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

Bowen RatioBowen 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)

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Heat Imbalance: Atmosphere vs. Earth’s Surface

Simplified Surface Energy Balance

NET R =

+SW (insolation)

–SW (reflection)

+LW (infrared)

–LW (infrared)

Figure 4.16

Global NET Radiation

Figure 4.17

Describe the spatial patterns: which areas have the highest net radiation? Why? The lowest? Why?

Latitude and Temperature

Figure 5.4

January Temperatures

Figure 5.14

July Temperatures

Figure 5.17

Global Temperature Ranges

Figure 5.19

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?

Temperature

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

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Heating Imbalance: Tropics vs. High Latitudes

Poleward heat transport brought about by• Air mass exchange• Storm systems• Ocean circulation

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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

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Source regions of air masses that regularly invade North America

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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

Blizzard of 1993

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

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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

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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)

The Gulf Stream

Figure 5.10

Sea-Surface Temperatures

Figure 5.11