Weather and ClimateWeather and Climate

What is the weather like today?What is the weather like today?

Is it like this EVERY day? Why?

What is the difference between WEATHER and CLIMATE?

Weather and ClimateWeather and Climate Weather Weather – The – The temporary temporary environmental environmental

conditions in a localized area over a short conditions in a localized area over a short period of time.period of time.

In other words…what it’s like OUTSIDE, right HERE, right NOW

ClimateClimate – – The long-term The long-term environmental environmental conditions across a large area and long time.conditions across a large area and long time.

In other words…the AVERAGE of all the WEATHERS

What affects weather and climate?What affects weather and climate?

There There are two major factors that affect the are two major factors that affect the overall environment and overall environment and climateclimate……

-The tilt of the Earth in relation to it’s orbit around the Sun

- The direction of that tilt that changes as the Earth travels around the Sun

First, some basic vocabulary…First, some basic vocabulary…

RevolutionRevolution – – one ORBITone ORBIT, or trip around the , or trip around the Sun. This takes the Earth Sun. This takes the Earth 365 ¼ days365 ¼ days

Rotation – one SPIN of the Earth on it’s axis. This takes about 24 hours…one DAY.

Earth’s Earth’s TILTTILT The Earth is not vertical (straight up-and-down) in relation to it’s The Earth is not vertical (straight up-and-down) in relation to it’s

orbital path, it’s orbital path, it’s tiltedtilted 23 ½ degrees from vertical23 ½ degrees from vertical..

This tilt means that the Sun’s energy doesn’t hit the Earth equally.

DRAW THIS ! ! !

Earth’s Earth’s TILTTILT

This This tilt results in uneven heating of the tilt results in uneven heating of the Earth’s surfaceEarth’s surface..

“Direct” sunlight

“Indirect” sunlight

From From TILTTILT to SEASONS to SEASONS As the Earth travels around the Sun, the As the Earth travels around the Sun, the tilttilt

changes in relation to the Sun. Sometimes changes in relation to the Sun. Sometimes “toward” the Sun, sometimes “away”, and “toward” the Sun, sometimes “away”, and sometimes neither. sometimes neither.

This creates a This creates a predictable predictable

cycle of cycle of warmer and warmer and

cooler periods, cooler periods, or seasons.or seasons.

DRAW THIS !!

SeasonsSeasons Because the direction of the tilt (“towards” or Because the direction of the tilt (“towards” or

“away”) is opposite for the Northern and “away”) is opposite for the Northern and Southern hemispheres, so are the seasons.Southern hemispheres, so are the seasons.

Here is the rule to remember… Tilted “toward” the Sun means Summer, tilted “away” from the Sun means winter

Solstice and EquinoxSolstice and Equinox SolSolsticestice – the point at which the Earth is pointed farthest – the point at which the Earth is pointed farthest

toward / away from the Sun, creating toward / away from the Sun, creating long summer days and long summer days and short winter daysshort winter days . (Latin root word “sol”) . (Latin root word “sol”)– Summer – around June 21Summer – around June 21– Winter – around December 21Winter – around December 21 EquinoxEquinox – the – the

point at which the point at which the Earth is not Earth is not pointed toward OR pointed toward OR away from the away from the Sun, creating Sun, creating equalequal day and day and nightnight. . (“equi-nox”)(“equi-nox”)-Spring (“Vernal”)around March 21- Fall (“autumnal”) around Sept. 21

Earth’s Earth’s tilttilt affects length of days affects length of days Places experiencing summer have Places experiencing summer have

“longer” days (more sunlight “longer” days (more sunlight per 24 hrs.)per 24 hrs.)

Places experiencing winter have Places experiencing winter have “shorter” days (less “shorter” days (less sunlight per 24 hrs.)sunlight per 24 hrs.)

Areas above 66 ½ degrees Areas above 66 ½ degrees N or S will experience 24 hr. N or S will experience 24 hr. extremes (light and dark) extremes (light and dark) depending on the seasondepending on the season

24hrs.of

darkfromMayto

August

24hrs.of

lightfromNov.

toFeb.

LongerSummer

days

ShorterWinterdays

Greenhouse EffectGreenhouse Effect RULE #1 OF NATURE – Energy can

be either absorbed or transferred Normally, when the Sun’s energy penetrates the atmosphere, some of it is absorbed, and some of it is reflected back to space.

