SCIENCE ~ CHAPTER 9 CLIMATE Miss Nelson SECTION 1 What Causes Climate? ANTICIPATORY SET Differences in pressure, heat, air movement, and humidity result in changes of weather. STANDARDS S 6.4.a – Students know the sun is the major source of energy for phenomena on Earth’s surface; it powers winds, ocean currents, and the water cycle S 6.4.e – Students know differences in pressure, heat, air movement, and humidity result in change in weather THE BIG IDEA The main factors that influence temperature are: Latitude Altitude Distance from larger bodies of water Ocean currents KEY TERMS Climate – the average long-term conditions of temperature, precipitations, winds, and clouds in an area Microclimate – climate conditions within a small area that dif fer from those in the surrounding area Marine climate – the climate of some coastal regions, with relatively warm winters and cool summers Continental climate – the climate of the centers of continents, with cold winters and warm or hot summers KEY TERMS Ocean current – a large stream of moving water that flows through the ocean in a regular pattern Windward – the side of a mountain range that faces the oncoming wind Leeward – he side of a mountain range that faces away from the oncoming wind Monsoon – sea or land breeze over a large region that changes direction with the seasons WHAT CAUSES CLIMATE? Scientists use two main factors to determine climate: Precipitation temperature FACTORS AFFECTING TEMPERATURE Main factors that influence temperature are: Latitude Altitude Distance from large bodies of water Ocean currents LATITUDE Review World Temperature Zones for the effects of latitude on temperature ALTITUDE In the case of high mountains, altitude is a more important climate factor than latitude As a result, highland areas everywhere have cool climates, no matter what their latitude DISTANCE FROM LARGE BODIES OF WATER Oceans or large lakes can affect temperature Oceans make the temperatures of nearby land less extreme (than they would be without the ocean) Water heats up more slowly than land Water cools down more slowly than land Winds off the ocean often prevent extremes of hot and cold in coastal regions OCEAN CURRENTS Marine climate are often influenced by ocean currents Some warm surface currents move heat from the tropics toward the poles Affects climate as the warm ocean water warms the air above it The best warm water current is the Gulf Stream View the Gulf Stream currents on page 349 of your textbook FACTORS AFFECTING TEMPERATURE Read Factors Affecting Temperature on pages 347 – 349 of your textbook FACTORS AFFECTING PRECIPITATION The main factors that affect precipitation are: Prevailing winds The presence of mountains Seasonal winds PREVAILING WINDS Weather patterns depend on the movement of huge air masses These air masses are move from place to place by prevailing winds The directional winds that usually blow in a region PREVAILING WINDS Air masses can be warm or cool, dry or humid The amount of water vapor in the air mass influences how much rain or snow will fall The amount of water vapor in the prevailing wind also depends on where the winds come from Winds that blow inland from oceans or large lakes carry more water vapor than winds that blow from over land MOUNTAIN RANGES A mountain range in the path of prevailing winds can also influence where precipitation falls When humid winds blow from the ocean to the coastal mountains, they are forced to rise As they rise the air cools and its vapor condenses, forming clouds MOUNTAIN RANGES The Sierra Nevada mountains have a major effect on California’s climate Extremely dry areas (such as Death Valley) are located on the leeward side of the mountains View Figure 4 on pages 350 – 351 of your textbook SEASONAL WINDS A seasonal change in wind patterns can affect precipitation Sea and land breezes over a large region that change direction with the seasons are called monsoons Thailand and parts of India receive much of their rain from the summer monsoons Monsoon winds also bring rain to coast areas in West Africa and northeastern South America SEASONAL WINDS Regions affected by monsoons receive very little rain in winter In the winter, the land cools and becomes colder than the ocean A “land breeze” blows from the land to the ocean, which carries little moisture SEASONAL WINDS The Santa Ana winds are hot, dry winds that often blow in Southern California during fall and early winter Cool air from the desert blows toward the coast As air flows down the mountain, it is compressed and warms up The humidity of the air drops and vegetation dries out, creating a potential fire hazard FACTORS AFFECTING PRECIPITATION Read Factors Affecting Precipitation on pages 350 – 351 of your textbook THE SEASONS The seasons are caused by the tilt of Earth’s axis as Earth travels around the sun TILTED AXIS The axis is an imaginary line through Earth’s center that passes through both poles The axis ALWAYS points in the same direction The north end of the axis is pointed away from the sun for part of the year, and toward the sun for another part of the year View Figure 7 on page 353 of your textbook EFFECT OF THE TILTED AXIS In June the northern hemisphere receives radiation (heat) from the sun at a more direct angle In December, the north end of Earth’s axis is tiled away from the sun THE SEASONS Read The Seasons on page 352 of your textbook CHECK FOR UNDERSTANDING Define climate. What are the factors that affect temperature? CHECK FOR UNDERSTANDING Define climate. Cimate refers to the long-term, average conditions of temperature, precipitation, winds, and clouds in an area. What are the factors that affect temperature? The facts that affect temperature are latitude, altitude, distance from large bodies of water, and ocean currents. MODELING / GUIDED / INDEPENDENT Complete the Modeling, Guided Practice, and Independent Practice Sections of your Climate 9-1 Worksheet.