## 3 Results
### Application of the Method
#### 3.1.2 Spectral Analysis Results  
The capacity of MODIS bands 1-7 for burned area identification was investigated based on the sample sets of five typical types extracted from Hot Pot Fire. Reflectance curves of the five types in the Hot Pot Fire are shown in Figure 6a. The results show that the average reflectance of cloud is much higher than that of the burned area, which means that it is easier to discriminate the cloud and burned area. Moreover, the reflectance of shadow is lower than that of burned area except for the slightly higher reflectance at band 3. Compared with the average reflectance of vegetation, the reflectance of burned area drops in the NIR spectral region. It accounts for 61.6% of the vegetation reflectance at  
Figure 5: Relationship between the reflectance at MODIS band 5 (1.24 \(\upmu\)m) and the reflectance at MODIS band 7 (2.13 \(\upmu\)m) of the samples extracted in Range 12 Fire: (**a**) scatter plot of samples in Box 1; (**b**) scatter plot of samples in Box 2; (**c**) Combined scatter plot of (**a**) and (**b**). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Empirical Formula** & **Coefficient** & **Hot Pot Fire** & **Range 12 Fire** & **Rey Fire** \\ \hline \(\rho_{5}<\alpha\times\rho_{7}+\beta\) & \(\alpha\) & 1.04 & 1.079 & 0.75 \\  & \(\beta\) & 0.02 & \(-\)0.003 & 0.06 \\ \hline \hline \end{tabular} \(\rho_{i}\) is the reflectance of MODIS band \(i\), \(\alpha\) is the slope of the line, \(\beta\) is the y-intercept of the line.  
\end{table} 
Table 5: Empirical formula and coefficients \(\alpha\) and \(\beta\) of the three wildfire cases. band 5, and the proportion is 72.7% at band 7; whereas the average burned area reflectance increases in the SWIR spectral region. It is 110.5% of the vegetation reflectance at band 6 and 189.1% at band 7. This also indicates that the NIR and SWIR spectral regions are more sensitive to the burned area. To demonstrate the capacity of the spectral bands to separate the burned area and unburned types, we calculated the separability index M of three comparisons: burned area vs. shadow, burned area vs. bare soil, and burned area vs. vegetation. The M statistic results of the three comparisons for the Hot Pot Fire are presented in Figure 6b. The results prove that the visible region (bands 1, 3 and 4) has low capacity to discriminate the burned area from three unburned types, and is especially weak in the separation of the burned area and shadow with M values lower than 0.4. Moreover, in the comparison between the burned area and bare soil, the M values of band 2 and band 5 are both 1.0, and in the comparison between the burned area and vegetation, the M values of band 2 and band 5 are both 1.1, which indicates that the NIR region shows high distinguishing capacity to the burned area. Furthermore, the M values of band 6 and 7 are higher than 1.8 in the burned and shadow comparison. This shows that the reflectance in the SWIR region is useful to discriminate the burned area and shadow. Overall, based on the samples of the Hot Pot Fire, the M values of band 5 in the three comparisons are all greater than 1.0, which demonstrates that the reflectance of band 5 has the optimal performance to discriminate burned area among bands 1-7. The sample sets extracted from the Range 12 Fire and Rey Fire consist only of three types including burned area, vegetation and bare soil. To determine the distinguishing capacity of band 5, we calculated the separability index M for two comparisons (burned area vs. bare soil and burned area vs. vegetation) at band 5 in these two wildfire cases. The results, presented in Figure 7, indicate that the M values between burned area and vegetation in these two wildfire cases are lower than 1.0, which means that the reflectance of band 5 has poor performance in separating the burned area from vegetation in different wildfires.