Chapter 2 – Weather Patterns Guided Notes
Objective(s): 7.E.1.4 Predict weather conditions and patterns based on information obtained from: • Weather data collected from direct observations and measurement (wind speed and direction, air temperature, humidity and air pressure) • Weather maps, satellites and radar • Cloud shapes and types and associated elevation
7.E.1.5 Explain the influence of convection, global winds and the jet stream on weather and climatic conditions.
• Learner Objective(s): Students will understand that the water cycle and atmospheric conditions are interconnected and create the weather we see on Earth.
Concept/Vocabulary Word Definition • Deposition - The process of water vapor changing from a gas directly into a solid. • Dew Point - The temperature at which water vapor will start to condense out of the air as liquid water. • Evaporation - The process of a liquid changing into a gas • Fog - Clouds that form at the surface of the Earth. • Ground Water - Water that has infiltrated (sunk) into the ground. • Hydrosphere - All of the Earth's water that is cycling within the water cycle. • Meteorologist - A scientist who studies the atmosphere, weather and climate • Precipitation - Any type of liquid or solid water that falls to Earth's surface.
• Run Off - Water that flows across the surface of • • • • • •
the Earth. Sublimation - The process of water changing from a solid directly into a gas. Transpiration - The process of water evaporating from the leaves of plants during photosynthesis. Water Cycle - The repeating processes that move water in different forms between Earth's surface and the atmosphere Water vapor - Water in the atmosphere that is in the form of a gas. Weather - The condition of Earth's atmosphere at a particular time and place Weather patterns - Weather that repeats itself in a predictable way.
I. SECTION 2.1 – The atmosphere’s air pressure changes •
A. Air exerts pressure Exploring air pressure – What does air do to the egg?
http://www.youtube.com/watch?v=2VHneRg0mhI&list=PLMWvLl-qJ8maQ15p
• • • • •
Air pushes or exerts a force Air pressure – is the force of air molecules pushing on an area As you move upward in the atmosphere, air pressure decreases The greater the force, the higher the air pressure Air pressure pushes in all directions
•
B. Pressure and Air motion • Air pressure decreases as you move to higher altitude Air moves from areas of higher pressure to areas of lower pressure
C.
Barometers and Air Pressure Barometer – is any instrument that measures air pressure
III. SECTION 2.2. – The atmosphere has wind patterns Wind blows from areas of high • pressure toward areas of low pressure. Earth's rotation causes long distance winds to curve.
area of high pressure
area of low pressure
A. Uneven heating causes air to move
• Weather – is the condition of Earth’s atmosphere
at a particular time and place • Wind – is air that moves horizontally, or parallel to the ground • Uneven heating causes pressure differences which set air in motion • Over a short distance, wind moves directly from higher pressure toward lower pressure • Global winds - travel thousands of kilometers in steady patterns and last for weeks • Uneven heating between the equator and the north and south poles cause global winds
B. Earth’s rotation affects wind direction
• Coriolis effect – influence on Earth’s rotation • Global winds curve as Earth turns beneath them • In the Northern Hemisphere, winds curve to the
right in the direction of motion • In the Southern Hemisphere, winds curve to the left in the direction of motion
• The Coriolis effect is noticeable only for winds that travel long distances
http://www.youtube.com/watch?v=uBqohRu2RRk&list=PLMWvLlqJ8maUvrKjCzRx27pJ9NnKCcWG&feature=mh_lolz
• Investigate: How does Earth’s rotation affect wind? C. Bands of calm air separate global wind belts • Calm regions – doldrums and horse latitudes – Doldrums – are a low-pressure zone near the equator – Horse latitudes – are high-pressure zones located about 30 degrees north and 30 degrees south of the equator
• Wind belts – trade winds, westerlies, and easterlies – Trade winds – blow from east, moving from the horse latitudes toward the equator – Westerlies – blow from the west, moving from the horse latitudes toward the equator. They bring storms across much of the United States – Easterlies – blow from the east, moving from the polar regions toward the mid-latitudes. Stormy weather often occurs when the cold air of the easterlies meet the warmer air of the westerlies http://www.youtube.com/watch?v=I0C4QR0OEH0&list=PLMWvLlqJ8mY36sh_gV7Ume-7kIPbtYIF&index=1&feature=plpp_video
D. Jet streams flow near the top of the troposphere • Jet Streams – usually flow in the upper troposphere from west to east for thousands of kilometers • Air often moves at speeds greater than 200 km/hr or 124 mph • Forms when earth’s surface is heated unevenly • Loop north and south • Each hemisphere usually has two jet streams
E. Patterns of heating and cooling cause local winds and monsoons • Local winds – sea breezes and land breezes – Occur near shorelines
