question

Air generally begins to flow from areas of _____pressure towards areas of ______ pressure

answer

Higher pressure; lower pressure

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If Earth did not rotate and if friction did not exist, that is precisely what would happen - a direct movement of air from a high-pressure region to a low-pressure region. However, rotation and friction both exist, so this general statement is usually not completely accurate. The direction of when movement is determined principally by the interaction of three factors

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The pressure gradient, the Coriolis effect, and friction

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If there is higher pressure in one area than in another, air will begin to move from

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Higher pressure toward lower pressure

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This is in response to

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Pressure gradient force

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The pressure gradient force acts at right angles to the isobars in the direction of

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Lower pressure

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If there were no other factors to consider, that is the way the air would move, crossing the isobars at 90°. However...

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Such a flow rarely occurs in the atmosphere

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Because Earth rotates, any object moving freely near Earth's surface appears to deflect to the right in the northern hemisphere and to the left in the southern hemisphere. This is known as

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The Coriolis effect

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This movement, right in the northern hemisphere and left in the southern hemisphere seems to be regardless of

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The initial direction of motion

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The apparent deflection is strongest at

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The poles

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The deflection decreases progressively toward

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The equator

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The deflection at the equator is

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Zero

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The Coriolis effect is proportional to

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The speed of the object

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So the fast moving object is deflected how in comparison with the slower one,

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A fast moving object is deflected more than a slower one

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The Coriolis effect influences the direction of movement only what doesn't it influence?

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Speed of an object

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The Coriolis effect as an important influence on the direction of

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Wind flow

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The Coriolis effect deflection acts from what degree from the direction of movement

answer

90°

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The Coriolis effect deflection acts at 90° from the direction of movement to the -_____ in the northern hemisphere and to the ____in the southern hemisphere

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Right: left

question

There is an internal battle, between the pressure gradient force moving air from high toward low-pressure and the deflection of the Coriolis effect 90° from its pressure gradient path: the Coriolis effect keeps the wind from blowing directly down a pressure gradient, whereas the pressure gradient force prevents the Coriolis effect from turning the wind back up the pressure slope. Where these two factors are in balance - as in usually the case in the upper atmosphere - wind moves parallel to the isobars. We call this

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Geostrophic wind

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Why do we say that most wins in the atmosphere are geostrophic?

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The winds flowed nearly parallel to the isobars. Only near the surface is another factor significant.

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What is another factor that is significant?

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Friction

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Where is friction and added factor?

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In the lowest portions of the troposphere friction influences when direction

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The frictional drag of Earth's surface slows wind movement is so the influence of the Coriolis effect is

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Reduced. Recall that rapidly moving objects are deflected more by the Coriolis effect and are slowly moving objects

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Instead of blowing perpendicular to the isobars parentheses in response to the pressure gradient) or parallel to them parentheses were pressure gradient force and the Coriolis effect or imbalance) the wind takes what course

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an intermediate course between the two and crosses the isobars and angles between 0° and 90°

question

In essence, friction affects wind how?

answer

It reduces windspeed which in turn reduces the Coriolis effect deflection - thus, although the Coriolis effect does introduce a deflection to the right in the northern hemisphere, the pressure gradient wins the battle and the air flows into the area of low pressure and away from the area of high pressure

question

As a general rule, the frictional influence is greatest near _______________ and diminishes progressively __________

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Earth's surface; upward

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The angle of wind flow across the isobars is greatest at ____ altitudes and becomes smaller and _____ elevations

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Low; increasing

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What's the friction layer?

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The friction layer of the atmosphere extends to only about 1000 m above the surface. Approximately 3300 feet above the surface. Higher than that, most wins follow a geostrophic or near geostrophic course

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What is inertia?

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The tendency of an object to resist change in its motion

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Speed of wind flow is determined primarily by

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Pressure gradient. If the pressure gradient is steep the air accelerate swiftly. If the gradient is gentle, acceleration is slow

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The closeness of the isobars in the map indicate

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The steepness of the pressure gradient

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In meteorology, windspeed is frequently described in terms of

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Knots. Knots are not miles per hour

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A nautical mile is how far in comparison to statute mile

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Another mile isn't bit longer than a statute mile

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Over most of the world most of the time, surface winds are

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Relatively gentle

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Average wind speed in North America is generally between

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Six and 12 kn

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The dubious distinction of being the windiest place on earth is

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Cape Dennison in Antarctica with 38 kn average wind speed

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The most persistent wins are usually where?

