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What is Wind and What is its basic Cause?
Wind is air that moves horizontally due to atmospheric pressure differences. Wind moves from high to low pressure to try to correct inequalities in air pressure.
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What is Standard Sea-Level Pressure, In pounds per square inch?
14.7 psi
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Describe atmospheric pressure in your own words.
Anywhere you stand there is essentially a column of air above you. The weight of this air exerts pressure through the constant collision of gas molecules against a surface. This is known as atmospheric pressure and is measurable.
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What is average sea-Level pressure when measured in Millibars? In inches of Mercury?
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Describe the operating priciples of the mercury barometer and the aneroid Barometer
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List two advantages of the aneriod Barometer
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What can an aneroid Barometer be used for other than measuring barometric pressure?
The aneroid barometer can also be used to determine altitude which is beneficial for aircraft and mountain climbers.
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Explain why air pressure decreases with an increase in altitude.
As altitude increases, the air becomes less dense as there is a decreased amount of air above you. With less weight of the air about you, the air pressure is decreased. This is why air pressure decreases as altitude increases.
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Why do climbers use supplemental oxygen when summiting mount Everest?
Density decreases with altitude so the air becomes "thinner" and climbers need to supplement their oxygen the higher they go.
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What is the U.S standard atmosphere?
The U.S. Standard Atmosphere is a depiction of the vertical distribution of atmospheric pressure. It shows atmospheric pressure as altitude increases and air molecules become more spread out as density decreases.
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Explain why a cold, dry air mass produces a higher surface pressure than a warm, humid air mass.
Water vapor is lighter than dry air so humid air masses would be expected to exert less pressure. Cold air is more dense than warm air, so a cold air mass would be expected to exert more pressure. The cold temperatures and dry air combined make it so that the cold and dry air mass exerts more pressure than a humid warm air mass.
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If all other factors are equal, does a dry or moist air mass exert more air pressure? Explain.
Moist air is actually less dense than dry air as water vapor is lighter than dry air. Therefore a dry air mass would exert more pressure.
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Explain how horizontal convergence affects surface pressure.
Horizontal air convergences "squeezes" air into a smaller space. This produces a more massive air column which will exert more pressure at the surface.
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List three forces the combine to direct horizontal airflow (wind).
Pressure Gradient force
Coriolis force
Friction
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What force is responsible for generating wind?
The pressure gradient force is responsible for generating wind. An imbalance of pressure produces a force directed toward the area of lower pressure causing the wind to blow. A larger difference in pressure creates a greater wind speed.
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Write a generalization relating the spacing of isobars to wind speed.
The greater the spacing between isobars, the smaller the pressure gradient which results in a weaker wind speed.
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Briefly describe how the Coriolis force modifies air movement.
The Coriolis force modifies airflow by causing the wind to be deflected to the right of its path of motion in the Northern Hemisphere (left in the Southern Hemisphere) as a result of the Earth's rotation.
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Which two factors influence the magnitude of the Coriolis force?
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Explain the formation of geostrophic wind.
When the Coriolis force is exactly equal in strength but acting in the opposite direction of the pressure gradient force, the airflow is said to be in geostrophic balance. The winds generated by this balance are called geostrophic winds.
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Describe how geostriophic winds blow relative to isobars.
Geostrophic winds will eventually flow parallel to isobars.
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Describe the direction of cyclonic and anticyclonic flow in both the Northern and Southern hemispheres.
In the Northern Hemisphere cyclonic flow is counterclockwise while anticyclonic flower is clockwise.
In the Southern Hemisphere cyclonic flow is clockwise and anticyclonic flow is counterclockwise.
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Unlike winds aloft, which blow nearly parrallel to the isobars, surface winds generally cross the isobars. Explain what causes this difference.
Friction affects winds near the Earth's surface and slows them down. The coriolis force is reduced so the pressure gradient force wins out - pulling the wind at an angle across the isobars
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A southwest wind blow from the _____ (direction) toward the ____ (direction)
A southwest wind blows from the southwest toward the northeast.
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When the wind direction is 315°, from what compass direction is it blowing?
Northwest
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What is the name of the prevailing winds the affect the contiguous United States?
Westerlies
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List the three major categories of atmospheric circulation and give at least one example of each.
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Describe how the size of a wind system is related to its duration (life span)?
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What scale of atmospheric circulation includes mid latitude cyclones, anticyclones and tropical cyclones (Hurricanes)?
Macroscale - and also a subdivision of macroscale: synoptic scale.
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The most intense sea breezes develop along tropical coasts adjacent to cool ocean currents. Explain.
