Transcript weather-conduction-convection

Introduction To
Weather Dynamics
Introduction to Weather - Video
What you will learn…
In this unit, you will…
•Describe Earth’s energy budget
•Explain how energy is transferred between and
among land, air and water
•Describe weather-related properties of the
atmosphere such as pressure and humidity
•Explain how areas of high and low pressure
move air and energy around the globe
Climate
Widespread,
long-lasting and
recurring
conditions of the
atmosphere.
Weather
(page 10)
The day to day
changes in the
atmosphere
at a particular
location
on Earth.
Meteorology
The study of
the Earth’s
atmosphere
and weather
systems.
• Weather – What is it?
Components of Weather
(see Table 1.1, page 11)
Temperature
Coolness or warmth of an object
(average of kinetic energy – oC)
Precipitation
Any form of water that falls to
Earth from atmosphere (mm or
cm)
Atmospheric Pressure
The force of the atmosphere per
square meter of surface below it
(kPa)
Humidity
The amount of water vapor in the
air (%)
Wind Speed
How quickly the air moves (km/h)
Wind Direction
Sky Cover
The winds direction (NSEW
bearings)
The portion of sky that is covered
by clouds
After Exam Activities
• Beside your “components of weather” foldable
on pg 97:
– Draw and caption a picture that shows how Earth’s
biosphere is made up of the atmosphere,
hydrosphere, and lithosphere. Use colour to help
show the difference. (Use figure 1.2 on page 13 of
your textbook.) In the caption, describe the difference
between the atmosphere, lithosphere, and
hydroshpere.
• Answer the following questions on page 98 of
your notebook:
– Pgs 4-7: #5, 7, 12, 16, 17, 25, 26
• Sheet to complete: Part A
Earth’s Energy Budget
(page 13)
Activity
• Read through pgs 13-14 in your textbook and
look at figure 1.4.
• Glue the figure into your notebook on page 99.
Beside and under the figure, explain what is
happening in the figure. In your answer think
about:
– What do they mean by “Earth’s energy budget?
– Where does solar radiation come from?
– What happens to solar radiation when it enters
Earth’s atmosphere?
– How does the Earth naturally keep from overheating?
Possible Answer
• Earth’s energy budget (AKA radiation
budget) is the method of how the Earth
absorbs and reflects solar radiation (which
comes from the sun) in order to keep the
Earth from over-heating.
Types of Energy Transfer Radiation
• Energy is transmitted as photons
(electromagnetic radiation)
• Think: The Sun!
Solar Radiation
• Solar constant is defined as the amount
of radiant energy that hits one square
meter of the Earth’s outer atmosphere
every second (1362 J/s/m2)
• Unit of energy  Joule (J)
• See Figure 1.4, page 14
• Greenhouse Effect – the warming of
Earth as a result of greenhouse gases
(like CO2), which trap some of the energy
that would otherwise leave Earth
Terrestrial Radiation
• Earth would constantly increase in
temperature if it did not radiate energy
back to space.
• It would take approximately 25 years for
the oceans to boil if no energy was emitted
back to space
• Terrestrial Radiation is composed primarily
of infrared photons (light)
Incoming and Outgoing Radiation
• About 49% of the solar energy that enters
Earth’s atmosphere is absorbed by the
land and ocean.
• About 42% is absorbed, reflected, and
scattered by clouds, gases, and aerosols
in the atmosphere.
• About 9 percent is reflected by Earth’s
surface.
• Figure 1.4
Solar Radiation Arriving at Earth’s
Surface (see Figure 1.4, page 14)
• Sheet to complete – Earth’s Energy
Budget etc.
Factors Affecting Absorption of
Energy
• 1. The colour of a surface:
– Which one reflects more light?
• Snow or a farmer’s field?
• Albedo - the reflectivity of a surface
– Field in the summer – 20%
– Field covered with snow – 70 or 80%
Factors Affecting Absorption of
Energy
• 2. The nature of a substance: Different
substances absorb energy at different rates.
– Which one will warm up more quickly? Water or
sand?
• The Specific Heat Capacity of a substance
determines how much and how quickly it
absorbs and releases energy.
• Water has a much higher specific heat capacity
than land and air do.