Human and natural events increase pollutants that trap the reflected energy and send it back to the Earth again, increasing the Earth’s heat.

Distributing the Sun’s Heat - Distributing the Sun’s Heat - WINDWIND RULE #2 OF NATURE – Nature seeks RULE #2 OF NATURE – Nature seeks

balance (equilibrium)balance (equilibrium) Wind is the movement of air from High pressure to Low pressure

Air Pressure changes with temp.“Hot” (more active) molecules need

room to move, so they spread apart, meaning LESS moleculesin a given space (LOW pressure)

“Cold” (less active) molecules don’t move as much, so they pack closer together, meaning MORE molecules in a given space (HIGH pressure)

HOT air

RISES

COLD air

SINKS

WINDWIND – – Sea BreezeSea Breeze When the sun shines, When the sun shines, land (solid) heats up land (solid) heats up

faster than water (liquid) faster than water (liquid) – – remember remember RULE #1RULE #1 ? ? Only the top 2-3 inches of earth get warm, then Only the top 2-3 inches of earth get warm, then

the heat is reflected back to the air. the heat is reflected back to the air. (Why do dogs dig in the dirt?)(Why do dogs dig in the dirt?)

The warm air rises, creating The warm air rises, creating LOW PRESSURE LOW PRESSURE over the land during over the land during the early/mid-morningthe early/mid-morning

This imbalance This imbalance ((RULE #2RULE #2)) creates a creates a COOL wind blowing COOL wind blowing in from the waterin from the water, , called a SEA BREEZEcalled a SEA BREEZE

HL

WINDWIND – – Land BreezeLand Breeze When the sun sets, the process reverses and When the sun sets, the process reverses and

land cools off faster than water land cools off faster than water ((RULE #1RULE #1))

This creates COOLThis creates COOLerer air (HIGH pressure) air (HIGH pressure) over the land and WARMover the land and WARMerer air (LOW air (LOW pressure) over the water at nightpressure) over the water at night

The The WARM wind WARM wind blowing out from the blowing out from the landland is called a is called a LAND BREEZELAND BREEZE H

L

WINDWIND - - MonsoonsMonsoons On a larger scale, the same factors create On a larger scale, the same factors create

monsoons - monsoons - seasonalseasonal winds winds Due to the Earth’s tilt, differences in the Due to the Earth’s tilt, differences in the

heating of land and ocean create long heating of land and ocean create long term wind patterns term wind patterns that bring that bring seasonal rainy and dry period seasonal rainy and dry periods.s.

Global Wind PatternsGlobal Wind Patterns RULE # 3 OF NATURE – Nature RULE # 3 OF NATURE – Nature

obeys the stronger forceobeys the stronger force The Earth gets the most direct sunlight in the tropics,

so HOT air RISES at the Equator. The least sunlight hits the polar region, so the COLD

air sinks at the poles These two extremes force the

middle latitude winds to flow “backwards”, rising

at 60 deg. and sinking at 30 deg., even though that is warmer air.

Coriolis EffectCoriolis Effect Because the Earth spins (rotates) under the winds Because the Earth spins (rotates) under the winds

as they travel N and S, they appear to curve as they travel N and S, they appear to curve because of the Coriolis effectbecause of the Coriolis effect. . (see it)

The result is curved The result is curved wind patterns across wind patterns across the Earth surface.the Earth surface.

All winds are named All winds are named for where they come for where they come FROM.FROM.

Areas of no major Areas of no major wind pattern are wind pattern are called called “doldrums” “doldrums” or or “horse latitudes”“horse latitudes”(Spanish explorers)(Spanish explorers)

Water CurrentsWater Currents Most ocean currents are affected by global Most ocean currents are affected by global

wind patterns blowing across the oceans.wind patterns blowing across the oceans.

Most

WARM

currents

flow

WEST

Most

COOLCOOL

currents

flow

EAST

Precipitation – Nature’s ThermostatPrecipitation – Nature’s Thermostat There are There are 3 basic causes for rain3 basic causes for rain. They are:. They are:

– Convection – due to evaporation and coolingConvection – due to evaporation and cooling Sun’s energy causes surface water to evaporate Sun’s energy causes surface water to evaporate

and become humidityand become humidity As the day cools off, the air cools and As the day cools off, the air cools and

condenses, causing storms and raincondenses, causing storms and rain Usually in tropical environmentsUsually in tropical environments

