A Winter Storm delivered snow across a large swath of the US during Thanksgiving weekend. Clearing behind the system revealed the fresh snowfall. As has been discussed in previous blog posts, the increased spectral resolution of the ABI compared to previous GOES Imagers makes it easier to identify/differentiate surface and atmospheric features. By combining multiple channels into channel differences and RGB’s, it makes the job of the forecaster even easier to analyze these complicated scenes.
The scene across the central US behind the system included bare ground, lakes, fresh snow, water clouds and ice clouds. The latter three features are all highly reflective and difficult to differentiate in visible imagery (Fig 1).
By combining the visible channel with the 1.61 um snow/ice near IR channel and the 10.3 um IR window channel, we have one image that contrasts those features while maintaining the 0.5 km high resolution of the VIS (Fig 2). This combination is known as the Day Cloud Phase Distinction RGB. In this example, the max bounds of the green and blue components were lowered to 50 and 40, respectively, while the min red component was decreased to 0. These changes were made in order to best highlight the features I was interested in for this situation (snow vs low clouds vs high clouds in a cold airmass). Bare ground is blue, water bodies are very dark blue to black, snow is green, water clouds are light blue/green, ice clouds are red.
Bill Line, NWS