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Weather Dynamics
Weather Dynamics
Section 13.1 A Closer Look at the EarthWeather: is a set of environmental conditions
encountered every day.
Climate: is the set of environmental conditions averaged over many years.
Main components of Earth that influence weather are …
Land formsAtmosphereWater in its various
forms (solid, liquid, gas)
Weather
Atmosphere
Land forms
Water
Section 13.2 Earth’s Energy BalanceLife on Earth depends on energy from the
Sun.
Changing weather is also directly related to the energy from the Sun
The energy from the Sun is in the form of electromagnetic energy that makes the Earth warm enough to support life.
Energy can be transferred from one place to another in four ways…
1. Radiation2. Conduction3. Convection4. Advection
Electomagnetic Spectrum
1. visible light 2. X-rays
3. gamma
rays4. UV rays
5. infrared radiation
6. microwa
ve
Radiation: is the transfer of energy in the form of waves
The Electromagnetic Spectrum – shows all types of radiation that can travel through space at the speed of light.
Conduction…the transfer of energy through the collision of particles, occurs mostly in solids but can happen in water.
Convection and Advection…transfer of energy by the movement of particles in a fluid, liquid or gas. Since weather systems depend on the movement of
particles in the atmosphere and oceans. Convection and advection apply to weather changes.
AnimationConduction, convection, advection animation
Reflection and Absorption…Some electromagnetic waves are reflected
back into space from the atmosphere. Others are absorbed by clouds , the oceans or the Earth’s surface.
Heat sink…any object that gets warmer by absorbing the Sun’s energy.
Albedo effect the ability of an object to reflect (rather than absorb) the sun’s rays. The higher the albedo, the greater the object’s ability to reflect.
Answer questions 1,2 4 – 10 on page 507
The Hydrosphere……All of Earth’s water, both fresh and salt, liquid and ice; the hydrosphere makes up around 70% of Earth’s surface.
Water distribution in the hydrosphere…The vast majority of Earth’s water is in the
oceans (salt water), with smaller, but geologically important, quantities of fresh water in lakes, rivers, and ground water.
Distribution of Water on Earth
The Water CycleEnergy from the sun causes water to evaporate,
or ice to sublimate. The invisible water vapour rises, and eventually,
as the pressure and temperature decrease, this vapour condenses (changes from vapour to liquid) into fog, mist, and clouds.
The resulting precipitation falls to the ground, and the cycle starts again.
YouTube - Water Cycle Animation(Nasa)The Water Cycle
The Water Cycle . . .Because so much of Earth’s surface is
covered by water, our weather systems depend greatly on water in its three states: solid, liquid, and gas.
The hydrosphere and human habitat…Water-borne diseases caused by impure
drinking water kill approximately 6,000 children per day.
3.575 million people die each year from water-related diseases.
Water borne diseases... Bilharzia...RyanswellRyan Hreljac
The hydrosphere and human habitat
Fresh water is vital for human survival. We live, in large part, near sources of water.
We need clean drinking water. Weather systems on or near large bodies
of water greatly affect large numbers of people.
Questions…
Page 524…#1, #2,#4, #5, #6, #7
Clouds and Fog…Section 13.11
Typical Cloud FormationWater in lakes, rivers, oceans and plants gains energy from the Sun. This energy causes the water molecules to heat up and move more rapidly. The water then changes from a liquid to a vapour. Water vapour then rises in the heated, less dense air. When it reaches higher elevations where it is colder, it condenses into liquid. This is how clouds form.
Cloud droplet formation...
How do clouds form? There are three main categories of cloud formation...
1. Convective clouds from previous slide ... 2. Frontal clouds... ...produced when air near
the ground absorbs energy from heated surfaces (oceans, lakes, asphalt, concrete, dirt) becomes warmer and less dense, and rises in the atmosphere. As the warm air rises, it carries water vapour with it.
...form where the leading edge, or front, of a large moving mass of air meets another mass of air at a different temperature. Warm air masses contain more water vapour. If a warm air mass moves over a cold one ( figure 3, 531) the warm air rises, expands, and cools. The moisture condenses to form clouds.
3. Orographic clouds......form when air
moves up a mountain, expands at the lower pressure, and cools. Moisture in this rising air condenses in the colder air as it goes up the mountain, producing clouds.
Animation
Fog...
• is a cloud that forms near the ground.• Mostly produced on clear nights when surface energy radiates upwards but is not reflected back by any clouds. • Air near the ground cools allowing water vapour to condense into fog. • Fog also forms when warm air passes over snow-covered ground or when moist sea air drifts over a cold current.
Classifying cloudsClouds are classified on three different levels;
1. Shape – clouds that are billowing, rounded shape are called cumulus. These clouds grow vertically and usually mean unstable weather.
Clouds that are mostly flattened and have a layered shape are stratus. The usually form horizontally, and often when a warm air mass overruns a cold air mass. They usually mean stable weather.