Specific Heat Capacity
Substance
Specific Heat Capacity at 25oC
(J/kg/oC)
Water
4186
Air
1020
Iron
444
Copper
385
Sand
290
Gold
129
Heat Sinks
• Because the specific heat capacity of
water is higher than that of land, water is
considered to be a better heat sink.
• Heat Sink: any substance that can
absorb and retain energy without changing
state.
Water is a good heat sink
• Because there is so much water on Earth,
and water is such a good heat sink, water
has a great influence on weather.
• Is it colder in the winter in Saskatoon or
Halifax?
• Is it colder in the summer in Saskatoon or
Halifax?
Figure 1.5
• The energy transformations that
happen between the time solar
radiation is absorbed and the time
it is re-emitted are what drive
weather systems.
• Questions – p. 15, 1-4
– Answers
Activity
•
•
•
•
Dotted lines mean fold
Solid lines mean cut
Fold your sheet into three sections
Cut the right side fold into 3 equal sections
Fold cut sections in first; the cover isn’t cut
Very top of outside flap title: Thermal
Energy Transfer
• Copy figure 1.6 (textbook pg 16) under the
title. Use 3 different colours to show the
difference between conduction,
convection, and radiation (see example)
On the inside cover (see example)
• Thermal Energy – Energy created by the
movement of particles in a substance.
• Heat: Thermal energy that is transferred
from one object to another
• There are three types of energy transfer.
Write the headers “conduction”,
“convection”, and “radiation” on each of
the three flaps (see example)
• Use the textbook to write a definition for
each type of heat transfer under each
header
Types of Energy Transfer Conduction
• Requires contact between atoms; more
energetic atoms collide with more
energetic atoms and energy is transferred
(solids with solids)
• Example: Warming a pot on a stove
Types of Energy Transfer Convection
• In a gas or liquid, atoms are free to move
and as they warm they become less dense
and rise. Atoms that are cold and denser
will then descend and create a convection
current.
– (liquids/gas)
Types of Energy Transfer Radiation
• Energy is transmitted through indirect
contact (heat travelling through air or
space…electromagnetic spectrum)
• Ex. Sun, fire
• Definitions – Conduction, Convection and
Radiation
• Video – Radiation , Conduction and
Convection
• Newer video (7:45)
Activity
•
•
Glue figure 1.7 onto page 100 of your
notebook.
Answer the following questions in
relation to figure 1.7
1. How does the Earth’s Atmosphere
transfer thermal energy?
2. What happens to hot air? Why?
3. What do you think creates wind?
Atmospheric Pressure
• Atmospheric Pressure – the pressure
exerted by air on its surroundings due to
the weight of the air
• Measured in kilopascals (kPa)
• At sea level, the atmospheric pressure is
101.3 kPa (or 1 kg/cm3)
Copy
Factors that reduce
atmospheric pressure
Copy
Three factors that can reduce
atmospheric pressure:
• Altitude:
– The higher you go, the lower the pressure
• Temperature:
– Warm air moves into cold air = atmospheric pressure
decreases.
– Cold air moves into warm air, atmospheric pressure
increases.
• Humidity:
– The more water vapour in the atmosphere, the lighter
the air is (so more humidity = less pressure)
Copy
• Video (4:28)– Atmospheric Pressure
Layers of the Atmosphere
See Figure 1.8,
page 19
Layers
the Atmosphere
Atmosphere
Layers of
of the
• Troposphere
– All water vapour is present here
– All weather occurs here
– From surface to ~10km
– Temperature ranges from -50°C to 50°C
• Stratosphere
– Ozone is present here
– From 10km-50km
– Temperature ranges -50°C to -30°C
Layers of the Atmosphere
• Mesosphere
–
–
–
–
Meteorites burn up here
Some ions are present here
From 50km to 85km
Temperature ranges from -30°C to -90°C
• Thermosphere
–
–
–
–
Aurora present
Some ions are present here
From 90km to 180km (space)
Temperature ranges from -90°C to over 200°C
Layers of the Atmosphere
• Video (5:05)– Layers of the atmosphere
• To do:
– Finish work sheet:
• Answers
– Vocabulary words:
• Humidity
• Dew point