Warm-up What is weather?

Chapter 12 Meteorology

Causes of Weather Meteorology – the study of atmospheric phenomena such as fog, clouds, snow, rain, and lighting Weather- is the condition of the atmosphere at a certain time and place

Climate Climate is the long term weather for a particular area. Usually averaged over 30 or more years. Ex. The climate is hot and humid in Miami, but it is snowing in the picture to the right.

Air masses Name Description c Continental Dry m Maritime Wet E Equatorial Hot T Tropical Warm P Polar Cold A Arctic Very Cold An air mass is a large body of air that takes on the characteristics of the area over which it forms.

Wind (review) Wind- the movement of air caused by differences in air pressure The greater the difference in pressure the faster wind moves

Global Wind Systems Pressure belts - As warm air rises at the equator and moves towards the poles, it cools As it cools, some of the air sinks around 30 degrees north and south of the equator At the poles, cold air sinks and moves towards the equator

Global Wind Systems Polar Easterlies- winds that blow from east to west between 60-90 degrees latitude in both hemispheres. Westerlies- The wind belt found between 30-60 latitude in both hemispheres Trade winds- Winds that blow northeast from 30 north latitude to the equator and that blow southeast from 30 degrees south latitude to the equator

Global Wind Systems The combination of pressure belts and the Coriolis effect are the cause of Global winds. Coriolis effect- deflection of particles to the right in the northern hemisphere and to the left in the southern hemisphere due to Earth’s rotation Doldrums- Located along the equator where no winds blow, this creates slow rising air with very little pressure. Horse Latitudes- weak winds that occur at 30 N and 30 S latitudes

Jet streams- Narrow belts of high speed winds that blow in the upper troposphere and lower stratosphere. They can reach speeds of up to 400 km/h

Fronts Front- An area in which two air-masses meet

Fronts Cold Front- occur when a cold air mass runs into a warm air mass, forcing the warm mass to rise

Fronts Warm Front- When warm masses run into cold masses and slowly displaces it

Fronts Stationary Front- Two air masses meet and neither advances; air masses “stall” Light wind and precipitation Occluded Front – Cold air mass moves so rapidly that it overtakes a warm front Strong winds, heavy precipitation

Pressure Systems High Pressure Systems - Air sinks, then hits the Earth’s surface and spreads out. Wind blows away from high pressure. Clockwise in N. Hemisphere Associated with fair weather

Pressure Systems Low Pressure System - Air rises, must be replaced. Wind blows toward center of low pressure Counter-Clockwise in N. Hemisphere Associated with clouds and precipitation

Pressure Systems Cyclone- an area in the atmosphere that has lower pressure than the surrounding areas that spiral towards the center Anticyclone- the rotation of air around a high pressure center opposite to Earth’s rotation

Pressure Systems

Pressure Systems

Weather Instruments Barometer- an instrument used to measure atmospheric air pressure. Thermometer- measures temperature by using a liquid that moves up and down due to temperature differences. Anemometer- an instrument used to measure wind speed. Windsock- an instrument to measure wind direction

Weather Maps Station Model

Weather Maps Isobars- lines that connect equal points of equal pressure Lines that are close = STRONG WINDS Lines that are far apart = LIGHT WINDS