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Coastal areas or high mountains

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Wind speed is quite variable from one altitude to another and from time to time increases with

answer

Height

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Wind speeds tend to move faster above what layer?

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Friction layer

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Very strongest tropospheric winds are usually found at intermediate levels in what are called

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Jet dreams

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Distinct and predictable wind flow patterns develop around all high pressure and low pressure centers - patterns determined by

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The pressure gradient, Coriolis effect, and friction

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A total of eight circulation patterns are possible. For in the northern hemisphere and for the southern hemisphere each hemisphere two are associated with high pressure and to our associate with low-pressure

answer

Just for your knowledge

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High-pressure center is known as

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An anti-cyclone

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The flow of air associated with an anti-cyclone is described as

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Being anti-cyclonic

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The four patterns of anti-cyclonic circulation

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1. In the upper atmosphere the northern hemisphere, the winds moved clockwise in a geostrophic manner parallel to the isobars 2. In the friction layer(lower altitudes) of the northern hemisphere, there is a divergent clockwise flow, with the air spiraling out away from the center of the anticyclone 3. In the upper atmosphere southern hemisphere there is a counterclockwise, geostrophic flow parallel to the isobars 4. In the friction layer of the southern hemisphere, the pattern is a mirror image of the northern hemisphere, but air diverging in a counterclockwise pattern

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Low-pressure centers are called

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Cyclones

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The associated wind movement of cyclone is called

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Cyclonic

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As with anti-cyclones, northern hemisphere cyclonic circulations

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Are mirror images of their southern hemisphere counterparts

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The four patterns of cyclonic circulation

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1. In the upper atmosphere of the northern hemisphere, air moves counterclockwise in a geostrophic pattern parallel to the isobars 2. In the friction layer of the northern hemisphere, a converging counterclockwise flow exists 3. In the upper atmosphere of the southern hemisphere, clockwise geostrophic flow occurs paralleling the isobars 4. In the friction layer at the southern hemisphere, the win converge in a clockwise spiral

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Prominent ________ component of air movement is associated with cyclones and anticyclones

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Vertical

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In anti-cyclones air

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Descends

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In cyclones air

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Rises

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These motions are particularly notable in the lower troposphere. The anticyclonic pattern can be visualized as upper air sinking down into the center of a high and then diverging near the ground surface. Opposite conditions prevail in a low-pressure center, with the air converging horizontally into cyclone and then rising. These patterns match early generalizations about pressure: what were they?

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Descending air is associated with high pressure at the surface and that rising errors associated with low pressure surface

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Cyclones and rising air also associated with

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Clouds

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Anticyclones and descending error associated with

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Clear conditions have

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Most important to the understanding of geography is the general pattern of

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Circulation, which involves major semipermanent conditions of both wind and pressure

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Circulation is the principal mechanism for

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Both latitudinal and longitudinal heat transfer

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And circulation is exceeded only by the global pattern of ________ as a control of world climate patterns

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Insolation

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Were nonrotating sphere with a uniform surface, we can expect a very simple global atmospheric circulation pattern. We would see

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A greater amount of solar warming in the equatorial region which would produce a band of low pressure around the world, and radiation cooling at the polls would develop a High pressure in those areas. Surface winds of the North northern hemisphere was flow directly down the pressure gradient from north to south, whereas those in the southern hemisphere would follow a similar gradient from south to north air would rise at the equator and a large convection sell and flow toward the poles, where it would subside into polar highs

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Does rotate, however, and in addition has an extremely varied surface. Consequently the broadscale circulation pattern of the atmosphere is much more complex. Apparently only the tropical regions have complete vertical convection circulation cell. Similar styles of been postulated for the middle and high latitudes, but observations indicate

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That the mid-laltitude and high latitude cells either do not exist or are weekly and sporadically developed

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The low latitude cells are

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Gigantic convection systems

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These two prominent tropical convection cells are called

