# GEO 115, ch. 7

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### ***any extreme weather events are associated with ___________. In fact, much of the damage caused by __________ and severe ________ is due to brute wind power.

Strong winds / Tornadoes / thunderstorm

### **** ________ is simply the mass of air above a given level. From the gentle breeze to the raging tornado, all winds form by the same process:________________

air pressure / differences in atmospheric pressure

### *7A* As we climb in elevation above the earth's surface, there are fewer air molecules above us; hence, atmospheric pressure always decreases with ______________.

increasing height.

### ***suppose we somehow force more air into the column (column of air in figure shown o pg 177). what would happen?

The added air would make the column more dense, and the added weight of the air in the column would increase the surface air pressure.

### *** likewise, if a great deal of air were ________ from the column, the surface air pressure would ___________.

removed / decrease

### ***It takes a shorter column of______, more-dense air to exert the same ___________ as a taller column of warm, less-dense air.

cold / surface pressure

pressure

### *7A* The pressure difference establishes a force called_____________ that causes the air to move from _______pressure toward ___________pressure.

pressure gradient / higher / lower

### *7A* what happens when the air aloft leaves column 2 (high pressure to low pressure (column 1)

the mass of the air in column two decreases, and so does the surface air pressure.

### *7A* what happens to column 1 as pressure from column 2 is entering?

column 1 causes the surface air pressure to increase.

### *7A*higher air pressure at the surface in column 1 and lower air pressure at the surface in column 2 causes the surface air to do what?

causes the surface air to move from city 1 towards city 2 (pg. 177)

### *7A* the heating and cooling of air columns causes what?

horizontal pressure variations aloft and at the surface.

wind to blow.

### *7A*AS the surface air moves out away from city 1, the air aloft slowly sinks to replace this outwardly spreading surface air. As the surface air flows into city 2, it slowly rises to replace the depleted air aloft. In this manner, a complete circulation of air--called a __________________-is established due to the________ and ________ of air columns.

direct thermal circulation,heating and cooling

### over large continental areas, especially the southwestern U.S in summer, hot, less-dense surface air is accompanied by ____________.

surface low pressure

### Bitter cold, dense arctic air in winter is often accompanied by _______________

surface high pressure

rises

station pressure

### *7BAtmospheric pressure always________ with increasing height, the higher a city is above sea level, the lower its ____________

decreases / station pressure

### Since variation in elevation have such a huge influence on a city's station pressure, readings of atmospheric pressure are usually adjusted to a common elevation--normally MEAN SEA LEVEL. what is the name of the adjusted reading called??

sea-level pressure

10 / 100

952+60=1012 mb

horizontal

surface map

### Because winds are produced by differences in pressure on a horizontal surface, surface maps are extremely useful tools in the analysis of________________.

wind-flow patterns

isobars

### The sea-level pressure chart described so far represents the ____________ pressure at a ________ level.

atmospheric / constant

### The preferred chart commonly in use in the study of weather above the surface is what kind of chart?

constant pressure chart or isobaric chart

isobaric chart.

### what's the difference between sea-level pressure chart and isobaric chart?

instead of showing pressure variations at a constant altitude, isobaric charts show height variations along a surface of constant pressure.

higher / cold

### *7D* __________, is where where the atmospheric pressure at all points along the surface is 500 mb.

constant pressure

contour line

### Contour lines and isobars usually decrease in value from ________to __________ because the air is typically warmer to the_______ and colder to the _________

south / north, south/ north

### *7E* _________ are where the air is warm and indicating depression (centers of low temp.)

Ridges (elongated highs) (high)

### _______ are where the air is cold.

troughs (elongated lows) (lowes)

### In a surface map the wind blows _____the isobars, compared to an upper-air map, the wind blows_______ to the _________lines.

across / parallel / contour lines

### why are upper-level charts valuable tools?

they show wind-flow patterns that are extremely important in forecasting all types of weather, including severe weather events. They can also be used to determine the movement of weather systems and to predict the behavior of surface pressure areas.

### *7f*what forces are involved with the movement of air?

pressure gradient force, Coriolis force, centripetal force, an friction.

### what would happen if we supppose the pressure in fig. 7.11 (p.184) were to change, and the isobars become closer together.

this condition would produce a rapid change in pressure over a relatively short distance, known as steep pressure gradient.

### what if the isobars spread farther apart?

difference in pressure would be small over a relatively large distance, known as gentle pressure gradient.

### when differences in horizontal air pressure exist there is a ______force acting on the air. this force, called the_______________is always directed from higher toward lower pressure at right angles to the isobars.

net / pressure gradient force (PGF)

steep

### the _____________is the force that causes the wind to blow. Because of this fact, closely spaced isobars on a weather chart indicate what type of pressure gradients?

pressure gradient forces / steep pressure gradients, strong forces and high winds.

### on the other hand, widely spaced isobars indicate what type of pressure gradients?

gentle pressure gradients, weak forces, and light winds.

Coriolis force

coriolis / left

Coriolis

Parallel

Geostrophic wind

isobars

slower

### *7g* the same pressure gradient force aloft will not produce the same_______at the surface, and the wind at the surface will not blow in the same_________ as it does aloft.

wind speed / direction

Friction

waves.

wind waves

### *7H*The amount of energy transferred to the water (and thus the height of which a wave can buid) depends opon three factors. what are they?

the wind speed, the lenght of time that the wind blows over the water, and the "fetch, or distance, of deep water over which the wind blows.

upwelling

parallel

### --**--if we compute the amount of pressure change that occurs over a given distance, we have the pressure gradient; thus:______

pressure gradient= difference in pressure divided by distance.

steep pressure

stronger

4

### on pg. 185, figure 7.13, why is the difference in pressure between X and X' 32 mb, producing a pressure gradient of 32 mb

because each isobar interval is 4mb, and if you count the spaces between each isobar you get 32 mb.

wind speed.

coriolis

### The ________force causes the wind to deflect to the _______ of its intended path in the Northern Hemisphere and to the _______of its intended path in the Southern Hemisphere.

Coriolis / RIGHT / LEFT/

### As the wind speed increases, the __________force increases; hence, the stronger the wind, the greater the _______.

corilois/ deflection.

### To an observer standing on the earth, however, it is the plane that appears to _________. the amount of ______ is greatest toward the_______ and nonexistent at the __________.

deviate / deviance / pole / equator

high / low

### in northern hemisphere, winds blow____________around lows and _________ around highs.

counterclockwise / clockwise

### low winds are also known as ________, the counterclockwise flow of air around them is often called _______________.

cyclones / cyclonic flow

### The clockwise flow of air around a high, or _________j, is called ______________

anticyclone / anticyclonic flow

outward / inward

Example: