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 water-

vapor 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