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Science 1206
Unit 1 – Weather Dynamics
Weather - Introduction
Weather is a daily topic for us here in
Newfoundland and Labrador.
Its unpredictability is what makes it such
a ‘hot’ topic!
But what is it really? What causes it?
How do they forecast the weather?
These are some of the questions that
we will answer in this unit.
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]
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
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
*Venus has a runaway greenhouse effect, its surface temperature is 462℃!! That can melt lead!!!
Questions to ponder:
1. How does specific heat capacity
explain temperature differences
between coastal and inland
communities in summer and winter?
2. What is the significance of Earth’s
energy budget to life on Earth?
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
https://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
https://www.youtube.com/watch?v=w_IbPRNZ6hohttps://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=obTrYt9ieg8
https://www.youtube.com/watch?v=VxGIiOTuAIshttps://www.youtube.com/watch?v=obTrYt9ieg8
How is this heat transferred?https://www.khanacademy.org/science/physics/thermodynamics/specific-heat-and-heat-
transfer/v/thermal-conduction-convection-and-radiation
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.
Albedo and heat sink activity
● P. 23 and 24 of text
● Read P. 21 (prelab notes for activity)
● Read P. 23 & 24 Lab activities
Heat transfer and Earths spheres
Activity 1-1E
Albedo and Surfaces
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?
● Yes, they 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!
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
● Well, remember, evaporation and
condensation require the absorption
and release of heat, and water can
absorb and release A LOT of heat,
and the Sun releases A LOT of heat
and Earth has A LOT of water!! ALL
that energy in the water cycle can fuel
all kinds of weather!!
Heat Transfer in the Water Cycle
● Heating curve lab
Effects of heat transfer in the
hydrosphere and atmosphere
● All this 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
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
Effects of heat transfer in the
hydrosphere and atmosphere
Effects of heat transfer in the
hydrosphere and atmosphere
Effects of heat transfer in the
hydrosphere and atmosphere
● Cold regions usually produce high
pressure systems and warm regions
create low pressure, but why?
Effects of heat transfer in the
hydrosphere and atmosphereHigh 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
Effects of heat transfer in the
hydrosphere and 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
Effects of heat transfer in the
hydrosphere and atmosphereLow 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
Effects of heat transfer in the
hydrosphere and atmosphere
● 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 opposite
Effects of heat transfer in the
hydrosphere and atmosphere● This graphic is for the southern hemisphere
Effects of heat transfer in the
hydrosphere and atmosphere● 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
https://www.youtube.com/watch?v=i2mec3vgeaI
Effects of heat transfer in the hydrosphere
and atmosphere
Global wind systems
These are common(prevailing) winds that
occur around different areas of Earth
caused by convection currents and the
Coriolis effect
Effects of heat transfer in the hydrosphere
and atmosphere
Global wind systems
● We very often get weather systems
from the west because the prevailing
westerlies
Effects of heat transfer in the hydrosphere
and atmosphere
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
Effects of heat transfer in the hydrosphere
and atmosphere
Jet Streams – narrow bands of fast
moving air created by a large
temperature difference in the upper
atmosphere and the Coriolis effect.
Effects of heat transfer in the hydrosphere
and atmosphere
We discussed air masses a little while ago (recall arctic, continental polar, maritime polar, etc.)
These air masses are different temperatures and thus as they move close they interact forming a boundary called a front
You may have seen one and not known it!
I took the following picture a couple summers ago while on a walk by the bay here in Springdale.
A large band of clouds coming from the west!
Effects of heat transfer in the hydrosphere
and atmosphere
Effects of heat transfer in the hydrosphere
and atmosphere
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 four fronts we need to know
(figure 1.18 of text)
Effects of heat transfer in the hydrosphere
and atmosphere
Effects of heat transfer in the hydrosphere
and atmosphere
Effects of heat transfer in the hydrosphere
and atmosphere
Effects of heat transfer in the hydrosphere
and atmosphere
● 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
Effects of heat transfer in the hydrosphere
and atmosphere
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
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
Effects of heat transfer in the hydrosphere
and atmosphere● 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!!
Effects of heat transfer in the hydrosphere
and atmosphere
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
Effects of heat transfer in the hydrosphere
and atmosphere
Deep ocean currents
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
Scientific explanations of extreme weather
Thunderstorms
Scientific explanations of extreme weather
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
Scientific explanations of extreme weather
Tornado
Scientific explanations of extreme weather
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
Scientific explanations of extreme weather
Hurricanes
Scientific explanations of extreme weather
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
Scientific explanations of extreme weather
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
https://www.youtube.com/watch?v=330pP8RSYUg
Scientific explanations of extreme weather
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
Scientific explanations of extreme weather
Page 37, 1-2D Extreme Weather
Activity