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UNIT 2 Chapter 1: Inquiring about Weather Unit 2: Weather Dynamics Chapter 1: Earth’s Energy Budget Science 10 Mrs. Purba UNIT 2 Chapter 1: Inquiring about Weather Section 1.1 Earth’s Energy Budget Explain why visible light is represented by a rainbow of colours in the figure below. • • Solar energy is energy generated by the Sun. It consists of 7 types of electromagnetic waves. UNIT 2 Chapter 1: Inquiring about Weather Section 1.1 Earth’s Energy Budget • • • • Solar energy travels to Earth by a process called radiation− thermal energy transfer in which atoms or molecules give off energy as electromagnetic waves when they interact with matter such as air, water, or soil. Solar energy is reflected, absorbed, or emitted (given off) by matter as it travels through the biosphere. The various wavelengths of solar energy are affected differently when they reach Earth. Earth maintains an energy and temperature balance because approximately the same amount of energy enters and leaves Earth’s atmosphere. UNIT 2 Chapter 1: Inquiring about Weather Incoming and Outgoing Radiation About 49% of the solar energy that enters Earth’s atmosphere is absorbed by the land. About 42% is absorbed, reflected, and scattered by clouds, gases, and aerosols in the atmosphere. About 9% is reflected by Earth’s surface. How can a cloud absorb thermal energy? Section 1.1 UNIT 2 Chapter 1: Inquiring about Weather Section 1.1 Factors Affecting Absorption of Energy Both the colour and type of a substance affect its ability to absorb energy. • Dark colours absorb energy. • Light colours reflect energy. A substance’s albedo is the amount of energy its surface can reflect. Give an example of a substance that has a high albedo and a substance that has a low albedo. UNIT 2 Chapter 1: Inquiring about Weather Section 1.1 Factors Affecting Absorption of Energy Different substances absorb energy at different rates. • The property of a substance that involves how a substance absorbs and releases energy (and how quickly) is called its specific heat capacity. • Water has a high specific heat capacity. • Water heats up and cools off more slowly than land does. Both water and land heat up and cool off more slowly than air does. Water is a heat sink. UNIT 2 Chapter 1: Inquiring about Weather Section 1.1 Keeping in the Heat Why doesn’t thermal energy radiate into space at night? • The greenhouse gases act as a heat sink. They absorb thermal energy and radiate the energy in all directions. • These gases cause the troposphere—where weather occurs—to retain more heat than it would if these gases were not present. What can occur when the atmosphere contains more greenhouse gases than normal? UNIT 2 Chapter 1: Inquiring about Weather Section 1.1 Thermal Energy Transfer by Conduction, Convection, and Radiation Thermal energy is transferred from a warmer object to a cooler object, and it is transferred in three ways. 1. Radiation is the transfer of thermal energy by electro-magnetic waves. 2. Conduction is the transfer of thermal energy between two objects or substances that are in direct contact. 3. Convection is the transfer of thermal energy by the movement of heated material (liquids or gases) from one place to another. UNIT 2 Chapter 1: Inquiring about Weather Section 1.1 Thermal Energy Transfer by Conduction, Convection, and Radiation Explain in your own words how thermal energy is transferred in the atmosphere by conduction, convection, and radiation. UNIT 2 Chapter 1: Inquiring about Weather Section 1.1 Atmospheric Pressure • The pressure exerted by the mass of air above any point on Earth’s surface due to the weight of the air. • The SI unit for atmospheric pressure is the Pascal (Pa) or kiloPascal (kPa) • Pascals are used to measure the force per unit area. One Pascal has a force of one Newton per square metre. UNIT 2 Chapter 1: Inquiring about Weather Section 1.1 Temperature & Atmospheric Pressure • As particles of air are heated, they move more quickly and move farther apart, because their kinetic energy has increased. • As a result, warm air is less dense than cold air because the gas particles that make up the air are farther apart. • When warm air pushes into an area of cold air near the ground, the atmospheric pressure in that location decreases. • When cold air pushes into a region of warm air, the atmospheric pressure in that location increases. UNIT 2 Chapter 1: Inquiring about Weather Section 1.1 Humidity & Atmospheric Pressure • Humidity is a measurement that describes the amount of water vapour in air. • The more water vapour in the atmosphere, the lighter the air is. • Humid, or “wet,” air exerts less atmospheric pressure than dry air. UNIT 2 Chapter 1: Inquiring about Weather Section 1.1 Atmospheric Pressure • • • • At sea level, the atmospheric pressure is about 101.3 kPa. As altitude increases, atmospheric pressure decreases. As altitude increases, temperature decreases. As altitude increases, the density of the atmosphere also decreases. • How would the changes in altitude, temperature, density, and atmospheric pressure affect a mountain climber on the peak of Mount Everest? UNIT 2 Chapter 1: Inquiring about Weather Section 1.1 Atmospheric Pressure Meteorologists—scientists who study weather– use atmospheric pressure readings to predict changes in the weather. • A decrease in atmospheric pressure suggests that warm, humid air is approaching and that the temperature will increase. • An increase in atmospheric pressure suggests that cool, dry weather is approaching.