Weather Factors Chapter Two

Energy in the Atmosphere Most energy from the sun reaches Earth in the form of visible light and infrared radiation, and a small amount of ultraviolet radiation. When Earth’s surface is heated, it radiates some of the energy back into the atmosphere as infrared radiation.

Key Terms: Electromagnetic waves: A form of energy that can travel through space. Radiation: The direct transfer of energy by electromagnetic waves. Infrared radiation: A form of energy with wavelengths that are longer than visible light. Ultraviolet radiation: A form of energy with wavelengths that are shorter than visible light. Scattering: Reflections of light in all directions Greenhouse Effect: The process by which heat is trapped in the atmosphere by wayer vapor, carbon dioxide, methane, and other gases that form a “blanket” around Earth.

Heat Transfer The energy of motion in the molecules of a substance is called thermal energy. Three forms of heat transfer work together to heat the troposphere. They are: Radiation Conduction Convection

Key Terms Thermal energy: The energy of motion in the molecules of a substance. Temperature: The average amount of energy of motion in the molecules of a substance. Thermometer: An instrument used to measure temperature consisting of a thin, glass tube with a bulb on one end that contains a liquid (usually) mercury or alcohol. Heat: The energy transferred from a hotter object to a cooler one. Conduction: The direct transfer of heat from one substance to another substance that is touching. Convection: The transfer of heat by the movement of a fluid.

Winds All winds are caused by differences in air pressure. Local winds are caused by unequal heating of Earth’s surface within a small area. The movement of air between the equator and the poles produces global winds. The major global wind belts are the trade winds, the prevailing westerlies and the polar easterlies.

Key Terms Wind: The horizontal movement of air from an area of high pressure to an area of lower pressure. Anemometer: An instrument used to measure wind speed. Wind-chill factor: Increased cooling caused by the wind. Local wind: Winds that blow over short distances. Global wind: Winds that blow steadily from specific directions over long distances. Sea Breeze: The flow of air from an ocean or lake to the land. Land breeze: The flow of air from land to a body of water. Coriolis effect: The way Earth’s rotation makes winds in the Northern Hemisphere curve to the right and winds in the Southern Hemisphere curve to the left. Latitude: The distance from the equator, measured in degrees.

Water in the Atmosphere Clouds of all kinds form when water in the air becomes liquid water or ice crystals.

Types of Clouds Meteorologists classify clouds into three main types: Cumulus Stratus Cirrus

Key Terms Evaporation: The process in which water molecules iin liquid water escape into the air as water vapor. Humidity: A measure of the amount of water vapor in the air. Relative humidity: The percentage of water vapor in the air compared to the maximum amount the air cloud hold at that temperature. Psychrometer: An instrument used to measure relative humidity, consisting of a wet-bulb thermometer and a dry-bulb thermometer. Condensation: The process by which molecules of water vapoar in the air become liquid water. Dew Point: The temperature in which condensation begins. Cumulus: Clouds that form least than 2 kilometers above the ground and look like fluffy, rounded piles of cotton. Stratus: Clouds that form in layers. Cirrus: Wispy, feathery clouds made mostly of ice crystals that form at high levels, above about 6 kilometers.

Precipitation Rain, sleet, freezing rain, hail and snow Rain is measured with a rain gauge Scientists have used cloud seeding to produce rain and to clear fog from airports

Key Terms Precipitation: Any form of water that falls from clouds and reaches Earth’s surface. Rain Gauge: An instrument used to measure the amount of precipitation, consisting of an open-ended can topped by a collecting funnel and having a collecting tube and measuring scale inside. Drought: Long periods of low precipitation.