2. Height – clouds are given names according to their height in the atmosphere;
Low level clouds are not given any prefix, simply known as cumulus or stratus
Mid level clouds begin with the prefix alto High level clouds begin with the prefix cirrus
3. Moisture finally clouds that contain precipitation are given the word nimbus.
Please do the following questions…
#’s 1,2,3,4,5 on page 534
North American Weather SystemsSection 14.2
Weather SystemsA weather system is a set of temperature,
wind, pressure and moisture conditions for a certain region that move as a unit for a period of days.
In some areas (ie. arctic) weather systems are easy to forecast because there is little change.
In most of North America, they are more difficult because are influenced by ground and atmospheric conditions from a larger geographical area.
Air MassesAn air mass is a pocket of air with relatively
the same temperature and pressure. The air masses that affect our weather are;Continental polar – cold and dryMaritime polar – cold and moistContinental tropical – hot and dryMaritime tropical – hot and moist
FrontA front is simply the boundary where two
different air masses meet. There are four general types of fronts;Warm front – occurs when a warm air mass
overtakes a cold air mass. Usually move north and slower than cold fronts.
Cold front – occurs when a cold air mass pushes under a warm air mass. Cold fronts tend to move west to east and can move faster than warm fronts and bring about more noticeable changes in weather.
Animation
Occluded front – forms when a cold air mass catches up to another cold air mass that has pushed under a warm air mass. The result is a warm air mass sandwiched between two cold masses.
Stationary front – occurs when the boundary between a warm air mass and a cold air mass remain still for a period of time, usually covering a large geographical area. There is no rotational movement of air masses with a stationary front.
Low Pressure SystemsBring cloudy skies and
stormy weather.Begin as cold and
warm front meet, creating a low pressure area near the ground.
This low pressure area pulls air near the surface in causing a counterclockwise rotation.
High Pressure SystemsBring clear sunny skies and in Canada is a
result of the cold, descending arctic air.High pressure systems rotate clockwise (in
the Northern Hemisphere)
Weather map – try forcasting!
Please do questions…Page 549 #1,2Page 576 # 1,4
Precipitation…is water that reaches the ground in either
liquid or solid form.
Section 14.5, page 556
Precipitation comes in four forms:
1. RAIN 2. SNOW – precipitation in the form of
very small ice crystals.3. HAIL- precipitation in the form of small
balls of ice.4. SLEET – precipitation in the form of
snow or hail, with rain.
1. Air cools as it rises.2. As air cools, water vapour (which is invisible)
condenses. • Clouds begin to form. Clouds are made up of
very tiny drops of liquid water, which are held aloft by air currents because they are so light.
3. If there is sufficient condensation, the cloud droplets will start to merge together and eventually start to fall as they get too heavy to stay aloft. This is precipitation.
There are three important points to remember about precipitation:
Air may be caused to rise in one of three ways:
1. As it crosses an area of higher elevation – causes orographic precipitation.
2. It absorbs heat from the ground and rises – causes convectional precipitation.
3. Cooler, denser air flows underneath it forcing air aloft – causes cyclonic precipitation.
Orographic Precipitation
http://www.nicholaskrebs.com/Hawaii/Kauai/Rain%20over%20Kahili%20Mountain.jpg
Warm, moist air from the ocean
Mountain range forces air to rise
Air expands as it rises and cools
Air cools to the point when condensation occurs – clouds form
If there is enough condensation, precipitation occurs
As air descends down the mountain, pressure increases and the air warms up.
Precipitation stops as clouds evaporate as air warms.
Rain shadow
Windward side
Leeward side
Convectional Precipitation
http://www.okeechobeeeoc.com/images/thunderstorm.jpg
Solar radiation heats the ground
Warm ground heats the air above it
Warm air rises (less dense)
Warm air expands as it rises and it cools
Air cools to the point where condensation occurs – clouds form
Warm air continues to rise
Heated ground
Condensation continues and clouds grow vertically
Summer thunderstorm clouds develop (called cumulonimbus)
Updrafts of warm air
Heavy rainfall occurs because of large amount of condensation.
Enormous amounts of condensation occur
Downdrafts of cold air
Lightning
Heated ground
Eventually the cooling effects of the rain, the cold down drafts, and the lack of solar heating because of the clouds stop the updrafts as the ground cools off.
The rain stops.
The down drafts and the clouds disappear
Cyclonic or Frontal Precipitation
http://www.engineering.usu.edu/uwrl/atlas/photos/ch2storm.gif
How Air Masses Influence Our WeatherThe air in the earth’s atmosphere (layer of gases
surrounding the earth) is constantly on the move.
An air mass is a large body of air with similar moisture and temperature content.
Whether an air mass is warm or cold depends on where it originates.
Generally, air masses originate in the south in the summer and the north in the winter.
The leading edge of an air mass is called a front.
When the fronts of two air masses meet a battleground is created in the sky.
Air masses do not mix.
A mass of warmer (and lighter) air is always forced to rise above a mass of colder (and heavier) air.
The Jet Stream is a river of air which moves from west to east.
Air above the Jet Stream is colder and that below is much warmer.
Direction is used to describe wind.
Most of the winds in Canada are called westerlies because they flow from the west.
As warm air rises it cools. Cold air does not hold moisture as well as warm air.
