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6

Sea Breezes and Santa Anas

Lecture no. 6 from the course: Meteorology: An Introduction to the Wonders of the Weather

Sea Breezes and Santa Anas

Taught by Professor Robert G. Fovell | 27 min | Categories: The Great Courses Plus Online Science Course

Gain an understanding of how wind works as you explore the way temperature and pressure drive sea breezes during the day and land breezes at night. Then apply these findings to a dramatic wind condition, the famous Santa Ana winds of California.

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p********m
October 17, 2017
I explain this topic to myself more simply. The two primary and opposing forces causing down/up air flow are: (i) GRAVITY, which pulls/compresses air from low-pressure at altitude to high pressure at the earth’s surface, and (ii) CONDUCTION which pushes/decompresses air from high pressure at the surface to low pressure at altitude. The force of gravity is usually stronger than the force of conduction, but when the earth/ocean surface heats up significantly, then the upward decompression force of conduction may overcome the downward compression force of gravity, resulting in the classic phrase: ‘warm air rises’. But, the rest of the time, cold air is sinking. There are also sidewards flows (advection) when warm & cold air mix due to rotation and topography of the earth, but that’s another topic. ‘Dry adiabatic’ is more easily explained as ‘compression heating’ and ‘decompression cooling’. This also helps to explain ‘thermally in/direct”. Thus, the all-important diagrams of air circulation should show: (i) warm air at surface (red) rising to cool air at altitude (light blue) due to decompression and distance from warm surface of earth/ocean, then (ii) cool air at altitude (light blue) becoming cold (dark blue) as it transits across high altitude, then (iii) cold air at altitude (dark blue) sinking to become cool at surface (light blue) due to warming by compression and surface heating, then (iv) cool air at surface (light blue) becoming warm (red) as it transits across the warm earth/ocean surface. The existing soup illustration is helpful and clear. The personal story of Santa-Ana-triggered fire is relevantly compelling, but the explanation could be clearer with an additional stylised diagram of cold Mojave desert air transiting to LA border range, followed by katabatic compression into LA basin. If increased pressure always increases temperature, then the funnelling effect through water-gaps in mountain range must cause some additional temperature increase.

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s********m
April 2, 2017

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t********g
September 6, 2015
I love how much I've learned already! I suggest to those saying this is dense material: don't binge watch these. Treat them as what they are! They're college-level course lectures, and your brain needs a break in between.

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