Science 1206

Unit 1 – Weather Dynamics

Part 1

Weather - Introduction

Weather is a daily topic for us here in

Newfoundland and Labrador.

Its unpredictability is what makes it such

a ‘hot’ topic!

Heat transfer and Earths spheres

Weather by definition is...

Weather – the physical conditions of the atmosphere at a specific time and place

These physical conditions include:

● Temperature – degree Celcius

● Precipitation – mm or cm

● Atmospheric pressure – high or low

● Humidity- moisture in air “feels like”

● Wind speed and direction – km/h N,S,W,E

● sky cover – overcast, clear etc

What creates weather?

The sun is what drives our weather, and it

is the transfer of this heat between the

different spheres on Earth that generate

the different weather conditions.

Spheres??

Earth’s energy budget

the balance between the energy Earth receives

from the Sun, and the energy Earth radiates

back into outer space after having been

distributed throughout the Earth’s spheres.

Some spheres receive and store this energy

differently, and it is this difference that creates

the different weather all over our planet!

Heat absorption is affected by:

1. Albedo – reflectivity of a surface e.g.) a very reflective surface (e.g. snow) will not absorb energy like a dark surface (e.g. dirt)

2. Specific heat capacity – heat energy needed to raise the temperature of a mass of substance by a degree. (J/g℃)

*[remember grade 8, water has a high heat capacity and heats slowly, but stays warm longer than land (low heat capacity) which heats quickly and cools quickly]

Title should be centered and underlined

Graph 1.1 Temperature of 3 Types of Material over 20 Minutes

For Table – See P. 23 in textbook

Heat Capacity

A measure of:

How much heat is required to increase the temperature of a substance.

OR

How much heat is released as the temperature decreases.

Indicates whether a substance is a good heat sink or not.

o Ex: Soil and rock are poor heat sinks so they will have a low heat capacity

o EX: Water is a good heat sink therefore it has a high heat capacity.

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

Water and the Weather

Water has a much higher specific heat capacity than land and air.Because there is so much water on Earth, and water is such a good heat sink, water has a great influence on weather. For example, because they are so close to large bodies of water, coastal locations generally have cooler summer weather and milder winter weather than inland locations.

Keeping in the HeatWhy doesn’t thermal energy just radiate into space at night, cooling off Earth

when the Sun sets?

Greenhouse gases (water vapour,

carbon dioxide, methane) absorb

infrared radiation before it leaves earth

surface and releases energy back to the

Earth’s surface. This radiation warms the

surface and the atmosphere before it is

eventually lost to outer space. Therefore,

the greenhouse gases in Earth’s

atmosphere act as a heat sink. They

cause the troposphere—where weather

occurs—to retain more heat than it

would if these gases were not present.

Greenhouse effect-the trapping of the sun's warmth in the gases(CO2,CH4, H2O) of a planet's atmosphere.- this trapped heat is released back to Earth’s surface maintaining a relatively constant global temperature-the atmosphere then acts as a heat sink- too much greenhouse gas can negatively impact Earth and cause climate change

How is this heat transferred?

1. Radiation – transfer of thermal energy

from energetic/unstable atoms or

molecules as electromagnetic waves

or particleshttps://study.com/academy/lesson/the-

energy-transfer-process-solar-radiation.html

2.Conduction – transfer of thermal energy

between objects in direct contact (i.e.

touching each other)

https://study.com/academy/lesson/heat-

transfer-through-conduction-equation-

examples.html

3. Convection – thermal energy transfer

by the movement of heated material

from one place to another, specifically

fluids. https://www.youtube.com/watch?v=obTrYt9ieg

8

How is this heat transferred?https://www.khanacademy.org/science/physics/thermodynamics/specific-heat-and-heat-

transfer/v/thermal-conduction-convection-and-radiation

Heat transfer and Earths spheres

After the land and water absorb solar energy, molecules from the landand water collide more frequently with molecules in the air that are closeto the surface.

