Lesson Notes By Weeks and Term v3 - Senior Secondary 2
Climate II
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Climate II
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Subject: Geography
Class: Senior Secondary 2
Term: 1st Term
Week: 1
Theme: Environment And Its Resources
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This lesson continues the exploration of climate, building upon the foundational concepts introduced in "Climate I." It delves into the intricate factors that influence climate, examines the distinct climatic types prevalent in Nigeria, and characterizes the specific climatic conditions experienced across the country. Understanding these concepts is critical for Nigerian learners as climate profoundly impacts various aspects of their lives, including agricultural practices, water resource management, infrastructure development, and preparedness for climate-related hazards like flooding and drought, which are increasingly relevant to Nigeria's environment and resources.
Nigeria, predominantly from November to March. This causes the dry season.
Relief (Topography): Explanation: Mountains and other high landforms act as barriers to prevailing winds, influencing rainfall patterns. The windward side (facing the wind) receives heavy orographic rainfall as moist air is forced to rise, cool, condense, and precipitate. The leeward side (sheltered side) experiences a rain shadow effect, with much drier conditions.
Nigerian Context: While Nigeria does not have very high mountain ranges to produce dramatic rain shadow effects, elevated areas like the Adamawa Highlands can experience slightly different rainfall patterns, with windward slopes receiving more moisture.
Vegetation Cover: Explanation: Dense vegetation, like forests, influences local climate by increasing humidity through evapotranspiration, reducing ground temperatures by providing shade, and moderating wind speeds. Areas with sparse vegetation or bare ground tend to have higher surface temperatures and lower humidity.
Nigerian Context: The rainforest belt in Southern Nigeria maintains a cooler, more humid local climate compared to cleared agricultural lands or urban areas, where concrete and asphalt absorb and radiate more heat. Deforestation contributes to localized temperature increases and reduced rainfall in affected areas.
Human Activities: Explanation: Industrialization, deforestation, urbanization, and agricultural practices release greenhouse gases into the atmosphere, contributing to global warming and climate change. Urban areas also create "urban heat islands" where temperatures are significantly higher than surrounding rural areas due to heat absorption by buildings and roads, and heat generation from human activities.
Nigerian Context: Large cities like Lagos and Kano exhibit urban heat island effects. Deforestation for agriculture, logging, and fuel wood extraction across Nigeria alters local microclimates and contributes to broader environmental degradation. 2.
3. Climatic Zones of Nigeria (Tropical Climates) Nigeria lies entirely within the tropical climatic zone, characterized by consistently high temperatures throughout the year. Variations exist primarily in rainfall amount, duration of wet/dry seasons, and humidity. Tropical Rainforest Climate (Equatorial/Humid Tropical) - Köppen: Af/Am Location in Nigeria: Southernmost Nigeria, particularly the Niger Delta, coastal areas from Calabar to Lagos, and parts of Cross River, Bayelsa, Rivers, and Delta States.
Characteristics: Temperature: High and uniform throughout the year (average 26-28°C) with a small annual range (1-3°C). Diurnal range is also small.
Rainfall: Very high annual rainfall (2000-4000mm), distributed almost evenly throughout the year with no distinct dry season or a very short, mild one. Often experiences a double maximum of rainfall (e.g., May-July and September-November).
Humidity: Very high all year round.
Vegetation: Dense tropical rainforest.
Example Cities: Port Harcourt, Calabar. Tropical Wet and Dry Climate (Savanna Climate) - Köppen: Aw Location in Nigeria: Covers the vast majority of Nigeria, extending northwards from the rainforest belt. It is often subdivided based on rainfall characteristics.
Characteristics (General): Temperature: High temperatures throughout the year, but with a more pronounced annual range than the rainforest climate. Marked seasonal variations in temperature between wet and dry seasons.
Rainfall: Distinct wet and dry seasons. Rainfall decreases progressively from south to north.
Vegetation: Grasslands (savanna) with scattered trees.
Sub-divisions in Nigeria: Guinea Savanna: Location: Immediately north of the rainforest belt (e.g., Oyo, Kogi, Benue, Enugu, Kaduna, FCT).