Valley breezes
• Monsoons – winds that change directions with the seasons
– Caused by the different heating and cooling rates of land and sea
III. SECTION 2.3 – Most clouds form as air rises and cools A.
Temperature affects water in the air • Water is always in the atmosphere • Evaporation – is the process by which a liquid changes into a gas. For water to evaporate, it needs extra energy.
http://techalive.mtu.edu/meec/module01/EvaporationandTranspiration.htm
* Condensation – is the process by which gas, such as water vapor, changes into a liquid. Condensation occurs when moist air cools.
B.
Water in the Air • Precipitation – any type of liquid or solid water that falls to Earth’s surface
C. Humidity and Relative Humidity • Humidity – is the amount of water vapor in the air • Saturation – a condition in which the rates of evaporation and condensation are equal • Unsaturated Air – more water evaporates into the air than condenses back into the water • Saturated Air – the amount of water that evaporates equals the amount that condenses
• Relative humidity – compares the amount of water vapor in air with the maximum amount of water vapor that can be present at that temperature – Air with 50% relative humidity has ½ the amount of water needed for saturation. If the amount of water vapor in air stays the same, relative humidity will decrease as the air heats up and increase as the air cools
• Dew point – is the temperature at which air with a given amount of water vapor will reach saturation – Air with a dew point of 26 degrees C (79 F) will become saturated if it cools to 26 degrees C
D. Water vapor condenses and forms clouds
• Clouds are made of condensed water vapor • Rising warm air can produce clouds. Water vapor begins •
to condense when the air cools to its dew point. Investigate – How does a cloud form? Pg. 59
Clouds are made of tiny water droplets that condense from water vapor in rising air. level where condensation begins
E. Characteristics of Clouds
• The shape and size of clouds are determined by air • •
movement Names of clouds that produce precipitation contain the word part nimbo- or nimbus Names of clouds that form at a medium altitude have the prefix alto-
• Cirrus Clouds – means “curl of hair.” Cirrus clouds
appear feathery or wispy – Form in very cold air in high altitudes – Made of ice crystals – Usually found in fair weather – They can be a sign that a storm is approaching
• Cumulus Clouds – means “heap” or “pile.” Cumulus type
clouds can grow to be very tall – Puffy white clouds with darker bases – Looks like cotton balls floating in the sky – Usually appear in daytime in fair weather, when warm air rises and its water vapor condenses. Cooler air sinks along the sides of the clouds, keeping them separate from each other
• Stratus Clouds – means “spread out.” Stratus type clouds form in
flat layers – Form in layers when air cools over a large area without rising or when the air is gently lifted – Are smooth because they form without strong air movement – Low stratus clouds are so dark that they completely block out the sun. These clouds produce steady, light precipitation – Ones that form at high altitudes are much thinner than low lying ones – you can see the sun and moon through them – Ice crystals in high clouds can make it seem as if there’s a circle of colored light around the sun or the moon
• Fog – is a cloud that rests on the ground or a body of water – Has a smooth appearance – Usually forms when a surface is colder than the air above it – Water vapor in the air condenses as it cools forming a thick mist – On land it tends to be heaviest at dawn, after the ground has cooled overnight. It clears as the ground is heated by the sunlight – Often makes transportation dangerous by limiting visibility – In the US, about 700 people die each year in automobile accidents that occur in dense fog
• 10 total clouds: – Cirrus – Cirrocumulus
• Cirrostratus
– Altocumulus
• Altostratus
• Cumulonimbus
• Nimbostratus
• Cumulus • Stratus
IV. SECTION 2.4 – Water falls to Earth’s surface as precipitation • • •
A. Precipitation forms from water droplets or ice crystals All precipitation comes from clouds Cloud droplets are held in the air by slight upward movement of air When cloud droplets combine, they form rain (precipitation)
• It takes about a million droplets to make a single • • •
raindrop When the temp is below freezing, water vapor turns into tiny ice crystals Crystals grow by collecting more water vapor or by colliding and merging with one another Most rain in the US starts out as falling ice crystals, however, before they can reach the ground they melt in a layer of warm air
'Dro' and the Weather Map More About Raindrops Here are a few of my raindrop mates! ...
