SIO 217C: Climate
Spring 2014
Tropical Circulation and Precipitation Discussion Questions
1. ACC Fig. 6.5 shows a schematic of the tropical circulation. Describe what transformations
occur in the potential, internal, and latent components of moist static energy as an air parcel
circulates through the tropical atmosphere.
2. ACC Fig. 6.5 shows a schematic of the tropical circulation. How and where does moist static
energy enter the tropical atmosphere? How and where does moist static energy leave the
tropical atmosphere?
3. ACC Fig. 6.5 shows a schematic of the tropical circulation. How and where does water enter
and leave the tropical atmosphere.
4. ACC Fig. 6.5 shows a schematic of the tropical circulation. Assuming the schematic
corresponds to the Hadley circulation, how and where does westerly momentum enter and
leave the tropical atmosphere. How is westerly momentum removed from the global
atmosphere?
5. Explain how the net radiative cooling rate and the vertical gradient of potential temperature
(or dry static energy) regulate the large-scale subsidence rate in the tropical atmosphere.
6. Explain how surface temperature, near-surface relative humidity, and wind speed regulate the
surface evaporation rate in the tropics.
7. Explain how the net radiative cooling rate is related to the average tropical precipitation rate.
8. Explain how the average precipitation rate is related to the average evaporation rate.
9. Explain how the vertical profile of potential temperature (or dry static energy) throughout the
tropics is related to surface temperature in regions undergoing deep convection.
10. Explain how clouds in regions of deep convection radiatively warm the tropical atmosphere
compared to clear sky. Explain how clouds over colder water in regions far from deep
convection radiatively cool the tropical atmosphere compared to clear sky.
Difficult Question
11. As the globe warms, the tropical zone is expected to expand (westerly jets shift polewards),
tropical circulation is expected to slow (subsidence and trade winds weaken), and
precipitation events are expected to become more intense. Provide reasons for this in terms of
the atmospheric and surface balances of energy, water, mass, and momentum.