NOAA-NESDIS
Regional And Mesoscale Meteorology Team
Daily Satellite Discussion
Monday April 6, 1998
Today's picture of the day introduces a new visible imagery enhancement scheme, and compares it with more traditional enhancements.
Fig. 1 (NOAA GOES-8 Visible, default enhancement)

click picture to enlarge

Figure 1 shows a visible image with the default enhancement, Figure 2 shows the same image after applying a linear stretch to the visible brightness counts. Figure 3 again shows the same image, but with the new enhancement scheme.

Figure 2
Fig. 2 (NOAA GOES-8 Visible, linearly stretched)
(click to enlarge)
Figure 3
Fig. 3 (NOAA GOES-8 Visible, new enhancement)
(click to enlarge)

In Figure 3, the visible image was divided into two parts, one which contains those pixels with a 10.7 um brightness temperature less than -30.2 C, and the other which contains those pixels with a 10.7 um brightness temperature greater than -30.2 C. These two partial visible images were then stretched independently and put back together to create the final image. The 'blockiness' seen on the edge of the thunderstorm anvils is due to the 10.7 um image, normally at 4 km resolution, having to be magnified to 1 km to match the visible resolution.
The idea behind this method is to be able to enhance both the low, warm clouds and the high, cold clouds at the same time. As can be seen, the contrast for both the low clouds and ground as well as the thunderstorm tops is best with this enhancement. The 'blockiness' around the thunderstorm tops, however, is a concern. Figures 4, 5, and 6 are low light examples of the three enhancements. Also, side by side comparisions can be viewed with the three loops. Loop 1 compares the default enhancement with the dual enhancement, Loop 2 compares the default enhancement with the single stretch enhancement, and Loop 3 compares the single stretch enhancement with the dual enhancement.
Figure 4
Fig. 4 (NOAA GOES-8 Visible, default enhancement)

click picture to enlarge


Figure 5
Fig. 5 (NOAA GOES-8 Visible, linearly stretched)
(click to enlarge)
Figure 6
Fig. 6 (NOAA GOES-8 Visible, new enhancement)
(click to enlarge)
I would like feedback concerning this new enhancement compared to the others, as it may be placed on the RAMSDIS 1 km visible loops. So please email me with your opinions, both positive and negative, or if you would like to see further examples.


Jack Dostalek
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