Each statement represents a primary learning objective for parts of this unit. After you complete the unit, you should be able to:

• Define air pressure and describe the instruments used to measure this weather element.

• Discuss the three forces that act on the atmosphere to either create or alter winds.

• Contrast the weather associated with low-pressure centers (cyclones) and high-pressure centers (anticyclones).

• Summarize Earth’s idealized global circulation and describe how continents and seasonal temperature changes complicate it.

• List three types of local winds and describe their formation.

• Describe the instruments used to measure wind and explain how wind direction is expressed using compass directions.

• Describe the El Niño-Southern Oscillation and its relationship to El Niño and La Niña and list the climate impacts of El Niño and La Niña on North America.

• Discuss the influence of pressure, wind, and other factors on the global distribution of precipitation.