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Chapter 12 Meteorology Meteorology = the study of meteors? • Meteoros = anything high in the air • Meteorologists study: – Hydrometeors: rain, snow, sleet, hail – Lithometeors: dust, smoke, haze, particles – Electrometeors: lightning, thunder • Weather (short term) vs. climate (long term) Imbalanced heating • What makes summer warmer than winter? • Number of hours of daylight and angle of the sun’s rays Air masses • Movement of air and water distribute heat around the earth • Air masses take on the properties of their source regions. – – – – – Polar = cold Tropical = warm Maritime = humid Continental = dry Arctic: very cold/dry Coriolis Effect • Moving air curves clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere • Creates global wind systems: – Polar easterlies – Westerlies – Trade winds – Horse latitudes – Equatorial low (ITCZ) Jet Streams • Narrow bands of fast westerly wind • Position varies seasonally • Polar and subtropical • Storms form along jet stream paths Weather Fronts Stationary front Pressure Systems • In a low pressure system, air rises, cools and forms clouds • Air sinks in a high pressure system, usually associated with fair weather Weather Observation Systems • Automated surface observing system • Radiosonde (upper atmosphere weather balloon) • Weather radar (including doppler) • Weather satellites (infrared, visible and watervapor imagery) Weather Data • Temperature (thermometer) • Air pressure (barometer) • Wind speed (anemometer) • Relative humidity (hygrometer) Weather Station Models • A station model is a record of weather data for a specific place at a specific time • Uniform way of communicating weather data • Lots of information in a small space Map with weather stations Same map with Isotherms Same map with Isobars Short and Long Term Forecasts Short-term • More detailed and accurate • Hourly forecast based on present weather • One- to three-day forecasts based on larger systems such as low pressure systems Long-term • Less reliable because of great number of variables involved • Based on large scale circulation patterns and weather cycles