Science 2200

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Weather dynamics is the study of how the motion of water and air causes weather

patterns.

Energy from the Sun drives the motion of clouds, air, and water.

Earth’s tilt at an angle of 23.5 degrees to the plane of its orbit around the Sun.

Major components of Earth that influence weather are: atmosphere, land forms, and

water. ( all states)

About 70% of Earth’s surface is covered by oceans.

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The atmosphere contains air, water vapour, and particles of dust and chemicals, all of which affect

weather, especially when the atmosphere is in motion.

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Weather is the set of environmental conditions encountered from day to day.

Climate is the set of environmental conditions averaged over many years.

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Longitude is the angle measured North or South from the 0 degree line which passes through Greenwich,

England.

Latitude is the angle measured East or Westof the equator.

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The Tropic of Cancer is at 23.5 degrees north latitude. It is the most northerly location reached by the Sun’s vertical rays on the first day of summer, June 21, each year.

The Arctic Circle is at 66.5 degrees north latitude. It is the most northerly location reached by any of the Sun’s rays on the first day of winter, December 21.

In the southern hemisphere we have the Tropic of Capricorn and the Antarctic Circle.

The region between the Tropic of Cancer and the Tropic of Capricorn is referred to as the tropics.

Most of Canada’s population lives in the mid-latitude region.

Polar regions would be any land that fall in between the earths 2 poles and the tropic of Cancer and Capricorn.

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Most of the energy used on Earth to sustain life and cause changing weather systems comes from the Sun.

The average surface temperature is 15 degrees C.

Different types of EM energy are emitted from the Sun.

Energy can be transferred from one place to another by 4 methods:

1) Radiation2) Conduction3) Convection4) Advection

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Radiation -transfer of energy by means of waves or particles. Radiation does not need a medium.The waves can travel from the Sun, through space,

and reach Earth.

Visible light is energy that can travel through space. Other examples are:1) Radio waves2) Microwaves3) X-rays4) Gamma rays5) Infrared rays

These travel at 300,000 km/s in a vacuum.

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The set of waves that can travel through empty space at the speed of light is called the

electromagnetic spectrum.

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The other methods of energy transfer require particles of matter.

Conduction -the transfer of energy through the collision of particles. Occurs most easily in metals, but also to a smaller extent in rock, sand soil and water.

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Convection and advection are the transfer of energy by the movement of particles in a fluid.

A fluid is either a liquid (water) or a gas(atmosphere).

Convection transfers energy vertically .Advection transfers energy horizontally.

Weather systems involve convection and advection.

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EM waves from the Sun reach Earth, some is reflected off the atmosphere and clouds back into space; some pass through the

atmosphere and bounce off Earth’s surface; some get absorbed by the atmosphere, the ground, or the water at the surface.

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The portion of energy reflected depends on the albedo of the material.

Clean snow has a high albedo, it reflects a lot of incoming energy. Black soil has a low albedo, it absorbs more energy than it reflects.

Any object or material that absorbs energy and becomes warmer is called a heat sink.

Water has a higher albedo than land and soil, the oceans are good heat sinks. When solar energy hits water , the water begins to move(convection), and transfer energy deep into the oceans.

Soil and rock are poor heat sinks. Heat is conducted slowly into these materials.

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An important property of all substances is their heat capacity, the measure of how much heat a substance

requires to increase its temperature or how much heat it releases as its temperature decreases.

Water has a high heat capacity. This means it can hold a lot of heat.

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Energy Transfer Worksheet

https://www.youtube.com/watch?v=7Y3mfAGVn1c

Transfer of Energy Song

https://www.youtube.com/watch?v=w_IbPRNZ6ho

Conduction – Energy Transfer

https://www.youtube.com/watch?v=WEDUtS0IMws

Convection Demos

https://www.youtube.com/watch?v=2JZciWtK6vc

Radiation Transfer of heat

https://www.youtube.com/watch?v=UJF6ap3wMWY

Cold air advection

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All of Earth’s water, both fresh and salt, forms what is called the hydrosphere.

About 70% of Earth’s surface is covered by water.

Freshwater makes up 2.5% of the total water on Earth. Most of this occurs as polar ice.

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Water vapour is essential to the water cycle and weather patterns.

Water vapour is responsible for clouds, fog, rain and snow.

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Precipitation Worksheet

The thin layer of gases that surround the earth is the atmosphere.

