INTRODUCTION TO PHYSICAL GEOGRAPHY
Have you heard the saying, "Red sky at night, sailor's delight. Red sky in morning, sailors take warning." This is actually a fairly accurate weather predictor for people living between 30 and 60° latitude because in these areas weather tends to move from west to east. A red sky in the evening after a day of storms indicates that the sky is clearing in the west and the weather should be improving. Red sky in the morning means clouds are beginning to move across the sky from west to east and a storm is on its way. So it is possible to explain the folk wisdom of those sayings, but then we still need to ask, "Why?" Why does our weather come from the west? Why would it be different if we lived in Scandinavia or in subtropical Africa? To answer these questions, we have to explore what is known as the global circulation pattern. Local winds can blow from any direction at any time. However, there is a distinct pattern to the average wind direction at any latitude, a pattern that is consistent enough to allow us to predict the movement of weather systems.
I. Global circulation patterns on a water covered, non-rotating planet
A. Temperature and Latitude
B. Regions of low and high pressure
C. Predicted pattern of global circulation
II. Adding the effects of rotation
A. The coriolis effect
B. Effect on wind patterns
C. Basic Global Circulation Patterns
-- Doldrums, Trade winds, Horse latitudes, Westerlies, Polar front, Polar easterlies.
III. Adding land masses
A. Patterns of heating and cooling
B. Effects of large land masses -- Asia and Africa
IV. Seasonal change
NOTE: UNDEDSTANDING THE GLOBAL CIRCULATION PATTERN IS AMONG THE MOST IMPORTANT CONCEPTS COVERED IN THIS SECTION OF THE COURSE.
Objectives/questions:
1. Using the world map locate the important zones in the global circulation pattern in both the northern and southern hemispheres.
2. Explain the relationship between horse latitudes, temperature and humidity.
3. Describe the effects of seasonal heating and cooling on the position of the various zones of the global circulation pattern.
4. Describethe effect of the Asian landmass on the circulation patterns in China and India.
5. Use the seasonal shifts of the polar front to explain the fact that
storms are much more common in the Philadelphia region in the winter than
they are in the summer.