## 4 Results and Discussion
### Comparison of Percentile Rank between HFRI, Revised FFMC, and DWI  
HFRI was compared to the revised FFMC and DWI using the percentile rank. To confirm the spatial accuracy, the percentile ranks of the forest fire pixels were calculated targeting all forest pixels every hour. Even if the indices (i.e., HFRI and DWI) have different ranges and distributions, since each index is spatially ordered for every pixel, it can be used to compare them which one is better at the discrimination between forest fire (representing high risk) and non-fire locations. For example, the percentile rank value of 95 means that the pixel is at the top 5% among all forest pixels at that time. Figure 6 shows the box plot of the percentile ranks of forest fire pixels.  
The mean percentile ranks of all forest fire pixels were 68, 59, 61 for HFRI, revised FFMC, and DWI, respectively. Revised FFMC and DWI had the almost same mean values but that of DWI was slightly higher, while HFRI had a remarkably higher mean value than the other two indices. The most noticeable part here is that the percentage of forest fire pixels with a percentile rank of 90 or higher in HFRI is 30%, whereas the other two indices were only 20%. Moreover, the percentage of forest fires with a percentile rank of over 50 was 72%, whereas 65% for DWI and 61% for the revised FFMC. HFRI showed a higher mean percentile rank than DWI thanks to the integrated model. When comparing the percentile rank of HFRI-I and HFRI-M, the percentile rank of HFRI-I appears at the same level as that of HFRI, whereas the percentile rank of HFRI-M is similar to that of DWI developed based on weather factors. Since the integrated model is focused on extracting high-risk areas by sampling non-fire samples only at the time of forest fire and using accessibility factors together, it could have a higher percentile rank in forest fire areas. Therefore, it can be said that HFRI simulates the forest fire risk better in spatial detail and accuracy than the DWI. Since the DWI showed better results than the revised FFMC, the DWI was used in the subsequent analysis and comparison to HFRI.  
Although HFRI had a high mean percentile rank, some forest fire pixels had values below 50. Such pixels were generally found in the spring (i.e., 74% in March and April) when forest fires were frequent. In the spring, the forest fire risk was high nationwide and many forest fire cases (e.g., 7) occurred at the same time. In that situation, the percentile rank of the forest fire pixels may be relatively lowered because the forest fire risk was nationwide high. However, it does not mean HFRI failed to simulate the forest fire risk because the actual forest fire risk index was high and only about 5-6% of the forest fire cases occurred in March and April fell into this category.  
Figure 6: The comparison of five models with percentile rank every hour. HFRI- I, M are the integrated model and the meteorological model, respectively. The left side is the box plot of each model percentile rank for forest fires. In the box plot, cases between 25 and 75% are displayed as boxes, and the red line means the average value. On the right side of the box plot, the percentage of the total forest fires in each section is additionally displayed.