Presentation on theme: "Warm Up 3/21/08 The deflection of wind due to the Coriolis effect is strongest at ____. a. the poles c. midnight b. the equator d. the midlatitudes."— Presentation transcript:
1 Warm Up 3/21/08The deflection of wind due to the Coriolis effect is strongest at ____.a. the poles c. midnightb. the equator d. the midlatitudesThe force exerted by the weight of the air above is called ____.a. convergence c. air pressureb. the Coriolis effect d. divergenceWhich force generates winds?a. gravity c. pressure differencesb. friction d. the Coriolis effectAnswers: 1) a. 2) c. 3) c.
2 Pressure Centers and Winds Chapter 19, Section 2
3 Highs and Lows Cyclones – centers of low pressure Anticyclones – centers of high pressureIn cyclones, pressure decreases from the outer isobars toward the centerIn anticyclones, the values of the isobars increase from the outside toward the centerWhen the pressure gradient and the Coriolis effect are applied to pressure centers in the Northern Hemisphere, wind blows counterclockwise around a low and clockwise around a highIn either hemisphere, friction causes a net flow of air inward around a cyclone and a net flow outward around an anticycloneThe usual “villain” in weather reports is the low-pressure center
5 Airflow Associated with Cyclones and Anticyclones
6 Concept Check With what type of weather is rising air associated? Cloud formation and precipitation
7 Global Winds on a Non-Rotating Earth The underlying cause of wind is the unequal heating of Earth’s surfaceThe atmosphere balances these differences by acting as a giant heat-transfer systemThe system (atmosphere) moves warm air toward high latitudes and cool air toward the equatorOn a non-rotating planet, the heated air at the equator would rise until it reached the tropopauseThe tropopause would act as a lid and deflect the air toward the polesThis upper-level airflow would reach the poles, sink, spread out in all directions at the surface, and move back toward the equator
9 Concept CheckHow does the atmosphere balance the unequal heating of Earth’s surface?The atmosphere transfers heat by moving warm air toward high latitudes and cool air toward the equator.
10 Global Winds on a Rotating Earth When the effect of rotation is added into the system, the two-cell convection model breaks down into smaller cellsNear the equator, rising air produces a pressure zone known as the equatorial low (has much precipitation)At 30 degrees north and south latitude, this air comes down, producing hot, arid conditions; this is the subtropical high (many of the world’s deserts are situated around this latitude)Trade Winds – two belts of winds that blow almost constantly from easterly directions and are located on the north and south sides of subtropical highsWesterlies – dominant west-to-east motion of the atmosphere that characterizes the regions on the poleward side of the subtropical highsPolar Easterlies – winds that blow from the polar high toward the subpolar lowPolar Front – stormy frontal zone separating cold air masses of polar origin from warm air masses of tropical origin
12 Concept Check What is the polar front? The stormy belt where subpolar westerlies and polar easterlies meet.
13 Global Winds – Influence of Continents Where landmasses break up the ocean surface, large seasonal temperature differences disrupt the global pattern of pressure zones in the atmosphereLarge landmasses can become cold in the winter when a seasonal high-pressure system develops, and the surface airflow will be directed off the landMonsoons – seasonal reversals of wind direction associated with large continents, especially Asia; in the winter, the wind blows from land to sea, and in the summer, the wind blows from sea to land