These collisions transfer energy from the surface to the air by conduction. Then convection occurs as air circulates and distributes the heat. As the

lower layer of the air warms, it expands, becoming less dense. Recall thatless-dense fluids (gases and liquids) rise, and more-dense fluids fall. Asthe cooler air falls, it takes the place of the rising warmer air.

Heat Transfer in the Water Cycle

● The water cycle is not only very important for recycling, purifying, and transporting water, it is also very important in transferring energy around Earth, which then affects weather.

● We will only focus on evaporation and condensation in this course

Heat Transfer in the Water Cycle

● Remember the particle theory of matter, we’ll focus on the movement and attractive properties of particles

● The particles of water in a liquid are moving quickly and are bound closely together (fairly strong attractive forces), whereas particles of water in a gas are moving very very quickly and are not bound together much at all(very weak attractive forces)

Heat Transfer in the Water Cycle

● If you recall, evaporation is the

changing of liquid water to water

vapour

● So, during evaporation particles held

closely(liquid) must move further

apart(gas), i.e. Bonds between

molecules must be broken!!

● How can this happen?

● Particles need lots of energy to break

the bonds holding them close!

Heat Transfer in the Water Cycle

● So energy must be added in order to break bonds holding water in a liquid phase to become a gaseous phase

● Therefore, energy must be releasedwhen the opposite happens! (i.e. water changes from a gas to a liquid!!)

● And the same is true when water changes from a solid to a liquid and vice versa.

Heat Transfer in the Water Cycle

Heat Transfer in the Water Cycle

● An easy way to think about it is to boil

(vaporize) water and to melt ice you

need to break bonds by adding heat

● But to make ice (fusion) from liquid

water and to make liquid water from

water vapour, you need to cool them

down (take heat away), thus slowing

down the molecules so new bonds

can form

Steps:

1. Solar energy causes evaporation from bodies of water and from plant leaves (transpiration) as well as sublimation of ice.

2. The water vapor (gas) rises and as pressure and temperature decrease with increasing altitude, the vapor undergoes condensation to form fog, mist and cloudsand/or sublimation into ice crystals

3. Precipitation falls to the surface in the form of rain, snow, etc.

4. Water seeps into the ground (percolation), and enters bodies of water as runoff from land.

The Cycle Continues!

Water cycle worksheet

Energy Changes During

Phase Changes

Latent Heat of Fusion (Melting) The amount of energy that must be absorbed by a substance

in order to melt (bonds are broken between particles).

Freezing is the opposite of fusion (melting). The same amount of energy is released in order for water to freeze (attractive forces and bonds formed).

Latent Heat of Vaporization (Evaporation): The amount of energy that must be absorbed by a substance

in order to evaporate (bonds are broken).

Condensing is the opposite of evaporating. The same amount of energy is released in order for water to condense (attractive forces and bonds formed).

Heat Transfer in the Water Cycle

Latent heat of vaporization

• Heat absorbed to change a liquid to a gas, or the heat released when a gas changes to a liquid

• There is no temperature change

• Notice how the definition states that the heat of vaporization is not only the energy needed to change a liquid to a gas but also a gas to a liquid!

Heat Transfer in the Water Cycle

Latent heat of fusion

• Heat absorbed to change a solid to a liquid, or the heat released when a liquid changes to a solid

• There is no temperature change

• Notice how the definition states that the heat of fusion is not only the energy needed to change a solid to a liquid but also a liquid to a solid!

Heat Transfer in the Water Cycle

Heat Transfer in the Water Cycle

● Heating curve lab

Section Review (page 25): #’s 4, 5, 6, 10, 11

These are already done – have a look over answers

for review

Effects of heat transfer in the

hydrosphere and atmosphere

● The suns energy is constantly moving

through the atmosphere and oceans

by means of:

Convection – vertical movement of heat

from one place to another

And

Advection – horizontal movement of

heat from one place to another

Read P. P. 26-30

Effects of heat transfer in the

hydrosphere and atmosphere

● Advection and convection happen at different rates around Earth.

