QUIZ BONUS List Four types of Air Masses (symbols are accepted) Name the Three Wind Systems “Zones” BONUS What are JET STREAMS??

Science News

GLOBAL WIND SYSTEMS Result of Earth’s rotation & uneven heating of surface Transports colder air to the Equator & warmer air to the Poles Help to equalize the thermal energy on Earth

Forces Influencing Wind Speed & Direction Gravitational Force: equal compression density decrease with altitude Friction Force: Earth’s rough surface adds to Pressure & Coriolis Coriolis Force: Earth’s rotation deflecting wind Pressure Gradient Force: High/Low systems

Coriolis Effect Earth’s rotation breaks air masses into smaller cells Moving air curves to the right in the N. Hemisphere & to the left in the S. Hemisphere

PRESSURE SYSTEMS Low Pressure system air coming up either cloud cover / precipitation or no clouds because no moisture High pressure system air coming down generally fair skies

Pressure Differences

Wind & Pressure Relationship 950 mb. 960 mb. 970 mb. 930 mb. H L WINDS ALWAYS MOVE FROM HIGH PRESSURE AREAS TO LOW PRESSURE AREAS!!!!!!!

Makes no sense without caption in book

Pressure Centers Cyclones: centers of low pressure, Storm & Clouds (L) the pressure decreases from the outer isobars toward the center Anticyclones: centers of high pressure, Calm & Clear (H) the pressure increases from the outside toward the center

Cyclonic & Anticyclonic Winds Anticyclones Winds in a high pressure area move clockwise (S Hemisphere) Cyclones Winds in a lower pressure area move counter-clockwise (N Hemisphere)

CYCLONE

ANTICYCLONE

Pressure Centers & Winds  Weather and Air Pressure Rising air is associated with cloud formation and precipitation, whereas sinking air produces clear skies.  Weather Forecasting Weather reports emphasize the locations and possible paths of cyclones and anticyclones. Low-pressure centers can produce bad weather in any season.

Pressure Systems Collisions Collision forms a front, boundary that separates air masses of different densities Air masses retain their identities Warmer, less dense air forced aloft Cooler, denser air acts as wedge

Warm air replaces cooler air 4 Types of Fronts Warm front Warm air replaces cooler air Clouds become lower as the front nears Slow rate of advance Light-to-moderate precipitation

Warm front

Cold Fronts Cold air replaces warm air Advances faster than a warm front Associated weather is more violent than a warm front Intensity of precipitation is greater Duration of precipitation is shorter

Cold front

Stationary front Occluded front Flow of air on both sides of the front is almost parallel to the line of the front Surface position of the front does not move Occluded front Active cold front overtakes a warm front Precipitation is associated with warm air being forced up

Formation of an Occluded front

HOMEWORK REVIEW TEXT p. 312 – 324 & CH 12 Notes