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 Atmosphere and 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  Key Question  How can you use weather data to make predictions? Observing the Weather

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.  Wind is 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  Snow usually 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 humidity is 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 ecosystem is 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?