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Hadley sells

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Around the world in equatorial latitudes, warm air rises, producing a region of relatively low pressure at surface. This air ascends to great heights mostly in a thunderstorm dress. By the time this air reaches the upper troposphere at elevations at about 50,000 feet. It is cool. The air that spreads North and South and moves poleward, eventually descending at latitudes of about 30° North and South, where form spans of high pressure at the surface. One portion of the air diverging from the surface high pressure zone flow toward the poles, whereas another portion flows back toward the equator - where the northern and southern hemisphere components converge and warm air rises again

answer

Just need to understand just need to understand

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Although the Hadley cell model is a simplification of reality, it is useful starting point for understanding the main components of the general circulation of the atmosphere. The basic pattern of seven surface components of pressure and wind, intimately linked together. The northern and southern hemisphere patterns are mirror images of each other. The seven components are

answer

Intertropical convergence zone Tradewinds subtropical highs Westerlies polar front (sub polar lows) Polar easterlies polar highs

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The pattern general circulation within the troposphere is essentially what kind of system

answer

Closed, with neither beginning or end

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Each ocean basin has a large semipermanent high pressure cell centered at about 30° of latitude called

answer

A subtropical high

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These gigantic anticyclones developed from

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The descending air of the Hadley cells

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They are usually elongated ____________ antinomy centered in the eastern portions of the ocean basin

answer

East - West

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Some of the subtropical highs have names because they are so persistent

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Azores high in the North Atlantic and the Hawaiian high in the North Pacific

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From a global standpoint, the subtropical highs represent intensified cells of high pressure in two general ridges of high pressure that extend around the world in these latitudes, one in each hemisphere

answer

Just review

question

The high-pressure ridges are ________ over the continents

answer

Broken up

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This is especially true in the summer when inland temperatures produce

answer

Low air pressure

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Even so, the subtropical highs normally persist over the ocean basins throughout the year why?

answer

Temperatures and pressures there remain constant

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Associated with these high-pressure cells is a general subsidence of air from higher altitudes in the form of a broadscale, gentle downdraft. A permanent feature of the subtropical highs is a

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Temperature inversion that covers wide areas in subtropics

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Within the subtropical highs the weather is

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Nearly always clear, warm, and calm

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Subtropical highs are also characterized with the absence of

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Wind

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Why?

answer

In a center of a subtropical high air is primarily subsiding; horizontal air movement and divergence began toward the edges

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These regions are sometimes called

answer

Horse latitudes presumably because 16th and 17th century sailing ships or sometimes becalled there and or cargoes of horses were thrown overboard to conserve ranking water

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The air circulation pattern around the subtropical high is

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Anti-cyclonic - diverging clockwise in the northern hemisphere and counterclockwise in the southern hemisphere

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The subtropics highs can be thought of as gigantic

answer

Wind wheels whirling in the lower troposphere, that would air sinking down from the above and spinning up wins horizontally in all directions.

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Although the global flow of air is essentially close circulation, the subtropical highs can be thought of as a source of the two of the world's three major surface wind systems

answer

Tradewinds and the westerlies

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Tradewinds are

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Wednesday verging from the equator were side of the subtropical highs that cover most of the earth between the latitude 25° North and latitude 25° south. They are particularly prominent over oceans but tend to be significantly interrupted and modified over landmasses.

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Why do Tradewinds dominate more the club than any other wind system

answer

Because of the vastness of the earth in tropical latitudes and because of this expanse is oceanic

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The trade brands are predominantly

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Easterly winds

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What is that mean?

answer

They generally blow from east to west

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In the northern hemisphere the tradewinds usually blow from

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The Northeast sometimes called the North East trades

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South of the equator, the tradewinds usually blow from

answer

they are from the southeast known as the Southeast trades

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There are exceptions to this general pattern where?

answer

Generally over the Indian Ocean, where westerly winds sometimes prevail

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Tradewinds are by far the most ______ of all winds.

answer

Reliable

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They are extremely consistent in

answer

Direction and speed

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They blow most of the time in the same

answer

Direction and speed day and night summer and winter

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The steadiness is reflected in their name why?

answer

Tradewinds really means winds of commerce. Mariners of the 16th century recognized early that the quickest and most reliable routes in their sailing vessels from Europe to the Americas lay in the belt of the north easterly winds of the southern part of the North Atlantic Ocean.

question

The trades originate as what kind of wins?

answer

Warning, drying wins capable of holding an enormous amount of moisture. They evaporate vast quantities of moisture and therefore have a tremendous potential for storming us precipitation. They do not release the moisture however unless forced to do so by being uplifted by topographic barrier or some sort of pressure disturbance.

