Super-cooled Clouds (2 of 3)

Because it distinguishes water clouds from ice clouds, regardless of temperature, the "fog product" can aid in the detection of supercooled water clouds at night, when used in combination with other data. This is done by locating the water cloud area within the "fog product", and then using the 10.7 um data, along with a representative rawindsonde or model sounding, to determine if cloud top temperatures and atmospheric vertical structure are within appropriate boundaries for supercooled water clouds.

An example is the fog product image (at top left) from 0345 UTC, on 9 Jan 1996. The bright regions are water clouds, while the noisy and darker regions are ice clouds. The area around Buffalo, NY (BUF) is covered by water clouds. The corresponding 10.7 um image (top right) shows the brightness temperature of those water clouds to be near -12 C. Similar cloud top and ground temperatures make it difficult to locate the cloudy area using the 10.7 um imagery alone. The 00 UTC sounding, from Buffalo on the 9th, shows a near-isothermal cloud deck just below 700 mb (hPa), with a temperature near -10 C. The entire water cloud region shown in this image must almost certainly be supercooled.

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