Meteorology - Chapter 7

air pressure

the pressure exerted by the weight of air above

air pressure

of the various elements of weather and climate, changes in _______ _______________ are the least noticeable

1 atmosphere

a column of air 1 square inch in cross section, measured from sea level to the top of the atmosphere would way 14.7 pounds and is referred to as...

(down, up, sideways)

air pressure is exerted in ________ direction

one atmosphere

our body is made to withstand ________________

1 kilogram per square centimeter
14.7 lbs per square inch

air pressure at sea level is about

gas molecules

move freely around the space provided to them

earth's surface

the atmosphere is confined from below by _____________ and from above by ______________

air pressure

what is the force exerted against a surface by the continuous collision of gas molecules

mercury barometer

An instrument that measures changes in air pressure, consisting of a glass tube partially filled with mercury, with its open end resting in a dish of mercury.


Metric unit of atmospheric pressure

1013.2 millibars

standard sea level pressure

inches of mercury

media use _______ ____ _________ to describe atmospheric pressure

Torricelli (galileo's student)

invented the barometer


a vast ocean of air that exerts pressure on us and all objects around us ( according torricelli )


when air pressure increases mercury _______

29.92 inches of mercury

standard atmospheric pressure at sea level equals ___________ inches of mercury

aneroid barometer

A smaller instrument that measures changes in air pressure without using a liquid.

metal chamber

an aneroid barometer uses a partially evacuated ______________ ___________

current air pressure

the ______________________________ is more important than the current pressure reading

high pressure
low pressure


Cloudiness and precipitation

falling pressure is often associated with increasing ________________ and possibility of __________________

clearing conditions

rising air pressure generally indicates _____________ ______________

increasing cloudiness and possibility of precipitation

falling pressure is associated with...

clearing conditions

rising pressure is associated with...


An instrument that continuously records air pressure changes over time


The horizontal movement of air from an area of high pressure to an area of lower pressure

solar radiation

___________________ __________________is the ultimate energy source for most wind

1. pressure gradient force
2. coriolis effect
3. friction

because earth rotates, wind is controlled by


air moves from a place of ______ pressure to a place of ________ pressure


Lines joining places on the map that have the same air pressure

the amount of pressure change occurring over a given distance / pressure gradient

the spacing of isobars indicates...

pressure gradient

the amount of pressure change occurring over a given distance

steep pressure gradient and high winds

Closely spaced isobars indicate

weak pressure gradient and light winds

Widely spaced isobars indicate

right angle isobars

the pressure gradient force is always directed at ________ ________ the the isobars

by converting all pressure measurements to sea level equivalents

how is pressure compensation for high elevations accomplished?

wind arrow shafts
wind bars

on a weather map, wind direction is shown as ____________ __________ __________ and speed is shown as ______ _________

horizontal pressure gradient

what is the driving force of wind?

Coriolis effect

The effect of Earth's rotation on the direction of winds and currents.


all free moving objects or fluids (including wind) are deflected to the _________ in the Northern hemisphere and to the ____________ in the Southern hemisphere

1. deflection is always directed at right angles to the direction of airflow
2. affects only wind direction not speed
3. is affected by wind speed (the stronger the wind the greater the deflection)
4. is strongest at the poles and weakens toward the equat

Deflection is...

few kilometers

the effect of wind is important only within a ______________________ of earthys surface


what acts to slow air movement and as a consequence alters wind directions?


the faster the wind speed the greater the _____________.

geostrophic wind

A wind usually above a height of 600 meters that blows parallel to the isobars and at higher speeds than surface winds.

jet streams

bands of high-speed winds about 10 kilometers above Earth's surface

jet streams

the most prominent features of upper level air flow are...


