The Earth's Atmosphere and Hydrosphere
Atmosphere: structure and energy
Know the layered structure (troposphere, stratosphere, mesosphere, thermosphere) and why temperature trends reverse with altitude - ozone absorption in the stratosphere, for example. Understand the greenhouse effect as selective absorption and re-emission of longwave radiation by gases with molecular vibration modes (CO2, H2O, CH4, N2O); it is a natural process, and the issue is its enhancement.
Circulation and climate
Uneven solar heating drives convection, pressure gradients, the Coriolis effect and prevailing winds. Ocean circulation redistributes heat: surface currents are wind-driven, deep circulation is density-driven (thermohaline). El Nino-Southern Oscillation shows coupled ocean-atmosphere variability with global rainfall effects.
Hydrosphere
Track the water cycle: evaporation, transpiration, condensation, precipitation, infiltration, runoff, groundwater flow, storage. Catchment behaviour depends on vegetation, soil, slope, geology and impervious surfaces. Groundwater is stored in aquifers and recharged slowly, so extraction can exceed recharge.
Common traps
- Confusing weather (short-term state) with climate (long-term statistics).
- Claiming the greenhouse effect is entirely human-made - it is natural but enhanced.
- Misattributing the ozone hole to climate change; they are linked but distinct problems.
- Forgetting that Coriolis deflects direction, not speed.
- Assuming urbanisation increases infiltration - it usually increases runoff.
Worked example: hydrograph reasoning
After a storm, a forested catchment shows a low, delayed peak; a paved catchment shows a high, rapid peak. Rule of thumb - less infiltration means more and faster runoff. Compare peak height (magnitude) and lag time (delay) separately when interpreting hydrographs.