Science 1206 Chapter 13,14,15 1
Weather dynamics is the study of how the motion of water and air causes weather patterns. Energy from the Sun drives the motion of clouds, air, and water. Earth s tilt at an angle of 23.5 degrees to the plane of its orbit around the Sun. Major components of Earth that influence weather are: atmosphere, land forms, and water. ( all states) About 70% of Earth s surface is covered by oceans. 2
The atmosphere contains air, water vapour, and particles of dust and chemicals, all of which affect weather, especially when the atmosphere is in motion. 3
Weather is the set of environmental conditions encountered from day to day. Climate is the set of environmental conditions averaged over many years. 4
Longitude is the angle measured East or West from the 0 degree line which passes through Greenwich, England. Latitude is the angle measured North or South of the equator. 5
The Tropic of Cancer is at 23.5 degrees north latitude. It is the most northerly location reached by the Sun s vertical rays on the first day of summer, June 21, each year. The Arctic Circle is at 66.5 degrees north latitude. It is the most northerly location reached by any of the Sun s rays on the first day of winter, December 21. In the southern hemisphere we have the Tropic of Capricorn and the Antarctic Circle. The region between the Tropic of Cancer and the Tropic of Capricorn is referred to as the tropics. Most of Canada s population lives in the mid-latitude region. Polar regions would be any land that fall in between the earths 2 poles and the tropic of Cancer and Capricorn. 6
Weather Lore Read Chapter 13 7
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Most of the energy used on Earth to sustain life and cause changing weather systems comes from the Sun. The average surface temperature is 15 degrees C. Different types of EM energy are emitted from the Sun. Energy can be transferred from one place to another by 4 methods: 1)Radiation 2)Conduction 3)Convection 4)Advection 9
Radiation -transfer of energy by means of waves or particles. Radiation does not need a medium. The waves can travel from the Sun, through space, and reach Earth. Visible light is energy that can travel through space. Other examples are: 1)Radio waves 2)Microwaves 3)X-rays 4)Gamma rays 5)Infrared rays These travel at 300,000 km/s in a vacuum. 10
The set of waves that can travel through empty space at the speed of light is called the electromagnetic spectrum. 11
The other methods of energy transfer require particles of matter. Conduction -the transfer of energy through the collision of particles. Occurs most easily in metals, but also to a smaller extent in rock, sand soil and water. 12
Convection and advection are the transfer of energy by the movement of particles in a fluid. A fluid is either a liquid (water) or a gas(atmosphere). Convection transfers energy vertically. Advection transfers energy horizontally. Weather systems involve convection and advection. 13
EM waves from the Sun reach Earth, some is reflected off the atmosphere and clouds back into space; some pass through the atmosphere and bounce off Earth s surface; some get absorbed by the atmosphere, the ground, or the water at the surface. 14
The portion of energy reflected depends on the albedo of the material. Clean snow has a high albedo, it reflects a lot of incoming energy. Black soil has a low albedo, it absorbs more energy than it reflects. Any object or material that absorbs energy and becomes warmer is called a heat sink. Water has a higher albedo than land and soil, the oceans are good heat sinks. When solar energy hits water, the water begins to move(convection), and transfer energy deep into the oceans. Soil and rock are poor heat sinks. Heat is conducted slowly into these materials. 15
An important property of all substances is their heat capacity, the measure of how much heat a substance requires to increase its temperature or how much heat it releases as its temperature decreases. Water has a high heat capacity. This means it can hold a lot of heat. 16
Energy Transfer Worksheet 17
All of Earth s water, both fresh and salt, forms what is called the hydrosphere. About 70% of Earth s surface is covered by water. Freshwater makes up 2.5% of the total water on Earth. Most of this occurs as polar ice. 19
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Water vapour is essential to the water cycle and weather patterns. Water vapour is responsible for clouds, fog, rain and snow. 22
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Worksheet # 5 Precipitation Worksheet 25
The thin layer of gases that surround the earth is the atmosphere. (about 10 km thick) The atmosphere is where all the weather happens. The atmosphere acts like a blanket which controls the temperature of the earth. 27
The earth's atmosphere is made up of dust and a mixture of invisible gases. Some of these gases include: Nitrogen (N2) 78% Oxygen (O2) 21% Other gases: 1% combined [water vapour, argon, carbon dioxide, neon, helium, krypton, hydrogen, ozone...] 28
Nitrogen and ozone act as a protection shield that blocks out harmful radiation from space( UV ). Oxygen is essential for life. Plants produce oxygen and we breathe it in. Carbon dioxide is essential for life too. We breathe out carbon dioxide and plants breathe it in. 29
The atmosphere can be divided up into distinctive layers. Exosphere Thermosphere Mesosphere Stratosphere Tropopause Troposphere 30
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Worksheet # 8 - Layers of the Atmosphere Layer and Gas in the Atmosphere Assignment Worksheet # 9 38
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1)Anemometer is a device used to measure wind speed 40
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The word aneroid means without liquid. 45
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High air pressure in a region indicates fair weather while low pressure indicates that storms are more likely. 47
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Weather satellite Weather Balloons Computers 50
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Humidity: a measure of the amount of water vapor in the air Warm air can hold more moisture then cold air Relative Humidity: The measure of the amount of water vapor compared to the Maximum amount possible
Saturated Air Relative humidity is 100% Over 100% results in condensation Dew Point Temp at which dew forms As air gets colder, it holds less moisture Releases excess as dew
Figure 1, pg. 558 Maximum Amounts
Relative Humidity concentration x100% maximum concentration Ex 1: What is the relative humidity if 1.9 g/kg of water in air is present at 0oC? Ex 2: What is the conc of H2O in the air at 20oC if the relative humidity is 50%?
