Climate II Elements of climate; climatic controls; differences between weather and climate.

GEOGRAPHY: SS 2 - Climate II

Welcome to our second lesson on Climate! In this note, we will explore the essential components that define climate and the factors that influence it across different regions. We will also clearly distinguish between weather and climate.

Core Concepts

1. Elements of Climate

These are the measurable atmospheric conditions that describe the weather and, over time, determine the climate of a place.

• Temperature: This is the degree of hotness or coldness of the atmosphere. It is measured using a thermometer. Places closer to the equator generally experience higher temperatures.
• Rainfall (Precipitation): This refers to any form of water falling from the atmosphere to the Earth's surface, such as rain, snow, or hail. It is measured by a rain gauge. Nigeria, for example, experiences significant rainfall, especially in its southern regions.
• Atmospheric Pressure: This is the weight of the air pressing down on the Earth's surface. It is measured by a barometer. High pressure usually indicates clear, stable weather, while low pressure often brings cloudy or stormy conditions.
• Wind: This is air in motion. Wind direction is measured by a wind vane, and its speed by an anemometer. Winds can bring moisture or dryness, depending on their origin.
• Humidity: This is the amount of water vapour present in the atmosphere. It is measured by a hygrometer. High humidity makes the air feel sticky and can lead to discomfort.
• Sunshine and Cloud Cover: This refers to the amount of sunlight a place receives and the extent to which clouds obscure the sky. More sunshine generally means higher temperatures, while extensive cloud cover can reduce incoming solar radiation.

A typical weather station equipped with instruments to measure various elements of climate.

2. Climatic Controls

Climatic controls are the geographical factors that influence the elements of climate, leading to different climatic conditions across the Earth.

• Latitude: This is the distance of a place from the equator. Places near the equator (low latitudes) receive more direct sunlight and are generally hotter, while those further away (high latitudes) are colder.
• Altitude: This is the height of a place above sea level. As altitude increases, temperature generally decreases (approximately 6.5°C for every 1000m rise). This is why highlands like the Jos Plateau are cooler than coastal lowlands like Lagos.
• Distance from the Sea (Continentality): Coastal areas tend to have more moderate temperatures (cooler summers, warmer winters) because large bodies of water heat up and cool down slowly. Inland areas, far from the sea, experience more extreme temperatures (hotter summers, colder winters).
• Ocean Currents: These are continuous, directed movements of ocean water. Warm ocean currents raise the temperature of adjacent coastal lands, while cold currents lower it.
• Prevailing Winds: These are the dominant winds that blow over a region. If they blow from the sea, they bring moisture and moderate temperatures. If they blow from land, they often bring dry conditions. For example, Nigeria's South-Westerly winds bring rain, while the Harmattan winds bring dryness.
• Relief (Mountains): Mountains act as barriers to winds. They force moist air to rise, cool, and condense, causing heavy rainfall on the windward side. The leeward side, in contrast, experiences dry conditions, known as a 'rain shadow'.
• Vegetation Cover: Areas with dense vegetation (like forests) tend to have lower temperatures, higher humidity, and more rainfall compared to barren areas. Vegetation influences the local water cycle and regulates temperature.

Lines of latitude (horizontal) on a world map, illustrating their role in climatic variations.

Diagram illustrating how mountains (relief) influence rainfall, creating windward wet slopes and leeward rain shadows.

3. Differences Between Weather and Climate

It is common to confuse weather and climate, but they refer to different aspects of atmospheric conditions.

• Weather refers to the day-to-day or short-term atmospheric conditions of a specific place. It describes what the atmosphere is like right now or over a period of hours or days. Examples include "It's sunny today," "There's a storm brewing," or "It was windy yesterday." Weather changes frequently.
• Climate refers to the average weather conditions of a place over a long period, typically 30-35 years. It describes the general pattern of atmospheric behaviour in a region. Examples include "Nigeria has a tropical climate," or "The Sahara Desert has an arid climate." Climate is stable and predictable over long periods.

Think of it this way: Weather is what you wear today, while Climate is your entire wardrobe.

An infographic highlighting the key differences between weather (short-term) and climate (long-term average).

Real-World Example

In Nigeria, the difference in climate between the coastal south and the Sahelian north is largely due to latitude and prevailing winds. The south, closer to the equator and influenced by moisture-laden South-Westerly winds from the Atlantic, experiences high rainfall and tropical humid conditions. The north, further from the equator and affected by dry Harmattan winds from the Sahara, has a longer dry season and generally hotter, arid conditions. This climatic variation significantly impacts agriculture, water availability, and lifestyle across the country.

Practice/Reflection

Observe the daily weather conditions (temperature, rainfall, wind) in your hometown for one week. How do these short-term observations align with or differ from your general understanding of your region's long-term climate?