What is a Santa Ana wind? What causes it and why is the wind so fast and dry?

Answer 1

A Santa Ana wind is a downslope wind that affects southern California, especially the greater Los Angeles basin. Downslope winds are warmed adiabatically, meaning that they derive their warmth from being compressed during descent from the high deserts to the northeast to the low coastal plain. They are very dry for similar reasons - the air is moving from the deserts which are already quite dry, and their relative humidity is decreased further during the descent which, as mentioned earlier, warms the air mass.

Downslope winds are often quite fast because the weather systems that create them have high pressure gradients, or differences between high and low. The affected areas are in the middle of that difference, and so air is moving quickly between high and low. Perhaps more importantly, however, downslope winds are fast because air moving down mountainous terrain is accelerating, and there are other hydrodynamic effects which cause localized areas to experience extremely fast winds.

Think of the eddies in water moving down a creek past rocks in the stream. In our atmosphere, the mountains are like those rocks, and the wind like the water. If you were a small critter in the water you'd experience occasional 'gusts' of water (wind) from those eddies - a Santa Ana wind (as well as other named downslope winds around the world, like the Chinook of Colorado or the foehn of the Alps) is a bit like that.

Oh, and I agree that cutting and pasting articles is lazy. At least try to put it in your own words.

Answer 2

Santa Anas are a type of föhn wind, the result of air pressure buildup in the high-altitude Great Basin between the Sierra Nevada and the Rocky Mountains. This air mass spills out of the Great Basin and is pulled by gravity into the surrounding lowlands. The air circulates clockwise around the high pressure area bringing winds from the east and northeast to Southern California (the reverse of the westerly winds characteristic of the latitude).

It is often said that the air is heated and dried as it passes through the Mojave and Sonoran Deserts, but according to meteorologists this is a popular misconception. The Santa Ana winds usually form during autumn and early spring when the desert is relatively cold, although they may form at virtually any time of year. The air heats up due to adiabatic heating while being compressed during its descent. While the air has already been dried by orographic lift prior to reaching the Great Basin, the relative humidity of the air declines rapidly as it descends and warms in its final stages as it passes over the Transverse and Peninsular Ranges.

The air is then forced down the mountain slopes out towards the Pacific coast; the air mass is further heated by compression as it drops in altitude before reaching the Los Angeles Basin western San Diego County and Tijuana (Baja California) at typical speeds of 35 knots. The southern California coastal region gets its hottest weather of the year during autumn while Santa Ana winds are blowing. During Santa Ana conditions it is typically hotter along the coast than in the deserts and the humidity plummets to less than 15%.

Answer 3

Santa Anas are a type of föhn wind, the result of air pressure buildup in the high-altitude Great Basin between the Sierra Nevada and the Rocky Mountains. This air mass spills out of the Great Basin and is pulled by gravity into the surrounding lowlands. The air circulates clockwise around the high pressure area bringing winds from the east and northeast to Southern California (the reverse of the westerly winds characteristic of the latitude).

It is often said that the air is heated and dried as it passes through the Mojave and Sonoran Deserts, but according to meteorologists this is a popular misconception. The Santa Ana winds usually form during autumn and early spring when the desert is relatively cold, although they may form at virtually any time of year. The air heats up due to adiabatic heating while being compressed during its descent. While the air has already been dried by orographic lift prior to reaching the Great Basin, the relative humidity of the air declines rapidly as it descends and warms in its final stages as it passes over the Transverse and Peninsular Ranges.

The air is then forced down the mountain slopes out towards the Pacific coast; the air mass is further heated by compression as it drops in altitude before reaching the Los Angeles Basin western San Diego County and Tijuana (Baja California) at typical speeds of 35 knots. The southern California coastal region gets its hottest weather of the year during autumn while Santa Ana winds are blowing. During Santa Ana conditions it is typically hotter along the coast than in the deserts and the humidity plummets to less than 15%.


QuikSCAT image showing the speed of the Santa Ana winds (m/s).As the Santa Ana winds are channeled through the mountain passes they can approach hurricane force. The combination of wind, heat, and dryness turns the chaparral into explosive fuel for the infamous wildfires the region is known for. Wildfires fanned by Santa Ana winds burned 721,791 acres (2,921 km²) in two weeks during October 2003.

Although the winds often have a destructive nature, they have some positive benefits as well. They cause cold water to rise from the bottom of the ocean to the top, bringing with it many nutrients that ultimately benefit local fisheries. As the winds blow over the ocean, sea surface temperatures drop about 4 °C (7 °F), indicating an upwelling of deep ocean water. Chlorophyll concentrations in the surface water go from negligible, in the absence of winds, to very active at more than 1.5 milligrams per cubic meter in the presence of the winds.

Answer 4

Not as complete, but the short version:
Fast..because of gravity

Dry..because the air mass has passed over the mountain and lost all it's water content in orographic rain, Santa Ana is in the rainshadow.

Warm: because pressure at sealevel is higher than in the mountains..so as the air falls the particles are squeezed back together and hit each other creating heat (adiabatic heating)

Answer 5

Sorry, I always give a thumbs down to people who simply quote entire Wikipedia articles. Not this this article is wrong, but it's the ultimate in laziness.

Edit: Oh sheesh...now two people have quoted the SAME wikipedia article. That's not only lazy, it's just plain stupid.