High and low pressure - Eniscuola
Moving masses of air · The Coriolis effect · High and low pressure · When air masses meet When a moving cold air mass meets a warm air mass, that is lighter, it tends to in the pressure and precipitations often characterized by thunderstorms. forcing all the warm air to rise to higher altitudes and the cold air is stratified. Air flowing from areas of high pressure to low pressure creates winds. . of Mexico and the Gulf of California meets air that has been heated by scorching desert. Places where air pressure is high are called high pressure systems. A low Winds blow towards the low pressure, and the air rises in the atmosphere where they meet. Winds of a high pressure system swirl in the opposite direction as a low.
Land and sea breezes are very important because they moderate coastal climates. In the hot summer, sea breezes cool the coastal area. In the cold winter, land breezes blow cold air seaward. These breezes moderate coastal temperatures. Land and sea breezes create the pleasant climate for which Southern California is known.
Monsoon Winds[ edit ] Monsoon winds are larger scale versions of land and sea breezes; they blow from the sea onto the land in summer and from the land onto the sea in winter. Monsoon winds are incredibly strong because they occur in coastal areas with extremely high summer temperatures. Monsoons are common wherever very hot summer lands are next to the sea. The southwestern United States has summer monsoon rains when relatively cool moist air sucked in from the Gulf of Mexico and the Gulf of California meets air that has been heated by scorching desert temperatures Figure The Arizona summer monsoon.
The most important monsoon in the world occurs each year over the Indian subcontinent. More than two billion residents of India and southeastern Asia depend on monsoon rains for their drinking and irrigation water. In the summer, air over the Indian subcontinent becomes extremely hot, so it rises. Warm, humid air from the northern Indian Ocean enters the region, and it too is heated and rises.
As the rising wet air cools, it drops heavy monsoon rains. In the winter, cool air from over the land moves seaward. Back in the days of sailing ships, seasonal shifts in the monsoon winds carried goods back and forth between India and Africa. Mountain and Valley Breezes[ edit ] Temperature differences between mountains and valleys create mountain and valley breezes.
- The Highs and Lows of Air Pressure
- High and low pressure
During the day, air on mountain slopes is heated more than air at the same elevation over an adjacent valley. As the day progresses, warm air rises off the slopes and draws the cool air up from the valley.
This uphill airflow is called a valley breeze. When the Sun goes down, the mountain slopes cool more quickly than the air in the nearby valley.
This cool air sinks, which causes a mountain breeze to flow downhill. Katabatic Winds[ edit ] Katabatic winds also move up and down slopes, but they are stronger mountain and valley breezes.
Katabatic winds form over a high land area, such as on a high plateau. The plateau is usually surrounded on almost all sides by mountains. In winter, the plateau grows cold, making the air above it extremely cold.
High School Earth Science/Air Movement
This dense air sinks down from the plateau through gaps in the mountains. Wind speeds depend on the difference in air pressure over the plateau and over the surroundings. If a storm, which has low pressure, forms outside the plateau, there is a big difference in wind pressure and the winds will race rapidly downslope.
Katabatic winds form over many continental areas. Extremely cold katabatic winds blow over Antarctica and Greenland. Foehn Wind Chinook Winds [ edit ] Foehn winds or Chinook winds develop when air is forced up over a mountain range. This takes place, for example, when the westerly winds bring air from the Pacific Ocean over the Sierra Nevada Mountains in California.
As the relatively warm, moist air rises over the windward side of the mountains, it cools and contracts. If the air is humid, it may form clouds and drop rain or snow. When the air sinks on the leeward side of the mountains, it forms a high pressure zone.
The windward side of a mountain range is the side that receives the wind; the leeward side is the side where air sinks. The descending air warms and creates very strong, dry winds.
The Highs and Lows of Air Pressure | UCAR Center for Science Education
If there is snow on the leeward side of the mountain, it may disappear by quickly melting and evaporating in the dry winds. If precipitation falls as the air rises over the mountains, the air will be very dry as it sinks on the leeward size of the mountains. This dry, sinking air causes a rainshadow effect Figure Many deserts are found on the leeward side of mountains due to rainshadow effect. Air cools and loses moisture as it rises over a mountain. It descends on the leeward side and warms by compression.
The resulting warm and dry winds are Foehn winds or Chinook winds. If the air loses precipitation over the mountain, the leeward side of the mountain will be dry, experiencing rainshadow effect. The name of these winds is a bit confusing. Some people refer to all of these winds as Foehn winds, others as Chinook winds, and still others as orogenic winds.
The names Foehn and Chinook are sometimes used for any of these types of winds, but are also used regionally. Although the description is apt, Chinook does not mean "snow eater". These winds are created in the late fall and winter when the Great Basin east of the Sierra Nevada cools. The high pressure is created when the Great Basin cools forces winds downhill and in a clockwise direction.
The air sinks rapidly, so that its pressure rises. At the same time, the air's temperature rises and its humidity falls. The winds blow across the Southwestern deserts and then race downhill and westward toward the ocean. Air is forced through canyons cutting the San Gabriel and San Bernardino mountains.