Rainfall: Annual rainfall 1000-1500mm. Longer rainy season (7-8 months) and a shorter, less severe dry season.
Vegetation: Tall grass with scattered broad-leaved trees (e.g., shea butter, locust bean).
Example Cities: Ibadan, Abuja, Makurdi.
Sudan Savanna: Location: North of the Guinea Savanna (e.g., Kano, Katsina, Sokoto, Borno, Yobe, Gombe).
Rainfall: Annual rainfall 500-1000mm. Shorter rainy season (5-6 months) and a longer, more severe dry season.
Vegetation: Shorter grass with more thorny, drought-resistant trees.
Example Cities: Kano, Sokoto, Maiduguri.
Sahel Savanna: Location: Extreme northern fringes of Nigeria (e.g., parts of Borno, Yobe, Sokoto, Jigawa).
Rainfall: Annual rainfall generally below 500mm. Very short rainy season (3-4 months) and a very long, harsh dry season.
Vegetation: Sparse, short, scrubby grass and scattered thorny shrubs and trees adapted to arid conditions. Semi-desert characteristics.
Example Cities: Damaturu, Nguru. 2.
4. Characteristics of Nigeria's Climate Temperature: * Generally high temperatures year-round due to low latitude. the Harmattan in the north exacerbates respiratory illnesses (asthma, meningitis). Heat stress during extreme temperatures.
Economy: Impacts on agriculture (a major employer) affect GDP, livelihoods, and food prices. Damage to infrastructure (roads, bridges, buildings) from floods requires significant repair costs. Disruption to transportation during heavy rainfall or intense Harmattan dust.
Environment: Desertification and land degradation in the northern parts due to prolonged drought and over-cultivation. Coastal erosion and saline intrusion in the south due to sea-level rise and storm surges. Loss of biodiversity due to habitat destruction and climatic stress. Increased frequency and intensity of extreme weather events. season.
Vegetation: Shorter grass with more thorny, drought-resistant trees.
Example Cities: Kano, Sokoto, Maiduguri.
Sahel Savanna: Location: Extreme northern fringes of Nigeria (e.g., parts of Borno, Yobe, Sokoto, Jigawa).
Rainfall: Annual rainfall generally below 500mm. Very short rainy season (3-4 months) and a very long, harsh dry season.
Vegetation: Sparse, short, scrubby grass and scattered thorny shrubs and trees adapted to arid conditions. Semi-desert characteristics.
Example Cities: Damaturu, Nguru. 2.
4. Characteristics of Nigeria's Climate Temperature: Generally high temperatures year-round due to low latitude. Mean annual temperature is around 27°C. Temperatures tend to be slightly higher in the north (closer to the Sahara) and during the dry season, especially just before the onset of rains (e.g., March/April). The annual temperature range is small in the south (e.g., Lagos 3-5°C) but increases northwards (e.g., Kano 7-10°C) due to continentality. Diurnal (daily) temperature range is often greater than the annual range, especially inland.
Rainfall: Distribution: Rainfall decreases progressively from the south to the north.
Coastal areas (South): 2,000 mm - 4,000 mm annually.
Middle Belt: 1,000 mm - 2,000 mm annually.
Extreme North: 250 mm - 1,000 mm annually.
Rainy Season: South: Long rainy season (8-10 months), often with a double maximum (peak rainfall periods, e.g., May-July and September-October), separated by a short "August Break" (a period of reduced rainfall in July/August).
North: Shorter rainy season (3-6 months), with a single maximum (peak rainfall typically July-September).
Dry Season: Conversely, the dry season increases in length and severity from south to north. The far north can experience 6-9 months of dry conditions. Wind Systems and the Inter-Tropical Convergence Zone (ITCZ): Inter-Tropical Convergence Zone (ITCZ): This is a low-pressure belt where the North-East Trade Winds (Harmattan) from the Sahara Desert meet the South-West Monsoon Winds from the Atlantic Ocean. It is a zone of convergence, uplift, and instability, characterized by heavy rainfall and thunderstorms.