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Islands in the trade winds zone are often

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Desert islands because the moisture laden winds pass over them without dropping any rain

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If there is even a slight topographic irregularity

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The air that is forced to rise may release abundant precipitation

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The Northeast and South East trades come together in the general vicinity of

answer

The equator

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There is a position shift latitudinally

answer

Shift seasonally northward and southward following the sun

question

The shift is greater over land and sea why?

answer

Because the land warms more

question

The zone where the air from the northern hemisphere at Southern Hemisphere meat is called

answer

Intertropical convergence zone or simply IT CZ. But it's also referred to as the doldrums

question

The ITC Z is a zone of what kind of airflow and winds?

answer

Convergence, weak, horizontal. Characterized by feeble and erratic wins

question

What are the surface conditions like? What about pressure? Rainfall? Stability? Rising or falling air?

answer

ITCZ is a globe girtling zone of warm surface conditions, low pressure associated with the high rainfall, instability, and rising air in the Hadley cells

question

Is it a region of continuously ascending air?

answer

No. Almost all the rising air of the tropics ascends and updrafts that occur in thunderstorms in the ITCZ and ease updrafts pump an enormous amount of sensible heat and latent heat of condensation into the upper troposphere, or much of it spreads poleward

question

The IT CZ often appears how?

answer

As a well-defined, relatively narrow cloud band over the oceans near the equator. Over continents, however, is likely to be more diffused and indistinct, although thunder storms activity is common

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The fourth component of the general atmospheric circulation is a great win system of the mid-latitudes commonly called

answer

The westerlies

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The westerlies flow basically from

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West to east around the world in the latitudinal zone between a 30° and 60° both North and South of the equator

question

The westerlies are less extensive than the trades. Why?

answer

Because the circumference of the Earth is smaller at these latitudes and in the tropics. But they still cover much of the earth

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How do they compare to the trades?

answer

The surface westerlies are much less constant and persistent in the trades, which is to say that in the mid-latitudes surface winds do not always float from the west that may come from almost any point on the compass. Near the surface there are interruptions and modifications of the westerly flow, which can be likened to eddie's and countercurrents in the river. These interruptions are caused by surface friction, by topographic barriers, and especially by migratory pressure systems, which produce airflow that is not westerly.

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Although the surface westerlies are somewhat variable, the geostrophic winds aloft, however, blow very prominently from the west. Moreover, there are two remarkable cores of high-speed winds in each atmosphere called

answer

Jet streams: one called the polar front jet stream (or simply the polar jet stream) and the other called the subtropical jet stream, at high altitudes in the westerlies

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The belt of the westerlies can therefore be thought of as a meandering river of air moving generally from west to east around the world in the mid-latitudes, with the jet streams

answer

As its fast-moving cores

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The polar front jetstream, which usually occupies a position 30,000 to 40,000 feet high, is not centered in the westerlies

answer

It is displaced poleward. As the name comes from the location

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This jetstream is a feature of

answer

The upper troposphere located over the area of greatest horizontal temperature gradient - that is, cold just poleward and warm just equatorward

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The jetstream is often portrayed as being a sharply defined narrow ribbon of wind. It is really

answer

A zone of strong winds within the upper troposphere westerlie flow

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Jetstream speed is variable but what is considered the minimum speed required for recognition as a jetstream?

answer

60 kn

question

What's the fastest recorded?

answer

Wind speeds five times that fast

question

What can be significantly influenced by the high-speed flow of upper tropospheric winds?

answer

Commercial air travel

question

Why is this?

answer

The cruising altitude of the commercial jetliner is usually 9 to 12 km or 30 or 40,000 feet a typical elevation for the polar front jetstream

question

Because of this what flights look like from East to West?

answer

It generally takes longer to fly from east to west across North America than it does to fly from West to East when one is traveling from the east, a headwind is likely to impede progress, whereas when traveling from the West, a tailwind reduces travel time

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The polar front to jetstream shifts its latitudinal position with some frequency, and this changes considerable influence on what?

answer

The path of the westerlies. Although the basic direction of movement is west to east, frequently sweeping undulations develop in the westerlies and produce a meandering jetstream path that wanders widely North and South. These curves are very large and generally referred to as longwave's or rossby waves waves.

question

At any given time, there usually are ___________ Rossby waves in the westerlies of each hemisphere

answer

3 to 6

question

These waves can be thought of as

answer

Separating cold polar air from warmer tropical air

question

When the polar front jetstream Pat is more directly west to east there is a ______ pattern in the weather, with cold air poleward of warm air

answer

Zonal flow

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When the jet streams begin to oscillate and the Rossby waves develop significant amplitude there is what kind of flow?