– Frontal – due to changes in temperatureFrontal – due to changes in temperature Starts with warm, moist air at the surface and aboveStarts with warm, moist air at the surface and above As a cold front approaches, it stays low, As a cold front approaches, it stays low,

forcing the moist air aloftforcing the moist air aloft This cools and condenses the air, This cools and condenses the air,

creating rain on the “leading edge” of creating rain on the “leading edge” of the frontthe front

Usually in mid-latitudes where warm and cold air systems Usually in mid-latitudes where warm and cold air systems collidecollide

Precipitation, Part IIPrecipitation, Part II Orographic – due to changes in elevationOrographic – due to changes in elevation

– Moist air travels over land and approaches a steep rise in Moist air travels over land and approaches a steep rise in elevationelevation

– As the air is forced up the side of the rise, the air cools, As the air is forced up the side of the rise, the air cools, causing causing precip. on the “windward” side of the mountainprecip. on the “windward” side of the mountain

– As the (now dry) air continues over and down the As the (now dry) air continues over and down the “leeward” side of the mountain“leeward” side of the mountain, it warms up and , it warms up and absorbs any available absorbs any available moisture, creating a moisture, creating a “rain shadow desert”“rain shadow desert”

– Found in areas of Found in areas of mountains or other mountains or other rapid elevation changerapid elevation change

CLIMATESCLIMATES The world is divides into three large climate The world is divides into three large climate

zones, based on latitude.zones, based on latitude.

Low Latitude (“Tropical”) climates – always hot

Mid Latitude (“Temperate”) climates – hot/cold seasons

High Latitude (“Polar”) climates – seasons either mild or extreme cold

DRAW THIS !!!

Climate ZonesClimate Zones

Climate zones are divided into regions Climate zones are divided into regions with differences in with differences in twotwo key characteristics: key characteristics:– Amount of moisture (rain), andAmount of moisture (rain), and– Typical temperature range through the yearTypical temperature range through the year

These two characteristics are affected by These two characteristics are affected by balancing the effects of four factors:balancing the effects of four factors: LLatitude atitude AAltitude ltitude NNearness to waterearness to water DDirection of atmosphere and ocean currentsirection of atmosphere and ocean currents

WRITE THESE DOWN !

LatitudeLatitude Due to the Earth’s tilt, the amount of sun Due to the Earth’s tilt, the amount of sun

energy changes over the earth’s surface…energy changes over the earth’s surface…

Tropical (Low Latitude) zone – year-round direct sunlight, always hot

Temperate (Mid-Latitude) zone – seasonal, most varied climates

Polar (High Latitude) zone – either mild temps. or extreme cold

RULE: The HIGHER the latitude, the COLDER the temps.

AltitudeAltitude (Elevation) (Elevation)

Higher elevation = thinner air, therefore Higher elevation = thinner air, therefore less air to hold heat makes it colder.less air to hold heat makes it colder.

RULE – The HIGHER the elevation, the COLDER the temperatures.

Nearness to WaterNearness to Water Land heats up and cools down QUICKLY.Land heats up and cools down QUICKLY. Water heats up and cools down SLOWLY.Water heats up and cools down SLOWLY. Therefore, Therefore, water acts like a blanket… holding heat and water acts like a blanket… holding heat and

releasing it slowlyreleasing it slowly.. This results in This results in smaller daily and seasonal temperature smaller daily and seasonal temperature

changes near large bodies of waterchanges near large bodies of water.. ““Coastal” areas are humid, “continental” areas are dryCoastal” areas are humid, “continental” areas are dry

30 degree change in Houston

45 degree change in Denver

Direction of CurrentsDirection of Currents Global wind and ocean currents transfer heat and Global wind and ocean currents transfer heat and

moisture around the world, moisture around the world, andand help carry help carry moisture from the oceans to the landmoisture from the oceans to the land– Warm water moving Warm water moving towardtoward the land brings moisture (H the land brings moisture (H22O)O)– Warm water moving Warm water moving parallelparallel to the coast brings heat, no H to the coast brings heat, no H22OO– Cool water brings cool, dry air -> mild or desert climatesCool water brings cool, dry air -> mild or desert climates

How it Works...How it Works...Tropical Wet ClimateTropical Wet Climate

Latitude – in the tropics HOT

Altitude – low land doesn’t stop air flow until mtns. in the west

Nearness – flat land “acts coastal”, allows moisture inland

Direction – air flow

brings in warm, moist air

from the ocean which then hits the mountain and rains