The atmosphere is where all the weather happens.

The atmosphere acts like a blanket which controls the temperature of the earth.

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The earth's atmosphere is made up of dust and a mixture of invisible gases. Some of these gases include:

Nitrogen (N2) 78%

Oxygen (O2) 21%

Other gases: 1% combined

[water vapour, argon, carbon dioxide, neon, helium, krypton, hydrogen, ozone...]

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Nitrogen and ozone act as a protection shield that blocks out harmful radiation from space( UV ).

Oxygen is essential for life. Plants produce oxygen and we breathe it in.

Carbon dioxide is essential for life too. We breathe out carbon dioxide and plants breathe it in.

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The atmosphere can be divided up into distinctive layers.

Exosphere

Thermosphere

Mesosphere

Stratosphere

Tropopause

Troposphere

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Worksheet # 8 - Layers of the Atmosphere

Layer and Gas in the Atmosphere - Worksheet

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The word aneroid means without liquid.

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High air pressure in a region indicates fair weather while low pressure indicates that storms are more likely.

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A Psychrometer measures relative humidity

◦ Two thermometers

◦ One dry, one kept wet

◦ Spun in the air, temp drops

◦ The difference between the two is used to find relative humidity

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Weather satellite

Weather Balloons

Computers

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Atmospheric pressure is the pressure the air exerts as gravity pulls it toward the center of Earth.

It is greatest at sea level, where the molecules are closet together.

At higher altitudes atmospheric pressure decreases.

Atmospheric pressure at a particular altitude depends on whether the air is rising or falling. There are two variations

to consider :vertical and horizontal.

Pressure gradient is a measure of the amount the atmospheric pressure changes across a set distance.

Pressure gradients can be vertical or horizontal.

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Bernoulli's principle:

Bernoulli’s principle helps explain that an aircraft can

achieve lift because of the shape of its wings. They are

shaped so that that air flows faster over the top of the wing

and slower underneath. Fast moving air equals low air

pressure while slow moving air equals high air pressure.

The high air pressure underneath the wings will therefore

push the aircraft up through the lower air pressure.

What happens to the pressure of air when air speed is increased?

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Worksheet # 7

Atmospheric Pressure

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As air rises it begins to cool and expand.

Cooled air can no longer hold all its moisture.

The water vapour begins to condense on dust particles as very tiny water droplets.

Depending on the temperature clouds may be made up of tiny water droplets and or tiny ice crystals.

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For Newfoundland it may bring cooler wetter conditions - lots of snow!

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1. Convective: formed when a land mass is heated and the warmed air begins to rise, expand, cool and water condenses.

We see these types of clouds

where thermals and sea

breezes are formed.

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2. Frontal:

form at the frontal zone where two large air masses meet.

The warmer air mass is forced to rise up over the cooler air mass.

It expands and cools resulting in the formation of condensation.

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3. Orographic:

formed because of geography when air is forced to rise up a large hill or mountain.

As the wind blows into the side of the mountain it rises up.

As the air rises it expands and cools causing water vapour to condense as clouds.

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Cloud shapes tell us about atmospheric

conditions.

Two general shapes of clouds:

1. Cumulus Clouds

2. Stratus Clouds

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Heaped" or "lumpy" clouds result when strong vertical (upward) motions exist in the atmosphere.

This shows us that the air mass is being forced to rise very rapidly.

A clue that the atmosphere is unstable and are usually associated with stormy or severe weather.

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Wide spread out, smooth, layered clouds.

These clouds gives a clue that the air motion is horizontal (across) rather than vertical (up and down).

The forming clouds are rising slowly which is a sign of a stable atmosphere.

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they are named by altitude in the atmosphere.

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stratocumulus

altocumulus

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cumulonimbus

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Clouds have a duel role:

1) Quite simply clouds act as a blanket.◦ Cloudy nights: traps heat keeping the air warm.

◦ Clear night sky: heat escapes and air cools quickly.

2) Keep the earth cool during the day.◦ The formation of white cloud cover reflects the

sun's energy away.

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Gravity pulls down on all matter.

Gases are matter and gravity pulls down on them.

This is why the troposphere (layer closest to the earth) has 99% of all the gases in the atmosphere.