Intense solar heating is continuous throughout the year, sea breeze develops of the cooler sea then moves towards the area of low pressure of the land.
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In what way ware land and sea breezes similar to mountain and valley breezes?
Like many other winds, mountain and valley breezes have seasonal preferences. Valley breezes are most common during warm seasons, when solar heating is most intense, whereas mountain breezes tend to be more frequent during cold seasons.
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What are chinook winds? Name two areas where they are common.
Chinook winds are warm, dry winds that move down the slopes of mountains. These are commonly seen on the east slopes of the Colorado Rockies in winter and spring. Another common one in the USA is the Santa Ana wind in southern California. They also are found in the Alps, but are called foehns there.
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In what way are katabatic (Fall) winds different from most other types of local winds?
When the frigid air descends from a highland area, it arrives colder and denser than the air it displaces even though it is heated adiabatically. It then can channel into narrow valleys and cause great destruction.
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Explain how cities create their own local winds.
Buildings and cities help to retain heat throughout the day. This warm air rises which allows country breezes to form as air from the country flows into the city.
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Briefly describe the idealized global circulation proposed by George Hadley. What are the shortcomings of the Hadley model?
His model proposed that there is a large convection cell in both the N and S hemispheres, Where air is circulated from the poles to the equator and back through adiabatic cooling. However this model does not take into account of the earths rotation.
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Which two factors cause air to subside between 20° and 35° latitude?
- 1) radiation cooling process develops are air moves from the equatorial region, causing air to be cooler and denser, and to sink.
- 2) the Coriolis force is stronger, causing upper air to be deflected into west-to-east flow around 30 degrees
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Referring to the idealized three-cell model of the atmospheric circulation, most of the united states is situated in which belt of prevailing winds?
The Prevailing Westerlies
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What wind belts are found between the equator and 30° latitude?
The Northeast Trade Winds
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What is the intertropical zone? (ITCZ)
The low pressure zone located at the equator where the trade winds converge.
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If earth had a uniform surface, east-west belts of high and low pressures would exist. Name these zones and the approximate latitude in which each would be found.
- Polar high
- Subpolar low
- Westerlies
- subtropical high
- trades
- equatorial low
- trades
- subtropical high
- westerlies
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During what season is the Siberian high strongest?
Strongest in winter.
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During what season is the Bermuda high strongest?
Strongest in summer.
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Define Monsoon.
Large Seasonal changes in Earth's global circulation are called monsoons.
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Explain the cause of the Asian Monsoon. Which Season (summer or winter) is the rainy season?
The cold dry Siberian high in the winter is developed and moves across southern Asia, producing offshore winds. In the summer, there is an opposite effect. This affect can be contributed to the movement of the ITCZ.
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What areas of North America experience a pronounced monsoon circulation?
Southwestern united states and nothwestern Mexico.
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Why is the flow aloft in the midlatitudes predominantly Westerly?
The temperature differences between the poles and equator drives these winds. The differences in pressure changes for the polar high and Equatorial low create a pressure gradient force acting against the Coriolis force, creating geostrophic winds
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What name is given to the long-wavelength flow that is apparent on upper air charts?
Rossby Waves
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How are jet streams generated?
Large temperature differences at the surface produce steep pressure gradients aloft and hence faster upper-air winds.
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At what time of year should we expect the fastest polar jet streams? Explain
winter because of the much stronger pressure gradient that exists in the middle latitudes during the winter
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Why is the polar jet sometimes referred to as the mid-latitude jet stream?
because in the winter particularly the jet stream is located in the middle latitudes
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Describe the expected winter temperatures in the north-central states when the polar jet stream is located over the central Florida.
the weather will be colder and dryer than normal
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Explain how the wavy flow centered on the jet stream helps balance Earth's heat budget.
The important function of heat transfer is accomplished by the wavy flow of the westerlies centered on the polar jet stream.
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What drives Earth's surface ocean currents?
Surface Winds
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Ocean currents tend to form spirals.
A) In what direction do these ocean currents travel in each hemisphere?
B) What general name is given to these spirals? Name major examples in each hemisphere.
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Give an example of how ocean currents affect the temperature of adjacent landmasses.
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Describe the role that ocean currents play in maintaining Earth's heat balance.
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Describe how a major El Nino event tends to affect the weather in Peru and Chile as compared to Indonesia and Australia.
Weather becomes very wet in Peru and Chile thus causing major flooding. In Indonesia or Australia, the weather ends up being dryer thus leading to droughts and increased risk of forest fires
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