Check it Out! Satellite Instrument Measures Night-time Illumination

The Visible Infrared Imaging Radiometer (VIIRS) instrument that was included in the payload on the Suomi Polar Orbiting satellite launched into orbit in October 2011 has the capability of measuring night-time illumination on the earth's surface.  Depending on the phase of the moon and stray light, the following can be detected by VIIRS at night:

Cities, Smoke, Dush, Ash, Low Clouds, Fog, Fires, Volcanoes (Lava), Auroras, Lightning, Boats

The below image was taken by VIIRS shortly after 2 am CST early Monday morning.  The image clearly shows city illumination and reflectance of the metropolitan areas across the southeastern U.S.  The moon phase at the time was waxing gibbous or increasing.  The moons surface was 95.9% lit, so the moon was nearly full.

Eastern CONUS Satellite Image

Here is a closeup from the above image of the Gulf Coast area south of Louisiana, Mississippi, Alabama and Florida.  Highlighted are boats and oil rigs located east and south of southeast Louisiana.  Lights or gas flares are allowing the oil rigs to be detected by the VIIRS instrument.

Satellite closeup

Below is a closeup of Wisconsin and the adjoining region from the same time.  The 1 am cloud bases, visibility and weather has been overlayed on the VIIRS satellite image.  Cloudy skies were located over much of central and northern Wisconsin at the time.  Some flurries were also falling in the Wausau and Stevens Point areas.

By measuring the illumination and reflectance, the thickness of the clouds can be visually estimated.  Another advantage is the depiction of the sharp edges of the clouds and clear areas.  Essentially, the VIIRS instument is able to give the meteorologist a visible snapshot of the cloud cover AT NIGHT! 

Wisconsin closeup

Unfortunately, the VIIRS images are only available when the Suomi NPP Polar Orbiting Satellite passes over the region of concern, which typically occurs 3-4 times each day.  Moon phase and stray light also can affect the quality of the images. 

More examples of the capabilities of the VIIRS instrument package is available on the Cooperative Institute for Meteorological Satellite Studies (CIMSS) satellite blog located at the following link:

CIMSS is located on the University of Wisconsin - Madison campus.

Marc Kavinsky
National Weather Service - Milwaukee/Sullivan

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