fog caused by nocturnal radiational cooling of the Earth's surface, which in turn cools the adjacent air to a degree sufficient to cause condensation of the water vapour within the air
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Valdkond ICAO lisade põhjal loodud klassifikaatori järgi: Lennumeteoroloogia
Radiatsiooni-ehk jahtumisudu on üks udu liikidest. See tekib (tugeva) jahtumise tagajärjel. ... Radiatsiooniudu tekkeks on vaja selget või väheste ülemiste pilvedega ilma. Seejuures peab olema tuul väga nõrk (enamasti mitte üle 3-4 m/s) või valitsema tuulevaikus. Soodustavaks asjaoluks on eelnenud sademete olemasolu, mis tõstavad õhu veeauruga küllastatusastet.
On clear nights, with relatively little to no wind present, radiation fog may develop. ... Usually, it forms in low-lying areas like mountain valleys. This type of fog occurs when the ground cools rapidly due to terrestrial radiation, and the surrounding air temperature reaches its dew point. As the sun rises and the temperature increases, radiation fog lifts and eventually burns off. Any increase in wind also speeds the dissipation of radiation fog. If radiation fog is less than 20 feet thick, it is known as ground fog.
