Tropical climates and drainage basins
H2 Geography - syllabus 9173, 2027
Explain tropical rainfall, track water through a drainage basin, and judge how well floods can be managed.
- Tropical climate zones and climographs
All tropical climates are hot, and what separates the humid and arid zones is how much rain falls and when.
- Hadley cells and the ITCZ
Rising moist air near the ITCZ brings rain, sinking air in the subtropics brings dryness, and both belts shift with the seasons.
- Summer and winter monsoons in Asia
Seasonal heating changes pressure and winds over Asia, and rain depends on whether the wind crosses the sea and meets mountains.
- Tropical cyclones and rainfall
Tropical cyclones need warm ocean water, moisture and organised rotation, and their rain can keep falling inland after the winds weaken.
- ENSO and Pacific rainfall
ENSO links ocean temperatures and winds across the tropical Pacific, shifting where the heaviest rain falls.
- Drainage-basin water budgets
Water coming in minus water going out equals the change in storage, so a river can keep flowing by using water stored earlier.
- Water storage in drainage basins
How much water a store can hold depends on its space, recent rain and human use.
- Infiltration, runoff and baseflow
Water can take fast routes over the surface or slower routes underground, depending on soil, rock, wetness and land use.
- Storm hydrographs and lag time
A storm hydrograph shows river flow over time, and a short lag with a high peak suggests water reached the river fast.
- Causes of fluvial flooding
A river flood happens when discharge is more than the channel can hold, so water spills onto normally dry land.
- Flood impacts and vulnerability
Flood impacts depend on the flood's depth, speed, length and timing, and on how well people can avoid, withstand and recover from it.
- Managing fluvial floods
Good flood management combines several measures and checks whether risk is reduced, moved elsewhere or left behind.
- Named examples: Tropical climates and drainage basins
A named place with a date or figure, linked to your point, turns a general answer into a developed one.
What you will be able to do
I can compare temperature and rainfall patterns across the tropical climate zones.
Syllabus 9173, Topic 2.1, 1. Tropical Climates. What are the similarities and differences in the temperature and rainfall patterns in the tropics?
Taught in Tropical climate zones and climographs, Named examples: Tropical climates and drainage basins
I can explain how global atmospheric circulation shapes tropical rainfall.
Syllabus 9173, Topic 2.1, 1. Tropical Climates. How does global atmospheric circulation affect rainfall in the tropics?
Taught in Hadley cells and the ITCZ
I can explain how monsoons, tropical cyclones and ENSO change rainfall in the tropics.
Syllabus 9173, Topic 2.1, 1. Tropical Climates. How does synoptic scale circulation affect rainfall in the tropics?
Taught in Summer and winter monsoons in Asia, Tropical cyclones and rainfall, ENSO and Pacific rainfall
I can explain how a drainage basin's inputs and outputs set its water balance, and why it varies.
Syllabus 9173, Topic 2.1, 2. Drainage Basin Hydrology. How does the balance between input and output in the drainage basin system vary in the tropics?
Taught in Drainage-basin water budgets
I can explain natural and human influences on water storage in a drainage basin.
Syllabus 9173, Topic 2.1, 2. Drainage Basin Hydrology. How does water storage in the drainage basin system vary in the tropics?
Taught in Water storage in drainage basins
I can explain natural and human influences on the pathways water takes through a drainage basin.
Syllabus 9173, Topic 2.1, 2. Drainage Basin Hydrology. How do pathways in the drainage basin system vary in the tropics?
Taught in Infiltration, runoff and baseflow, Storm hydrographs and lag time
I can explain what causes fluvial floods, using rainfall, discharge and basin conditions.
Syllabus 9173, Topic 2.1, 3. Floods in the Humid Tropics. What factors contribute to fluvial flooding in the humid tropics?
Taught in Storm hydrographs and lag time, Causes of fluvial flooding
I can explain the positive, negative and unequal impacts of floods.
Syllabus 9173, Topic 2.1, 3. Floods in the Humid Tropics. Why do fluvial floods affect places and people differently?
Taught in Flood impacts and vulnerability
I can evaluate flood-management strategies and how much people can control floods.
Syllabus 9173, Topic 2.1, 3. Floods in the Humid Tropics. Can fluvial floods be effectively managed?
Taught in Managing fluvial floods