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Unit 4 Weather and Climate

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1 Unit 4 Weather and Climate
Big Idea: Air pressure, temperature, air movement, and humidity in the atmosphere affect both weather and climate.

2 Unit 4 Lesson 1 Elements of Weather
What is weather? Weather - condition of Earth’s atmosphere at a certain time & place. Temperature - measure of how hot or cold something is. -thermometer Humidity -amt of H2O vapor in the air. -psychrometer Precipitation -any form of H2O that falls from clouds. -rain gauge, meterstick Air pressure –the force of air molecules pushing on an area. -barometer Wind -air that moves horizontally, or parallel to ground -anemometer or wind vane/wind sock Visibility –measure of the distance an object or light can be clearly seen. Uses 3 or 4 landmarks Weather conditions in the atmosphere can be recognized through direct observation. Temperature: Some thermometers use the thermal expansion of a liquid to determine temperature. Electrical thermometers use the strength of an electric current to determine temperature. Humidity: As more water evaporates, humidity of the air increases. Relative humidity -amount of water vapor in the air compared to the amount of water vapor needed to reach saturation. When air is saturated, the rates of evaporation and condensation are equal Dew point is the temperature at which more condensation than evaporation occurs. When air temperature drops below the dew point, water vapor condenses to form dew, fog, and clouds Precipitation: It includes rain, snow, hail, and sleet. Inside a cloud, water droplets can collide to form larger droplets, and when they become heavy enough, they fall as rain. Snow forms when air temperatures are low enough to turn water vapor into a solid. Fallen snow may be measured with a meterstick. When balls or lumps of ice fall from clouds during thunderstorms, it is called hail. Sleet forms when rain falls through a layer of freezing air, producing falling ice. Air pressure is the force of air molecules pushing on an area. Air pressure and density decrease with altitude. Wind is air that moves horizontally, or parallel to the ground. Over a short distance, air moves from higher pressure to lower pressure. Visibility: Visibility is measured by using three to four known landmarks at different distances. Air pollution or fog can cause poor visibility. Weather data can be collected at ground stations, by weather buoys, by ships, by airplanes, and by satellites. Copyright © Houghton Mifflin Harcourt Publishing Company 2

3 Watching Clouds Unit 4 Lesson 2 Clouds & Cloud Formation Cirrus clouds -made of ice and appear feathery or wispy. Cumulus clouds -appear as heaps or piles. They form in fair weather but can produce thunderstorms. Stratus clouds -form flat layers that can block out the sun and produce steady rain. Clouds are visible because water droplets and ice crystals reflect light. Clouds are usually associated with precipitation, but most cloud types do not produce precipitation. Stratus is a Latin word that means “layer.” Stratus clouds often merge into one another and may look like a single layer that covers the entire sky. Cumulus is a Latin word that means “heap.” thick and puffy on top and generally flat on the bottom. These clouds have well-defined edges and can change shape rapidly. They can be bright or dark, and they can produce severe weather. Cirrus is a Latin word that means “curl.” their ends curl. They are made of ice crystals rather than liquid water droplets. They do not produce precipitation that reaches Earth’s surface. Low clouds form between Earth’s surface and 2,000 m altitude. They are commonly made up of water droplets. The three types of low clouds are stratus, stratocumulus, and nimbostratus. There is no special prefix for naming low clouds. However, nimbus means “rain,” so nimbostratus clouds are rain clouds. Middle clouds form between 2,000 m and 6,000 m altitude. They are commonly made up of water droplets, but may be made up of ice crystals. The prefix alto- is used to name middle clouds. The two types of middle clouds are altocumulus and altostratus. High clouds form above 6,000 m altitude, where air temperature is below freezing. Therefore, high clouds are made up of ice crystals. The prefix cirro- is used to name high clouds. Cirrus, cirrocumulus, and cirrostratus are the types of high clouds. A cloud of vertical development can have its base at low altitude, but its top can reach higher than 12,000 m. The two types of clouds of vertical development are cumulus and cumulonimbus. Cumulonimbus clouds are linked to severe weather and can produce rain, hail, lightning, tornadoes, and rapidly sinking columns of air. Copyright © Houghton Mifflin Harcourt Publishing Company 3

