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 mm) and Band 4 (10.7 mm) 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.

Fog Depth example

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

Graph of fog depth enhancement

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

Segment
Input
DT (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

For further information please contact: Gary Ellrod