Synoptic-scale IR (10.7 um) Imagery

This is the 1200 UTC GOES-9 longwave infrared image; it is at the same time, resolution, and projection as the water vapor image seen in the previous example (and available here again for comparison purposes). The longwave infrared channel is centered at 10.7 microns, a wavelength at which none of the earth's atmospheric gases absorb very well. Therefore, this channel will be able to sense the earth's surface and clouds. In this image, note the warm (low), light gray clouds over the Pacific Ocean to the southwest of CA and the Baja Peninsula. These clouds are not seen in the corresponding water vapor image because the middle- and upper-level water vapor is obscuring them.
10.7 um Image

On the other hand, because it is insensitive to atmospheric gases, the 10.7 um image gives no indication of the upper-level shortwave other than the clouds in western CO; the water vapor image, however, shows the shortwave much more clearly.

The color tables applied to these two examples are the same for brightness temperatures below -45.2C. Because there is little water vapor attenuation, even at 6.7 um, at the upper levels of the atmosphere, high, thick clouds will have the same colors in these two channels. An example of this is the thunderstorm in TX.

Thin cirrus clouds will have a different appearance in these two channels since the signal at 10.7 um is warmer than at 6.7um, due to a larger radiance component originating from below the cloud. An example of this can be seen in the clouds over northern Alberta and northern Saskatchewan.

Comparisons between channels can be very important in understanding both the cloud and surface features as sensed by GOES.