Chapter 12 Section 12.1 The causes of weatherMain Idea: Air masses have different temperatures and amounts of moisture because of the uneven heating of earth's surface.

What is Meteorology

• The study of atmospheric phenomena

• Anything high in the sky including; Rain drops, rainbows, dust, snowflakes, fog and

lightning.

Weather vs. Climate

• What is the difference between weather an climate?

•Weather-Short term varations; days, weeks, months

• Climate-Long term average of vatiaonns in weather for a

particular area

Defined by data over the last 30 years

Example; dry climates or tropical climates

Imbalanced heating

•In January why is it warmer in Florida than it is in Michigan?

•Reason 1- More hours of daylight

•Reason 2- the angle of the earth; Florida receives more direct sunlight

Thermal energy redistribution

•Areas around Earth maintain about the same average temperature

•The constant movement of air and water helps redistribute thermal energy around the world

Air Masses

• Air Mass- Large volume of air that has the same characteristics as its source regionTemperature

Humidity

Types of air masses

• Artic

Lake effect snow

•As cold polar air moves over the warmer great lakes air gains thermal energy and moisture this modified air is uplifted due to convection and topographic features producing lake effect snow.

•The uplifted warmer moist air cools and condenses forming snow

Global Wind systems

12.2 Weather results When air masses with different pressures and temperatures move change and collide.

Winds are named from whence they came

ITCS (Intertropical convergence zone)• Near the equator shift a little north or south depending on

the seasons

• Known to sailors as the doldrums

• Lots of uplifting of warm moist deliver moisture to the worlds tropical regions

Jet streams• Atmospheric conditions and events occur at boundaries between wind

zones

• Strongly influence earths weather

• Click pic for video

4 Types of fronts

•Cold

•Warm

•Stationary

•Occluded

Cold front

• Intense precipitation

• Sometimes thunderstorms

Warm Front• Widespread

light precipitation

• Gentle slope

Stationary front • Neither advance (does not move)

• Small temp differences

• Light winds and some precipitation

• Symbols

Occluded front• Cold air moves fast and

overtakes warm front

• Strong winds & heavy precipitation

Pressure systems

•Sinking cold air= High Pressure

•Rising warm air= Low Pressure

•When you combine Coriolis effect you get rotating high and low pressure systems

•Air move in a circular motion around a high or low pressure center

Low pressure systems• Air rises

• When air outside the system replaces the rising air this air spirals inward toward the center and then upward

• As air cools it forms clouds and precipitation

•Moves counter clockwise=northern hemisphere

• Clockwise in southern hemisphere

High Pressure system

•Sinking air moves away from systems center

•Coriolis effect causes outgoing air to move to the right

•Clockwise in northern hemisphere

•Counterclockwise in southern hemisphere

12.3 Gathering weather dataMain point: Accurate measurements of atmospheric properties are a critical part of weather analysis and prediction.

12.3 Gathering weather data•Before a doctor can diagnose a patient they must accurately asses the patients state of health. This usually includes checking temperature and blood pressure similar to diagnosing the weather.

How do we measure Temperature?

How do we measure air pressure

How do we measure wind speed? • Anemometer

How do we measure relative humidity? • Hygrometer

Automated surface observing system

Data from the upper atmosphere• Radiosonde

Weather Radar• Radio detection and ranging

• Generate radio waves and when they come in to contact with larger particle in the atmosphere they bounce back to the sensory indication rain and clouds.

• Doppler radar- (video) uses the Doppler effect to tell how fast the clouds are traveling and weather they traveling towards or away from station.

Weather satellites• Photos of earth

• Can use infrared, visible light, or water vapor imagery to observe atmosphere.

12.4 Weather Prediction and analysis Main Idea: Several methods are used to develop short term and long term weather forecasts.

Station models

Draw a station model for the current conditions in Mt. Pleasant MI