Chapter 5 study guide 1.   Describe the relationship between atmospheric pressure and elevation. 2.   Describe the relationship between temperature and atmospheric pressure. 3.   Describe an isobar. 4.   What is wind? Describe the function of the wind on the earth. 5.   What two factors influence wind direction? How do these factors function to influence wind direction? 6.   How are winds named? Define windward, leeward and prevailing winds. 7.   Describe the idealized model of Earth’s pressure and wind systems. (Figure 5.12)

Study Guide Chapter 5 8. Define gyres. 9.   Describe the effects of seasonal migration in California. 10. What is El Nino? 11. Describe local winds in our area. (land breeze- sea breeze, Santa Ana winds, mountain & valley breezes) 12.  Describe the upper air wind system.  

Weight of the Atmosphere The atmosphere exerts a pressure of 14.7lbs/sq in. (1034 grams/cm) Atmospheric pressure is important because variation in pressure causes our atmospheric circulation 3

Pressure Units Meteorologists prefer to work in millibar (mb) units Standard sea-level pressure of 1013.2 mb will cause mercury to rise to 76 cm or 29.92 inches. See Fig. 5.1 text. 4

Variations in Air Pressure Air pressure decreases with elevation Humans not generally sensitive to small variations in air pressure 5

Mapping Pressure Distribution Isobar = lines of equal pressure 6

The air moves down a pressure gradient The air moves down a pressure gradient. Just like water rolling down a hill from high to low elevation.

Low Atmospheric Pressure 8

High Atmospheric Pressure 9

Which is High Pressure Which is Low? 10

Cyclones and Anticyclones Fig 5.3 11

Horizontal Variation in Air Pressure Unequal distribution of insolation results in uneven heating of planet. Pressure and temperature. relationship? Other factors include: differential heating of land and water, different albedos of surfaces Equator low pressure why?relationship pressure and temperature 5.13 12

Wind Wind is the horizontal movement of air. Winds are named from the direction they are coming from. A North wind is coming from the North.

Fig. 5-7, p. 121 14

Winds are transportation for energy and moisture. Winds are an attempt to keep the Earth’s temperature in equilibrium.

Wind circulation patterns would be simple if pressure driven by temperature changes were the only influence on global wind circulation. 16

Fig. 5-13, p. 127 17

Fig. 5-15, p. 130 18

Global Wind Systems Subtropical High Pressure Source of Trade Winds and Westerlies Horse Latitudes Trade Winds 50-250 N and S Northeast and Southeast Trades Pilots flying West Hawaiian islands pleasant

Global Wind Systems ITC (Intertropical Convergence Zone) Doldrums (50N-50S) Winds converge Weak winds Idealized model Changes due to land and ocean masses Seasonal changes-pressure belts move North in summer.

Coriolis Effect Surface Friction The second factor that influences our global wind circulation patterns is the Coriolis Effect. The Coriolis Effect is the apparent shift in the path of a fluid or object moving over Earth’s surface, caused by the rotation of the Earth. This force causes moving objects near the Earth’s surface to be turned westward from their original paths. 21

Effects of Seasonal Migration Seasonal migration will most affect those regions near the boundary zone between two wind or pressure systems California is an example of a region located within a zone of transition 5.16 22

Land and Sea Breeze Fig. 5-9, p. 123 23

Mountain & Valley Breezes (local) Mountain Breeze Valley breeze 5.10 24

Local Winds 5.11 Chinook (USA rocky mtns) Santa Ana- compressed warm and dry air. Foehn wind- Alps Santa Ana- High Pressure build up in desert- through mountain areas. Down- warm up, dry desert. Page 129 5.11 25

p. 125 26

Upper Air Winds Include the upper air Westerlies and polar jet streams. About 16,500 ft. 25-100 miles in width 1-2 miles in depth “Internal ribbon of air” See Fig. 5.19 Less complex than surface winds. Fast moving- 100 mph west to east move weather.

Jet streams

Ocean currents Like winds ocean currents distribute heat and energy of the Earth. Surface currents that move in broad circulatory patterns are called gyres. Ocean currents are affected by the Coriolis Effect, winds, salinity, and temperature.

Fig. 5.24

El Niño El Niño is a warm, weak counter current that replaces the normally cold (upwelling) coastal waters El Niño can last for many months and water temperatures are raised for thousands of miles Exceptionally strong El Niños impact worldwide weather . 31

El Niño Sir Gilbert Walker discovers a “seesaw” pattern of air pressure in the Pacific called the Southern Oscillation 32

Fig. 5-25, p. 140 34

Interactivity Envrs-chp. 6 number 3.