WFO Raleigh, NC (RAH) has been collaborating with the NASA/MSFC’s Short-term Prediction Research and Transition (SPoRT) team and 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 image below is the Night-Time Microphysics RGB satellite product from 0713 UTC 08 January 2013 along with the 0700 UTC surface ceiling and visibility plot across the Carolinas and Virginia as displayed in the RAH AWIPS D2D. This image shows an area of stratus clouds across southern North Carolina and eastern South Carolina along with a few wisps of cirrus clouds in northeastern North Carolina and southeastern Virginia.
If you examine the shading of the stratus clouds across the Carolinas closely, you will notice a difference in the shading with the stratus in southern North Carolina with VFR ceilings of 4,500-6,000 feet and the stratus in South Carolina with VFR/near MVFR ceilings of around 3,000-3,500 feet. The VFR/near MVFR ceilings are shaded with an aqua enhancement while the higher clouds with VFR ceilings has more of a brighter tan shading. This is consistent with the color curve structure and interpretation noted in a previous blog post highlighting the NTM RGB product in this same region.
One of the questions I often hear from forecasters about this product is “what is the added value?” While this may not be a Cadillac example, the four panel image below from the same time with the Night-Time Microphysics RGB satellite product in the upper left, the traditional 11-micron IR image in the upper right, and the 11-3.9 micron product in the lower left highlights some of the additional information the NTM RGB product provides. The stratus is barely visible in the traditional 11-micron IR image. While the 11-3.9 micron product highlights the presence of stratus, the clouds bases and potential categorical difference in the aviation conditions cannot be ascertained.