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You are watching: Describe each of the four mechanisms that cause air to rise


Lifting mechanisms are develops of background that reason air come rise. In this topic we cover orographic lift, frontal lift, convergence, and convective lift.

Why perform I care? Lifting mechanisms are necessary for the development of clouds and also rain (in mix with moisture and instability).

I should already be acquainted with:Fronts,Stability,Convergence and Divergence,Convection

Air have the right to move vertically because that several reasons covered below. The upward motion of air have the right to lead to the development of clouds and precipitation if over there is enough moisture to reach condensation as the air cools while relocating up. In stable conditions, the vertical activity of air will be smooth and also is not likely to cause deep convection favor thunderstorms. However, if stormy air is lifted through one of the instrument below, that can reason the explosive advance of thunderstorms and flooding rains.

Orographic elevator
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number A. Orographic lift.

Orographic lift in the south-east occurs greatly along the Appalachian Mountains. When air moves across the Ohio and also Tennessee valleys, the encounters the Appalachian Mountains. Because the air has actually nowhere come go yet up, it is required up the side of the mountains. As the waiting rises, it starts to cool and condense, and depending on just how moist the wait mass is, showers or thunderstorms might form. ~ the air passes throughout the hill range, it will begin to sink and also dry out, and also in some instances greatly heat the neighboring air. Countless times during the Spring and Fall, squall present or significant weather solution will overcome the Appalachian Mountains and weaken significantly. The Appalachians in a sense act as a barrier against solid storm equipment that head towards the Southeast indigenous the central United States. In Georgia and also Alabama at the south end of the Appalachians, winds native the south are most likely to cause clouds and also rain together the air rises end the southern finish of the mountains, and also the mountainous areas of these states have the highest annual rainfall since of orographically-induced rain.

Frontal Lift

As pointed out in ahead topics, fronts top top weather maps represent the top edge that either heat or cold air. Both type of fronts can carry out lift because that rain showers and also thunderstorms, but they execute not have the same qualities as disputed below.

Cold Fronts

Cold wait is more dense than heat air, and also as a result, it undercuts and also pushes the warmth air vertically front of it together it moves. The steep of the cold air v a cold former is very steep, so the waiting is rapidly moved up and also can sometimes an outcome in strong to significant thunderstorms if ample moisture and also instability space available.

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number B. Cold front advancing. Warm Fronts

At first, it might seem counter-intuitive that warm fronts can administer lift; however, heat fronts can produce widespread precipitation. Unequal a cold front the undercuts the air at the surface, the heat air of a warmth front will climb over the cooler air at the surface due to its lower density. This offers lift because that clouds and showers to type along and ahead the the heat front. The slope of the cold/warm wait in a heat front is no as steep as a cold front. Together a result, thunderstorms are an ext likely to form with cold fronts fairly than heat fronts.

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number C. Heat front advancing. Convergence
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figure D. Converging of air in ~ the surface.

In the center of low press areas, winds converge toward the center of the low because of the results of friction. Due to the fact that the air cannot go down into the earth, it need to rise up. This lift due to convergence leader to the visibility of clouds and also precipitation close to low push centers. The more powerful the convergence, the more powerful the vertical motion and also the an ext clouds and also precipitation are likely to form.

Convective Lift

(Also seeconvection)

When the sunlight heats the ground, the warmed air at the surface will rise under the influence of convection. The increasing thermals are comparable to the hot bubbles of water that increase from the bottom of a cook pot. If the air is stable, climate the balloon of warm air will form scattered fair weather cumulus clouds and also not lot else. If the waiting is unstable, climate the lifting from convection will result in rapid expansion of clouds right into deep cumulonimbus clouds, or thunderstorms. The greater the surface ar temperatures, the more convection can occur.

How go this relate come agriculture?

Precipitation in the south-east is influenced by a variety of lifting mechanisms. In parts of Virginia, phibìc Carolina, southern Carolina, and also Georgia, orographic lift gives rain for the windward slopes that the Appalachian Mountains. Lake Toxaway, one of the rainiest regions in north Carolina, has an yearly average that 80+ customs of rain because that a offered year due to orographic lift. The prevailing winds in that region are largely from the south and also west, and also Lake Toxaway is top top the windward side of the Appalachian mountains, do orographic lift an effective precipitation mechanism.

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number E. Air Converging Inland over Florida. (Image native the American Meteorological Society).

A standard example of air converging and also forming rain showers and thunderstorms is thesea breezein Florida. Throughout the summer, sea breezes will often type on the west and also east sides of Florida. Due to distinctions in temperature between the land (which heats quickly) and the s (which heats up much more slowly) as checked out in number E. Together the two sea breezes relocate landward top top the Florida peninsula, they collide with each other, and also the wait is compelled to relocate upward. Where the two sea breezes collide, over there is regularly intense rainfall and also thunderstorms, and this gives much the the summer rain for numerous parts of Florida.

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Convective elevator is the many common kind of background in the Southeast throughout the summer due to the fact that fronts execute not pass with as regularly as they do during the remainder of the year. If the waiting is moist sufficient (as it typically is throughout the summer), thunderstorms can type and carry out rainfall come crops and plants. Florida regularly sees most of the precipitation throughout the summer months together convective lift (along v the sea breeze) cause thunderstorms to form practically every day.