Atmospheric Movement in Weather Change Atmospheric Movement in Weather Change

WeatherWeather The short-term (a few hours or days) The short-term (a few hours or days)

condition of the atmosphere at a condition of the atmosphere at a given location. given location. WaterWater and and airair move move constantly---together they create constantly---together they create WEATHER!WEATHER!– The weather of an area is due to four The weather of an area is due to four

atmospheric factors: atmospheric factors: heat energyheat energy, , airair pressurepressure, , windswinds, and , and moisturemoisture..

MeteorologistsMeteorologists are are scientists who study scientists who study and predict the weatherand predict the weather

WeatherWeather is the is the conditioncondition of of Earth’s Earth’s atmosphereatmosphere at a at a particular time and place.particular time and place.

Composition of the Atmosphere

Other gases:– Oxygen and nitrogen = 99% of dry air.

Carbon dioxide and argon make up most of the other one percent (1%).

The remaining gases are called trace gases because only small amounts of them are present.

Composition of the Composition of the AtmosphereAtmosphere

Nitrogen is the most abundant gas in the atmosphere– Makes up a little more than three fourths of

the air we breathe– Essential to living things

Most living things cannot obtain nitrogen directly from the air

– Bacteria convert nitrogen into substances – Plants then absorb the nitrates from the soil and use

them to make proteins. – Animals must eat plants or other animals.

Getting Energy

All energy on Earth All energy on Earth comes from the Sun, comes from the Sun, but there are three but there are three

different ways things different ways things can get the energy can get the energy

once it is here.once it is here.

RadiationRadiation – is the absorption of energy.

Energy travels from the sun in electromagnetic waves.

These waves are absorbed by the things on earth.

(Ground is warmed by (Ground is warmed by radiation)radiation)

HeatHeat is is transferred to transferred to the air when the air when

the air touches the air touches the ground.the ground.

The The warmerwarmer something something gets the gets the moremore energyenergy its its

molecules have. molecules have.

The more energy The more energy molecules have the molecules have the fasterfaster

they move.they move.

The faster molecules The faster molecules move the more move the more volumevolume (space) they take up.(space) they take up.

Basic Ingredients for Weather

The solar radiation The solar radiation heats the surface heats the surface

of the earth.of the earth.

Heat is transferred to air Heat is transferred to air molecules that come in contact molecules that come in contact

with the ground.with the ground.

As the As the

Hot Air Rises…Hot Air Rises…

Cooler air is Cooler air is pulled in pulled in

from other from other placesplaces

Do you Do you know what know what this is this is called?called?

Air PressureAir Pressure

Properties of Air

Air pressure occurs as a result of the Air pressure occurs as a result of the weightweight of the air pressing down on the of the air pressing down on the Earth. AEarth. A changechange in air pressure usually in air pressure usually indicates a change in indicates a change in weatherweather is going is going to occur. A body of air that has to occur. A body of air that has similarsimilar temperature, humidity, and air pressure temperature, humidity, and air pressure

is called an air massis called an air mass..

There is a column of air

above you all the time. The weight

of the air in the atmosphere

causes air pressure.

Air push in all directions—down, up, and sidewaysAir push in all directions—down, up, and sideways

Ground warmed by radiation

As the air

becomes less

dense it rises

Ground warmed by radiation

Rising air spreads heat throughout the atmosphere.

Increasing AltitudeIncreasing Altitude

Altitude, or elevation, is the distance above sea level, the average level of the surface of the oceans.– Air pressure decreases as altitude increases.

As air pressure decreases, so does density.

Alt

itu

de

Alt

itu

de

Units of Air Pressure  

Weather reports Most weather reports use inches of mercury. – National Weather

Service maps indicate air pressure in millibars.

3033.87x

1016.1

An air mass with An air mass with lowlow pressure pressure

is likely to be is likely to be stormystormy. An air . An air mass with mass with highhigh pressure is pressure is likely to be likely to be fairfair. . Air moves fromAir moves from areas of areas of highhigh pressure pressure toto areas areas of of lowlow pressure. This pressure. This movement occurs as the movement occurs as the differences in air pressure differences in air pressure cause windcause wind. .

The Wind Winds are the result of

uneven heating of the Earth’s surface– This uneven heating

causes differences in air pressure to develop.

the transfer of the transfer of heat through heat through

movement in the movement in the atmosphere.atmosphere.

Where Does Wind Go?

Winds always blow from areas of high pressure to areas of low pressure.– The closer wind

is to the low pressure area the faster it blows.

Moves pressure Moves pressure systems from systems from WestWest

to to EastEast..

Pacific Ocean

Atlantic Ocean

Gulf of Mexico

COLD FRONT or WARM COLD FRONT or WARM FRONT?FRONT?

Air massesAir masses are large are large bodies of air classified bodies of air classified by their by their temperaturetemperature (warm or cold) and (warm or cold) and

amount of amount of waterwater (wet (wet or dry). or dry).

Warm FrontWarm Front

COLD FRONTCOLD FRONT