## 2 Materials and Methods
### Satellite Data
The MODIS Land Surface Temperature Product (LST) (MYD11A2) was used as measure of canopy temperature, which is an environmental factor that may drive production [50; 52; 81]. To achieve the best comparisons among OCO-2 and MODIS metrics, each MODIS metric location was extracted based on the matching OCO-2 footprint location and closest time and date. Only MODIS data onboard the Aqua platform were used in analyses because the overpass time matches OCO-2 (1330 local). For the purposes of this study, \(\text{SIF}_{\text{i}}\), \(\text{SIF}_{\text{d}}\), \(\text{SIF}_{\text{y}}\), GPP, NDVI, and EVI are considered productivity metrics, and fPAR and LAI are considered intermediate variables because LAI and fPAR products from MODIS are used to model GPP from MODIS data. To examine the relationships among SIF, GPP, and environmental factors potentially controlling photosynthetic activity in this study, skin temperature (T\({}_{\text{can}}\)), 2 m temperature (T\({}_{\text{air}}\)), and vapor pressure deficit (VPD) from the European Center for Medium-Range Weather Forecasts (ECMWF) available within the OCO-2 SIF dataset were used. Land \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Variable** & **Name** & **Sensor/Product** & **Spatial Resolution** & **Temporal Granularity** & **Units** \\ \hline \multicolumn{6}{c}{**Productivity Metrics**} \\ \hline GPP & gross primary production & MODIS MYD17A2 & 500 m & 8 Day & \(\text{g}\) \\  & & & & \(\text{C/m}^{2}\)/day \\ \hline NDVI & normalized difference vegetation index & MODIS MYD13Q1 & 250 m & 16 Day & none \\ \hline EVI & enhanced vegetation index & MODIS MYD13Q1 & 250 m & 16 Day & none \\ \hline SIF & solar-induced fluorescence & OCO-2 & \textasci{}1.2 km \(\times\) 2 km & 16 days & \(\text{Wm}^{2}\)/\(\upmu\)m/sr \\ \hline GPP & gross primary production & MODIS MYD17A2 & 500 m & 8 Day & \(\text{g}\) \\  & & & & \(\text{C/m}^{2}\)/day \\ \hline NDVI & normalized difference vegetation index & MODIS MYD13Q1 & 250 m & 16 Day & none \\ \hline EVI & enhanced vegetation index & MODIS MYD13Q1 & 250 m & 16 Day & none \\ \hline \multicolumn{6}{c}{**Intermediate Variables**} \\ \hline fPAR & fraction photosynthetically active radiation & MODIS MYD15A2H & 500 m & 8 Day & none \\ \hline LAI & leaf area index & MODIS MYD15A2H & 500 m & 8 Day & \(\text{m}^{2}\)/\(\upmu\)m\({}^{2}\) \\ \hline \multicolumn{6}{c}{**Environmental Variables**} \\ \hline LST & land surface temperature & MODIS MYD11A2 & 1 km & 8 Day & K \\ \hline T\({}_{\text{can}}\) & canopy temperature & ECMWF (OCO-2) & \textasci{}1.2 km \(\times\) 2 km & 16 days & K \\ \hline T\({}_{\text{air}}\) & air temperature & ECMWF (OCO-2) & \textasci{}1.2 km \(\times\) 2 km & 16 days & K \\ \hline VPD & vapor pressure deficit & ECMWF (OCO-2) & \textasci{}1.2 km \(\times\) 2 km & 16 days & kPa \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Summary of satellite products used in this study. surface temperature (LST) from MODIS was also collected for the study period as a second approximation of canopy temperature. Proxies of production, i.e., satellite measurements of VIs and satellite-based SIF, were compared to one another in terms of phenology and relationships that may help inform the interpretation of SIF measurements [82; 83; 84; 85; 86; 87].