1. Monsoons

2. Does “Monsoon” mean really heavy rainfall?

3. Or does Monsoon mean big fluctuations in rainfall?

4. Answer: Neither! A Monsoon is a seasonal change in the prevailing wind direction. The Trade winds are very constant in direction, but they move with the ITCZ throughout the year.

5. The wind shift is enhanced by different vertical motion over the world’s largest continent. When Asia is cold, the Siberian High is strong with northerly winds. When it is warm, rising air creates the Monsoon Low and southerly winds.

6. Asia is not the only place to get a Monsoon. Wherever the ITCZ passes, the wind shifts direction. Over Asia, the shift is magnified.

7. When the ITCZ is near or north of you, it rains (a lot!). When it is south, the subtropical Highs are over you and it doesn’t rain much (or at all). The most obvious places to see it are India and central Africa.

8. Monsoon exercise Match the places shown with their monthly precip records

9. Here is a loop of surface winds for each month. You have a link to this loop (as a PowerPoint) on the course Blackboard page in the content section.

10. Match the station records to the three cities, Beijing, Hong Kong, and Semarang. Then justify your choices using complete sentences and logic.

11. Zooming in, here are 4 places with Monsoon climates. First, check India. Two famous Indian cities are Calcutta and Bombay, now called Mumbai

14. Khartoum is in Sudan. Kano is in Nigeria.

17. Reminder: The monsoon itself is the seasonal change of wind direction.

18. Other than Africa and Asia, another surprising place that gets a monsoon is Arizona!

19. This is from August, 2009 Notice the way the precipitation areas are moving.

20. In south Texas, New Mexico, and Arizona you have easterly winds on this day.

22. The wind direction in the southwest U.S. is what creates the monsoon rainfall in Arizona. Note the pressure change also. It’s similar to Africa and India but NOT caused by the ITCZ

23. Big difference in the Circumpolar vortex. Why does Arizona have easterly winds at the surface in the summer? That’s the top of a Subtropical High!

24. Next: El Niño