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• A cloud that forms near the ground

• Can form on cool, cloudless nights

• When warm air passes over snow-covered ground

• When moist sea air drifts over a cold current

• When moist air rises up a mountain side

Forms when warm moist air moves over a colder surface (land or water) releasing its moisture as very fine water droplets.

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The atmosphere is made up of areas of different densities.

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Assignment:

Cloud Formation

Precipitation and Humidity

Humidity:◦ a measure of the amount

of water vapor in the air

◦ Warm air can hold more moisture then cold air

Relative Humidity:◦ The measure of the

amount of water vapor compared to the Maximumamount possible

Saturated Air◦ Relative humidity is 100%

◦ Over 100% results in condensation

Dew Point◦ Temp at which dew forms

◦ As air gets colder, it holds less moisture

◦ Releases excess as dew

Figure 1, pg. 214 – Maximum Amounts

%100ionconcentrat maximum

ionconcentratHumidity Relative x

Ex 1:

What is the relative humidity if 1.9 g/kg of water in air is present at 0oC?

Ex 2:

What is the conc of H2O in the air at 20oC if the relative humidity is 50%?

Dry Bulb Wet Bulb Relative Humidity

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Higher humidity◦ causes perspiration to evaporate slowly.

◦ Sweating doesn’t cool us as well

Low humidity◦ Air is dryer

◦ Skin may be uncomfortable

Humidex:◦ Reports how hot the humidity makes us feel

Hail:

◦ created in cumulonimbus clouds

◦ Frozen raindrops are circulated up and down

◦ Layers of ice are formed

Dew:◦ Water vapour condenses near

the ground as the air cools

◦ Cold Days : Frost

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Water in the Air Worksheet #4

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Sailors discovered that in certain areas the winds tend to blow in the same directions most of the time.

Close to the equator the winds would blow to the west (from the east).

Further North they found that the winds would blow most often to the east (from the west).

This regular pattern of winds is known as prevailing winds.

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Wind is a movement of air in the atmosphere from areas of high pressure to areas of low pressure.

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Winds that affect large areas in regular patterns.

Blowing to the east they called the Northeast trade winds.

The winds blowing from the west (taking them back home) were called the mid-latitude Westerlies (prevailing Westerlies).

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Spin

The earth rotates east to west.

As the earth spins it deflects the wind.

◦ Winds blowing north get deflected to the right.

◦ Winds blowing south get deflected to the left.

The deflection of the wind caused by the earth's rotation is called the Coriolis effect.

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Earth’s rotation causes anything that moves, to appear to change direction. This apparent change of direction of a moving object in a rotating system is called the

Coriolis effect.

Viewed above the North pole, Earth rotates eastward or counter clockwise.

Objects in the Northern hemisphere appear to move to the right.

In the Southern hemisphere moving objects appear to move to the left.

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Early explorers like Columbus used trade winds to cross the Atlantic Ocean.

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Prevailing winds are caused by convection currents and rotation.

In the Northern hemisphere....

• Solar energy strikes the equator, heating the air, land, water• The warm air rises and expands, leaving a low pressure area• Rising air moves northward• At 30 degrees latitude the cooled air sinks, creating high pressure

• The moving air is twisted right as it moves south (Northeast Trade Winds)

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In the Northern hemisphere.....

At 30 degrees latitude descending air is deflected northward, to an area of low pressure at 60 degrees latitude.

The surface air moving northward to the low pressure area twists to the right causing the mid-latitude westerlies.

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At the North Pole the air is cold and dense, so it sinks, creating a high pressure region. This surface air moves south, twisting to the right

and creating the polar easterlies.

A narrow band of spinning air is created in the places where these convection currents rise and fall.

The spinning causes the air to speed up creating a tube of fast moving air known as a jet stream.

The winds of the jet stream travel from west to east and can reach speeds of up to roughly 500 km/h.

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Aircraft use this to their advantage when flying form west to east.◦ pick up to a 500 km/h tail wind which saves

time and fuel.

Going from east to west pilots try to avoid the jet streams.

Jet streams steer major

weather systems.

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Jet Streams – high speed winds in the troposphere

(241 to 482 kilometres per hour)

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Prevailing winds help to distribute large amounts of solar energy from the equator to colder parts of the world.

Convection currents create a return flow of air southward.

Prevailing winds carry moisture causing rain, snow.

Rising air is warm and moist.Falling air is cool and dry.

At 30 degrees N latitude we have cool, dry air. Many deserts are found in this latitude.

