Experimental DNB Outage Product Following Super Typhoon Haiyan

The beginnings of disaster assessment and recovery are underway across the Philippines following the landfall of Super Typhoon Haiyan late last week.  As the storm approached landfall, several dramatic perspectives were provided from a variety of satellites, including the Japanese Meteorological Agency’s MTSAT (geostationary), NASA’s MODIS instruments, the Tropical Rainfall Measurement Mission, and the Visible Infrared Imager Radiometer Suite (VIIRS) aboard the Suomi National Polar-Orbiting Partnership.  As shown here before, the VIIRS has a unique capability provided by the day night band, which detects light from fires, cities, and reflectance of moonlight when the moon is well-lit and visible in the night sky.  SPoRT continues to explore applications of the day-night band, including quantitative approaches to identifying impacts from major disasters.  By comparing current observations to a trusted baseline, we can attempt to gauge the “percent of normal light” being emitted by a location.  Sudden drops in emitted light from known, populated areas are likely due to damaged infrastructure as long as clouds are not obstructing a view of the surface.  Here are some examples of this approach as applied to the Philippines, using data from November 9 in comparison to the NOAA/NASA “Black Marble” composite of clear sky “average” light emissions.  As the region begins to recover, light emissions can be monitored as a very high-level metric for ascertaining progress.  Similar applications were developed by the SPoRT Center following Superstorm Sandy.

black_marble

NOAA/NASA Black Marble composite of average day-night band emission over the area affected by Super Typhoon Haiyan, with radiance values enhanced to emphasize light emissions. Note that some lights are present in the composite outside of cities, such as  lights from boats over the open water.

after_storm

VIIRS day-night band radiance as observed around 1720 UTC on November 9, with outages apparent along the track of Haiyan when compared against the Black Marble composite. The track of Haiyan is provided by the Joint Typhoon Warning Center.

ir_dnb_outages

Derived “percentage of normal light” based upon comparison of current conditions to the NOAA/NASA Black Marble baseline, with infrared brightness temperatures of clouds also shown to clarify where lost light may be due to passing cloud cover. Areas with significant decreases are highlighted in warm colors (orange to red, with red the most severe) and most of these areas are located along the track of Haiyan. Missing lights over water (believed due to changes in boat locations from the Black Marble) are removed via a land-water mask. This product is experimental.

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