3. Results and concluding remarks
Among the fire events in the Red River Basin (Fig. 1), eight fire spots undetected by the MODIS contextual algorithm are numbered in Panel (a) and (c). Taking fire spot 2 as an example, the improved algorithm detected this thermal anomaly at 17:15 GMT (Panel a), and both algorithms identified this spot as an active fire with an obvious smoke plume at 18:50 GMT (Panel c and d). In Table 1, both T22 and ΔT for fire spot 2 increased by approximately 20 K during a period of 1.5 h. This proves that the fire at 17:15 GMT was an active fire. Fire spot 3 at 17:15 GMT and 18:50 GMT, and fire spot 5 at 17:15 GMT satisfy the threshold of T22 N310 K (Table 1) and contextual thresholds, but they are not identified by the MODIS contextual algorithm. This indicates that the false alarm rejection thresholds in the MODIS contextual algorithm cause omission errors.