https://peertube.dngr.us/videos/watch/00745000-53ca-4a17-ba6e-d31eb78b9e24 Part of a series of color, animated aerology films produced for the U.S. Navy in World War II, "The Theory of Fog Formation" (1943) was made for trainee pilots, with an aim to improve their understanding of fog and safe flight through it. After outlining the theory of fog formation, the film overviews various types of fog and how each one impacts air travel. It also reviews the combined effects of air temperature and wind. The film concludes with an anecdote about a bomber plane mission. The other films in this seven film series discuss such subjects as ice formation on aircraft, warm and cold fronts and the serious weather associated with each, cloud formations, and flight planning through and around weather conditions. Fog is a form of moisture near the Earth's surface that reduces visibility and can be hazardous, especially during takeoffs and landings. It forms when the air temperature cools to the dew point, causing moisture to condense. There are two main types: ground fog, which develops on clear, cool nights with light winds and high moisture, often in valleys or polluted areas; and advection fog, which covers larger areas when warm, moist air moves over cooler surfaces, commonly near coastlines and over the sea. Fog can form rapidly and is difficult to predict, making it crucial for pilots to plan alternate airports and carry sufficient fuel. Failure to recognize fog conditions, especially near coasts, has historically led to serious flight accidents. 0:00 – Fog is moisture in visible form that lies close to the Earth’s surface, reducing visibility to near zero. 0:44 – From above, fog looks like a low sheet of clouds, making it hard to distinguish from cloud ceilings. 1:05 – Modern navigation aids make fog less of a concern en route, but fog at airports makes takeoffs and landings hazardous. 1:37 – Fog forms rapidly, is hard to forecast, and poses an unexpected hazard; pilots should always have alternate airports planned. 2:12 – Air contains moisture as invisible vapor that condenses into visible moisture (fog) when cooled to the dew point. 3:33 – The difference between air temperature and dew point (spread) is key to fog prediction: smaller spreads mean higher fog formation chances. 4:33 – Lowering air temperature by contact cooling is the main process causing fog formation; moisture increase is usually negligible. 5:10 – Fog is classified mainly into ground fog and advection fog. 5:30 – During clear nights, land cools quickly, and if land temperature drops to the dew point, ground fog forms. 6:44 – Ground fog forms best on clear, cool nights with high moisture and light winds. 7:34 – Cloudy nights keep the ground warm, preventing the temperature from dropping enough to form fog. 8:49 – High moisture content (e.g., after rain or near water bodies) increases fog likelihood by reducing temperature-dew point spread. 9:10 – Light winds can intensify ground fog by distributing cold air to higher levels, deepening the fog. 10:30 – Winds over 5-8 knots mix the air too much, preventing sufficient cooling and fog formation. 11:22 – Ground fog is more frequent in lowlands and industrial areas due to cooling air drainage and smoke particles aiding droplet formation. 12:12 – Ground fog usually forms early morning, reaches maximum density around daybreak, and clears 2-4 hours after sunrise. 13:27 – Advection fog covers wide areas, forms over land and sea, when warm air moves over colder surfaces and cools to dew point. 14:25 – Coastal regions often experience advection fog due to contrasting land and water temperatures. 15:53 – In winter, warm moist air from the Gulf of Mexico causes widespread advection fog in the eastern US. 16:10 – When water is colder than land with offshore winds, fog forms over water and extends out to sea. 16:48 – Fog forms over open sea when warm air moves over colder water currents; common near Newfoundland and Aleutian Islands. 18:00 – Advection fog severely impairs flight operations, especially in widespread coastal and sea areas. 18:24 – Over land, advection fog thins during the day due to solar heating unless a cloud deck keeps it dense. 19:27 – Over the sea, advection fog thickness remains constant day and night due to stable water temperatures. 20:35 – A WWII-style case study: a squadron encountered coastal fog after mission completion; poor weather recognition led to 17 planes lost and 2 deaths. 22:19 – The accident resulted from failure to recognize offshore fog and onshore breeze conditions that typically cause coastal fog after sunset. 23:02 – Pilots should always study weather carefully before flights, especially fog factors, and plan alternate airports with enough fuel. This film is part of the Periscope Film LLC archive, one of the largest historic military, transportation, and aviation stock footage collections in the USA. Entirely film backed, this material is available for licensing in 24p HD, 2k and 4k. For more information visit http://www.PeriscopeFilm.com Source: https://www.youtube.com/watch?v=yhEP4t8TrpA Mirrored from Periscope Film (https://www.youtube.com/@PeriscopeFilm) Sat, 13 Jun 2026 12:57:55 GMT https://validator.w3.org/feed/docs/rss2.html PeerTube - https://peertube.dngr.us https://peertube.dngr.us/lazy-static/avatars/41a6fee9-7f57-42d0-a5fc-5db4f1af2e31.png https://peertube.dngr.us/videos/watch/00745000-53ca-4a17-ba6e-d31eb78b9e24 All rights reserved, unless otherwise specified in the terms specified at https://peertube.dngr.us/about and potential licenses granted by each content's rightholder.