SIO 217C: Climate
Spring 2014
Water Cycle Discussion Questions
Note that the values in CD Table 2.1 appear to be too large by a factor of 10.
1. Quantitatively demonstrate that the residence time of water in the atmosphere is about one
week. What is the residence time in the ocean?
2. Why is there net transport of water vapor from ocean to land by the atmosphere?
3. How are seasonal variations in the latitude of maximum zonal mean precipitation and
minimum zonal mean precipitation related to seasonal variations in zonal mean temperature
and circulation in the 30°S-30°N zone?
4. Why is zonal mean precipitation rate small at high latitudes?
5. ACC Fig. 6.3 and CD Fig. 2.26 indicate that precipitation rate over eastern subtropical
oceans is as small as over many desert land areas. Why is there so little precipitation when so
much moisture is available from the ocean?
6. A comparison of CD Fig. 2.15 and CD Fig. 2.29 indicates that is evaporation generally not
largest where the ocean is warmest. Why is this?
7. ACC Fig. 6.2 indicates that relative humidity is high near the surface. Why is this? Relative
humidity is also high in the upper troposphere near the equator. Why is this? Relative
humidity is lowest in the middle troposphere in the subtropics. Why is this?
8. ACC Fig. 6.4 and GPC Fig. 5.2 indicate that local precipitation greatly exceeds local
evaporation near the equator. From where does the extra water for precipitation come?
Difficult Question
9. ACC Fig. 6.3 and CD Fig. 2.27 indicate that precipitation is greater in winter than summer
for midlatitude oceans but greater in summer than winter for midlatitude land. Why is this?