathrm{T_{ opt}}-10-\mathrm{T_{e}}\right)\bigr{)}\right)\times 1/\left(1+\exp\bigl{(}0.3\times \left(-\mathrm{T_{opt}}-10+\mathrm{T_{e}}\right)\bigr{)}\right) \tag{23}\]  
where Te represent the average temperature (\({}^{\circ}\)C), and \(\mathrm{T_{opt}}\) represent the most suitable average temperature in the month (\({}^{\circ}\)C). \[\mathrm{S(VPD)}=\left\{ \begin{array}{c}1-0.05\mathrm{VPD}\,,\;0<\mathrm{VPD }\leq 15\\ 0.25,\;VPD>15\end{array} \right.