● Why??

● Our planet is a sphere and this affects the angle at which the Sun’s rays hit it, and thus we get uneven heating of the planets surface

● This means places around the equator are warmer than places around the poles of the Earth

Effects of heat transfer in the

hydrosphere and atmosphere

● The consistent unequal heating causes the air to expand in some areas(warm air) on Earth and contract in others(cold air), thus creating massive convection currents, in turn creating air masses so predictable that we can actually name them!

● Air Mass – very large mass of air with approximately the same temperature, pressure and humidity

● We will describe 5 global air masses

P. 27

5 Global Air Masses

● Cold regions usually produce high

pressure systems and warm regions

create low pressure……..

Normal Atmospheric Pressure

is 101.3 kPa

Cold weather Warm weather

High pressure system

● When the air cools, it’s particles will

slow and draw closer together

(condense), the space created will in

turn draw in surrounding air from

above.

● This added air will make for even

more dense, heavy air and create a

high pressure area in the atmosphere

High pressure system

● This dense high pressured air will then

move into areas of lower pressure

thus creating winds!

● The air that is drawn in from above will

become drier and that is why high

pressure systems often bring clear

skies and thus no precipitation

Low pressure system

● In warm areas, air rises drawing in air from below

● As the air rises it cools and condenses, producing clouds or precipitation

● Low pressure systems are associated with rain or snow

● The rotation of the Earth also affects

the winds created by the interaction of

high and low pressure systems

● In the northern hemisphere, wind

travels clockwise around high

pressure areas and counter-clockwise

around areas of low pressure

● In the southern hemisphere, wind

directions are the oppositehttps://ca.video.search.yahoo.com/yhs/search?fr=yhs-trp-001&hsimp=yhs-

001&hspart=trp&p=corioulis+effect+on+equator+video#id=1&vid=247b7aecc23cf54c5ebe1a946

8afd057&action=click

● Because the rotation of the Earth is

consistent in speed and direction it

influences winds

Coriolis effect – a change in the

direction of moving air, water, or any

object on Earth’s surface due to its

rotation.

● the Coriolis effect directs winds to the

right in the northern hemisphere and

to the left in the southern hemisphere

Important

Global wind systems

These are common(prevailing) winds that

occur around different areas of Earth

caused by convection currents and the

Coriolis effect

P. 29

3 types of global wind systems

● We very often get weather systems

from the west because the prevailing

westerlies● Winds and weather systems have a tendency to travel from

west to eat on the map

Jet Streams – narrow bands of fast

moving air created by a large

temperature difference in the upper

atmosphere and the Coriolis effect.

● Can have speeds in excess of

300km/h

● Flows west-to-east normally

● the polar jet stream affects us most

● Storms form along jet streams by

transporting cold air towards the

tropics and warm air towards the poles

https://www.

netweather.t

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data/global-

jetstream#2

019/01/21/1

200Z/jetstre

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81.47,43.60,

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Effects of heat transfer in the hydrosphere

and atmosphere – P. 31

The 5 large air masses are different temperatures and thus as they move close they interact forming a boundary called a front

Front moving in

Important characteristics of Fronts

Fronts usually bring precipitation, as

warm moist air rises over the cooler

dense air mass, clouds form as the air

condenses

If enough condensed water vapour

forms, precipitation will occur

There are 4 types of

fronts - (figure 1.18 of text)

1. Cold front

2. Warm front

3. Occluded front

4. Stationary front https://www.youtube.com/watch?v=9NZz-

EeveJ8 – weather map

https://www.youtube.com/watch?v=PJ4M6sERLM4 – air fronts

https://www.youtube.com/results?search_query=global+circulation

Part 1,2 and 3

https://www.youtube.com/watch?v=G7Ewqm0YHUI – Weather fronts explained

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

Weather experiment

1. Cold front

https://youtu.be/xdgqkc2YJ1Q

Clouds

form on

the

boundaryRain

once

passes

2. Warm Front

https://www.youtube.com/watch

?v=tsD6zkBMmck

Clear

skies on

this side

Rain in front

Clouds

form on the

boundary

3. Occluded Front

● Like the name says, a stationary front

doesn't move much, and often

happens when there isn’t much

difference in pressure or temperature

in the opposing fronts

4. Stationary Front

P. 31 – 13-16

Warm air can hold more

moisture

● 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.

