WFO Raleigh, NC (RAH) has been collaborating with the NASA/MSFC’s Short-term Prediction Research and Transition (SPoRT) project to evaluate several unique NASA research satellite products or displays during the past year or two. This fall we have been evaluating the Night-time Microphysics RGB product from VIIRS and MODIS for use with observing fog and low clouds.
The Night-time Microphysics RGB imagery uses the common IR spectral difference for fog/low cloud detection as well as inputs related to optical thickness and the cloud’s thermal property in order to help differentiate low clouds and near-surface fog. The SPoRT folks have setup a SPoRT Real-time Data Fog and Low Cloud web page.
The RGB product includes 3 inputs and requires some skill to interpret the products correctly. The three inputs included in the product are 1) the optical depth 2) particle phase size and 3) the temperature of the surface. The table below breaks down the 3 inputs and provides insight into how to interpret the image and discern regions of fog, stratus, and other clouds using blends of these colors.
The image below is the Night-time Microphysics RGB satellite product from 0643 UTC 28 November 2012 along with the 0700 UTC surface ceiling and visibility plot across the Mid-Atlantic and Southeast as displayed in the RAH AWIPS D2D. This image shows multiple cloud features across the region and provides an example of the enhanced information the Night-time Microphysics RGB imagery can provide forecasters. The regions that are highlighted and numbered are described in further detail below the image.
1) Shallow fog with reduced visibilities and no ceilings is indicated in south-central VA area as noted by the purple enhancement. The purple results from lesser amounts of red (thin clouds), lesser amounts of green (mix of fog/ground emissions), larger amounts of blue (warmer clouds)
2) Fog with probable IFR ceilings and IFR visibilities is indicated southwest of the Savannah GA area as noted by the aqua/light blue enhancement. The aqua/light blue results from moderate amounts of red (medium thickness), lesser amounts of green, moderate amounts of blue (warmer clouds).
3) Stratus with IFR/MVFR ceilings and some fog with VFR visibilities are indicated near and southwest of Roanoke VA as noted in the bright aqua enhancement. The bright aqua color results from lesser amounts of red (medium thickness), larger amounts of green, moderate amounts of blue (warmer clouds).
4) Mixed low and mid-level clouds with some thickness is indicated in an axis from near Lynchburg VA to near Greensboro NC as noted in the tan colored enhancement. The tan color results from larger amounts of red (thicker clouds), lesser amounts of green (mixed particle size), and lesser amounts of blue (colder and taller clouds).
5) High level thick clouds are indicated in a large area to the southeast of Cape Hatters as noted in the dark red enhancement. The dark red color results from larger amounts of red (thicker clouds), lesser amounts of green, and lesser amounts of blue (cold and high clouds).
6) Pockets of high level thin clouds are indicated in areas off of the NC and VA coast as noted in patches of dark blue and dark purple. The dark blue and dark purple enhancement results from lesser amounts of red (thin clouds), lesser amounts of green and larger amounts of blue (cold and high clouds).
7) Warm bodies of water associated with Kerr Lake and Lake Gaston near the VA/NC border are associated with warmer temperatures (larger amounts of blue) than the adjacent land surface emissions.