Seasonal Migration: The ITCZ shifts seasonally with the apparent movement of the sun: Northern Summer (June-August): The sun is overhead at the Tropic of Cancer, and the ITCZ moves northward, reaching its maximum extent over the Sahara Desert. This brings the South-West Monsoon (moist air) far inland, resulting in the rainy season across most of Nigeria.
Northern Winter (December-February): The sun is overhead at the Tropic of Capricorn, and the ITCZ shifts southward, beyond Nigeria's coast. This allows the dry, dusty North-East Trade Winds (Harmattan) to dominate Nigeria, resulting in the dry season.
Impact: The oscillation of the ITCZ is the primary driver of Nigeria's distinct wet and dry seasons, dictating the onset, duration, and intensity of rainfall across different regions. 2.
5. Impacts of Climatic Variations on Human Activities and the Environment in Nigeria Agriculture: Rainfall reliability and distribution determine crop suitability. E.g., root crops (cassava, yam) in the wet south; cereals (millet, sorghum) in the drier north. Droughts in the north lead to crop failure, food insecurity, and livestock loss. Floods in the south and coastal areas destroy farmlands, homes, and infrastructure. Changing rainfall patterns disrupt traditional planting and harvesting seasons.
Water Resources: Reduced rainfall and increased evaporation in the north lead to drying up of rivers, lakes (e.g., Lake Chad), and groundwater depletion, exacerbating water scarcity. Increased demand for irrigation in drier regions. Flooding in the south contaminates water sources and damages water infrastructure.
Health: High temperatures and humidity in the south promote vector-borne diseases like malaria. Dust from the Harmattan in the north exacerbates respiratory illnesses (asthma, meningitis). Heat stress during extreme temperatures.
Economy: Impacts on agriculture (a major employer) affect GDP, livelihoods, and food prices. Damage to infrastructure (roads, bridges, buildings) from floods requires significant repair costs. Disruption to transportation during heavy rainfall or intense Harmattan dust.
Environment: Desertification and land degradation in the northern parts due to prolonged drought and over-cultivation. Coastal erosion and saline intrusion in the south due to sea-level rise and storm surges. * Loss of biodiversity This section provides the essential knowledge base for the teacher to deliver the lesson. 2.
1. Definition of Climate (Review) Climate refers to the average weather conditions of a place recorded over a long period, typically 30-35 years. It encompasses various elements like temperature, rainfall, humidity, atmospheric pressure, wind, and sunshine. 2.
2. Factors Affecting Climate The climate of any region is determined by a combination of several interacting factors: Latitude: Explanation: Latitude is the angular distance of a place north or south of the Equator. It determines the angle at which the sun's rays strike the Earth's surface. At lower latitudes (near the Equator, 0°), the sun's rays are more direct and concentrated, leading to higher temperatures. At higher latitudes, the rays are more oblique and spread over a larger area, resulting in lower temperatures.
Nigerian Context: Nigeria lies within 4°N and 14°N of the Equator. This low latitude ensures high temperatures throughout the year. While temperature differences due to latitude within Nigeria are less extreme than globally, the northern parts generally experience slightly higher annual temperature ranges due to their relatively higher latitude and continentality.
Altitude (Height above sea level): Explanation: Temperature generally decreases with increasing altitude at an average rate of 6.5°C per 1000 metres (or 0.65°C per 100 metres), known as the environmental lapse rate. This is because higher altitudes have thinner air, which absorbs less longwave radiation from the Earth's surface and retains less heat.
Nigerian Context: The Jos Plateau, with an average elevation of over 1,200 meters, experiences significantly cooler temperatures (e.g., mean annual temperature of ~22°C) compared to surrounding lowlands like Makurdi or Abuja (~27°C). This makes it a popular destination for its relatively temperate climate.
Distance from the Sea (Continentality): Explanation: Land heats up and cools down faster than water. Coastal areas experience a moderating effect from the sea, leading to smaller annual temperature ranges (cooler summers, warmer winters) and higher humidity. Inland areas, far from the moderating influence of the sea, experience larger annual temperature ranges (hotter summers, colder winters) and lower humidity, a phenomenon known as continentality.
