Meteorology Basics Lecture Science 2201 (chapter 18) “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 Region where air has piled up Warmer and dryer than surrounding air Low Pressure Region where air has stretched out Tends to rise and cool, 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

Check your neighbor. Make a sketch to explain your answer. 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