Chapter 15: The Hot, Wet Equatorial Climate
This climate is found in the “Lowland Tropics” between 5° and 10° North and South of the Equator. Key areas include the Amazon Basin, Congo Basin, Malaysia, and Indonesia.
1. Climate Characteristics
- Uniformity: There is no “winter” or “summer.” The temperature is constant throughout the year (Average 27°C27 °C27°C).
- Rainfall: Very heavy annual rainfall (200 cm to 250 cm).
- Daily Rhythm: Mornings are bright and sunny; afternoons bring heavy Convectional Rain with thunder and lightning (often called “4 o’clock rain”).
- Humidity: Extremely high relative humidity makes the air feel sticky and “oppressive.”
2. Natural Vegetation (Selvas)
The equatorial region supports the most luxuriant vegetation in the world:
- Evergreen Forest: Trees do not have a collective season to shed leaves.
- Multi-layered Structure:
- Emergent Layer: Tallest trees (up to 150 ft) poking through the top.
- Canopy: A continuous thick “roof” of foliage that blocks out 90% of sunlight.
- Undergrowth: Very sparse due to lack of sunlight, except along river banks.
- Variety: Unlike temperate forests where one species dominates, tropical forests have hundreds of species mixed together (making commercial logging difficult).
- Special Plants: Epiphytes (plants that grow on trees) and Lianas (thick woody vines).
3. Life and Economy
- Sparsely Populated: Heat and humidity lead to diseases (Malaria, Yellow Fever).
- Tribes: Home to primitive tribes like the Pygmies (Congo), Semangs (Malaysia), and Amazon Indians.
- Shifting Cultivation: Traditional farming where a patch of forest is cleared, burned, farmed for a few years, and then abandoned.
- Plantation Crops: Modern development focuses on Rubber (Malaysia/Indonesia), Cocoa (West Africa), and Palm Oil.
10 Revision Questions with Mnemonics
Q1: What is the latitudinal extent of the Equatorial Climate?
- A: 5° to 10° North and South.
- Mnemonic: “Five to Ten is the Forest Tenant.”
Q2: What is “4 o’clock rain”?
- A: Daily convectional rainfall that occurs in the late afternoon due to intense morning heating.
- Mnemonic: “Four is for Flooding.”
Q3: Why is commercial logging difficult in these forests?
- A: Because of the Lack of Pure Stands (hundreds of species are mixed together).
- Mnemonic: “Mixed means Messy.”
Q4: Name the three layers of the rainforest.
- A: Emergents, Canopy, and Undergrowth.
- Mnemonic: “E.C.U.” (Emergent, Canopy, Undergrowth).
Q5: What are “Lianas”?
- A: Thick woody vines that climb to the canopy to reach sunlight.
- Mnemonic: “Lianas are Ladders.”
Q6: What is the main characteristic of the temperature here?
- A: Low Annual Range (The difference between the hottest and coldest months is very small, usually only
2°C).
- Mnemonic: “Range is Rare.”
Q7: Which tribe lives in the Congo Basin?
- A: The Pygmies.
- Mnemonic: “Congo Pygmies” (CP – like Computer Program).
Q8: Why is the forest floor so dark?
- A: Because of the thick Canopy layer.
- Mnemonic: “Canopy is a Curtain.”
Q9: What is “Shifting Cultivation” called in Malaysia?
- A: Ladang.
- Mnemonic: “Ladang on the Land.”
Q10: What is the primary plantation crop of Malaysia?
- A: Natural Rubber.
- Mnemonic: “Malaysia makes Many Mats” (Rubber).
Quick Summary Table: Life in the Jungle
| Feature | Detail | Mnemonic |
|---|---|---|
| Rain | Convectional (Afternoon) | Convection = Cloudburst |
| Trees | Mahogany, Ebony, Greenheart | M.E.G. (Hardwoods) |
| Disease | Malaria, Tsetse Fly | Malaria in the Mud |