As a result water vapour in the cooling air condenses into droplets. These droplets form clouds.
Eventually, they become too heavy for the air to hold and they fall to the ground in the form of snow or rain depending on the air temperature.
This is called cyclonic or frontal precipitation.
Condensation
Cross-section of a mid-latitude cyclonic stormBecause the air is being forced to
rise, mid-latitude storms are also called low pressure cells or systems.
Warm
Front
Warm Air
Cold Air
Cold Air
Cold Front
Air rises
Air cools
Precipitation
Clouds and Humidity Precipitation is not the only form of
water to be considered part of weather and climate.
Clouds and humidity are also mentioned in weather forecasts.
Clouds are made of water droplets that are not heavy enough to fall.
There are two basic types of clouds:1. Stratus Clouds – a flat low lying cloud layer.
2. Cumulus Clouds – dense, usually white cloud with a dome-shaped top.
The term humidity is the amount of water vapour in the air, this is sometimes described as “dampness” in the air.
This is described in weather forecasts as “relative humidity” – the amount of water vapour in the air relative to the temperature.
This is described as a percentage.
The higher the relative humidity the “damper” or “stickier” the air.
Please do the following questions...Page 557 #’s 1,2,3,4
Extreme WeatherBlizzards, Tornados, Hurricanes, Thunderstorms . . .
Thunderstorms…
A thunderstorm is a storm with lightning, thunder, heavy rain, and sometimes hail.
Two conditions must be met for a thunderstorm to form…
1. Moisture is needed to form clouds and precipitation.
2. the lifting of the air, or uplift, must be very strong in order to produce clouds that reach high in the atmosphere
Three stages of a thunderstorm…
Cumulus stage----------Mature stage----------------Final stage
Stage 1…Cumulus stageUpdrafts of warm air
carry moisture upward. As the warm air rises it condenses. Updrafts are caused by convection currents caused by the heating of the Earth’s surface by solar radiation.
Stage two…Mature stage.Cumulonimbus cloud
forms and spreads out at the top. Cold air containing ice, rain, and sometimes hail falls downward in large downdrafts.
Stage 3…In the final stage the
downdrafts reduce the upward flow of air, and the storm weakens.
Lego Animation
Tornados…
Tornados form in the most severe thunderstorms. Fast-rising air begins spinning, forming a rising funnel of air and moisture
Tornado formation graphic…
Tornado Formation and Intensity Scale…
More rising air is replaced by cooler air on the surface; the rotation then becomes faster and faster. At the center of a tornado the wind speed can be as much as 500 km/h.
Tornado formation...
Tornado Intensity Scale
Tornado numbers…
Funnel clouds can be from a few meters to 500 meters across and can last from a few seconds to several hours. They travel at speeds up to 100 km/h and move usually southwest to northeast. Canada experiences, on average, over 100 per year.
Did you know…in May of 1986, thirteen school children in China were hoisted into the air by a tornado and carried 19 km before falling gently to the ground!!!
Black Friday in Edmonton…The tornado remained on
the ground for an hour, cutting a swath of destruction 40 kilometres long and up to a kilometre wide in places, and peaking at F4 on the Fujita scale, but may have briefly become an F5. The tornado killed 27 people, injured more than 300 people, destroyed more than 300 homes, and caused more than 330 million dollars worth of damage.
Storm tracking…Doppler radar is an
important technology used to track t’storms and tornados. Radio waves sent out by the instrument bounce off water drops and ice particles in the storm. Reflected waves reveal the location of the drops and particles. A map can then be drawn of the storm.
Tornado footage
HurricanesSection 15.6
Hurricanes…severe cyclones. A cyclone is a low
pressure swirling air mass. Develops in the mid-latitudes when cold and warm air fronts interact.
Cyclogenesis is the process of creating a cyclone.
Hurricanes and typhoons
Hurricanes…a severe cyclone that occurs in the western Atlantic, the Caribbean Sea, the Gulf of Mexico, or eastern Pacific ocean.
Typhoons…a severe cyclone that develops in the northwestern Pacific Ocean or the China Sea.
Atlantic Ocean Hurricanes.Hurricanes that affect us are Atlantic Ocean
hurricanes. These begin their life in the eastern Atlantic as low pressure systems which then build with the presence of warm ocean waters. They continue to move westward and grow as they move.
Water temp and hurricane formation…
The Engine of the Hurricane…
If the water temperature is at least 27degrees Celcius, evaporation occurs rapidly and the warm, rising air carries a lot of moisture with it. As this air reaches colder altitudes it condenses, releasing heat that increases the rate at which the air rises.
Warm ocean water acts as fuel for a hurricane.
The hurricane is fed by convection currents.
Evolution of a Hurricane…It begins with hot
ocean water and evaporation setting up convection currents. The ensuing low-pressure system turns to the left, or counterclockwise. Animation
Hurricane structure…
Terms to know…
Eye,Eye wall, Rain bands
PEI Hurricanes…Hurricane Juan.At its strongest was a
Category 2 storm. Caused extensive damage in Nova Scotia and PEI. One last animation!
Please do questions…#2,3,5,7 on page 597
