1. Arizona Climate Arizona Geography GCU 221

2. Game Plan 1. Why is it so hot! 2. General Summer Circulation - Monsoons 3. General Winter Circulation - Cold Fronts 4. Phoenix Climagraph 5. Where do we get our water from?

3. 1. Why is it so hot in Phoenix? Located in a sub-tropical high (clear skies) Located in the westerlies, down wind of the Pacific ocean (keeps pressures high) Located downhill from mountains in California (air warms adiabatically on the downhill portion of mountains) keeping it dry

4. 1. Sub-Tropical High

5. 1. High Pressure Clear Skies, let’s in a lot of sunshine Descending air, very stable, low winds and low circulation

6. 1. Pacific High Pressure

8. 1. Westerlies and the Pacific

9. 1. Mountains and Adiabatics

11. Monsoon means a “change in the winds” Winds shift from “West” to “East” Azores High Pressure moves westward, driving winds off the Gulf of Mexico and California into Arizona. 2. Summer Monsoons

12. 2. Azores High Pressure

13. 2. High Dew Points and Lifting Mechanism Arizona’s monsoon starts when three days in a row have dew points 55 degrees or higher. Moisture comes from the Gulf of Mexico and Gulf of California. Lifting Mechanisms: Convection, Orographic, Downdraft Need to lift the air to cool it and generate rain

14. 2. Lifting Mechanisms: Convection

15. 2. Lifting Mechanisms: Orographic

17. 2. Lifting Mechanisms: Downdraft

18. 3. Winter Frontal Systems Dominant air masses: Warm Moist to the south Cold and Dry to the north Low pressures from the jet stream spin counter-clockwise This forces the warm moist air over cold dry air, causing storms

19. 3. Winter Frontal Systems

22. 4. Phoenix Climate graph

23. 5. Arizona Watersheds Major Water Sheds – Mogollon Rim, Colorado Rockies, Wind River Mountains, and Utah Highlands Major Rivers – Colorado River, Salt River, and Verde River

24. 5. Arizona Water issues

25. Lowering groundwater table Groundwater contamination Lake Mead at low levels Arizona watersheds not sufficient to support Phoenix and sensitive to climate change

26. Things to know: 1. Why is it so hot! 2. Why do we get rain in the summer time? 3. Why do we get rain in the winter time? 4. Where do we get our water from, highlands and rivers? 5. What are some issues facing our water supply Help: Ask Dr. Douglass