UNIT THREE: Matter, Energy, and Earth • Chapter 8 Matter and Temperature • Chapter 9 Heat • Chapter 10 Properties of Matter • Chapter 11 Earth’s Atmosphere and Weather
Chapter Eleven: Earth’s Atmosphereand Weather • 11.1 Earth’s Atmosphere • 11.2 Weather Variables • 11.3 Weather Patterns
11.2 Learning Goals • Explain the causes of weather. • Discuss the role of convection in moving air through Earth’ s atmosphere. • Describe the characteristics of Earth’s major climate regions.
Investigation 11B Observing the Weather • Key Question • How can you use weather data to make predictions?
11.2 Weather Variables • Weather is a term that describes the condition of the atmosphere in terms of temperature, wind, and atmospheric pressure. • There are many conditions on earth that affect how and why weather changes.
11.2 Convection, pressure, and wind • Convection occurs naturally in Earth’s atmosphere due to the heating and cooling of air. • A thermal is a small, upward flow of warm air caused by convection. Gliding birds like hawks often ride a thermal as they hunt.
11.2 Convection • Heated air near a hot surface is less dense than the colder air above it. • The heated air rises, forcing the colder air to move aside and sink toward the ground. • Then this colder air is warmed by the surface, and it rises. • Windis created.
11.2 Wind • An air mass is a large body of air with consistent temperature and moisture content throughout. • Wind is the horizontal movement of air that occurs as a result of a pressure difference between two air masses.
11.2 Convection in the atmosphere • Convection near coastlines causes sea breezes during the day and land breezes at night.
11.2 Global Convection • The combination of global convection and Earth’s rotation sets up a series of wind patterns called convection cells.
11.2 Global patterns • Three important global wind patterns exist in each hemisphere: • Trade winds • Prevailing westerlies • Polar easterlies
11.2 Coriolis effect • The bending of currents of air due to the Earth’s rotation is called the Coriolis effect.
11.2 Polar fronts • At a boundary called the polar front, the dense, polar air forces the warmer, westerly air upward. • During the winter, polar fronts slide toward the equator and during the summer they retreat northward.
11.2 Air and water vapor • Water in gas form is called water vapor. • Like a soggy sponge, air reaches a point and can’t hold anymore vapor. • The vapor turns back into liquid and form droplets. Use these pictures to explain how the cycle can continue.
11.2 Precipitation • Rain is the result of a cooling air mass. • Cooling an air mass is like wringing out a wet sponge. • Tiny droplets form a cloud or fog. • Larger droplets fall as rain.
11.2 Precipitation • Tiny water droplets are suspended in the atmosphere. • Whether the particles are liquid water or water vapor depends changes in pressure and temperature.
11.2 Precipitation • When the rate of evaporation is greater than the rate of condensation, we see clearing skies. • When the rate of condensation exceeds the rate of evaporation, it rains.
11.2 Snow • Snowusually forms when both ice crystals and water droplets are present in the sky. • The water droplets attach to ice crystals and freeze. • When the ice crystals are large enough, they will fall to the ground.
11.2 Relative Humidity • Relative humidityis a measure of how much water vapor an air mass contains.
11.2 Climate and biomes • Climate is the type of weather that a place has, on average, over a long period of time. • Climate depends on many factors: • latitude, • precipitation, • elevation, • topography, and • distance from large bodies of water.
11.2 Climate and biomes • Scientists divide the planet into climate regions called biomes. • Earth has six main biomes: deserts, grasslands, temperate deciduous forests, rainforests, taiga, and tundras. • Each biome has a unique set of plants and animals that thrive in its climate.
11.2 Climate and biomes • The Serengeti is a home to thousands of predators species and 1.6 million herbivores.
11.2 Climate and biomes • Humidity is related to plant and animal diversity. • From the poles to the equator, humidity and the diversity of plants and animal increases.
11.2 Biomes and temperature • At the equator, sunlight is direct and intense. • As a result, the average yearly temperature at the equator is 27 °C (80 °F), while at the North Pole it is -18 °C (0 °F).
11.2 Biomes and elevation • Elevation is another important factor in determining the type of biome.
11.2 Biomes and temperature • Compare the data below for Portland, OR and Minneapolis, MN. • If these cities are about the same latitude, why don’t they have the same climate?
11.2 Biomes and temperature • The differences in temperature between the two cities have to do with water. • Water warms up and cools down slowly. • Regions near water—like Portland, OR—do not have extremely hot or cold weather, even though they are farther north.
11.2 Plants and animals in biomes • A biome consists of plant and animal communities. • The plants and animals in a community survive in a shared environment.
11.2 Plants and animals in biomes • Within a biome, there are many interrelated ecosystems. • An ecosystemis made up of the plants and animals that live there, plus nonliving things like soil, air, water, sunlight, and nutrients.
11.2 Plants and animals in biomes • What features of this jackrabbit help it survive in it’s desert biome?