2Unit Nine: Energy in the Earth System Chapter 27 Weather and Climate27.1 Earth's Heating and Cooling27.2 Global Winds and Currents27.3 Weather Patterns27.4 Storms27.5 Weather and Climate
3Chapter 27 Learning Goals Learn how Earth’s rotation, Earth’s axial tilt, and distance from the equator cause variations in the heating and cooling of Earth.Learn how the heating of Earth’s surface and atmosphere by the sun causes convection cycles in the atmosphere and oceans, producing winds and ocean currents.Learn about tools meteorologists use to predict weather, and how to read a weather map.Make and test your own weather instrument.Model a Doppler radar system.Learn about the physical features that interact to form the climate of each of six important land biomes.
527.1 Variations in Earth's Heating and Cooling Key Question:What causes seasons?*Read text section 27.1 AFTER Investigation 27.1
627.1 Heating and Cooling Earth Satellite data is used to map patterns of heating and cooling.The National Oceanic and Atmospheric Administration (or NOAA) uses infrared photography to map how much heat is reflected or emitted from different areas of Earth each day.
727.1 Latitude Latitude lines measure distance from the equator. These lines run parallel to the equator and are labeled in degrees north or degrees south.
827.1 LongitudeLongitude lines run vertically from the north pole to the south pole.The line that runs through Greenwich, England, is labeled 0 degrees longitude and is called the prime meridian.Lines east of the prime meridian are numbered from 1 to 179 degrees east, while lines west of the prime meridian are numbered from 1 to 179 degrees west.The 0- and 180-degree lines are not labeled east or west.
927.1 Temperature and Latitude Earth’s temperature varies with latitude.At higher latitudes, solar radiation is less intense.The same thing happens to the sun’s energy when it reaches the south pole at an angle.
1027.1 Temperature and Rotation As Earth rotates, the portion of the globe facing the sun warms as it absorbs more solar radiation than it emits.Earth constantly emits some of the absorbed energy as infrared radiation.This emission of heat cools the dark side of the planet.
1227.2 Global Winds and Ocean Currents Thermals are small convection currents in the atmosphere.While thermals form on a local level, there are also giant convection currents in the atmosphere.These form as a result of the temperature difference between the equator and the poles.
1327.2 Coriolis EffectBending of air currents is called the Coriolis effect, after the French engineer mathematician Gaspard Gustave de Coriolis ( ), who first described the phenomenon in 1835.
1427.2 Global WindsThere are three important global surface wind patterns in each hemisphere:trade windspolar easterliesprevailing westerlies
1627.2 Ocean CurrentsGlobal wind patterns and Earth’s rotation cause surface ocean currents to move in large circular patterns called gyres.
1727.2 Global Winds and Ocean Currents Key Question:How do temperature and salinity cause ocean layering?*Read text section 27.2 BEFORE Investigation 27.2
1827.3 Weather PatternsThree important factors that shape the weather in a given region are:temperaturepressurewaterA sling psychrometer can measure water in the air.
1927.3 Phase changes of waterWater in the atmosphere exists in all three states of matter.High in the troposphere, there are ice crystals.Tiny water droplets, much too small to see, are suspended throughout the troposphere virtually all the time.Other water molecules in the atmosphere are truly in the gas state, separate from all other molecules.
2027.3 Cloud formation Different conditions cause different clouds. Cumuliform clouds form when convection causes rising pockets of air in the atmosphere.Cumuliform clouds include:cirrocumulusaltocumuluscumuluscumulonimbus
2127.3 Cloud formation Different conditions cause different clouds. Stratiform clouds form when a large mass of stable air gradually rises, expands, and cools.Stratiform clouds include:cirrostratusaltostratusnimbostratus
2227.3 Cloud formationSometimes a cloud formation combines aspects of both cumuliform and stratiform clouds.We call these clouds stratocumulus clouds.
2327.3 Cloud formationCirrus clouds are thin lines of ice crystals high in the sky, above 6,000 meters.They are just a thin streak of white across a blue sky.
2427.3 PrecipitationA raindrop begins to form when water molecules condense on a speck of dust.At first it is round, but when it is large enough that it begins to fall, air resistance causes the underside of the drop to flatten, so that it looks more like a hamburger bun.As it grows larger, it looks more like an upside down bowl with a thick rim.If it hasn’t hit the ground by this point, it will break up into smaller droplets and the process repeats itself.
2527.3 Air masses and frontsAn air mass is a large body of air with consistent temperature and moisture characteristics throughout.Changing atmospheric conditions and global wind currents eventually cause these air masses to move.
2627.3 Low and high pressure areas When a cold front moves into a region and warm air is forced upward, an area of low pressure is created near Earth’s surface at the boundary between the two air masses.A center of high pressure tends to be found where a stable cold air mass has settled in a region.Isobars show areas with the same atmospheric pressure on map.
2727.3 Weather Patterns Key Question: How can we measure water content in the atmosphere?*Read text section BEFORE Investigation 27.3
2827.4 StormsThunderstorms arise when air near the ground is strongly warmed and rises high into the troposphere.As the air rises, it cools and condenses, forming a towering cumulonimbus cloud.Eventually some of the cloud droplets become large enough to fall as rain.a storm cell
2927.4 HurricanesSeveral conditions must be present for a rotating system to become a hurricane:wind speeds of at least 74 miles an hour.warm ocean water must be at least 46 meters deep.the air must be warm and moist to a point at least 5,500 meters above sea level.a tropical cyclone
3027.4 TornadoesA tornado, like a hurricane, is a system of rotating winds around a low pressure center.An average tornado is tiny, compared with the average diameter of a hurricane.However, the wind speeds of a tornado are much greater than those of a hurricane.A tornado’s wind speed can reach 400 kilometers per hour.a tornado