Sub-topic 4: Temperature: Factors Affecting and Distribution
Understanding temperature is crucial for grasping climate patterns. This section delves into the primary factors that influence temperature variations across the globe and how these factors contribute to the observed distribution of temperatures.
Factors Affecting Temperature
Latitude is the primary determinant of solar insolation and thus temperature.
Areas closer to the equator receive more direct sunlight throughout the year, leading to higher average temperatures. As you move towards the poles, sunlight becomes more oblique, spreading the energy over a larger area and resulting in lower temperatures.
The angle at which solar radiation strikes the Earth's surface is directly related to latitude. At the equator, the sun's rays are nearly perpendicular, concentrating solar energy. At higher latitudes, the rays strike at a more oblique angle, spreading the energy over a larger surface area and passing through more atmosphere, which absorbs and reflects some of the radiation. This fundamental difference in insolation is the primary reason for the general decrease in temperature from the equator to the poles.
Altitude significantly reduces temperature due to atmospheric density and pressure.
Temperature generally decreases with increasing altitude. This is because the atmosphere is thinner at higher elevations, meaning there are fewer air molecules to absorb and re-emit heat.
As altitude increases, atmospheric pressure decreases. This leads to adiabatic cooling, where air expands and cools as it rises. Furthermore, thinner air at higher altitudes has a lower heat capacity, meaning it heats up and cools down more rapidly. For every 1,000 meters of ascent in the troposphere, temperature typically drops by about 6.5°C (the environmental lapse rate).
Proximity to large bodies of water moderates temperature extremes.
Oceans and large lakes have a moderating effect on coastal temperatures, making them cooler in summer and warmer in winter compared to inland areas at the same latitude.
Water has a high specific heat capacity, meaning it takes a lot of energy to change its temperature. This property allows large water bodies to absorb significant amounts of heat during summer, releasing it slowly during winter. This process buffers coastal regions from the extreme temperature fluctuations experienced in continental interiors, leading to a more moderate climate.
Ocean currents can transport heat, influencing regional temperatures.
Warm ocean currents can warm coastal regions, while cold currents can cool them.
Ocean currents act as massive conveyor belts, moving heat from tropical regions towards the poles and cold water from polar regions towards the equator. For example, the Gulf Stream significantly warms the western coast of Europe, making its climate much milder than other regions at similar latitudes. Conversely, cold currents like the California Current can lead to cooler coastal temperatures and fog.
Prevailing winds can transport air masses with different temperature characteristics.
Winds blowing from warmer regions will increase local temperatures, while winds from colder regions will decrease them.
The direction and origin of prevailing winds play a significant role in regional temperatures. For instance, winds blowing from large continental landmasses in summer can bring hot, dry air, while winds from polar regions in winter can bring frigid air. Maritime winds, influenced by the moderating effect of oceans, tend to be less extreme.
Aspect, or the direction a slope faces, affects solar radiation absorption.
In the Northern Hemisphere, south-facing slopes receive more direct sunlight and are warmer than north-facing slopes.
The orientation of a slope relative to the sun's path influences the amount of solar radiation it receives. In the Northern Hemisphere, south-facing slopes receive more direct sunlight throughout the day and year, leading to higher temperatures and different vegetation patterns compared to north-facing slopes, which are generally cooler and shadier.
Cloud cover and albedo influence the amount of solar radiation reaching the surface.
Clouds can reflect incoming solar radiation, leading to cooler daytime temperatures, and trap outgoing heat, leading to warmer nighttime temperatures. Surfaces with high albedo (like snow and ice) reflect more sunlight, keeping temperatures lower.
Clouds act as a blanket. During the day, they reflect a significant portion of incoming solar radiation back into space, reducing surface heating. At night, they trap outgoing terrestrial radiation, preventing heat loss and leading to warmer nights. Albedo refers to the reflectivity of a surface. Bright, light-colored surfaces like snow and ice have high albedo and reflect most solar radiation, while dark surfaces like asphalt have low albedo and absorb more radiation, leading to higher temperatures.
Global Temperature Distribution
The interplay of these factors creates distinct patterns of temperature distribution across the Earth's surface, often visualized through isotherms on climate maps.
The Earth's surface receives varying amounts of solar radiation based on latitude. This differential heating is the primary driver of global temperature patterns. The equator receives the most direct sunlight, leading to the highest average temperatures, while the poles receive the least direct sunlight, resulting in the coldest temperatures. This latitudinal gradient is modified by factors like altitude, proximity to water bodies, ocean currents, and prevailing winds, creating a complex mosaic of global temperature distribution.
Text-based content
Library pages focus on text content
| Factor | Effect on Temperature | Mechanism |
|---|---|---|
| Latitude | Decreases towards poles | Angle of solar insolation |
| Altitude | Decreases with height | Atmospheric density, adiabatic cooling |
| Proximity to Water | Moderates extremes | High specific heat capacity of water |
| Ocean Currents | Warms or cools coasts | Heat transport |
| Prevailing Winds | Transports air mass temperatures | Advection of heat/cold |
| Aspect (Slope) | Affects solar absorption | Directness of sunlight on slope |
| Cloud Cover/Albedo | Reduces daytime, warms nighttime (clouds); Lowers (high albedo) | Reflection and absorption of solar radiation |
Key Concepts and Terminology
The angle of solar insolation; rays are more direct at the equator and oblique at the poles.
Temperature decreases with increasing altitude due to thinner atmosphere and adiabatic cooling.
Albedo
Think of temperature distribution like a gradient. The equator is the 'hot' end, and the poles are the 'cold' end, with many factors creating variations along the way.
Learning Resources
Provides a foundational understanding of temperature as a physical quantity and its measurement.
Explains the key geographical factors influencing temperature variations across the globe.
A UK Met Office resource detailing how temperature is measured and what influences it.
An accessible explanation of Earth's temperature and how it's changing, suitable for understanding basic concepts.
Explains the greenhouse effect, a crucial factor in Earth's overall temperature balance.
Defines the atmospheric lapse rate, essential for understanding temperature changes with altitude.
An introduction to ocean currents and their role in heat distribution around the planet.
Details the concept of albedo and its impact on Earth's energy balance and temperature.
A video lesson explaining the relationship between temperature, latitude, and climate zones.
A concise overview of the main factors affecting temperature, suitable for exam preparation.