answer

meridionl flow: cold heirs brought equatorward and warm air moves poleward, bringing frequent and severe weather changes to the mid-latitudes

question

The subtropical jet stream is usually located where?

answer

High altitudes - just below tropopause - over the poleward margins of the subsiding air of the subtropical high

question

It is less influence on the surface weather patterns why?

answer

Because there is less temperature contrast and the associated airstreams

question

Do the polar front jet in the subtropical jet ever merge

answer

Yes sometimes. They will merge and produce a broad belt of high-speed winds in the upper troposphere - a condition that can intensify the weather conditions associated with either zonal or meridianal flow of the Rossby waves

question

No other portion of earth experiences

answer

Set short run variability of whether as the mid-latitudes

question

Situated over both polar regions are high pressure cells called

answer

Polar highs

question

The Arctic high, which forms over an extensive, high elevation, very cold continent, is

answer

Strong, persistent, and almost a permanent feature above the Antarctic continent

question

What about the Arctic high?

answer

The Arctic high is much less pronounced and more transitory, particularly in winter

question

The Arctic high forms

answer

Over northern continental areas rather than over the Arctic Ocean

question

Air movement associated with these cells is typically

answer

Anti-cyclonic

question

What is that mean?

answer

Air from above sinks down into the high and diverges horizontally near the surface, clockwise in the northern hemisphere and counterclockwise in the southern hemisphere, forming the third of the world's wind systems,

question

So air from above sinks down into the high and diverges horizontally near the surface, clockwise in the northern hemisphere and counterclockwise in the southern hemisphere, forming the third of the world wind system

answer

The polar easterlies

question

The third broadscale global wind system occupies most of the area between

answer

The polar highs and about 60° latitude

question

The winds moved generally from East to West and are called

answer

Polar easterlies

question

They are typically

answer

Cold and drive to quite variable

question

Thefinalsurface of the general pattern of atmospheric circulation is

answer

A zone of low pressure at about 50° to 60° latitude in both Northern and Southern hemispheres and commonly called the polar front

question

Sometimes it's most clearly visible by the presence of semipermanent zones of low pressure called

answer

So polar lows

question

The polar front is a meeting ground and zone of conflict between

answer

The cold winds of the polar easterlies and the relatively warmer westerlies. The sub polar low of the southern hemisphere is nearly continuous over the uniform ocean surface of the cold sea surrounding Antarctica in the northern hemisphere the low-pressure zone is discontinuous being interrupted by the continents. It is much more prominent in winter and in summer and is best developed over the northernmost reaches of the Pacific and Atlantic oceans, forming the Aleutian low and the Icelandic Low

question

The polar front area is characterized how?

answer

Rising air, widespread clouds, precipitation, and generally unsettled or stormy weather conditions

question

Many of the migratory storms that travel with the westerlies have their origin in

answer

The conflict zone of the polar front

question

As we've seen over tropical regions between the equator and 20 to 25° latitude surface winds generally blow

answer

From the East

question

In the mid-latitudes, the surface wends are generally

answer

Westerly

question

In the highest latitudes, surface winds are again

answer

Easterly

question

In the upper altitudes of the troposphere, however, the wind patterns are

answer

Somewhat different from the surface winds. The most dramatic differences seen over the tropics. After Equatorial air has risen in the ITCZ, the high elevation poleward flow of the air in the Hadley cell is deflected by the Coriolis effect this results in upper elevation winds blowing from the southwest in the northern hemisphere and from the Northwest in the southern hemisphere in anti-Tradewinds. This flow eventually becomes more westerly and encompasses the subtropical jet stream thus at the surface within the tropics, Windsor generally from the east, whereas high above the anti-Tradewinds are blowing from the west

question

The seven service components of the general circulation shift latitudinally with

answer

Changing seasons

question

When sunlight, and therefore surface warming, is concentrated in the northern hemisphere, all components are displaced

answer

Northward. During the ops's season everything shifted southward

question

Where is this displacement the greatest and where is this displacement the least?

answer

It's the greatest in low latitudes and the least in the polar regions

question

Weather is affected by shifts in the general circulation components only by how much in the polar regions?

