October 24th Objective: Explain the relationship between temperature, air pressure & wind direction. DO NOW Update T.O.C. Complete the K & W sections of the KWL chart. Update Agenda Pad – HW: Complete “L” portion of the KWL chart.

Weather is comprised of the elements of: Weather & Climate Weather is comprised of the elements of: a) air temperature b) air pressure c) humidity d) clouds e) precipitation f) visibility g) wind Climate represents long-term averages of weather. (e.g. 30 yr)

Why does air move? Wind is the movement of air from areas of high pressure to low pressure. It’s caused by: Air pressure differences Temperature differences Differences in air pressure are generally caused by the unequal heating of the Earth.

Why is there unequal heating on Earth? There is unequal heating because: The earth is curved The tilt of the earth in relation to the sun varies throughout the year. Varying daylengths – Daylength changes so when there is more daylight the earth heats more. When days are shorter (less daylight) the earth doesn’t heat as much. Daylength at the equator is almost always 12hrs. The most on earth. Since they get the most direct sunlight for the longest period, that location is the hottest on earth. That’s why the poles are the coldest. The varying temperatures produce PRESSURE BELTS that are found every 30O of latitude.

Equator vs. Poles Equator Receives more direct solar energy than other latitudes Air at the equator is warmer & less dense than the surrounding air. Warm, less dense air rises & creates an area of low pressure. Warm, rising air flows toward the poles WHY? On the equator the length of days changes very little throughout the year. Day light shines for almost exactly 12 hours, and darkness reigns for almost exactly 12 hours. The further away that one travels from the equator however, the more variation in length of day that will be observed. In the summer days stretch out, becoming much longer than the nights, while the opposite is true in the winter, when night lasts longer than day. Air travels toward the poles obeying the 2nd law of thermodynamics: heat travels from areas of high heat to low heat.

Equator vs. Poles Poles At the poles, the air is colder & denser than the surrounding air, so it sinks. Why is the air colder at the poles? As the cold air sinks, it creates areas of high pressure around the poles Why does cold air create areas of high pressure? Cold polar air then flows toward the equator Air is colder at the poles because less sunlight reaches the poles compared to the equator. Cold air creates areas of high pressure because it is dense and sinks toward the surface so there is more air pressure and density when it is colder. Have students discuss why cold air creates areas of high pressure with a partner (1-2 min). The movement of warm & cold air around the globe occurs in convection cells within the pressure belts.

Warm, less dense air rising 60oN & S Warm air creates low pressure area Cold, dense air sinking Cold air creates high pressure area The convection cells are separated by pressure belts, bands of HIGH PRESURE and LOW PRESSURE found about every 30O. Warm air rises from the equator and at 30O North & South latitude, some air cools, becomes more dense and falls back to the equator where it warms and rises again. At the poles, cold air sinks and moves toward the equator. Air warms as it moves away from the poles (becomes less dense) and at about 60O North & South latitudes, it begins to rise again. The warm air creates an area of low pressure. HAVE STUDENTS TURN TO A PARTNER AND DISCUSS HOW COLD AIR CREATES AREAS OF HIGH PRESSURE AND HOW WARM AIR CREATES AREAS OF LOW PRESSURE. (1 MIN). Then review. Earth Rotates This Way

Think-Pair-Share Using the large globe at the back of the packet (Pressure Belts) draw in arrows to show how wind would move in straight line in each of the pressure belts indicated. Refer to your notes as needed In your PPT notes, summarize your understanding of how temperature and air pressure affect wind direction. Then share your thoughts with a partner. Be sure to raise your hand if you have any questions!

Practice Drawing Indicate where the poles are Down the middle, indicate where there is high & low pressure every 30o starting at one of the poles. Draw in convection cell wind patterns between each pressure belt