4 Unit 4 Lesson 3 What Influences Weather?
Putting Up a Front How do air masses affect weather? Air mass-large volume of air in which temperature & moisture content are nearly the same throughout. Front- forms between air masses with differing densities. Warm front An air mass forms when air remains over a region for many days and takes on the temperature and humidity of the land below it. Fronts cause a change in weather as they pass. The temperature and moisture content of the air masses that meet and their movement relative to each other determine the type of front formed. Cold fronts form as a cold air mass pushes an existing warm air mass up. Warm fronts form as a warm air mass slides up over a retreating cold air mass. Stationary fronts form when a cold air mass and a warm air mass remain in one place. Stationary front Cold front Copyright © Houghton Mifflin Harcourt Publishing Company 4

5 Unit 4 Lesson 3 What Influences Weather?
Feeling the Pressure! Areas of different air pressure cause changes in the weather. High-pressure system - air slowly sinks down and spreads outward. Low-pressure system - air rises and cools A high-pressure system can form a low-pressure system. Sinking air in a high-pressure system generally produces clear skies and calm air or gentle breezes. Rising air in a low-pressure system generally produces clouds and rain. Copyright © Houghton Mifflin Harcourt Publishing Company 5

6 Cloudy with a Chance of …
Unit 4 Lesson 5 Weather Maps and Weather Prediction Weather forecasting -analysis of scientific data to predict future weather conditions. Meteorology - study of weather and Earth’s atmosphere Doppler radar is important for detecting and tracking severe storms and tornados. Cloudy with a Chance of … Checking the weather forecast helps determine what the weather is and how it might change. Scientists who study meteorology are called meteorologists. They observe eight elements of weather: air temperature, humidity, wind direction, wind speed, clouds, precipitation, atmospheric pressure, and visibility. The Hurricane Hunters of the National Oceanic and Atmospheric Administration (NOAA) fly into the eye of tropical storms and hurricanes. Their planes are equipped to collect data with special instruments such as radar and radiometers. Meteorologists gather data using advanced technologies at ground stations and in balloons, aircraft, and satellites. Land-based ground stations, called automated surface stations, collect weather data from the lower atmosphere 24 hours a day. Many stations are located near airports and transmit computer-generated voice observations to aircraft regularly. Copyright © Houghton Mifflin Harcourt Publishing Company

7 Unit 4 Lesson 5 Weather Maps and Weather Prediction
What can you conclude from this weather map about the weather happening in different parts of the United States? Copyright © Houghton Mifflin Harcourt Publishing Company

8 Climate is usually determined by temperature and precipitation.
Unit 4 Lesson 6 Climate Climate -describes the weather conditions in an area over a long period of time. Climate is usually determined by temperature and precipitation. Temperature ranges include all of the temperatures in an area, from the coldest extreme to the warmest extreme, and they are used to describe climate. Precipitation patterns over time, rather than average precipitation, are used to determine climate. Climate is directly related to the amount of energy from the sun, or solar energy, that an area receives. The amount of solar energy depends on latitude. Latitude is a location’s angular distance in degrees north or south from the equator. Solar energy powers the water cycle and winds, which affect the temperature, precipitation, and other factors that determine climate. As latitude increases, the angle of the sun’s rays becomes greater. This reduces temperatures. Locations near the poles are cooler than locations near the equator. The sun powers the water cycle, which causes the evaporation, condensation, and precipitation necessary to create weather. Uneven heating of Earth’s surface by the sun causes differences in air pressure, which create winds. The speed, direction, temperature, and moisture content of winds affect the climate and weather. Copyright © Houghton Mifflin Harcourt Publishing Company 8

