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Meteorology Basics Lecture “Climate is what you expect, weather is what you get.” Distinguish between… • Weather • Seasons • Climate Chemical Composition of the Atmosphere • • • • • • Nitrogen 78% Oxygen 21% Argon 0.9% Carbon Dioxide 0.03% Trace substances Water Vapor Vertical Structure of Atmosphere 5 variables influence the atmosphere: • • • • • Temperature Pressure Humidity Cloudiness Winds Variables influencing the atmosphere… temperature: • Measure of heat • Average kinetic energy of molecules • Weather reports give air temperature at ground level Variables influencing the atmosphere… pressure: • High Pressure • Low Pressure • Region where air has • Region where air has piled up stretched out • Warmer and dryer than • Tends to rise and cool, surrounding air vapor condenses into clouds Variables influencing the atmosphere… humidity: • “relative humidity” – the ratio of amount of water vapor in air at current temp to max amount vapor air can hold at that temp Variables influencing the atmosphere… cloudiness: • Water droplets • Ice crystals • Warm air rises, cools and condenses (phase change) Variables influencing the atmosphere… winds: • Due to differential heating of the earth’s surface • Warm air rises • Cooler air flows in Why is it warmer near the Earth’s equator and colder near the poles? What patterns of global air flow occur? Check your neighbor. Make a sketch to explain your answer. Global Air Circulation Patterns Where does your weather forecast come from? • National Weather Service • World Weather Building in Camp Springs, Maryland • Media weather specialists Weather Forecasting • Wrong half the time? • Many features, all are changeable • Nowcast Forecast • CNN Weather link The Instruments • • • • • Thermometer Hygrometer Barometer Weathervane Anemometer The Instrument Carriers • • • • • • 10,000 land-based & 7,000 ocean-based Weather Balloons (1,000 released 2X/day) Buoys (300 drift or are moored at sea) Automated Weather Stations (about 1,000) Doppler Radar Satellites Reading a Weather Map • • • • • Pressure Centers Fronts Precipitation Temp. Readings Surface Winds Winter Air Masses • Continental Polar • Maritime Polar • Maritime Tropical Summer Air Masses • Continental Polar • Maritime Tropical • Continental Tropical “Fronts” = a clash of air masses • Cold Front • digs in underneath a warm air mass • Warm air rises, mixes with colder air, & condenses into clouds “Fronts” = a clash of air masses • Warm Front • rides up above the cold air • In the rising warm air, clouds form far ahead of advancing warm front Air Masses Doing Battle link Cloud Classification link
