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	Coverage of this dataset spans January 1998 to June 2002.
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Product description: These fire data, derived from Tropical Rainfall Measuring Mission (TRMM) Visible and Infrared Scanner (VIRS) measurements, show the number of 4.4 square kilometer pixels in each half-degree grid cell (each cell is 2500 square kilometers at the equator) that are hot enough to contain a large fire. These data, summarized for each month, are currently being used to monitor natural and man-made fires in the Tropical and Sub-tropical zones (+/- 40° from the equator). Forest and savanna fires in the tropics are known to affect both regional and global climate, ecology, biodiversity, and air quality. (Courtesy L. Giglio & J. Kendall, SSAI; data from TRMM VIRS) Additional Notes: 1. Relevant VIRS information Although the VIRS instrument is designed primarily to study clouds and precipitation, it offers an additional opportunity for the remote sensing of tropical fire activity. VIRS is a 5-channel imaging radiometer with characteristics very similar to the Advanced Very High Resolution Radiometer (AVHRR). The TRMM orbit causes the local overpass time to drift over the entire 24 hours of a day approximately once each month, enabling observation of regional diurnal burning cycles. 2. Fire data compositing Due to TRMM orbit characteristics, the higher latitudes (closer to 40°N and 40°S) are sampled more frequently than those closer to the equator. This can have the affect of counting the same fire more than once. To compensate for this, the cumulative fire counts for each grid cell are normalized by overpass frequency (scaled to match the number of overpasses along the equator).

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