GOES-R Proving Ground At the Great Lakes
Louie Grasso, Dan Lindsey, J. Braun
GOES-R ABI will have several channels in the window region from which channel difference products can be produced. Three of the channels, 8.53, 11.02, and 12.03 µm are available from MODIS. From these three channels, three channel differences can be produced. In this example, one of the channel differences highlights lake ice more effectively than any of the three separate channels and the other two channel differences. Figures 1 through 3 (click for larger images) show MODIS images at 8.53, 11.02, and 12.03 for 19 February 2010.
In the 8.53 – 11.02 difference (Figure 4) lake ice shows up as blue against the green background of open water and the blue surrounding land mass (see white circles). The contrast between the ice and surrounding land mass is relatively small in these locations. Further, the sign of the channel difference (negative) is the same for ice, land, and open water in this image. A somewhat different pattern appears in the 11.02 – 12.03 difference (Figure 5). The ice has a channel difference that is of the opposite sign as the land mass and a different enough color contrast. However, differences between the ice and open water are of the same sign and small enough that contrast differences are relatively small. Finally, the 8.53 – 12.03 difference (Figure 6) exhibits ice that has a channel difference that is of the opposite sign compared to the surrounding land and open water. Furthermore, the color of the ice is a sharp contrast to the color of the surrounding land and open water. Thus, this example illustrates the usefulness of channel differencing in the identification of lake ice.