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What is the large-scale atmospheric motions over the entire earth
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The general circulation only represents --- air flow around the world.
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Weather Test 4;Sec3
| Question | Answer |
|---|---|
| What is the large-scale atmospheric motions over the entire earth | General circulation of the atmosphere |
| The general circulation only represents --- air flow around the world. | The average |
| The underlying cause of the general circulation is what? | The unequal heading of the earth’s surface |
| What is the three cell model? | when we allow the earth to spin and the simple convection system breaks into a series of cells |
| What are the similarities between the single and the three cell model? | the tropical regions still receive an excess of heat and the poles a deficit; in each hemisphere, three cells instead of one have the task of energy redistribution; a surface high-pressure area is located at the poles, and a broad trough of surface low pr |
| What is the circulation from the equator to latitude of 30 degrees? | Hadley cell |
| What is the region over equatorial water, where the air is warm, horizontal pressure gradients are weak, and winds are light? | doldrums |
| In the doldrums, the warm air rises, often condensing into huge cumulus clouds and thunderstorms called what? | convective”hot” towers |
| What does the heat from the convective towers do? | – makes the air more buoyant and provides energy to drive the Hadley cell |
| What happens when rising air reaches the tropopause? | acts like a barrier, causing the air to move laterally toward the poles; Coriolis force deflects poleward flow toward the right in NH and left in SH proving westerly winds aloft in both hemispheres |
| What happens as air moves poleward from the tropics? | it constantly cools by giving up infrared radiation and at the same time it also begins to converge, especially as it approaches the middle latitude |
| As air moves poleward from tropics it converges, what does this convergence do? | increases the mass of air above the surface, which in turn causes the air pressure at the surface to increase |
| At latitudes near 30 degrees, the convergence of air aloft produces belts of high pressure called what? | subtropical highs (anticyclones) |
| What happens as the converging, relatively dry air above the highs slowly descends? | it warms by compression |
| What is the belt of latitude at about 30-35 degrees where winds are predominantly light and the weather is hot and dry? | Horse latitude |
| What is the winds that occupy most of the tropics and blow from the subtropical highs to the equatorial lows? | Trade winds |
| What is the boundary zone separating the northeast trade winds of the Northern Hemisphere from the southeast trade winds of the Southern Hemisphere? | Intertropical convergence zone (ITCZ) |
| What is the dominant westerly winds that blow in the middle latitudes on the poleward side of the subtropical high-pressure areas? | Westerlies |
| What is a semi permanent, semi continuous front that separates tropical air masses from polar air masses? | Polar front |
| What is a belt of low pressure located between 50-70 degrees latitude? | Subpolar low |
| In the NH, the subpolar low consists of what in the North Pacific and what is the North Atlantic? | Pacific-Aleutian low Atlantic-Icelandic low |
| In the SH, what does the subpolar low exist around? | around the periphery of the Antarctic continent |
| A shallow body of earterly winds located at a high latitude poleward of the subpolar low? | Polar easterlies |
| Air aloft eventually reaches the poles, slowly sinks to the surface, and flows back toward the polar front, completeing the weak ---? | polar cell |
| At the surface, there are two major areas of high pressure and 2 of low pressure, where do these areas exist? | areas of high pressure exist near latitude 30 degrees and the poles; areas of low pressure exist over the equator and near 60 degrees latitude in the vicinity of the polar front |
| Why is it helpful to know the way the winds blow around these systems? | we have a generalized picture of surface winds throughout the world |
| The trade winds extend from what? | from the subtropical high to the equator |
| The westerly winds extend from what? | extend from subtropical high to the polar front |
| The easterly winds extend from what? | from the poles to the polar front |
| How does the three cell model compare with actual observations of winds and pressure? | agrees closely with the winds and pressure distribution at the surface |
| During the summer, the Pacific high drifts where? | drifts northward to a position of the California coast |
| The rainy season typically occurs when? | in winter when the high moves south and the polar front and storms are able to penetrate the region |
| In both hemispheres, the air is warmer over what? Colder over what? | over low latitudes and cooler over high latitudes |
| The horizontal temperature gradient establishes what? | a horizontal pressure (contour) gradient that causes the winds to blow from the west, especially in middle and high latitudes |
| The winds aloft are stronger in (winter/summer)? | winter |
| In the middle and high latitudes, the westerly winds continue to increase in speed above what? | the 500mb level |
| The wind speed increases up through the friction layer, why should it continue to increase at higher levels? | a greater pressure gradient will result in stronger wind, and so will a decrease in air density; air density decreases with height, the same pressure gradient will produce stronger winds at higher levels |
| The north-to-south temperature gradient causes the horizontal pressure gradient to do what? | increase with height up to the tropopause |
| What is a result of the horizontal pressure gradient increase with height up to the tropopause? | the winds increase in sped up to the tropoause |
| What happens to the temperature gradient above the tropopause? | the temperature gradients reverse-reduces the strength of the westerly winds |
| What is it called where strong winds tend to concentrate into narrow bands at the tropopause? | jet streams |
| What are swiftly flowing air currents thousands of kilometer long, a few hundered kilometers wide, and only a few kilometers thick? | jet streams |
| Jet streams are usually found at what elevation? | found at the tropopause at elevations between 10-15 km (6-9 miles) |
| Jet streams were first encountered by who? | high flying military aircraft during WWII |
| What are the two jet streams both located in tropopause gaps where mixing between tropospheric and stratospheric air takes place? | subtropical jet stream & polar front jet stream |
| What is the jet stream situated near 30 degrees latitude at about 13 km above the subtropical high? | subtropical jet stream |
