# Comparison of EPIC-Simulated and MODIS-Derived Leaf Area Index (LAI) across Multiple Spatial Scales
## 3 Results
### Comparison 2: 12.0 km--EPIC LAI v. MODIS (Mc5/Mc6) LAI
#### 3.2.3 MODIS Mc5 and Mc6 LAI Comparison to EPIC LAI  
At the Fairystone site, the weighted LAI means for both MODIS collections exceeded EPIC LAI across the four dates, with one date exception for Mc6 (Mc5: 4/4 dates exceedance, Mc6: 3/4 dates exceedance) (Figures 8 and 9, Table 9). The weighted means were highest in this 100% hardwood site, varying under 0.10 LAI for both Mc5 (LAI = 1.34) and Mc6 (LAI = 1.27) (Tables 10 and 11). The LAI medians were significantly different between both collections and EPIC, except for 6 September and for the Mc6 collection only from 1 May (Figure 8). This trend of small median agreement between EPIC LAI and the MODIS LAI collections was seen at the other three research sites, with only Mc5 showing no significant differences for half of the LAI dates at Hertford (Figure 8). The Umstead site, like the Fairystone site, showed similar weighted mean differences for both MODIS LAI collections (Mc5 LAI = 1.31 and Mc6 LAI = 1.38) as did Appomattex with differences of 1.29 LAI for both Mc5 and Mc6. Hertford weighted LAI mean differences were the smallest among the four sites (Mc5 LAI = 0.60 and Mc6 LAI = 0.59). In summary, three of the four research sites showed similar weighted mean LAI differences (LAI 1.29-1.34), with both Mc5 and Mc6 exceeding EPIC LAI across most dates. Only Umstead showed EPIC LAI exceeding both MODIS LAI collections across both dates. For all four research sites, both MODIS collections showed a positive bias when compared to EPIC LAI, with Mc6 (LAI = 0.40) aligning closer to EPIC than the Mc5 (LAI = 0.61) counterpart (Tables 10 and 11). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Site** & **LAI Dataset** & **No. of Dates** & **No. of Grids** & **Mean (\%) Difference** \\ \hline
**Umstead** & Mc5 & 2 & 14 & 0.99 \\  & Mc6 & 2 & 0 & N/A \\ Hertford & Mc5 & & 17 & 0.52 \\  & Mc6 & 4 & 19 & 0.54 \\ Fairystone & Mc5 & & 30 & 0.41 \\  & Mc6 & 4 & 6 & 0.64 \\ Appomattex & Mc5 & 3 & 19 & 0.33 \\  & Mc6 & 3 & 8 & 0.42 \\ \hline Total & Mc5 & 13 & 80 & 0.51 \\  & Mc6 & 33 & 0.53 \\  & Overall & & 113 & 0.21 \({}^{*}\) \\ \hline \hline \end{tabular} Note: \({}^{*}\) LAI = 0.21 bias in MODIS Mc5 LAI; ** For Umstead, two of the possible nine 12.0 km grid cells were not included in LAI calculations due to dominance of urban LC in these grid cells; No.—’number’.  
\end{table} 
Table 8: 12.0 km grid-based mean differences per LAI research site over all Mc5 and Mc6 data collections. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Fairstone** & 1 **May \(\overline{x}\)(s)** & 26 **June \(\overline{x}\)(s)** & 12 **July \(\overline{x}\)(s)** & 6 **September \(\overline{x}\)(s)** \\ \hline Mc5 & 3.94 (0.19) & 4.46 (0.39) & 4.38 (0.44) & 3.86 (0.40) \\ Mc6 & 3.43 (0.43) & 4.42 (0.35) & 4.39 (0.34) & 3.47 (0.48) \\ EPIC & 2.72 (1.11) & 3.21 (1.26) & 3.28 (1.24) & 3.26 (1.29) \\ Mc5-EPIC & 1.22 & 1.25 & 1.10 & 0.60 \\ Mc6-EPIC & 0.71 & 1.21 & 1.11 & 0.21 \\ \hline
**Hertford** & 6 **March \(\overline{x}\)(s)** & 15 **April \(\overline{x}\)(s)** & 18 **June \(\overline{x}\)(s)** & 5 **August \(\overline{x}\)(s)** \\ \hline Mc5 & 0.88 (0.29) & 1.51 (0.36) & 3.04 (0.79) & 3.59 (0.64) \\ Mc6 & 0.96 (0.16) & 1.95 (0.23) & 3.30 (0.33) & 3.70 (0.34) \\ EPIC & 1.64 (0.44) & 1.72 (0.41) & 2.97 (0.50) & 2.97 (0.48) \\ Mc5-EPIC & \(-\)0.76 & \(-\)0.21 & 0.07 & 0.62 \\ Mc6-EPIC & \(-\)0.68 & 0.23 & 0.33 & 0.73 \\ \hline
**Appomatox** & 6 **March \(\overline{x}\)(s)** & 25 **May \(\overline{x}\)(s)** & 5 **August \(\overline{x}\)(s)** & \\ \hline Mc5 & 1.01 (0.09) & 4.09 (0.40) & 3.76 (0.24) & \\ Mc6 & 0.81 (0.03) & 3.95 (0.40) & 3.82 (0.55) & \\ EPIC & 1.45 (0.60) & 2.27 (0.71) & 2.31 (0.73) & \\ Mc5-EPIC & \(-\)0.44 & 1.82 & 1.45 & \\ Mc6-EPIC & \(-\)0.64 & 1.68 & 1.51 & \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Mean EPIC and MODIS (Mc5 and Mc6) LAI comparisons at 12.0 km scale within 3 \(\times\) 3 grid (\(n\) = nine 12 km grid cells per date).