Transcript Weather and Climate
Weather and Climate
What is the weather like today?
Is it like this EVERY day? Why?
What is the difference between WEATHER and CLIMATE?
Weather and Climate
Weather – The
temporary
environmental conditions in a localized area over a short period of time.
In other words…what it’s like OUTSIDE, right HERE, right NOW Climate –
The long-term
environmental conditions across a large area and long time.
In other words…the AVERAGE of all the WEATHERS
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 it’s orbit around the Sun - The direction of that
tilt
that changes as the Earth travels around the Sun
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 it’s axis. This takes about 24 hours…one DAY.
Earth’s
TILT
The Earth is not vertical (straight up-and down) in relation to it’s orbital path, it’s
tilted 23 ½ degrees from vertical
.
DRAW THIS ! ! !
This tilt means that the Sun’s energy doesn’t hit the Earth equally.
Earth’s
TILT
This tilt results in uneven heating of the Earth’s surface.
“Direct” sunlight “Indirect” sunlight
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.
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
Sol
stice
Solstice and Equinox
– 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
Earth’s
tilt
affects length of days
Places experiencing summer have “longer” days (more sunlight per 24 hrs.) Shorter Winter days Longer Summer days Places experiencing winter have “shorter” days (less sunlight per 24 hrs.) Areas above 66 ½ degrees N or S will experience 24 hr. extremes (light and dark) depending on the season 24 hrs.
of light from Nov.
to Feb.
24 hrs.
of dark from May to August
Greenhouse 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 -
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 don’t move as much, so they pack closer together, meaning MORE HOT air RISES molecules in a given space (HIGH pressure) COLD air SINKS
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
H
in from the water,
L
called a SEA BREEZE
WIND
– Land Breeze
When the sun sets, the process reverses and land cools off faster than water ( RULE #1 ) This creates COOL
er
air (HIGH pressure) over the land and WARM
er
air (LOW pressure) over the water at night The WARM wind blowing out from the land is called a LAND BREEZE
L H
WIND
- Monsoons
On a larger scale, the same factors create monsoons -
seasonal
winds Due to the Earth’s tilt, differences in the heating of land and ocean create long term wind patterns that bring seasonal rainy and dry periods.
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.
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)
Water Currents
Most ocean currents are affected by global wind patterns blowing across the oceans.
Most
WARM
currents flow WEST Most
COOL
currents flow EAST
Precipitation – Nature’s Thermostat
There are 3 basic causes for rain. They are: – Convection – due to evaporation and cooling Sun’s 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
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
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
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 WRITE THESE DOWN !
Nearness to water Direction of atmosphere and ocean currents
Latitude
Due to the Earth’s tilt, the amount of sun energy changes over the earth’s 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.
Altitude (Elevation)
Higher elevation = thinner air, therefore less air to hold heat makes it colder.
RULE – The HIGHER the elevation, the COLDER the temperatures.
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
Direction of Currents
Global wind and ocean currents transfer heat and moisture around the world,
and
moisture from the oceans to the land help carry – Warm water moving
toward
the land brings moisture (H 2 O) – Warm water moving
parallel
to the coast brings heat, no H 2 O – Cool water brings cool, dry air -> mild or desert climates
How it Works...
Tropical Wet Climate
L
atitude – in the tropics HOT
A
ltitude – low land doesn’t stop air flow until mtns. in the west
N
earness – flat land “acts coastal”, allows moisture inland
D
irection – air flow brings in warm, moist air from the ocean which then hits the mountain and rains