1. Latitudinal Heat Imbalances
Current Weather
Finish Surface Energy Balance  
Controls of Air Temperature
Tropics vs. Middle and High Latitudes
Mechanisms of Polar Heat Transport
For Next Class: Read Chapter 6
Thin Ice Screening at 7 PM on September 2

2. Bowen Ratio Bowen ratio = (sensible heating)/(latent heating)
High Bowen ratio implies more sensible heating than latent heating (i.e., deserts)
Low Bowen ratio implies more latent heating than sensible heating (i.e., oceans or water bodies)

3. Heat Imbalance: Atmosphere vs. Earth’s Surface
© AMS

4. Simplified Surface Energy Balance
NET R =
+SW (insolation)
–SW (reflection)
+LW (infrared)
–LW (infrared)
Figure 4.16

5. Global NET Radiation
Describe the spatial patterns: which areas have the highest net radiation? Why? The lowest? Why?
Figure 4.17

6. Latitude and Temperature
Figure 5.4

7. January Temperatures
Figure 5.14

8. July Temperatures
Figure 5.17

9. Global Temperature Ranges
Figure 5.19

10. Temperature
Where is the coldest location in the world likely to be in January? Why?
In July? Why?
Which location has the greatest annual temperature range? Why?

11. General circulation of the atmosphere and ocean is driven by latitudinal heating imbalances (i.e. surplus in tropics and deficit in polar regions)

12. Heating Imbalance: Tropics vs. High Latitudes
Poleward heat transport brought about by
Air mass exchange
Storm systems
Ocean circulation
© AMS

13. Heating Imbalance: Tropics vs. High Latitudes
Heat Transport by Air Mass Exchange
Air Mass: huge volume of air covering thousands of square kilometers that is relatively uniform horizontally in temperature and humidity
Properties depend largely on characteristics of source region
© AMS

14. Source regions of air masses that regularly invade North America
© AMS

15. Heating Imbalance: Tropics vs. High Latitudes
Heat Transport by Storms
Acquisition and subsequent release of latent heat in migratory storm systems transports heat to the poles
Tropical storms and hurricanes are greater contributors to poleward heat transport than ordinary middle latitude storms
© AMS

16. Blizzard of 1993
Developed in association with an extremely amplified Rossby Wave. Note the strong cold front in Honduras!

17. 17

18. Heating Imbalance: Tropics vs. High Latitudes
Heat Transport by Ocean Circulation
Contributes to poleward heat transport via wind-driven surface currents and the deeper thermohaline circulation
Surface water that is warmer than the overlying air is a heat source for the atmosphere
Surface water that is cooler than the overlying air is a heat sink for the atmosphere
© AMS

19. Heating Imbalance: Tropics vs. High Latitudes
Heat Transport by Ocean Circulation
Thermohaline circulation: density-driven movement of water masses, traversing the lengths of the ocean basins
Also known as the meridional overturning circulation (MOC)
© AMS

20. The Gulf Stream
Figure 5.10

21. Sea-Surface Temperatures
Figure 5.11