For this reflectivity range the dust radiative effect at 2.2 m is small, and the surface reflectance in the blue and red channels can be retrieved.

Abstract. The National Aeronautic and Space Administration (NASA) plans to launch the moderate resolution imaging spectroradiometer (MEDIS) on the polarorbiting Earth Observation System (EeS) providing morning and evening global observations in 1999 and afternoon and night observations in 2000. These four MEDIS daily fire observations will advance global fire monitoring with special 1 km resolution fire channels at 4 and 11 /xm, with high saturation of about 450 and 400 K, respectively. MEDIS data will also be used to monitor burn scars, vegetation type and condition, smoke aerosols, water vapor, and clouds for overall monitoring of the fire process and its effects on ecosystems, the atmosphere, and the climate. The MEDIS fire science team is preparing algorithms that use the thermal signature to separate the fire signal from the background signal. A database of active fire products will be generated and archived at a 1 km resolution and summarized on a grid of 10 km and 0.5 ø, daily, 8 days, and monthly. It includes the fire occurrence and location, the rate of emission of thermal energy from the fire, and a rough estimate of the smoldering/flaming ratio. This information will be used in monitoring the spatial and temporal distribution of fires in different ecosystems, detecting changes in fire distribution and identifying new fire frontiers, wildfires, and changes in the frequency of the fires or their relative strength. We plan to combine the MEDIS fire measurements with a detailed diurnal cycle of the fires from geostationary satellites. Sensitivity studies and analyses of aircraft and satellite data from the Yellowstone wildfire of 1988 and prescribed fires in the Smoke, Clouds, and Radiation (SCAR) aircraft field experiments are used to evaluate and validate the fire algorithms and to establish the relationship between the fire thermal properties, the rate of biomass consumption, and the emissions of aerosol and trace gases from fires.

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The moderate resolution imaging spectroradiometer (MODIS) flown on-board NASA's first earth observing system (EOS) platform, Terra, offers complete global data coverage every 1 -2 days at spatial resolutions of 250, 500, and 1000 m. Its ability to detect emitted radiation in the short (4 Am)-and long (12 Am)-wave infrared regions of the electromagnetic spectrum, combined with the excellent geolocation of the image pixels ( f 200 m), makes it an ideal source of data for automatically detecting and monitoring high-temperature volcanic thermal anomalies. This paper describes the underlying principles of, and results obtained from, just such a system. Our algorithm interrogates the MODIS Level 1B data stream for evidence of high-temperature volcanic features. Once a hotspot has been identified, its details (location, emitted spectral radiance, satellite observational parameters) are written to an ASCII text file and transferred via file transfer protocol (FTP) to the Hawaii Institute of Geophysics and Planetology (HIGP), where the results are posted on the Internet (http:// modis.higp.hawaii.edu). The global distribution of volcanic hotspots can be examined visually at a variety of scales using this website, which also allows easy access to the quantitative data contained in the ASCII files themselves. We outline how the algorithm has proven robust as a hotspot detection tool for a wide range of eruptive styles at both permanently and sporadically active volcanoes including Soufriere Hills (Montserrat), Popocatépetl (Mexico), Bezymianny (Russia), and Merapi (Java), amongst others. We also present case studies of how the system has allowed the onset, development, and cessation of discrete eruptive events to be monitored at Nyamuragira (Congo), Piton de la Fournaise (Réunion Island), and Shiveluch (Russia). D