________ lowers the wind speed, so it reduces the coriolis effect


over smooth ocean terrain, friction is _______
over rugged terrain, friction is ________


centers of low atmospheric pressure


high pressure centers of dry air


in a low pressure cyclone, the values of the isobars ______________ as they move toward the center
in high pressure anticyclones, the value of the isobars _________ as they move toward the center

inward and counterclockwise

in the NH, in a low pressure system, winds blow ___________ and ____________

outward and clockwise

in the NH, in a high pressure system, winds blow ___________ and ____________


the coriolis effect deflects winds to the _________ in the NH and to the _________ in the SH


a net inflow around a cyclone


a net outflow around an anticyclone


what produces clear skies?

rising air

what is associated with cloud formation and precipitation?

horizontal convergence

the net inward transport of air causing a shrinking of the area occupied by the air mass

Barometric Tendency (Pressure)

the change of atmospheric pressure during the last few (generally three) hours before a regular observation.

converges horizontally

when air ______________ ________________is must pile up (increase in height to allow for the decreased area in now occupies

exerts less pressure than that occurring in surrounding regions

a surface low can only exist as long as the column of air ____________________________________________________________________________.

net accumulation of air

a low pressure center causes a _________________________________, which increases its pressure

at some layer aloft

in a low pressure cyclone, for a surface low to exist for very long, a compensation must occur _________________________________________.


in a low pressure cyclone, surface convergence could be maintained if _____________ aloft occured at a rate _________ to the inflow below


in a low pressure cyclone, __________________ aloft can intensify a storm or maintain them

surface convergence

winds that blow in at the surface

equatorial low

a belt of low pressure lying near the equator and between the subtropical highs

abundant precipitation

the equatorial low is marked by ______________ _______________

unstable conditions and stormy weather

because rising air often results in cloud formation and precipitation, a low pressure center is generally related to __________________ _________________ and _______________ ________________


because descending air is compressed and warmed, cloud formation and precipitation is unlikely in a(n) ____________________

west to east
a week

low pressure cyclones move _______ to ______ and last for about __________

unequal heating

the underlying cause of wind is ___________ ___________ of the earths surface

warm air
cool air

the atmosphere acts as a giant heat transfer system, moving __________ air poleward and __________ air equatorward

spread out

on a nonrotating earth,the heated equatorial air would rise until it reaches the ____________ , which acts like a lid and deflects air _____________.
eventually, this upper level airflow would reach the _________, _________, _________ __________ in all di


this hypothetical circulation system of the nonrotating earth has upper level air flowing _____________ and surface air flowing _____________

Intertropical Convergence Zone (ITCZ)

a low pressure zone where winds from the north and south converge

subtropical high

A belt of high pressure located at approximately 30o N and 30o S, which pushes heavy subsiding air outward toward both north and south.

trade winds

Prevailing winds that blow northeast from 30 degrees north latitude to the equator and that blow southeast from 30 degrees south latitude to the equator


Dominant winds of the mid-latitudes. These winds move from the subtropical highs to the subpolar lows from west to east.


the steep temperature gradient across the middle latitudes in the winter months corresponds to a __________ flow aloft


in the winter the jet stream moves _______
in the summer the jet stream moves ________


the Northern Hemisphere is rainy in the _______________
the Southern Hemisphere is rainy in the

polar easterlies

Prevailing winds that blow from east to west between 60degrees-90degrees latitude in both hemisphere.

subpolar low

a low pressure area formed sixty degrees N when the prevailing westerlies rise above the polar easterlies

polar front

boundary at which cold polar air meets the warmer air (causes a stormy belt) of the middle latitudes

polar high

The source region for the variable polar easterlies

subtropical and polar highs

the __________ and _____________________ are areas of subsiding air that flows outward at the surface, producing the prevailing winds

equatorial and subtropical

the low pressure zones of the _________________ and __________________ regions are associated with inward and upward accompanied by clouds and precipitation

subpolar low in the southern hemisphere

the only true and continuous pressure belt is the ______________ in the ______________________________ where the ocean is interrupted by land masses

seasonal differences

in the Northern Hemisphere, land masses break up the ocean surface and large _______________ _______________ disrupt the pattern


the circulation over the oceans is dominated by semi permanent cells of _________ pressure in the subtropics and cells of _______ pressure over the subpolar regions

Trade winds and westerlies

subtropical highs are responsible for the


seasonal wind patterns that cause wet and dry seasons


summer monsoons are _____
winter monsoon are ______


the general circulation is produced by semipermanent cells of high and low pressure over the ________ and is complicated by seasonal pressure changes over _________

local winds

small scale winds produced by a locally generated pressure gradient

topographic effects or variations in surface composition - land and water

local winds are caused by _____________________________________ or _____________________________ in the immediate area

sea breeze

movement of air from sea to land during the day when cooler air from above the water moves over the land, forcing the heated, less dense air above the land to rise

mid to late afternoon

Sea breeze is most intense at

land breeze

movement of air from land to sea at night, created when cooler, denser air from the land forces up warmer air over the sea


in coastal areas during the summer months, _______ is heated most intensely during the daylight hours

valley breeze

The movement of air created by warm air rising and flowing up the slope of a mountain.