9 How do Earth’s features affect climate?
Unit 4 Lesson 6 Climate How do Earth’s features affect climate? Topography -Surface features on Earth combine to form an area. Elevation -height of an area above sea level. Rain shadow -happens when warm, moist air rises over a mountain and drops its precipitation on one side, leaving the other side dry. Air at higher elevations rises, cools, and expands, resulting in lower temperatures. Topography influences wind patterns in an area. Copyright © Houghton Mifflin Harcourt Publishing Company 9

10 Unit 4 Lesson 7 Climate Change
Studies show that the average global surface temperature has risen by about 0.3 °C to 0.8 °C over the last 100 years. Global warming -gradual increase in average global temperature. It will affect global sea level, global weather patterns, and life on Earth. Scientists predict that storms will increase in power and frequency, and as much as half of Earth’s surface may be affected by drought. Rising temperatures will lead to an increase in the melting of glaciers, arctic sea ice, and ice sheets that cover Greenland and Antarctica. A 2010 report observed record-setting high temperatures, resulting in record melting of the Greenland ice sheet. Global sea level rose by 10 to 20 cm during the 1900s. Scientists project that sea level may rise by 60 cm by 2100. Scientists predict that global warming will change ecosystems, threatening the survival of many species. Some species may benefit, however. If Earth warms more than a few degrees Celsius, many of the world’s farms could suffer, though less severe warming would help agriculture. Warmer temperatures could increase the number of deaths related to heat and certain diseases, but deaths associated with extreme cold could drop. Copyright © Houghton Mifflin Harcourt Publishing Company

11 Unit 3 Lesson 3 Nonrenewable Energy Resources
Energy resource -natural resource that humans use to generate energy, and it can be renewable or nonrenewable. Nonrenewable resources -used up faster than they can be replaced. Nuclear energy Crude oil/petroleum Natural gas Coal Be Resourceful! Nonrenewable resources provide much of the energy that humans need to power transportation, warm homes, and produce electricity relatively cheaply. However, the methods of obtaining and using these resources can have negative effects on the environment. Nuclear fission produces a large amount of energy and does not cause air pollution. However, nuclear power plants produce dangerous wastes that remain radioactive for thousands of years. The wastes require special storage. Harmful radiation may be released into the environment accidentally. Also, the power plant releases hot water that, if not cooled, may disrupt aquatic ecosystems. Fossil fuels are relatively inexpensive to obtain and use, but their use entails some problems. Burning coal releases sulfur dioxide, which combines with moisture in the air to produce acid rain. Coal mining disturbs habitats and pollutes water. Oil has been associated with occasional oil spills, damaging the environment. Also, burning fossil fuels can cause smog and releases carbon dioxide, a greenhouse gas. Copyright © Houghton Mifflin Harcourt Publishing Company

12 Renewable resources replaced by natural processes at least as quickly as they are used.
Wind energy Hydroelectric energy. Solar energy Biomass Geothermal energy Wind: Production and maintenance of the equipment is expensive and produces some pollution. The turbine blades can be hazardous to birds. Water: Another disadvantage is that hydroelectric dams and their technology are expensive to build. Dams can block the movement of fish between the sea and their spawning grounds, and special ladders must be built to allow fish to swim around the dam. Solar: The only pollution generated by solar heating systems comes from the manufacture and maintenance of the equipment. Like fossil fuels, biomass produces pollutants when burned. Biomass material can be used to produce an alcohol called ethanol. The sugars or cellulose in plants are eaten by microbes, which give off carbon dioxide and ethanol. The ethanol is collected and burned as a fuel, or it can be mixed with gasoline to make a fuel called gasohol. Geothermal: However, production of the equipment generates pollution, and the technology is expensive to make and maintain.

13 Unit 4 Lesson 7 Climate Change
How can people reduce their impact on climate change? Clean-energy technologies are being researched and used in different parts of the world. New biofuels, solar power, wind power, and water power reduce the need to burn fossil fuels. However, many new technologies are currently more expensive than fossil fuels. Copyright © Houghton Mifflin Harcourt Publishing Company


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