## 1 Introduction  
Forests play an important role in the global ecological, environmental and recreational functions [1,2]. It is well recognized that the forests can absorb atmospheric carbon, regulate rainfall, moderate temperature, and restrain soil erosion [3,4]. To a large extent, the forest fire is a dominant disturbance factor in almost all the forest vegetation zones throughout the World, and it is considered to be a potential hazard causing physical, biological, and environmental consequences [5-8]. Furthermore, forest fires can have adverse societal impacts regardless of whether they are caused by natural forces or human activities. The forest resources are very limited in China, and only account for 20.36% of the whole national's territory [9]. According to the Seventh National Forest Resources Inventory during 2004 to 2008, the forest area was estimated at 195 million ha and its stock volume was 13.72 billion cubic meters, ranking fifth in the world after Russia, Brazil, Canada, and the U.S.A [9,10]. It was reported that the forest fires burn an average of 0.86% of the total forest area every year in China [11]. Temporally, over the past 40 years, the number of forest fires has increased significantly [12]. During the period from 1950 to 1997, about 676,000 forest fires occurred and the average burned area reached about 822,000 ha each year [13]. One of the largest forest fires occurred in the Daxing'anling Forest of the Northeast China during the period from 6 May to 2 June, 1987. The burned area was in excess of 1.3 million ha of the prime forest, resulting in the loss of over 200 lives and over 50,000 homes [14]. As a result, the frequent occurrence of forest fires has become an important issue in view of the forest degradation in China [11,15-17]. Early detection and real-time monitoring of fire activities are essential for fire management and planning. Given the high cost and potential hazards associated with the ground-based and air-borne fire monitoring, space-borne satellite sensors have been widely used to detect and monitor forest fires in recent years [18-21]. Earth observations provide useful data for developing consistent method for detecting area and severity of active burning at national, continental or global scales. Sensors onboard many satellites with multi-spatial and multi-spectral resolutions, such as NOAA/AVHRR (the National Oceanic and Atmospheric Administration/the Advanced Very High Resolution Radiometer) [19,20], EOS-MODIS (Earth Observing System-Moderate Resolution Imaging Spectroradiometer) [21-24], Landsat ETM (Enhanced Thematic Mapper) [25-28] were designed to measure reflected and emittedradiation in the visible (VIS, 0.4-0.7 \(\upmu\)m), the near infrared (NIR, 0.7-1.3 \(\upmu\)m), the short-wave infrared (SWIR, 1.3-8 \(\upmu\)m), the middle infrared (MIR, 3-8 \(\upmu\)m), and the thermal infrared (TIR, 8-13 \(\upmu\)m). The satellite sensors such as NOAA/AVHRR, Chinese FY (FengYun)-series, MODIS, CBERS (China-Brazil Earth Resources Satellite), and ESA (European Space Agency) ENVISAT (Environmental Satellite) have been widely applied to detect forest fire hot spots and burned areas in China [29]. The relatively high temporal and spatial resolution data acquired by the polar orbiting satellites, such as NASA EOS Terra/Aqua, and Chinese FY polar orbiting series, increase the likelihood that cloud-free data can be obtained for mapping the distribution of the large-scale burned areas. In contrast, the Geostationary platforms, such as NOAA GOES (Geostationary Operational Environmental Satellite), MTSAT (Meteorological Satellite), and Chinese FY geostationary orbiting series satellites can provide continuous observations over large geographic regions, making it possible to detect the short duration fires and also to resolve the diurnal behavior of large fires [29]. Biomass burning is a major contributor of particulate matter (PM) and trace gases to the global troposphere [30, 31].