the air along the slopes of the mountains is heated ________ intensely than the air at the same elevation over the valley floor

mountain breeze

The movement of air caused by cool air sinking and moving down the slope of a mountain.

next to the ground

rapid radiation cooling along the mountain slopes produces a layer of cooler air _________ _____ ______ __________


Valley breezes are most common during the ________ seasons
Mountain breezes are more common in the ________ season


dry warm wind moving down on the eastern slopes of the Rocky Mountains; occurs when a strong pressure gradient develops in a mountainous region


because condensation may have occurred as the air ascended the windward aside, releasing latent heat, the air descending the leeward slope will be _________ and _________ than it was at a similar elevation on the windward side

santa ana

a very dry and often dusty wind that blows in Southern California that puts it at risk for fires

wind sock

A cloth cone open at both ends mounted in a high place to show which direction the wind is blowing

ther direction in which they blow

winds are always labeled by ...

wind vane

Instrument used to measure wind direction
(has a dial of N,S,E,W or 0 to 360)


winds are always labeled by the _________ from where they blow


a wind vane always points ________ the wind

cup anemometer

An instrument used to measure wind speed

prevailing winds

winds that consistently blow in the same direction over large areas of Earth


what wind dominates the midlatitudes and move weather from west to east?

El Nino

(oceanography) a warm ocean current that flows along the equator from the date line and south off the coast of Ecuador at Christmas time


during an el nino, strong equatorial countercurrents amass large quantities of ___________ than normal water along the west coast of South America


during a la nina, it has ___________ than normal water along the central and eastern pacific

heavy rain
major flooding
cold nutrient water

The warm water and and associated low pressure arid areas of Peru and Chili to receive unusually ________ _______that can lead to _________ ___________ and the blocking of _________ __________ ________ needed by fish to survive.

2 to 7
9 months to 2

an el ni´┐Żo may happen in intervals of ___ to ____ years and usually persist or spans of ____ months to ____ years

La Nina

A cooling of the ocean surface off the western coast of South America, occurring periodically every 4 to 12 years and affecting Pacific and other weather patterns.

upwelling of deep nutrient rich water

during a la nina, the cold Peru current that flows equatorward along the coast of Chili and Peru intensifies, which encourages ___________________________________________

Atlantic hurricanes

one major benefit of El nino is a lower than normal average number of ___________- ___________


one major deficit of la nina is more frequent _______________

south america; from ecuador to peru

Where does the el nino current flow?

south america; from australia to indonesia

where does the la nina current flow?

1. winter temperatures are warmer than normal
2. wetter winters in the North america southwest and Mexico northwest
3. wetter and cooler conditions in southeast US
4. lower than average number of Atlantic hurricanes

what is the result of an el nino in North America?

1. cooler and wetter conditions over the northwestern US
2. cold winter temperatures in the Northern plain states
3. unusually warm conditions occur in the southwest and southeast
4. in the western pacific they experience wetter than normal temps
4. more

what is the result of an la nina in North America?

Southern Oscillation

the atmospheric pressure conditions corresponding to the periodic warming of El Nino and cooling of La Nina.


A linkage between weather changes occurring in widely separated regions of the world.


Each time an el nino occurs barometric pressure _______ over large portions of the eastern Pacific and ______ in the tropical potions of the western pacific

swings back in the opposite direction

As an el nino comes to an end the pressure difference ___________________________________________ triggering a la nina

climate predictions for distant locations

understanding teleconnection patterns allow meteorologists to make _____________________________

climate outlook

national weather service predictions for periods from 1 to 13 months into the future are called climate outlooks

relatively dry conditions

regions influenced by high pressure, with its associated subsidence and diverging winds experience...

amply precipitation

regions under the influence of low pressure and its converging winds and ascending air experience...


areas dominated by subtropical high pressure cells receive much _____________ amounts of precipitaton


the warm humid trade winds converge to yield abundant _________ throughout the year


cold air has a ______ capacity for moisture with warm air

1. pressure
2. wind belts
3. water capacity
4. distribution of land and water
5. mountain barriers

what affects global precipitation?