answer

Minimally

question

But the effects can be quite significant where

answer

In the tropics in mid-latitudes

question

By far the most significant deviation from the pattern of general circulation is the development of

answer

Monsoons in certain parts of the world, particularly Southern and Eastern Eurasia.

question

The word monsoon is derived from the Arabic mawsim

answer

Which means season

question

However over time it has come to mean

answer

A seasonal reversal of wins, a general sea to land movement called onshore flow in summer and a general land to sea movement called offshore flow in winter

question

Associated with the monsoon when pattern is a distinctive seasonal precipitation regime

answer

Heavy summer rains derived from the moist maritime air of the onshore flow and pronounced winter dry season when Continental air moving seaward dominanates the circulation

question

What causes a monsoon?

answer

A strong thermal low-pressure cell generated over cotton landmass and summer attracts oceanic air onshore; similarly, a prominent thermal anticyclone in winter over the continent produces an offshore circulation. It is clear that these thermally induced pressure differences contribute to monsoon development but that's not the whole story. Monsoon winds essentially represent unusually large latitudinal migrations of the tradewinds associated with a large seasonal shifts of the ITCZ over southeastern Eurasia. The Himalayas evidently also play a role - the significant topographic barrier allows a great winter temperature contrast between South Asia and the interior of the continent to the north, and this in turn may influence the location and persistent of the subtropical jet stream in the region

question

It is difficult to overestimate the importance of monsoon circulation to humankind. Why?

answer

More than half the world's population inhabits the regions in which climates are largely controlled by monsoons. These are generally regions in which the majority of the populace depends on agriculture for its livelihood. Their lives are intricately bound up with the reality of monsoon rains, that are essential for both food production and cash crops. The failure, or even late arrival of monsoon moisture inevitably causes widespread hunger and economic disaster.

question

There are two major monsoon systems and two minor systems and several other regions were monsoon patterns develop. The first of which is the South Asian monsoon

answer

The most notable environmental event each year in South Asia is the annual burst of the summer monsoon. In this first of the two major monsoon systems, prominent onshore wind spiral and from the Indian Ocean, bringing life's giving rains to the parched subcontinent. In winter, South Asia is dominated by outlawing dry air diverging generally from the Northeast. This flow is not very different from the normal North East trades except of its low moisture content

question

East Asian monsoon

answer

Second of the two major monsoon systems, we see that winter is the more prominent season in the East Asian monsoon system, which primarily affects China Korea and Japan. A strong outflow of dry Continental air largely from the Northwest is associated with anticyclonic circulation around the massive thermal high-pressure sell over western Eurasia called the Siberian high. Notable as that in South Asia, they just bring southerly and southeasterly winds, as well as considerable moisture, to the region

question

One of the two minor systems found in Australia

answer

The northern quarter of the Australian continent experiences a distinct monsoon circulation, with onshore flow from the north during the height of the Australian summer and dry, southerly, offshore flow during most of the rest of the year

question

One of the two minor systems found in west Africa

answer

The south facing coast of the west Africa is dominated by second to minor monsoonal circulation. Moist oceanic airflows onshore from the South and Southwest during summer and dry northerly Continental flow prevails in the opposite season

question

What is the so-called Arizona monsoon?

answer

The so-called Arizona monsoon of the southwestern United States is actually part of a broader minor monsoon pattern called the North American monsoon. These onshore winds in summer carry moisture from the Gulf of California and the Gulf of Mexico into New Mexico, Arizona, and Northwestern Mexico, Ray burst of thunderstorm activity

question

A common local wind system along tropical coastlines and to lesser extent during the summer in mid-latitude coastal areas is

answer

The cycle of sea breezes during the day and land breezes at night

question

Sea breezes during the day and land breezes at night are essentially what kind of circulation?

answer

Convection all circulation caused by the differential warming of land and water surfaces. The land warms up rapidly during the day, warming the air above the conduction and re-radiation. This warming causes the air to expand and rise creating low-pressure the track surface breezes from over the adjacent water body. Because the onshore flow is relatively cool and moist, it holds down daytime temperatures in the coastal zone and provides moisture for afternoon showers. Sea breezes are sometimes strong but they are rarely influential for more than 15 to 30 km inland

question

The reverse flow at night is normally considerably

answer

Weaker than the daytime went. The land and air above it cool more quickly than the adjacent water body, producing relatively higher pressure over land thus airflows offshore in a land breeze

question

Another notable daily cycle of airflow is characteristic of many hills and mountain areas. During the day what happens?

answer

Conduction and re-radiation from the land surface causes air near the mountain slopes to warm more than the air over the valleys. The warmed air rises creating a low-pressure area and in cooler air from the valley floor close upslope from the high pressure area to the low pressure area. This upslope flow is called a Valley breeze. The rising air often causes clouds to form around the peaks, afternoon showers are common in the high country as a result. After dark the pattern is reversed. The mountain slopes lose warmth rapidly through radiation, which chills the adjacent air causing it to slip down slope as a mountain breeze

question

Valley breezes are poor particularly prominent in

answer

Summer when solar warming is most intense

question

None breezes are often weakly developed in what season and are more likely to be prominent in which season?

answer

Weekly developed in summer and more likely to be prominent in winter

question

Indeed, a frequent winter phenomenon in areas of even gentle slope is cold air drainage, which is simply the

answer

nighttime sliding of cold air downslope to collect the lowest spots; this is a modified form of the mountain breeze

question

Related to simple air drainage is the more general and powerful spelling of their downslope in the form of

answer

katabatic winds.

question

These wins originate in cold upland areas and cascade toward lower elevations under the influence of gravity; they are sometimes referred to as

answer

Gravity flow wins

question

The air in them is

answer

Dense and cold

question

And although warmed adiabatically as it descends, is usually

answer

Colder than the air it displaced in its downslope flow

question

Where are katabatic winds particularly common

answer

Greenland and Antarctica, especially where they come whipping off the edge of the high, cold ice sheets

question

Sometimes a katabatic wind will be come channeled through a narrow valley. It may develop

answer

High speed and considerable destructive power

question

What is foehn winds?

answer

Another downslope wind in the Alps

question

What is chinook winds?

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Another downslope wind in the Rocky Mountains

question

The foehn and chinook winds originate only when

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a steep pressure gradient develops with high pressure on the windward side of a mountain and a low pressure trough on the leeward side. Air moves down the pressure gradient, which means from the windward side to the leeward size

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What is the downflowing air on the leeward side like?

answer

dry and relatively warm: it has lost its moisture through precipitation on the windward side, and it is warm relative to the air on the windward side because it contains all the latent heat on condensation given up by the condensing of the snow or rain that feel at the peak. As the wind blown down the leeward slope, it is further warmed adiabatically, and so it arrives at the base of the range as a warming, drying wind.

question

Why is it known as a snow eater?

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It can produce a remarkable rise of temp leeward on the mountains in just a few minutes. It not only melts the snow rapidly but also quickly dries the resulting mud

question

What are the drying winds called in California?

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Santa Ana Winds

question

They develop when

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a cell of high pressure persists over the interior of the western US for several days. The wind diverges clockwise out of the high, bringing dry, warm northerly or easterly winds to the coast (instead of the more typical cool, moist air off the ocean from the westerlies

question

What are the Santa Ana winds known for?

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high speed, high temps, and extreme dryness

question

What does the Santa Ana winds create a good environment for?

answer

wildfires

question

What is El Nino?

answer

an episodic atmospheric and oceanic phenomenon of the equatorial Pacific Ocean, particularly prominent along the west coast of South America

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During an El Nino event, what is going on with the waters?

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abnormally warm waters appears at the surface of the ocean off the west coast of South America, replacing the cold, nutrient rich water that usually previals

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We used to think El Nino was a local phenomenon, what do we know know?

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El Nino is associated with changes in pressure, wind, precipitation, and ocean conditions over large regions of Earth

question

During a strong El Nino, we see what in some regions and the opposite in others

answer

heavy rains in some regions, and droughts in others

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Why is this phenomena called El Nino?

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A slight periodic warming of Pacific coastal waters has been noticed by South American fisherman for many generations. It typically occurs around Christmas, hence the name

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What happens ever three to seven years?

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the warming of the ocean is much greater, and fishing is likely to be much poorer

question

How far back do we have records of El Nino?