| What is the jet stream situated at about 10 km, near the polar front? | polar front jet stream (polar jet stream) |
| Since the subtropical jet stream and the polar front jet stream are both found at the tropopause, they are referred to as what? | tropopause jets |
| What may happen when the polar jet stream flows in broad loops that sweep north and south? | it may merge with the subtropical jet |
| Occasionally, the polar jet does what? | splits into two jet streams |
| When the polar jet splits into two jet streams, the jet stream to the north is called? | the northern branch (of the polar jet) |
| When the polar jet splits into two jet streams, the jet stream to the south is called? | the southern branch (of the polar jet) |
| What direction does a jet stream flow? | wavy west-to- east direction |
| What is the fastest flowing air? | air core |
| Why is the looping pattern of the polar jet stream an important function? | In NH where the air flows southwards, swiftly moving air directs cold air equataorward; where the air flows northward, warm air is carried to the poles |
| Jets streams play a major role in what? | the global transfer of heat |
| Since the polar front is a boundary separating what?, the greatest contrast in air temperature occurs along what? | separating cold polar air to the north from warm subtropical air to the south; frontal zone |
| The rapid change in temperature produces what? | a rapid change in pressure |
| The sudden change in pressure along the front sets up a steep pressure (contour) gradient that intensifies what? | the wind speed and causes the jet stream |
| The north-south temperature contrast along the polar front is (strongest/weakest) in the winter and (strongest/weakest) in the summer? | strongest in winter and weakest in the summer |
| What is the boundary where warm air carried poleward by the Hadley cell produces sharp temperature contrasts along? | subtropical front |
| In the vicinity of the subtropical front, sharp contrasts in temperature produce what? | sharp contrasts in pressure and strong winds |
| What would happen if the earth should suddenly stop rotating? | the air above would continue to move eastward until friction with the surface brought it to a halt; the air keeps moving because it have momentum |
| What is a straight-line that is the product of the mass of the object times its velocity? | linear momentum |
| An increase in either the mass or the velocity produces an increase in what? | the linear momentum |
| Along with the mass and the speed, angular momentum depends upon what other thing? | the distance (r) between the mass of air and the axis about which it rotates |
| What is defined as the product of the mass (m) times the velocity (v) times the radial distance? | angular momentum |
| Angular momentum-xyz? | mvr |
| As long as there are no external twisting forces acting on the rotating system, the angular momentum of the system (does/does not) change? | does not |
| We say that angular momentum is conserved, what does that mean? | the product of the quantity mvr at one time will equal the numerical quantity mvr at some later time |
| A decrease in radius must produce an increase in what? | speed (and vice versa) |
| As a heated air parcel rising from the equatorial surface approaches the tropopause, what happens? | it spread laterally and begin to move poleward |
| If we follow the air parcel rising from the surface, what do we see? | we see that because of the curvature of the earth, air constantly moves closer to its axis of rotation (r decreases) |
| Because angular momentum is conserved (and since the mass of air is unchanged) what must be compensated? | the decrease in radius must be compensated for by an increase in speed |
| What is a jet stream that forms in summer near the tropopause above Southeast Asia, India, and Africa? | tropical easterly jet stream |
| What is the altitude of the tropical easterly jet stream? | 15 km |
| What are the jet forms that are on the equatorward side of the upper-level subtropical high, where the winds are easterly? | tropical easterly jet stream |
| What is the cause of the formation of jet streams? | during the summer, the air above is warmer than the air above the ocean to the south and this contrast in temperature produces a north-to-south pressure gradient and strong easterly winds that usually reach a maximum speed near 15 degrees N latitude |
| Do all jet streams for at the tropopause? | no, there is a jet stream that forms near the top of the stratosphere over polar latitudes |
| Wind maximum that occurs in the stratosphere during the dark polar winter? | stratospheric polar night jet stream |
| In summer, the polar regions experience (more/less) hours of sunlight than do tropical areas? | more |
| Stratospheric temperatures over the poles increase more than at the same altitude above the equator, which causes what? | the horizontal temperature gradient to reverse itself |
| When the jet stream disappears, what comes in its place? | weaker easterly winds |
| What is the wind speed maximum, which usually flows from the south or southwest? | low-level jet |
| Low-level jet typically forms at night above a temperature inversion so what is another name for it? – | nocturnal jet stream |
| What are the two major semipermanent subtropical highs that influence the weather of North America? | the Pacific high situated off the west coast and the Bermuda high situated off the southeast coast |
| What is a zone of low pressure where cyclonic storms often form? | the polar front |
| What separates the mild westerlies of the middle latitudes from the cold, polar easterlies of the high latitudes? | polar front |
| In equatorial regions, what is a boundary where air rises in response to the convergence of the northeast trades and the southeast trades? | the intertropical convergence zone (ITCZ) |
| In the Northern Hemisphere, what direction do the major global pressure systems and wind belts shift? | northward in summer and southward in winter |
| The northward movement of the Pacific high in summer tends to do what? | keep summer weather along the west coast of NA relatively dry |
| Jet streams exist where strong wind become concentrated in what? | in narrow bands |
| The polar front jet stream is associated with what? | the polar front |
| What meanders in a wavy, west to east pattern, becoming strongest in winter when the contrast in temperature along the front is greatest? | the polar jet |
| The subtropical jet stream is found on the poleward side of the Hadley cell, between what latitudes? | 20-30 degrees |
| The conservation of angular momentum plays a role in producing what? | strong westerly winds aloft |
| What happens as air aloft moves from lower latitudes toward higher latitudes? | its axis of rotation decreases, which results in an increase in its speed |
Created by:
arcall