Nigerian Context: Lagos (coastal) has a smaller annual temperature range and higher humidity with more consistent rainfall throughout the year, compared to Maiduguri (inland), which experiences extreme heat during the dry season, cooler nights, and a much wider diurnal and annual temperature range, along with less rainfall.
Ocean Currents: Explanation: Large masses of ocean water (currents) flow in specific directions, transporting heat from tropical to polar regions (warm currents) or cold from polar to tropical regions (cold currents). Warm currents tend to raise the temperature and humidity of coastal areas, while cold currents lower them and can lead to arid conditions.
Nigerian Context: Nigeria's coast is influenced by the warm Guinea Current, which flows eastward along the Gulf of Guinea. This current contributes to the high temperatures and humidity along the coast and plays a role in the formation of rainfall by supplying moisture.
Prevailing Winds: Explanation: The direction from which winds predominantly blow carries specific atmospheric characteristics (e.g., moisture content, temperature) from their source regions. Winds blowing over large bodies of water (maritime air masses) bring moisture, while winds blowing over continents (continental air masses) bring dryness.
Nigerian Context: South-West Monsoon Wind: Originates from the Atlantic Ocean, bringing moist, warm, rain-bearing air to Nigeria, especially from April to October. This is responsible for the country's rainy season.
North-East Trade Wind (Harmattan): Originates from the Sahara Desert, bringing dry, dusty, and relatively cool air (especially at night) to Nigeria, predominantly from November to March. This causes the dry season.
Relief (Topography): Explanation: Mountains and other high landforms act as barriers to prevailing winds, influencing rainfall patterns. The windward side (facing the wind) receives heavy orographic rainfall as moist air is forced to rise, cool, condense, and precipitate. The leeward side (sheltered side) experiences a rain shadow effect, with much drier conditions.
Nigerian Context: While Nigeria does not have very high mountain ranges to produce dramatic rain shadow effects, elevated areas like the Adamawa Highlands can experience slightly
Agriculture and Food Security: Application: Knowledge of Nigeria's climatic zones helps farmers select appropriate crops. For instance, rice and cassava thrive in the high-rainfall south, while millet, sorghum, and groundnuts are suited for the drier northern savanna regions. Understanding rainfall patterns helps determine planting and harvesting seasons, informing decisions on irrigation needs and drought-resistant crop varieties.
Nigerian Context: Farmers in Kano (Sudan Savanna) must plan for a shorter rainy season and potential droughts, often relying on traditional knowledge or modern irrigation. Conversely, farmers in the Niger Delta must contend with heavy rainfall and potential flooding. This knowledge is crucial for national food production strategies. Infrastructure Development and Disaster Management: Application: Climatic understanding guides decisions on urban planning, road construction, and housing design. Areas prone to heavy rainfall require robust drainage systems to prevent flooding (e.g., Lagos). Structures in hot, humid areas benefit from designs that promote ventilation (e.g., traditional Southern Nigerian homes). Knowledge of Harmattan's impact on visibility affects aviation and road transport planning.
Nigerian Context: The recurring flood disasters in coastal cities and along major river basins (e.g., River Niger and Benue floodplains) necessitate climate-informed land-use planning, early warning systems, and construction of resilient infrastructure like elevated roads and flood barriers.
Water Resource Management: Application: Understanding regional rainfall variations is vital for managing Nigeria's water resources. Areas with scarce rainfall (e.g., Northern Nigeria) rely heavily on boreholes, wells, and dams for irrigation, drinking water, and livestock. The sustainability of major water bodies like Lake Chad is directly linked to climatic patterns.
Nigerian Context: The shrinking of Lake Chad due to climate change and increased demand has severe implications for livelihoods, regional security, and migration in the northeastern part of Nigeria. Effective water resource planning involves assessing rainfall reliability, groundwater potential, and designing appropriate water storage and distribution systems across different climatic zones.