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 • 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

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