5. How does the seasonal temperature variation of the continents compare with that of the oceans?
6. Is it greater or smaller?
7. How does the low heat capacity of rock influence the seasonal temperature variation of the continents?
8. How will the differences between the seasonal temperature variations in the oceans and continents affect the locations of high and low pressure systems in the atmosphere? Another way of asking this question is: How will these differences affect atmospheric circulation?
To the right are average atmospheric pressure maps for summer and winter.
Contour lines of equal atmospheric pressure (isobars) are also shown. In a very broad sense, low pressure systems are most often located near the equator and near 60º, whereas high pressure systems are most often located near 30º.
Focus on the differences between summer and winter.
Complete the table on your answer sheet by showing whether the region has high or low pressure during the summer or winter. Follow the North America example.
Why do you think the southern hemisphere oceans show less seasonal variation in terms of atmospheric pressure than do the northern hemisphere oceans?
Which way do the winds blow? Use for Questions 11-13.
To answer this question we need to understand how the P ressure G radient F orce (PGF) and the coriolis effect interact to create circular wind patterns around high and low pressure systems.
The PGF is the force that pushes air away from high pressure systems and pulls it towards low pressure systems.
The coriolis effect (caused by the earth’s rotation) deflects this moving air, to the right in the northern hemisphere and to the left in the southern hemisphere.
The result is that winds blow counterclockwise around low pressure systems and clockwise around high pressure systems in the northern hemisphere.
14. Draw on the big map (last page of handout) the wind directions that you would predict from the location of high and low pressure systems.
You can check your answers by clicking to see the August wind stress and January wind stress maps, or the North America maps.
15. Based on your predictions, complete the table for North America for wind directions that you would feel if you were standing on the west or east coast…
East Coast West Coast
July : Winds from (N or S)
Air temp (warm/cool)
January: Winds from (N or S)
Air temp (warm/cool)
16. Now, which has a more moderate climate, the east coast or west coast of North America?
17. Do you think this is true for other continents?
18. Air masses attain their characteristics from the ground over which they flow. When would you predict the rainy season is in India and the rest of continental Southeast Asia?
19. When is the dry season in India and the rest of continental Southeast Asia?
The Aleutian Low – Pacific High Today. Questions 20-23
Look at today's satellite images here. Click on the Pacific region to see a more close-up image of that area. Press “back” to get back here.
20. Which is more predominate today, the Aleutian Low or the Pacific High?
21. What is it that you see on the satellite image that makes you say this?
22. Does your assessment agree with what you would predict for the current season?
23. Draw a generalized picture of today's high and low pressure systems in the Pacific. On your picture draw in and label all the examples of the Coriolis effect that you can see. This current atmospheric pressure map may help you identify the location of the high and low pressure systems.
On your map handout, draw the major surface currents of the worlds oceans, which should include:
The California Current, North Pacific,The Kuroshio Current, South Pacific,The Gulf Stream, North Atlantic, The Canary Current, South Atlantic, West Wind Drift, Indian, The Peru Current (Note: All of these are also called subtropical gyres) The North Equatorial Current,The South Equatorial Current
Thus the availability of nutrients determines the location and abundance of organisms, especially those at the base of the food web such as plankton.
The location of plankton blooms in the oceans can be identified by satellite because the plankton contains chlorophyll and appear as different colors to sensitive satellite instruments such as the Sea-viewing Wide Field-of-View Sensor (SeaWiFS).
In general, high concentrations of nutrients, and thus plankton, correspond to areas of upwelling and high productivity.
Ocean Circulation and Biologic Productivity ?’s 35-37
Examine the map of global chlorophyll concentrations (which corresponds to plankton concentrations and thus nutrient concentrations and biologic productivity).
As usual, reds and yellows are high values, whereas blues and purples are low values.
The polar regions generally have high plankton concentrations because of the 24-hour light during summer months in high latitudes.
Click the image to the right to answer questions 35-37.
Click on Image to See Animation of Changing Chlorophyll Values
Recall: El Niño is defined as the warming of the eastern equatorial Pacific.
Under typical conditions, the waters off the west coast of equatorial South America is relatively cool (left figure), high pressure dominates in the eastern equatorial Pacific, low pressure dominates in the western equatorial Pacific, and the trade winds blow strongly to the west.
During El Niño conditions (fig to right) the eastern equatorial Pacific is abnormally warm, the low pressure system moves eastward, and the trade winds weaken.