# 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  
#### 3.2.1 MODIS Mc5 and Mc6 LAI Aggregated to 12.0 km  
Mc5 and Mc6 LAI was processed for nearly 100 percent of the 1.0 km and 0.5 km pixels respectively within each 12.0 km grid cell for three of the four LAI research sites (Appomattax, Hertford, Fairystone) (Figure 7). The more urban dominated Umstead site, located in Wake and Durham counties, had a higher percentage of non-processed MODIS 1.0 km pixels across the nine grid cells (\(\hat{x}\) = 43.1%, \(\sigma\) = 28%) as compared to the Mc6 pixels (\(\hat{x}\) = 21.0%, \(\sigma\) = 25.1%). In general, the main radiative transfer algorithm was employed across early and late season growth to arrive at an LAI solution across all four research sites for both Mc5 and Mc6 MODIS products.  
The mean LAI of the nine 12.0 km grid cells per site were similar for both the Mc5 1.0 km (\(n\) = 144) MODIS LAI and Mc6 0.5 km (\(n\) = 576) MODIS LAI products with Mc5 LAI exhibiting slightly higher LAI values than the Mc6 counterpart for the Appomattax site (3.0-4.7% LAI) (Table 7). Umstead Mc5 exhibited in a larger difference when compared to Mc6 LAI across the two dates (35.5-42.3% LAI). Fairystone exhibited larger Mc5 LAI values than Mc6 over three of the four dates (\(-\)0.9-12.9%). Hertford Mc6 LAI trended larger than Mc5 LAI (8.6-29.1). A grid-by-grid analysis for all four research sites (\(n\) = 113 12.0 km grids) over all dates showed Mc5 LAI exceeding Mc6 LAI over 71.0% of the grid cells by a mean LAI of 0.21 (Table 8). Only Hertford showed a majority of 12.0 km grid cells where Mc6 LAI exceeded the older collection.  
Figure 6: Appomattax and Umstead MODIS LAI (Mc5 and Mc6) comparisons to LAI-RM.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Site** & **Date** & **Mc5 \(\overline{\textbf{x}}\)(s)** & **Mc6 \(\overline{\textbf{x}}\)(s)** & **Mc5–Mc6** & **\% Difference (Mc5 to Mc6)** \\ \hline Umstead & 23 Apr & 3.38 (0.54) & 1.95 (0.78) & 1.43 & \(-\)42.3 \\ Umstead & 24 Oct & 1.52 (0.23) & 0.98 (0.42) & 0.54 & \(-\)35.5 \\ Appomatrox & 6 Mar & 0.85 (0.09) & 0.81 (0.03) & 0.04 & \(-\)4.7 \\ Appomatrox & 25 May & 4.08 (0.36) & 3.95 (0.40) & 0.13 & \(-\)3.2 \\ Appomatrox & 5 Aug & 3.94 (0.23) & 3.82 (0.55) & 0.12 & \(-\)3.0 \\ Fairystone & 1 May & 3.94 (0.19) & 3.43 (0.43) & 0.51 & \(-\)12.9 \\ Fairystone & 26 Jun & 4.46 (0.39) & 4.42 (0.35) & 0.04 & \(-\)0.9 \\ Fairystone & 12 July & 4.38 (0.44) & 4.39 (0.34) & \(-\)0.01 & 0.2 \\ Fairystone & 6 Sep & 3.86 (0.40) & 3.47 (0.48) & 0.39 & \(-\)10.1 \\ Hertford & 6 Mar & 0.88 (0.29) & 0.96 (0.16) & \(-\)0.08 & 9.1 \\ Hertford & 15 Apr & 1.51 (0.36) & 1.95 (0.23) & \(-\)0.44 & 29.1 \\ Hertford & 18 Jun & 3.04 (0.79) & 3.3 (0.33) & \(-\)0.26 & 8.6 \\ Hertford & 5 Aug & 3.04 (0.79) & 3.7 (0.34) & \(-\)0.66 & 21.7 \\  & Mean (\(\overline{\alpha}\)) & 2.92 & 2.83 & 0.09 & 13.46 \\  & SD (s) & 1.31 & 1.36 & - & 13.67 \\ \hline \hline \end{tabular}
\end{table}
Table 7: Mean LAI differences across each 3 × 3 grid of 12.0 km grid cells per site per date.  
Figure 7: Data quality differences for MODIS Mc5 and Mc6 data over all four research sites over 13 dates: (**A**) Appomatrox/Umstead, (**B**) Fairystone, (**C**) Hertford. \({}^{*}\) RT—radiative transfer.