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Surface Standing Water Algorithm Overview

Floods are usually disastrous events occurring in short period of time. Satellite-derived flood maps in near-real time are invaluable to stake holders and policy makers for disaster monitoring and relief efforts. Precise mapping of the floods/standing water is also required for detecting deficiencies in existing flood control and for damage claims afterwards.

The sensors used in river/flood studies may be classified into two types: (1) passive, in which the sensor receives energy naturally reflected by or emitted from the earth's surface; and (2) active, in which the sensor provides its own illumination and records the amount of incident energy returned from the imaged surface (Smith, 1997). Passive sensors include all of the visible and infrared instruments such as the Landsat Thematic Mapper (TM) and Multi-Spectral Scanner (MSS), the Advanced Very High Resolution Radiometer (AVHRR), the Satellite Pour l'Observation de la Terre (SPOT) and the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), Moderate-Resolution Imaging Spectroradiometer (MODIS) and Landsat-7 sensors. The Advanced Baseline Imager (ABI) onboard future GOES-R belongs to this type of sensor.

Passive microwave radiometers such as the Special Sensor Microwave/Imager (SSM/I) can penetrate clouds and measure the amount of microwave energy naturally emitted from the Earth's surface. However, the poor spatial resolution of spaceborne microwave radiometers (ca. 27 km at 37 GHz) limits their use to very large areas. The potential of GOES-R ABI data in large area flood monitoring should not be ignored. Although the ABI offers coarser spatial resolution than many polar-orbiting sensors such as MODIS and LANDSAT, the high temporal resolution of geostationary satellites (5 minutes for the ABI), make them very useful for dynamic monitoring of flood events, because they usually occur quickly in short period of time. Compared to the previous GOES series, the new near-infrared channel 3 (0.86 ?m) of the GOES-R ABI makes it suitable to monitor Standing Water/Floods. In the age of climate change, severe floods appear to be occurring more frequently than before. This makes the GOES-R ABI observations more attractive in dynamic flood monitoring.

A primary objective of the GOES-R Standing Water/Flood development team is to provide a state-of-the-art Water Fraction algorithm that meets the GOES-R mission requirement.

Finally, algorithm simplicity and robustness is also a concern in order to produce the Water Fraction product every fifteen minutes which is the goal of ABI Water Fraction product refresh rate.