1. Weather Dynamics

2. Section 13.1 A Closer Look at the Earth • Weather: is a set of environmental conditions encountered every day. • Climate: is the set of environmental conditions averaged over many years.

3. Main components of Earth that influence weather are … • Land forms • Atmosphere • Water in its various forms (solid, liquid, gas)

4. Section 13.2 Earth’s Energy Balance • Life 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.

5. Energy can be transferred from one place to another in four ways… • 1. Radiation • 2. Conduction • 3. Convection • 4. Advection

6. 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.

7. 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. • Animation • Conduction, convection, advection animation

8. 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.

10. Answer questions 1,2 4 – 10 on page 507

11. The Hydrosphere… …All of Earth’s water, both fresh and salt, liquid and ice; the hydrosphere makes up around 70% of Earth’s surface.

12. 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.

13. Distribution of Water on Earth

14. The Water Cycle • Energy 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

15. 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.

16. 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... • Ryanswell • Ryan Hreljac

17. 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.

18. Questions… Page 524… #1, #2,#4, #5, #6, #7

19. Clouds and Fog… Section 13.11

20. Typical Cloud Formation • Water 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.

21. Cloud droplet formation...

22. 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.

23. Figure 3

24. 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

25. 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.

26. Classifying clouds Clouds are classified on three different levels; • Shape – clouds that are billowing, rounded shape are called cumulus. These clouds grow vertically and usually mean unstable weather.

27. 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.

28. 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 • Moisturefinally clouds that contain precipitation are given the word nimbus.

30. Please do the following questions… • #’s 1,2,3,4,5 on page 534

31. North American Weather Systems Section 14.2

32. Weather Systems • A 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.

33. Air Masses • An 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 dry • Maritime polar – cold and moist • Continental tropical – hot and dry • Maritime tropical – hot and moist

34. Front • A 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.

35. 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

36. 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.

37. 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.

38. Low Pressure Systems • Bring 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.

39. High Pressure Systems • Bring clear sunny skies and in Canada is a result of the cold, descending arctic air. • High pressure systems rotate clockwise (in the Northern Hemisphere)

40. Weather map – try forcasting! • Please do questions… • Page 549 #1,2 • Page 576 # 1,4

41. Precipitation …is water that reaches the ground in either liquid or solid form. Section 14.5, page 556

42. Precipitation comes in four forms: • RAIN • SNOW – precipitation in the form of very small ice crystals. • HAIL- precipitation in the form of small balls of ice. • SLEET – precipitation in the form of snow or hail, with rain.

43. There are three important points to remember about precipitation: • Air cools as it rises. • 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. • 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.

44. 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.

45. Orographic Precipitation http://www.nicholaskrebs.com/Hawaii/Kauai/Rain%20over%20Kahili%20Mountain.jpg

46. If there is enough condensation, precipitation occurs Leeward side Windward side Precipitation stops as clouds evaporate as air warms. Air cools to the point when condensation occurs – clouds form Air expands as it rises and cools Warm, moist air from the ocean As air descends down the mountain, pressure increases and the air warms up. Rain shadow Mountain range forces air to rise

47. Convectional Precipitation http://www.okeechobeeeoc.com/images/thunderstorm.jpg

48. Air cools to the point where condensation occurs – clouds form Warm air expands as it rises and it cools Warm air rises (less dense) Solar radiation heats the ground Warm ground heats the air above it

49. Condensation continues and clouds grow vertically Warm air continues to rise Heated ground

50. Lightning Heavy rainfall occurs because of large amount of condensation. Summer thunderstorm clouds develop (called cumulonimbus) Enormous amounts of condensation occur Updrafts of warm air Downdrafts of cold air Heated ground