The winds are especially fast through Santa Ana Canyon, which gives them their name. Santa Ana winds blow dust and smoke westward over the Pacific from Southern California. The Santa Ana winds often arrive at the end of California's long summer drought season.
The hot dry winds dry out the landscape even more. If a fire starts, it can spread quickly, causing large-scale devastation. In late OctoberSanta Ana winds fueled many fires that together burnedacres of wild land and more than homes Figure The Santa Ana winds contributed to the loss ofacres to wild fires.
The fire is being pushed along by Santa Ana winds. High summer temperatures on the desert create high winds, which are often associated with monsoon storms. A haboob forms in the downdrafts on the front of a thunderstorm Figure Air spins and lifts dust and sand into a cloud of dirt that may include dust devils or tornadoes. Haboobs cause many sandstorms. A haboob in the Phoenix metropolitan area, Arizona Dust devils, also called whirlwinds, may also form on hot, clear desert days.
The ground becomes so hot that the air above it heats and rises. Air flows into the low pressure and begins to spin. Dust devils are small and short-lived but they may cause damage.
Atmospheric Circulation[ edit ] You have already learned that more solar energy hits the equator than the polar areas. The excess heat forms a low pressure cell at the equator.
Warm air rises to the top of the troposphere where half of the warmed air moves toward the North Pole and half toward the South Pole. The air cools as it rises and moves along the top of the troposphere. When the cooled air reaches a high pressure zone, it sinks. Back on the ground, the air then travels toward the low pressure at the equator.
The air rising at the low pressure zone at the equator and sinking at a high pressure in the direction of the North or South Pole creates a convection cell. If the Earth was just a ball in space and did not rotate, there would be only one low pressure zone and it would be at the equator.
There would also be one high pressure at each pole. This would create one convection cell in the northern hemisphere and one in the southern.
But because the planet does rotate, the situation is more complicated. The planet's rotation means that the Coriolis Effect must be taken into account. The Coriolis Effect causes freely moving objects to appear to move right in the Northern Hemisphere and to the left in the Southern Hemisphere.
The objects themselves are actually moving straight, but the Earth is rotating beneath them, so they seem to bend or curve. An example might make the Coriolis Effect easier to visualize. If an airplane flies miles due north, it will not arrive at the city that was due north of it when it began its journey. Over the time it takes for the airplane to fly miles, that city moved, along with the Earth it sits on.
The airplane will therefore arrive at a city to the west of the original city in the Northern Hemisphereunless the pilot has compensated for the change. A common misconception of the Coriolis Effect is that water going down a drain rotates one way in the Northern Hemisphere and the other way in the Southern Hemisphere. This is not true because in a small container like a toilet bowl, other factors are more important.
These factors include the shape of the bowl and the direction the water was moving when it first entered the bowl. But on the scale of the atmosphere and oceans, the Coriolis Effect is very important.
Let's look at atmospheric circulation in the Northern Hemisphere as a result of the Coriolis Effect Figure Air rises at the equator as described above. But as the air moves toward the pole at the top of the troposphere, it deflects to the right. Remember that it just appears to deflect to the right because the ground beneath it moves. This air is cool because it has come from higher latitudes.
Both batches of air descend, creating a high pressure cell. Once on the ground, the air returns to the equator. The atmospheric circulation cells, showing direction of winds at Earth's surface.
There are two more convection cells in the Northern Hemisphere. This cell shares its southern, descending side with the Hadley cell to its south. There are three mirror image circulation cells in the Southern Hemisphere. In that hemisphere, the Coriolis effect makes objects appear to deflect to the left. Global Wind Belts[ edit ] Global winds blow in belts encircling the planet. The global wind belts are enormous and the winds are relatively steady Figure Suggest they tell you more about how they see their suggestion playing out.
You can ask, "tell me how you would do that? I used this technique after my company had attempted to complete a project in an unreasonable timeline to meet the customer's needs. The project had been painful and the customer was unhappy. When I asked her how she would have approached the project differently, she admitted that she wouldn't have.
Once she thought it through, she conceded that the approach was the best given the circumstances. Re-Affirm that You Are Working Towards the Same Goal A common problem in high-pressure situations is that the parties forget they are working towards a common goal.
Simply remind everyone that you are trying to reach the same objective. This technique allows everyone to lower their guard and start listening to each other's point objectively.
Pointing out this fact eliminates the feeling of competition and reinforces teamwork and collaboration. Don't be afraid to be direct and to the point when communicating.
When stakes get high, a common reaction is to start watching your words. But this is the exact opposite of what is needed when negotiations breakdown. Meaning is lost as individuals start to dance around the real problem. Telling it like it is moves the conversation forward. Not only is "not knowing" okay, it makes you more approachable and allows others room to be vulnerable. Saying "I don't know" or admitting that you need to ask someone else on your team provides room for a follow up and time to diffuse a high-pressure situation.