Dry Bulb Wet Bulb 22 17 18 14 32 30 32 22 Relative Humidity
Higher humidity causes perspiration to evaporate slowly. Sweating doesn t cool us as well Low humidity Air is dryer Skin may be uncomfortable Humidex: Reports how hot the humidity makes us feel
See Fig 2, pg. 556 Hail: created in cumulonimbus clouds Frozen raindrops are circulated up and down Layers of ice are formed Dew: Water vapour condenses near the ground as the air cools Cold Days : Frost
Water in the air assignment Worksheet 4 59
Weather can be affected by local landforms in a specific area Thermal: A local convection current set up during the day The sun heats the ground, causing the air to rise
From water to land A thermal formed near water The sun heats the land. The air rise, and a cool breeze blows in from the water. Where are the highs and lows?
from land to water After sunset, the land cools quickly. Air above the warmer water rises, replaced by air from the land. Where are the highs and lows?
When air moves over water it picks up moisture. In winter, water is warmer then the land (more moisture) When the air reaches the cold land, the moisture becomes snow
A gentle warm, dry wind on the leeward side of the Rocky mountains
Atmospheric pressure is the pressure the air exerts as gravity pulls it toward the center of Earth. It is greatest at sea level, where the molecules are closet together. At higher altitudes atmospheric pressure decreases. Atmospheric pressure at a particular altitude depends on whether the air is rising or falling. There are two variations to consider : vertical and horizontal. Pressure gradient is a measure of the amount the atmospheric pressure changes across a set distance. Pressure gradients can be vertical or horizontal. 65
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Worksheet: Air Pressure 73
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As air rises it begins to cool and expand. Cooled air can no longer hold all its moisture. The water vapour begins to condense on dust particles as very tiny water droplets. Depending on the temperature clouds may be made up of tiny water droplets and or tiny ice crystals. 76
For Newfoundland it may bring cooler wetter conditions - lots of snow! 77
1. Convective: formed when a land mass is heated and the warmed air begins to rise, expand, cool and water condenses. We see these types of clouds where thermals and sea breezes are formed. 78
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2. Frontal: form at the frontal zone where two large air masses meet. The warmer air mass is forced to rise up over the cooler air mass. It expands and cools resulting in the formation of condensation. 80
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3. Orographic: formed because of geography when air is forced to rise up a large hill or mountain. As the wind blows into the side of the mountain it rises up. As the air rises it expands and cools causing water vapour to condense as clouds. 84
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Heaped" or "lumpy" clouds result when strong vertical (upward) motions exist in the atmosphere. This shows us that the air mass is being forced to rise very rapidly. A clue that the atmosphere is unstable and are usually associated with stormy or severe weather. 89
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Wide spread out, smooth, layered clouds. These clouds gives a clue that the air motion is horizontal (across) rather than vertical (up and down). The forming clouds are rising slowly which is a sign of a stable atmosphere. 91
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they are named by altitude in the atmosphere. 93
altocumulus stratocumulus 94
cumulonimbus 95
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Clouds have a duel role: 1) Quite simply clouds act as a blanket. Cloudy nights: traps heat keeping the air warm. Clear night sky: heat escapes and air cools quickly. 2) Keep the earth cool during the day. The formation of white cloud cover reflects the sun's energy away. 97
Gravity pulls down on all matter. Gases are matter and gravity pulls down on them. This is why the troposphere (layer closest to the earth) has 99% of all the gases in the atmosphere. 98
A cloud that forms near the ground Can form on cool, cloudless nights When warm air passes over snow-covered ground When moist sea air drifts over a cold current When moist air rises up a mountain side Forms when warm moist air moves over a colder surface (land or water) releasing its moisture as very fine water droplets. 99
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The atmosphere is made up of areas of different densities. 102
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Assignment: Cloud Formation 109