VIIRS Day-Night Band (DNB) RGB Imagery assisted by Nighttime Microphysics RGB

VIIRS_dnbref_rgb_CO_snowvscloud_19Feb2014_0905_annotated

VIIRS DNB Reflectance RGB within AWIPS/D2d for 17 February 2014 at 0905 UTC over the Colorado, Wyoming, Nebraska, Kansas region

The VIIRS Day-Night Band (DNB) RGB imagery from SPoRT uses the DNB channel for both the red and the green components of the RGB, and then the single channel 11 micron band for the blue component.  So warm, reflective clouds have both red and green and result in a shade of yellow while cold, reflective clouds appear in shades of blue to white.  The image above from 17-February-2014 has a mixture of yellow, blue, and white objects, but the question is: Are all of these areas clouds?  Some of the city lights appear to be distinct, sharp yellow points on the ground with little diffusion of light through clouds even though they are surrounded by shades of yellow.  Notice the area at the intersection of the CO, WY, and NE borders as well as some of the inter-mountain regions of western Colorado and how the city lights in these regions are not blocked, nor spread over a large area due to scattering by the clouds.

VIIRS_ntmicro_rgb_CO_snowvscloud_19Feb2014_0905_annotated

VIIRS Nighttime Microphysics RGB within AWIPS/D2d for 17 February 2014 at 0905 UTC over the Colorado, Wyoming, Nebraska, Kansas region

The Nighttime Microphysics RGB imagery from VIIRS is provided above as a comparison to the DNB.  Using this RGB one can identify areas of clouds and their type.  Several of the areas in question turn out to be surface features as opposed to clouds.  This realization that clouds do not exist in some of the yellow shaded areas of the DNB as well as the fact that city lights are not scattered in these regions, leads one to conclude that the DNB is showing snow on the ground.  Several areas are labeled as “Snow Cover”.  However, note that some clouds do exist.  In fact some low clouds in the inter-mountain west of Colorado are evident in yellowish-green tones, and low- and mid-level clouds are highlighted in northwest Kansas and northeastern Colorado.  The Nighttime Microphysics RGB also hints at the potential of fog in southeast Colorado with dull gray to shades of aqua.  Perhaps snow cover has melted to some extent to provide a moist ground with clear skies overnight that resulted in some very thin, to scattered fog or low clouds. Below are images of the same time but over a wider area in order to provide greater perspective.  Note that much of the yellow shaded areas in the DNB RGB are the result of snow cover vs low cloud features.  Hence VIIRS demonstrates valuable insight to both clouds and surface features at night via reflected moonlight.

VIIRS_dnbref_rgb_CO_snowvscloud_19Feb2014_0905_wideview

VIIRS DNB RGB within AWIPS/D2d for 17 February 2014 at 0905 UTC over the western U.S.

VIIRS_ntmicro_rgb_CO_snowvscloud_19Feb2014_0905_wideview

VIIRS Nighttime Microphysics RGB within AWIPS/D2d for 17 February 2014 at 0905 UTC over the western U.S.

One thought on “VIIRS Day-Night Band (DNB) RGB Imagery assisted by Nighttime Microphysics RGB

  1. Thanks for posting Kevin! This is a great example of the use of multiple types of imagery for our users. A good AWIPS procedure for identifying nighttime fog/low clouds/snow could utilize both of these sets of imagery, perhaps with a standard 11-3.9 image as well, since A2 will allow for more than 2 images. I noticed the advantage of the DNB in showing some lower features (probably snow) beneath the high thin cirrus over southern Idaho.

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