Matching MODIS Incidents to NFIRS Incidents
Our analysis revealed that 1.1% of MODIS observations and 1.6% of MODIS incidents occurred within 24 hours and 1 kilometer of an NFIRS incident.
We grouped MODIS observations and NFIRS incidents and found a total of 1,212 fires consisting of 1,800 MODIS observations and 2,042 NFIRS incidents. Of these fires, 876 included only 1 MODIS observation apiece, and 1,345 NFIRS incidents in total. The remaining 336 fires included a total of 924 MODIS observations and 697 NFIRS incidents (Table 7).
Table 7: MODIS-NFIRS Matches
| MODIS observations | NFIRS incidents | Total fires | |
|---|---|---|---|
| All Grouped Fires | 1,800 | 2,042 | 1,212 |
| Fires with a single MODIS observation | 876 | 1,345 | 876 |
| Fires with multiple MODIS observations | 924 | 697 | 336 |
1,800 MODIS observations out of 162,093 matched at least 1 NFIRS incident, which produces a MODIS observation match rate of 1.1%. Another 1,212 MODIS incidents out of 77,054 matched at least 1 NFIRS incident, which produces a MODIS incident match rate of 1.6%.
The 2,042 NFIRS incidents that matched at least 1 MODIS observation (in All Grouped Fires in Table 6) included several incident types, suggesting that a fire detected by MODIS may be recorded as something other than a wildfire incident. Incident types 140-143 (Natural vegetation fire, other; Forest, woods or wildland fire; Brush or brush-and-grass mixture fire; Grass fire) and 561, 631 and 632 (Unauthorized burning; Authorized controlled burning; Prescribed fire) were more common among NFIRS incidents that matched MODIS observations than among all NFIRS incidents (Figure 3).
Figure 3: Distribution of NFIRS Incident Types for MODIS Matches and for NFIRS, 2017
We also compared the NFIRS incidents that matched MODIS observations to the criteria that Butry and Thomas used to select their NFIRS incidents. Overall, only 701 of the 2,042 NFIRS incidents that matched 1 or more MODIS observations would have been included by Butry and Thomas' criteria. The figure below shows the number of matching NFIRS incidents by each criterion and the total indicates that number of matching NFIRS incidents that match at least 1 of them (Figure 4). Of the 701 matching incidents, 37 incidents matched 3 criteria, 224 incidents matched 2 criteria, and 440 incidents matched 1 criterion.