14 April 2012 - Simulated Band Difference

Part of the NSSL-WRF simulated satellite imagery that we get from CIRA includes a band difference unique to GOES-R that we began looking at during last year's Spring Experiment. One of the advantages of simulating satellite data from a model is that we have the opportunity to produce channels that we don't have currently, and we take full advantage of this by producing all 9 of the non-solar GOES-R IR bands. The 10.35 micron channel is a very clean window, and thus is very sensitive to surface temperature. The 12.3 micron channel however is sensitive to low- and mid-level water vapor. As moisture moves into a clear pixel area, the 12.3 micron brightness temperature will decrease, whereas the 10.35 micron temperature should stay the same. When this occurs, the 10.35-12.3 micron channel difference will become strongly positive and indicates areas of moisture convergence or pooling, which can lead to destabilization and subsequent convective initiation.
Unfortunately, because the imagery is generated by a numerical model, it is a) not an observation and b) only available on an hourly timescale. However, we can use the imagery generated from the model as a experimental tool to demonstrate some of the unique things we can do once we have the increased spectral resolution of the GOES-R Advanced Baseline Imager (ABI). In this example from the 14 April 2012 outbreak the 10.35-12.3 micron channel difference is useful in identifying the evolution of the dryline across western KS, OK and TX from 1900 UTC on the 14th to 0100 on the 15th (see images below). As moisture converges at the surface, the difference becomes more positive. These positive values show up as yellow, orange and red on the images below. The edge of the dryline is easy to detect and follow using this simple band difference within the NSSL-WRF. It will be very interesting to see observations of this band difference, and other imagery techniques such as RGBs, every 5 minutes over the continental US once we have the GOES-R ABI available to us.