64

Ocean Currents

65

● 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.

66

● 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. When seawater –

salt – evaporates, the salt is left behind and

makes the remaining water denser. This

dense seawater sinks and creates a deep

water current.67

What Causes Ocean

Currents?

● Cooler, denser water sinks and rushes in to

replace the warmer water.

● This movement of water creates enormous

convection currents.

68

● 1. Convection currents – explained before this slide

● 2.prevailing winds and the Coriolis effect

● 3. Earth’s rotation

● 4. Shapes of the continents

● 5. Heat capacity of water

● 6. Amount of salt

Causes of ocean currents…

69

● 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.

70

Effects of Ocean Currents

Ocean surface currents● Surface currents are created by wind and carry

thermal energy around the Earth

● The Coriolis effect causes currents in the northern hemisphere to move clockwise and counter clockwise in the Southern hemisphere

● Warm currents created at the equator move north, bringing warm air created by conduction

● This warm water cools as it moves north and then is deflected by land back towards the equator

Ocean current wkst

Scientific explanations of extreme weather

Hurricanes

The tropics contain very warm waters and

winds that move moist air into the

atmosphere

This air condenses releasing energy moving

the air further into the atmosphere

This produces a low pressure system below

and warm air rushes in to replace rising air

Coriolis effect causes the air to rotate counter

clockwise in the northern hemisphere

Effects of heat transfer in the hydrosphere

and atmosphere – P. 32

● As we discussed in Grade 8, the Gulf

Stream brings warm water from the south

and the Labrador current brings cold water

from the north

● These currents warm and cool the air

above them, and when these air masses

meet they create fog!!

Deep ocean currents

These move due to temperature and

salinity of the water

Cold water sinks displacing warmer

water and saltier water sinks

displacing less salty water

Both these actions create the great

ocean conveyor belt moving thermal

energy all over the world as a result

Deep ocean currents P. 33

Effects of heat transfer in the hydrosphere

and atmosphere

Questions to ponder

Scientific explanations of extreme weather

Thunderstorms

Occur when water vapour in rising

warm air condenses releasing thermal

energy

This causes large clouds rising far into

the atmosphere (anvil shaped)

Usually occur when moist air rises

quickly in a cold air mass

Thunderstorms

Tornado

Forms when high altitude horizontal

winds meet large thunderstorms

The winds cause the rapidly rising air in

the thunderstorm to rotate, creating a

funnel cloud

If this funnel cloud touches the ground it

will become a tornado

Tornado

Hurricanes

the warm waters at the equator keep

causing vapour to rise and more air

enters the low pressure system

created causing the hurricane to rotate

faster and faster

Hurricanes

Nor’easters

A powerful storm the brings high winds,

heavy precipitation, storm surges, and

flooding

These occur as a result of the

interaction of a large cold dry Arctic air

mass (high pressure), interacting with

a warm humid air mass (low pressure)

from the gulf of Mexico or gulf stream

Nor’easters

The interaction of this warm low

pressure system with the cold high

pressure system causes the storm

The storm spins in a counter clockwise

direction up the coast and where the

systems meet, you get your north east

winds

El Niño and La Niña

During El Niño years, the pacific is

warmer brining warmer weather during

our winters and fewer hurricanes

During La Niña years, stronger winds in

the pacific, cooling its surface, and

thus we get colder, snowier winters

Page 37, 1-2D Extreme Weather

Activity