Satellite-detected active fires (NASA FIRMS) — Roi Et
5-year mean across 2021-2025, MODIS Collection 6 sensor (MODIS_SP)
- Data through
- RefreshAnnual (next refresh January 2027)
- Source NASA FIRMS
- Inside the province (per-year mean)
- 221
- Within 150 km of the centroid (per-year mean)
- 1,679
Detections that fall inside the province polygon (HDX RTSD ADM1 boundaries). Counts inside Thailand only.
Captures fires in adjacent Thai provinces and cross-border fires from Laos that the polygon-only count misses.
About this data — source, citation, and how it relates to PM2.5
Source. NASA FIRMS (Fire Information for Resource Management System), operated by NASA's Earth Science Data and Information System (ESDIS) at the Goddard Space Flight Center. Distributed through firms.modaps.eosdis.nasa.gov.
Product. MODIS Collection 6 Standard-Processing active-fire detections (MODIS_SP), Terra and Aqua satellites, roughly 1 km resolution, calendar years 2021-2025. VIIRS sensors (Suomi NPP, NOAA-20) are queued for the v1.1 release.
Algorithm citation. Giglio, L., Schroeder, W., & Justice, C. O. (2016). The collection 6 MODIS active fire detection algorithm and fire products. Remote Sensing of Environment, 178, 31-41. doi.org/10.1016/j.rse.2016.02.054.
Confidence filter. MODIS detections with confidence below 30 are dropped — the low-quality and possible-fire flagged categories per the FIRMS user guide. The remaining nominal and high categories are retained.
What each detection means. A "fire pixel" represents an area of roughly one square kilometer hot enough to register against MODIS infrared bands. Detections include agricultural burning, forest fires, industrial flaring, and rare false positives from highly reflective surfaces.
How it relates to PM2.5. Fire counts and the PM2.5 indicators in Environment & Climate (annual mean and days exceeding the WHO threshold) correlate strongly during the northern burning season, February through April. The two indicators measure opposite ends of the same chain: fire source upstream, air-quality impact downstream. Including both in the composite would double-count one phenomenon. The fire counts shown here serve as informational context.