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We have documentation that goes back several hundred years and archaeological and paleoclimatological evidence that goes back several thousands

question

El Nino did not receive worldwide attention until 1982 to 1983. What was going on?

answer

Over a period of several months, there were crippling droughts in Australia, India, Indonesia, the Philippines, Mexico, Central America, and southern Africa; devastating floods in the western and southeastern US, Cuba, and northwestern South America; destructive tropical cyclones in parts of the Pacific (such as in Tahiti and Hawaii) where they are normally rare; and a vast sweep of the ocean water as much as 8 degrees warmer than normal stretched over 8000 miles of the equatorial Pacific, causing massive die offs of fish, seabirds, and coral. Directly, attributable to these events were more than 1500 human deaths, damage estimated at nearly $9 billion, and vast ecological changes

question

About 15 years after that, in 1997-1998, another strong El Nino Cycle took place. What happened?

answer

30 billion in worldwide property damage and at least 2100 people dead and 10 of 1000 of people displaced. Blizzards in the Midwest, devastating tornadoes in the southeastern US and much higher than average rainfall in California

question

To understand what happens during El Nino that correlates with such widespread changes in the weather, we need a review of normal conditions

answer

The waters off the west coast of South America are cool. The wind and pressure patterns in this region are dominated by the persistent subtropical high associated with the subsiding air of the Hadley cell circulation. As the trade winds diverge from the subtropical high, they flow from east to west across the Pacific - this tropical airflow drags surface ocean water westward across the Pacific basin in the warm Equatorial Current. As surface water pulls away from the coast of South America, an upwelling of cold, nutrient rich ocean water rises into the already cool Peru current. This combo of cool water and high pressure result in relatively dry conditions along much of the west coast of South America.

question

So what changed in the South America areas?

answer

In contrast to the cold water and high pressure near South America, in a normal year on the other side of the Pacific Ocean near Indonesia things are quite different. The trade winds and the Equatorial Current pile up warm water, raising sea level in the Indonesian region as much as 60 centimeters (about 2 feet) higher than near South America, turning the tropical western Pacific into an immense storehouse of energy and moisture

question

What about Australia and Indonesia?

answer

Warm water and persistent low pressure prevail around northern Australia and Indonesia; local convective thunderstorms develop in the intertropical convergence zone (ITCZ), producing high annual rainfall in this region of the world. After this air rises in the ITCZ, it begins to flow poleward but is deflected by the Coriolis effect into the upper-atmosphere westerly antitrade winds; some of this airflow aloft eventually subsides into the subtropical high on the other side of the Pacific.

question

This general circuit of airflow described above is known as?

answer

Walker Circulation

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Every few years, the normal pressure patterns in the Pacific change how?

answer

High pressure develops over northern Australia and low pressure develops to the east near Tahiti.

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This seesaw of pressure is known as

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Southern Oscillation

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Southern Oscillation was first recognized by Gilbert Walker when he noticed that in most years pressure is low over northern Australia and high over Tahiti and in those years, the monsoon came as expected. In some years, pressure was high over Australia and low over Tahiti, and in those years the monsoon did not come. This observation wasn't enough to predict monsoons but the connection that was found was

answer

a connection between Walker's Southern Oscillation and the occurence of strong El Nino warming new South America.

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This connection, the overall coupled ocean atmosphere pattern is now known as

answer

El Nino Southern Oscillation (ENSO)

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A typical El Nino cycle

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For many months before the onset of an El Nino cycle, the trade winds pile up warm water in the western Pacific near Indonesia. A bulge of warm equatorial water perhaps 25 cm (10 inches) high then begins to move to the east across the Pacific toward South America. Such slowly moving bulges of warm water are known as Kelvin waves. A Kelvin wave might take 2 or 3 months to arrive off the coast of South America. The bulge of warm water in a Kelvin wave spreads out little as it moves across the ocean since the Coriolis effect effectively funnels the eastward moving water toward the equator in both hemispheres. When the Kelvin wave arrives at South America, sea level rises as the warm water pools. The usual high pressure in the subtropics has weakened; upwelling no longer brings cold water to the surface, so ocean temps increase still further - an El Nino is underway. By this time, the trade winds have weakened or even reversed directions and started to flow from the West - blowing moist air into the deserts of coastal Peru. The themocline boundary between near surface and cold deep ocean waters lowers. Pressure increases over Indonesia and the most active portion of the ITCZ in the Pacific shifts from the now cooler western Pacific, toward the now warmer central and eastern Pacific basin. Drought striked northern Australia and Indonesia; the South Asian monsoon may fail or develop weakly. The subtropical jet stream over the eastern Pacific shifts its path, guiding winter storms into the SW US - California and Arizona experience more powerful winter storms than usual, resulting in high precipitation and flooding.

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