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S.3 Geography Notes

Equatorial Climate

Location:  It is mainly found between 50 North and South of Equator, but extend to 100 north and south of 00..  

It is well developed in central Africa, West Africa in the southern Ghana, southern parts of Nigeria, Cameroon, Gabon, Republic of Congo, Democratic Republic of Congo, Guinea, southern Ivory Coast, east coast of coastal Malagasy Republic and east African highlands. It is characterized by the following:

  • It has uniformly warm to hot temperatures of about 260C, small (low) annual range of about 20C to 30c, and small diurnal range of 10c to 80c. The temperature ranges between 220c - 290c. 
  • Heavy and well distributed rainfall throughout the year with a double maxima/two peaks of rainfall: march-may (long rains) and October- November (short rains) and April is the wettest month 
  • The rainfall is normally conventional type of rainfall from towering cumulonimbus clouds, accompanied by thunderstorms and lightening; and rainfall occurs in the afternoons and evenings. 
  • Humidity is very high throughout the year and relative humidity is constantly high over 80%. 
  • Heavy clouds cover throughout the year.
  • The sun rising is between 6:00am and 6:30am and setting is between 6:00pm-6:30pm (almost equal).
  • The mid-day sun is always near vertical and overhead twice a year at the equinoxes. •  Morning weather is often quite sunny and clear, but heat builds up during the day until by about 2.00pm. Cumulus clouds develop growing into towering Cumulo nimbus which gives heavy rain. 
  • There is little or no dry season. 

Summary: Hot and wet throughout the year.

Economic activities carried out in this type of climate:

Growing of annual and perennial crops/traditional and non-traditional crops on both small and large farming, Livestock farming, harvesting the forest resources/lumbering, Mining and quarrying, Art and craft, Fishing, Tourism and wild life conservation

Activity: Study the climate figures below answer the questions that follow:

Draw suitable graph to represent the information in the table for Libreville.Activity:

  • Describe the characteristics of climate of Libreville.

Hint 1: How to draw graph climate graphs:

  • The vertical axis should be labeled ‘rainfall in mm’, temperature in 0c and the horizontal axis ‘months of the year’
  • Use the space on the graph profitably by drawing an appropriate graph. Remember that all the information [tittle, scale, labeling of the horizontal and vertical lines] should fit on the graph paper.
  • On top of the axis for rainfall add another for temperatures. Label its Degrees centigrade.
  • Use appropriate scale to draw the climatic graph. A suitable scale is 1cm for 5 degrees centigrade. State that 1cm represents 5 degrees centigrade of temperature. If you make a big scale the temperature graph will be exaggerated and misleading. The line graph tends to suggest high range of temperature which may not be the case.
  • Use a line graph for temperature graph. Plot neat points/dots in the right locations and join them together from the left axis to the right axis.
  • Plot vertical bars with uniform width to show variations of rainfall amounts for each of the month.
  • Preferably use between 1 to 2 cm for about 100 mm of rain for equatorial and tropical climates.
  • It is advisable to use 2 cm for 100 mm of rain for dry climates for example desert/semi- arid climates to bring out the low rainfall months of the year. State that 1cm represent ….mm of rainfall.
  • Shade uniformly the bars to add on visual impression.
  • All writings MUST be horizontal on the graph paper
  • Finish your graph with the correct heading or tittle for example: A bar and line graph showing rainfall and temperatures of Cairo

Hint 2: How to describe the climate from a graph:

To describe the main characteristics of a climate, we have to use the correct words. The list below gives the terms/adjectives which should be used;

Temperature:

Mean monthly temperature

  • Above 300c------------- very hot temperatures
  • Between 200c-290c—--hot temperatures
  • Between 100c-190c----warm temperatures
  • Between 00c-10oc-----cool/mild temperatures
  • Below 00c-------------- very cold temperatures

Annual range of temperature

  • Large >200
  • 50
  • Small < 50

Avoid the use of terms like good or bad temperature which are not measurable when describing temperatures.

Rainfall

Annual rainfall

  • Above 1500mm per annum − very wet
  • Between 1000mm - 1500mm per annum − wet
  • Between 500mm - 1000mm per annum – moderate
  • Between 250mm - 500mm per annum − dry
  • Less than 2500mm per annum − very dry

Monthly rainfall

  • Above 125mm − very wet
  • 80-125mm− wet
  • Less than 80mm – dry

Other terms:

Heavy, Moderate, Reliable, well distributed, poorly distributed, Unreliable, unevenly distributed

AVOID using terms like good rainfall, high rainfall, low rainfall, poor /bad rainfall which are not measurable.

Discussion

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