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Low-Cloud/Fog Imagery - Basic Information

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Figure 1. Example of the Low-Cloud/Fog image product during the daytime over the western United States. The product depicts low clouds (when present) in white, thick high clouds in bright colors, land and water surfaces as gray, and snow and forested areas as dark gray. Thin cirrus also appears white in this daytime image, but at night thin cirrus appears black, as in Figure 2.

Who is developing and distributing this product?

The Cooperative Institute for Research in the Atmosphere (CIRA) in Fort Collins, Colorado, together with the NOAA/NESDIS RAMM Branch is developing and distributing the Low-Cloud/Fog Product.

Who is receiving this product, and how?

The Low-Cloud/Fog product is created at CIRA, and is sent to NWS Central Headquarters, and then distributed to the WFO's as a product on their AWIPS.

Figure 2. Example of the Low-Cloud/Fog image product at night over the western United States, a few hours earlier than the image in Figure 1. The product depicts low clouds (when present) in white, thick high clouds in bright colors, and land and water surfaces as gray, and snow and forested areas as dark gray. Unlike the daytime version of this product, thin cirrus appears black at night.

What is the product size?

The size of one east or west Low-Cloud/Fog image is 20 MB, with updates available every 30 minutes.

Purpose of this product.

The Low-Cloud/Fog satellite imagery product, developed at CIRA, is demonstrated on the RAMSDIS Online web page for both GOES-West and GOES-East. The product displays standard GOES Imager data in a unique way using a simple algorithm, producing a similar product day or night except for the white/black appearance for thin cirrus during the day/night. Inputs are the 3.9um (shortwave) and 10.7 um (longwave) infrared window bands from the GOES Imager.

Why is this a GOES-R Proving Ground Product?

The Low-Cloud/Fog product demonstrates a unique kind of imagery that is already available, but is under-utilized, as well as a continuing product in the GOES-R era. GOES-R will feature the Advanced Baseline Imager (ABI) sensor which will be able to produce both a higher spatial resolution (2 km) and higher temporal resolution (5 min) version of the Low-Cloud/Fog product.

How is this product created now?

Here is a brief description of how the Low-Cloud/Fog product is created from GOES Imager data:

The Low-Cloud/Fog product can be computed from two (longwave and shortwave) infrared window bands available on nearly all operational geostationary and polar-orbiting satellites, such as GOES, MODIS, etc...

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Product Examples and Interpretation.

Figures 3 and 4 are further examples of the Low-Cloud/Fog product, but for the eastern U.S.

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Figure 3. Example of the Low-Cloud/Fog image product during the daytime over the eastern United States. Note the thick high clouds, presented in bright colors, along the front stretching across the Ohio Valley, surrounded by some lower clouds in white. Other areas where low clouds are apparent are the panhandle of Texas and over the Great Lakes region. Other cloudy areas that are not either bright white or colored are mixed-phase middle-level clouds. The darkest parts of the product are typically forested land or open water surfaces, or they could be snow-covered ground. For an earlier nighttime image, see Figure 4.

Figure 4. An example of the Low-Cloud/Fog image product at night over the eastern United States, a few hours earlier than the image in Figure 3. Here the thick frontal clouds are again brightly colored, but are surrounded by low clouds in white and thin cirrus in black. The thickest low clouds are mainly found in parts of Florida, southern Texas, and in the Great Lakes states/provinces.

Advantages and Limitations.

The Low-Cloud/Fog product provides a simple yet visually powerful display of different types of clouds. The color enhancement clearly shows higher, colder clouds as distinct from lower clouds, which appear white. Low clouds are clearly differentiated from snow, which appears dark due to its low reflectivity in the shortwave region.

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