Ecosystems (cont'd)
By Marjorie Henry, Contributor

Dr. Omar Davies converses with students at a Gleaner Editors' Forum, recently. From left are Bradford Bolt and Kamille Adair of Ardenne High School; Shernette Rose and Errol Campbell from Camperdown High School and Garfield Grandison, editor-in-chief at The Gleaner Company. In front (from left) are Romaine Isaacs, Renee Miller and Toni-Ann Falconer of Glenmuir High School. - Rudolph Brown/Chief Photographer

As the study on ecosystems continues, the focus in this lesson is on the tropical continental ecosystem. This climatic type is located between latitudes five degrees north and south of the equator and is also referred to as Savanna or Sudan Climate. In terms of distribution, the textbook, Certificate Physical and Human Geography, written by Goh Cheng Leong, informs us of the following:-

'The Savanna or Sudan climate is a transitional type of climate found between the equatorial forests and the tradewind hot deserts. It is confined within the tropics and is best developed in the Sudan where the dry and west seasons are more distinct, hence its name, the Sudan climate. The belt includes West African Sudan, and then curves southwards into East Africa and southern Africa, north of the Tropic of Capricorn as shown in the map below. In South America, there are two distinct regions of savanna north and south of the equator, namely the llanos of the Orinoco Basin and the campos of the Brazilian highlands. The Australian savanna is located south of the monsoon strip running from west to east north of the Tropic of Capricorn.

Again, I am encouraging you to be familiar with these areas. Practise outlining them on a blank map of the world, from memory. Know also the different names that this climate is known by in the different countries.

In reference to the textbooks, we can identify the characteristics of this climate type. Let us first look at precipitation.

• The climate is characterised by an alternate hot, rainy season and cool, dry season.
  
  
• The wet season occurs when the sun moves overhead bringing with it the heat Equator, the ITCZ (Inter-Tropical Convergence Zone) and the equatorial low pressure belt.
  
  
• In the Northern Hemisphere, the wettest months are usually July and August, while in the Southern Hemisphere, these months are usually January and February.
  
  
• The dry season corresponds to the moving away of the ITCZ, leaving the area with the strong and steady tradewinds. These are dry because they warm up as they blow towards the Equator and will have shed any moisture on distant coastal areas.
  
  
• These dry, hot and dusty winds are called the Harmattan, in West Africa, where they are particularly noticeable. These winds are so dry that the relative humidity seldom exceeds 30 per cent.
  
  
• The rainfall varies much from year to year and from region to region. Regions close to the equatorial latitudes record more rain than regions close to the hot deserts.
  
  
• The annual rainfall is about 762 mm (30 inches) although amounts of up to 1500 mm have been recorded.

  The heavy rains that occur in summer are usually the convectional type.

  Let us now turn our attention to the characteristics of the temperature for this climate.

• Although temperature are high throughout the year, there is a short, slightly cooler season (in comparison with the equatorial) when the sun is overhead at the tropic in the opposite hemisphere.

  The summers are hot with temperatures around 32 degrees C (about 90 degrees F). Winters are cooler, 21 degrees C (70 degrees F). An annual temperature range of 11 degrees C (20 degrees F) is typical, but the range increases as one moves further away from the Equator. It is, however, interesting to note that the highest temperatures do not coincide with the period of the highest sun (for example, June in the Northern Hemisphere), but occur just before the onset of the rainy season. There is also a distinct drop in temperature in the rainy period owing to the overcast sky and the cooler atmosphere.

• Days are hot, and during the hot season, noon temperatures of over 38 degrees C (100 degrees F) are quite frequent. When night falls, the clear sky, which promotes intense heating during the day, also causes rapid radiation in the night. Temperatures drop to well below 10 degrees C (50 degrees F) and night frosts are not uncommon at this time of the year. The climate, therefore, has extreme diurnal range of temperature.

Review

Here are a few questions to review today's lesson:

1. Where is the tropical continental climate best developed?

2. What are the names of the areas of tropical continental climate in South America?

3. What is the outstanding characteristic of this climatic type?

4. Describe the 'Harmattan'.

5. When does this climate experience the highest temperatures?

6. Account for the extreme diurnal range of temperature.

The vegetation of this climatic type will be done in the next lesson.

References:

General Geography in Diagrams by R. B. Bunnett

Certificate Physical and Human Geography by Goh Cheng Leong

The Caribbean Environment by mark Wilson

Marjorie Henry teaches at Glenmiur High School.