Weather and Climate

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Weather and Climate

• What is the weather like today?

Is it like this EVERY day? Why?
What is the difference between WEATHER and
CLIMATE?
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Weather and Climate

• Weather The temporary environmental conditions
  in a localized area over a short period of time.

In other wordswhat its like OUTSIDE, right
HERE, right NOW

• Climate The long-term environmental conditions
  across a large area and long time.

In other wordsthe AVERAGE of all the WEATHERS
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What affects weather and climate?

• There are two major factors that affect the
  overall environment and climate

• The tilt of the Earth in relation to its orbit
  around the Sun
• - The direction of that tilt that changes as the
  Earth travels around the Sun

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First, some basic vocabulary

• Revolution one ORBIT, or trip around the Sun.
  This takes the Earth 365 ¼ days

Rotation one SPIN of the Earth on its axis.
This takes about 24 hoursone DAY.
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Earths TILT

• The Earth is not vertical (straight up-and-down)
  in relation to its orbital path, its tilted
  23 ½ degrees from vertical.

? DRAW THIS ! ! !
This tilt means that the Suns energy doesnt hit
the Earth equally.
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Earths TILT

• This tilt results in uneven heating of the
  Earths surface.

Direct sunlight
Indirect sunlight
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From TILT to SEASONS

• As the Earth travels around the Sun, the tilt
  changes in relation to the Sun. Sometimes
  toward the Sun, sometimes away, and sometimes
  neither.

? DRAW THIS !!
This creates a predictable cycle of warmer and
cooler periods, or seasons.
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Seasons

• Because the direction of the tilt (towards or
  away) is opposite for the Northern and 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
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Solstice and Equinox

• Solstice the point at which the Earth is
  pointed farthest toward / away from the Sun,
  creating long summer days and short winter days .
  (Latin root word sol)
• Summer around June 21
• Winter around December 21

• Equinox the point at which the Earth is not
  pointed toward OR away from the Sun, creating
  equal day and night. (equi-nox)
• Spring (Vernal)
• around March 21
• - Fall (autumnal) around Sept. 21

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Earths tilt affects length of days

• Places experiencing summer have longer days
  (more sunlight per 24 hrs.)
• Places experiencing winter have shorter days
  (less sunlight per 24 hrs.)

Longer Summer days
Shorter Winter days
24 hrs. of dark from May to August
24 hrs. of light from Nov. to Feb.

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

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Greenhouse Effect

• RULE 1 OF NATURE Energy can be either absorbed
  or transferred

• Normally, when the Suns 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 Earths heat.

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Distributing the Suns Heat - WIND

• RULE 2 OF NATURE Nature seeks 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 molecules
• in a given space (LOW pressure)
• Cold (less active) molecules dont
• move as much, so they pack closer
• together, meaning MORE
• molecules in a given space (HIGH pressure)

HOT air RISES
COLD air SINKS
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WIND Sea Breeze

• When the sun shines, land (solid) heats up faster
  than water (liquid) remember RULE 1 ?
• Only the top 2-3 inches of earth get warm, then
  the heat is reflected back to the air. (Why do
  dogs dig in the dirt?)
• The warm air rises, creating LOW PRESSURE over
  the land during
  the early/mid-morning
• This imbalance
  (RULE 2) creates a
  COOL wind blowing
  in from the water,
  called a SEA BREEZE

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WIND Land Breeze

• When the sun sets, the process reverses and land
  cools off faster than water (RULE 1)
• This creates COOLer air (HIGH pressure) over the
  land and WARMer air (LOW pressure) over the water
  at night
• The WARM wind
  blowing out from the
  land is called a
  LAND BREEZE

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WIND - Monsoons

• On a larger scale, the same factors create
  monsoons - seasonal winds
• Due to the Earths tilt, differences in the
  heating of land and ocean create long
  term wind patterns that bring
  seasonal rainy and dry periods.

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Global Wind Patterns

• RULE 3 OF NATURE Nature obeys 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.

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Coriolis Effect

• Because the Earth spins (rotates) under the winds
  as they travel N and S, they appear to curve
  because of the Coriolis effect. (see it)
• The result is curved
  wind patterns across
  the Earth surface.
• All winds are named
  for where they come
  FROM.
• Areas of no major
  wind pattern are
  called doldrums
  or
  horse latitudes
• (Spanish explorers)

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Water Currents

• Most ocean currents are affected by global wind
  patterns blowing across the oceans.

Most COOL currents flow EAST
Most WARM currents flow WEST
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Precipitation Natures Thermostat

• There are 3 basic causes for rain. They are
• Convection due to evaporation and cooling
• Suns energy causes surface water to
  evaporate and become humidity
• As the day cools off, the air cools and
  condenses, causing storms and rain
• Usually in tropical environments
• Frontal due to changes in temperature
• Starts with warm, moist air at the surface and
  above
• As a cold front approaches, it stays
  low, forcing the moist air aloft
• This cools and condenses the air,
  creating rain on the leading edge
  of the front
• Usually in mid-latitudes where warm and cold air
  systems collide

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Precipitation, Part II

• Orographic due to changes in elevation
• Moist air travels over land and approaches a
  steep rise in elevation
• As the air is forced up the side of the rise, the
  air cools, causing precip. on the windward side
  of the mountain
• As the (now dry) air continues over and down the
  leeward side of the mountain, it warms up and
  
  absorbs any available
  moisture, creating a
  rain
  shadow desert
• Found in areas of
  mountains or other
  rapid
  elevation change

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CLIMATES

• The world is divides into three large climate
  zones, based on latitude.

? DRAW THIS !!!
Low Latitude (Tropical) climates always hot
Mid Latitude (Temperate) climates hot/cold
seasons
High Latitude (Polar) climates seasons either
mild or extreme cold
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Climate Zones

• Climate zones are divided into regions with
  differences in two key characteristics
• Amount of moisture (rain), and
• Typical temperature range through the year

• These two characteristics are affected by
  balancing the effects of four factors
• Latitude
• Altitude
• Nearness to water
• Direction of atmosphere and ocean currents

? WRITE THESE DOWN !
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Latitude

• Due to the Earths tilt, the amount of sun energy
  changes over the earths surface

Polar (High Latitude) zone either mild temps.
or extreme cold
Temperate (Mid-Latitude) zone seasonal, most
varied climates
Tropical (Low Latitude) zone year-round direct
sunlight, always hot
RULE The HIGHER the latitude, the
COLDER the temps.
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Altitude (Elevation)

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

RULE The HIGHER the elevation, the
COLDER the temperatures.
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Nearness to Water

• Land heats up and cools down QUICKLY.
• Water heats up and cools down SLOWLY.
• Therefore, water acts like a blanket holding
  heat and releasing it slowly.
• This results in smaller daily and seasonal
  temperature changes near large bodies of water.
• Coastal areas are humid, continental areas
  are dry

30 degree change in Houston
45 degree change in Denver
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Direction of Currents

• Global wind and ocean currents transfer heat and
  moisture around the world, and help carry
  moisture from the oceans to the land
• Warm water moving toward the land brings moisture
  (H2O)
• Warm water moving parallel to the coast brings
  heat, no H2O
• Cool water brings cool, dry air -gt mild or desert
  climates

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How it Works...Tropical Wet Climate

• Latitude in the tropics? HOT

• Altitude low land doesnt 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