Cloud droplets are so small that you need a magnifying glass to see them. Most people think that raindrops look like tear drops. Like the one below.
This is not true. They are round like me or a little flatter like 'Megadrop'.
This is 'Megadrop'. It is a large raindrop. It is 5 millimeters in size. As it falls from the sky it flattens out.
This is 'Dropoid'. It is a small raindrop. It is only 1 millimeter in size.
B. Measuring Precipitation • Scientists uses a rain gauge to measure rainfall • Snow depth can be measured with a long ruler • Types of Precipitation Water droplets in clouds merge to form raindrops. Ice crystals in clouds can form snow, rain, and other types of precipitation. Freezing rain is rain that freezes when it hits the ground or other surfaces.
Sleet is rain that freezes into ice pellets while falling through cold air.
Snow forms from ice crystals that merge in clouds.
Hail forms when ice pellets move up and down in clouds, growing larger as they gain layers of ice.
• Rain and Drizzle – Most common type of precipitation – Raindrops form from liquid cloud droplets or from ice crystals that melt as they fall – A light rain with very small drops is called drizzle – Drizzle usually comes from stratus clouds, which don’t have enough air movement to build up larger raindrops
• Freezing Rain AKA Ice – Rain that freezes when it hits the ground or other surfaces in cold weather – Covers surfaces with a coating of ice – Can make roads slippery and dangerous – Weight of the ice can bring down trees and power lines
• Sleet – Rain that freezes before it hits the ground – Are small pellets of ice
• Snow
Ice crystals that grow and merge in clouds become snowflakes Snowflakes come in different shapes and sizes but usually has 6 sides or branches When snow falls through moist air that is near freezing, flakes tend to join together in clumps When snow falls through colder and drier air, snowflakes don’t join together and snow is powdery
• Hail – – –
Largest type of frozen precipitation Arrives in warm weather Are lumps or balls of ice that fall from cumulonimbus clouds – During a thunderstorm, violent air currents hurl ice pellets around the cloud – Pellets grow as water droplets freeze onto them at high elevations. Some start to fall but are pushed back up again. This may repeat several times adding a layer of ice each time. Eventually they fall to the ground. – Largest hailstone weighed 1.7 pounds and was as wide as a CD
– Precipitation can carry pollution • Rainwater is naturally a little acidic • Acid rain – is rain that has become much more
acidic than normal because of pollution • Factories, power plants, automobiles, and some natural sources release sulfur dioxide and nitrogen oxides into the air. Theses gases combine with water vapor to form sulfuric acid and nitric acid. The acids mix with cloud droplets or ice crystals and falls to the surface as precipitation. • Acid rain harms trees and raises the acidity of lakes, making it difficult for fish to live in them • Acid rain also damages the surfaces of building and sculptures