Fog Depth Color Enhancement

Forecast Products Development Team (NOAA/NESDIS)

A special fog depth color enhancement based on the temperature difference between GOES IR Band 2 (3.9 m m) and Band 4 (10.7 m m) shows approximate depth of low level clouds and fog. The color steps show increasing cloud depth, from green (0 - 200 m) to black (> 500 m). The cloud depths obtained from this product are valid only for single cloud layers.

Here is a sample fog depth image from GOES-10 for the Southwest United States on 3 April 2001 at 1200 UTC. The thicker cloudiness in the High Plains is upslope stratus.

The graph below shows how the Red-Green Blue (RGB) color intensities vary with input brightness level (counts).

Here is a table showing breakpoint color values for input brightness ranges and IR D T values for Band 4 (10.7 m m) - Band 2 (3.9 m m).

Segment | Input | D T (4-2) | Blue | Green | Red | Feature
1 | 0-100 | -13 to -3 K | 230-80 | 200-80 | 0 | Cirrus
2 | 101-148 | -3 to +2 K | 80 | 80 | 80 | No cloud
3 | 149-158 | 2 to 3 K | 0 | 180 | 0 | Low cloud <200 m
4 | 159-168 | 3 to 4 K | 255 | 0 | 0 | Low cloud 200-300 m
5 | 169-179 | 4 to 5 K | 0 | 0 | 255 | Low cloud 300-400 m
6 | 180-190 | 5 to 6 K | 0 | 255 | 255 | Low cloud 400-500 m
7 | 191-255 | > 6 K | 0 | 0 | 0 | Low cloud >500 m