Snow Storm of 1997
GOES Simulation
Since the GOES Bands 1, 2, 4 and 5 are similar to the AVHRR Bands 1, 3, 4 and 5 we can actually use data from the AVHRR sensor to see what the results of the snowstorm would have looked like from a GOES orbiting the Earth at 90 deg west longitude!
We only need to use three of the four bands of similar data since the AVHRR Bands 4 and 5 show similar features.
Here are examples of AVHRR Bands 1, 3 and 5 as they simulate GOES Bands 1, 2 and 5.
As you can see, the snow cover shown in AVHRR Band 1 (GOES Band 1)
cannot be easily distinguished from some of the clouds in the scene. Also, because
of the high reflectance, one cannot see much detail in the left side of the image.
In contrast, the other two bands both allow for increased discrimination between snow and
clouds. This is because they are thermal bands and are representing the different
temperatures of the snow and cloud surfaces. The clouds are colder than the snow
cover and thus appear as white features, while the warmer snow appears as gray-toned
features. The difference between the two thermal bands is that AVHRR Band 3 (GOES
Band 2) sensitive is more sensitive to higher temperatures, this causes snow to possess
greater contrast relative to the warmer ground. This same feature causes details in
the cloud structures to be lost.
However, in the context of snow identification, AVHRR Band 3
(GOES Band 2) appears to be able to delineate snow from clouds very well.
It is regretable that this type of information is not used more often.
However, if you would like to take a look at some GOES data, try the NASA website at ftp://rsd.gsfc.nasa.gov/pub/Weather/. It is a great source of GOES-8 and GOES-9 data!