At 60 degrees N latitude two air systems meet and rise giving birth to winter storms.

Normal Year El Niño Year

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During an El Niño year the Pacific Ocean undergoes a greater than normal amount of heating.

This disrupts and changes the normal patterns of convection currents and wind patterns in the Pacific Ocean.

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During El Niño years:

the jet stream tends to push further north.

As result North America tends to receive warmer than normal average temperatures.

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About every four to five years, a pool of cooler-than-normal water develops off South America.

This usually shifts the jet stream farther south which steers’ colder drier winters to the Canadian west.

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Weather can be affected by local landforms in a specific area

Thermal:

◦ A local convection current set up during the day

◦ The sun heats the ground, causing the air to rise

◦ From water to land

◦ A thermal formed near water

◦ The sun heats the land. The air rise, and a cool breeze blows in from the water.

Where are the

highs and

lows?

from land to water◦ After sunset, the land cools quickly.

◦ Air above the warmer water rises, replaced by air from the land.

Where are the

highs and

lows?

When air moves over water it picks up moisture. In winter, water is warmer then the land (more moisture)

When the air reaches the cold land, the moisture becomes snow

A gentle warm, dry wind on the leeward side of the Rocky mountains

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Worksheet # 6 Wind

Worksheet #12 Movement of the Air

Section 13.9

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In 1992 a container ship in the middle of the Pacific Ocean lost 29 000 bath tub toys over the side. Rubber duckies started washing ashore all over the west coast of North America.

In 1990 in a similar type accident 80,000 pairs of Nike shoes were swept off a Korean ship headed for the United states. Nike shoes started showing up from Hawaii to Oregon and as far north as Alaska.

These two accidents provided valuable information to oceanographers regarding ocean currents.

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Another spill occurred in 1999.

An oceanographer is a scientist that studies ocean currents.

Ocean currents are compared to large conveyor belts that move around the globe.

The ocean currents circulate the sun’s energy from the equator to the poles.

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They serve to warm the poles and at the same time cool the waters of the equator.

In other words the ocean current spread out the heat energy all over the earth so that one area doesn't become too hot or too cold.

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The main cause of ocean currents is unequal heating of the ocean by the sun.

At the equator the sun strongly heats the water.

As the water warms is gets lighter (less dense) and begins to rise.

Cooler, denser water sinks and rushes in to replace the warmer water.

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This movement of water creates enormous convection currents.

We see warm surface currents flowing toward the poles (N & S).

At the same time, we get cold deep water currents flowing toward the equator.

The surface currents are pushed along and steered around the earth by the prevailing winds.

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The warmer the air is above a body of

water, the more water it is capable of holding.◦ Evaporation rate is high and clouds form.

◦ Large amounts of precipitation.

Colder water has cool and dry air above it.◦ Weather it brings is cool and dry.

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Worksheet # 13 – Major Ocean Currents

Meteorology: The study of the atmosphere and weather forecasting

Weather System: ◦ A set of weather variables that move as a unit for a

few days

Air Mass:◦ Large body of air in which temp and moisture is

fairly uniform

6 different air masses

Combinations of

◦ Maritime or Continental

(Moist or Dry)

◦ Tropical or Polar

◦ (Warm or cold)

Air Masses TemperatureMoisture

Content

Maritime Polar

(West Coast)

Maritime Polar

(East Coast)

Continental Polar

Maritime Tropical

(West Coast)

Maritime Tropical

(East Coast)

Continental Tropical

Front: the boundary between a cold air mass and a warm air mass

Warm front: the leading edge of a warm air mass

Cold front: the leading edge of a cold air mass

Occluded Front◦ cold front catches

up with a warm front; the warm air is lifted above the earth’s surface and is cut off (occluded) from the cooler air below

Stationary front: warm and cold air masses remains still for some time

A: Warm and Cold front meet

B:Main Stage:

Warm air is pushed up, lots of precipitation

C: Occluding Stage: Storm weakens as fronts combine

D:Final Stage

Flow of air dissipates, storm ends

Spins CCW in Northern Hemisphere

CW in Southern Hemisphere

Usually brings clear skies

Air moves outward from the centre of the high

Rotates clockwise in the Northern Hemisphere (CCW in S. Hemisphere)

Worksheet # 14 – WEATHER FORECASTING

Worksheet # 15 – Extreme Weather

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