Microclimates

Have you ever been to the beach on a sunny day? It may look warm, but you might find yourself feeling colder than expected in the sea breeze. What causes this unexpected temperature change? Well, it's all to do with the microclimate of the beach. Or have you stepped into a forest and noticed a change in humidity? That's another kind of microclimate. Keep reading to learn more about factors affecting microclimates, facts, and more.

Microclimates Microclimates

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Contents
Table of contents

    Microclimate Definition

    A microclimate is the distinct, localised climate of a small-scale area.

    Microclimates could include valleys, parks, forest clearings or city centres.

    Weather conditions vary within a microclimate, differing from the general prevailing conditions of an area as a whole. The combination of many microclimates makes up the overall climate for a rural or urban area.

    It's important to understand microclimates as they represent the physical conditions actually experienced by organisms.

    Climate vs Microclimate

    While climate refers to the average temperature and precipitation of the region, a microclimate is a smaller area that differs from the surrounding macroclimate. An example of this would be a mountain range where one side of the mountain receives rain while the other remains dry.

    Analysing Climates

    Choropleth maps are colour-coded maps with differences in shading techniques that represent a certain value, such as temperature or precipitation.

    Climate graphs are useful graphs that combine a bar graph (indicating precipitation) and a line graph (indicating temperature) to inform us of the average yearly climatic conditions in a region.

    Factors Affecting Microclimates

    A range of biotic and abiotic factors can affect microclimates. Microclimates can also be affected by geologic or man-made features that can cause precipitation, heat pockets, or additional shading.

    Topography is the shape of the land.

    On a large scale, weather systems are predictable due to the Earth's rotation and the interaction between ocean and land. However, these patterns can be disrupted by local topography, such as aspect and relief.

    Microclimates mountain topography aspect slope StudySmarterFig. 1 – Mountain topography is steep and uneven. Source: unsplash.com

    Aspect is the direction that a slope faces.

    Aspect can determine the amount of sunlight an area receives. In turn, this affects temperature and shading. In the Northern Hemisphere, south-facing slopes are exposed to more direct sunlight, casting longer shadows on the opposite side of the slope. This affects the species of plants present. However, it's not just mountains that lead to microclimates. Small dips and depressions in valleys and low-lying areas can form collection points for cold air, leading to frost pockets in winter.

    Relief is the way that the landscape changes in height.

    Areas at a higher altitude experience a different microclimate. Temperatures are colder and oxygen availability is lower, limiting the species that can survive in these conditions.

    Soil

    Soil composition affects an area's microclimate through water retention or evaporation. For example, clay soils retain more water than sandy soils. Soil moisture retention influences the humidity and temperature above it. The degree of soil coverage can also impact temperature – bare soils reflect more light and heat.

    Vegetation interacts with soil and water in the microclimate in many ways. It covers the soil, preventing heat loss and radiation, releases water via evapotranspiration, regulates temperature, filters the air, and acts as a windbreak or suntrap.

    Evapotranspiration refers to the combined processes by which water is transferred from the land to the atmosphere. It includes evaporation from the soil and transpiration from plants.

    Forests often have their own microclimates. Trees cast shade, alter soil evaporation and change wind patterns. Because of the effect of trees, forest clearings typically experience greater temperature extremes than the forest interior. Within forests, the low-lying ground is typically wetter than higher ground, thus supporting different tree species.

    Artificial structures can modify climates – absorbing and releasing heat or providing protection from wind and sunlight.

    We'll go into more detail about urban areas later on.

    Even something minor, like a large stone, can shelter invertebrates and amphibians from extremes of temperature and moisture.

    Water Bodies

    Bodies of water can positively affect the microclimate. Evaporation is enhanced, which is associated with an uptake of latent heat and removal of thermal energy from the body of water. As a result, bodies of water provide a cooling source.

    Macroclimates and Microclimates

    Microclimates can be confused with macroclimates, but it is important to understand the difference between the two.

    A macroclimate is the overall climate of a region or a large geographic area. These occur at scales of up to thousands of kilometres.

    There are five main classifications of macroclimate:

    • Tropical
    • Dry
    • Temperate
    • Continental
    • Polar
    Subclassifications are used to provide more detail on the climate of a region. For example, the UK, like most of Western Europe, experiences a temperate oceanic climate.

    Temperate oceanic climates experience moderate temperatures year-round and lack a dry season.

    Biomes

    A biome is a large area characterised by its climate and biodiversity.

    There are five major types of biomes:

    • Aquatic

    • Grassland

    • Desert

    • Tundra

    • Savanna

    Climatic factors, like temperature and rainfall, influence biomes.

    Microclimates

    Microclimates are found within macroclimates and biomes. They occur at much smaller scales, spanning an area of up to 10 kilometres. Let's refer back to the UK's temperate oceanic macroclimate. Within this macroclimate, we can find a range of microclimates – forests, cities, coastal areas, lakes, and valleys.

    Microclimate Facts and Examples

    In the UK, there are four main types of microclimate – upland areas, coastal regions, forests and urban areas (this one will be discussed in more detail later).

    Upland Areas

    • Temperature tends to decline with altitude – a drop of 5 to 10°C per every 1000m above sea level. As a result, upland areas experience longer winters and shorter summers. Higher ground is often windy, making winter weather even harsher. Different plants and animals are adapted to these colder, harsher conditions.
    • The leeward side of hills and mountains is usually much drier than the windward side. This is because as air descends the slope, it dries and warms. This is known as the Föhn effect.
    • However, occasional temperature inversions can make it warmer in upland regions than at sea level. This can happen on clear nights with little wind. During these conditions, valley fog forms, which can last for days in calm conditions.
    • Coastal climates are more strongly influenced by the sea than by the land. Typically, coastlines are milder during the winter and cooler during summer than regions inland.

    • However, short-term variations can be considerable. Coastal regions can be prone to showers, whilst inland areas remain dry. Furthermore, sea fogs can be brought ashore and persist for hours. Daytime heating would cause the fog to clear inland.

    • Sea breezes are a key feature of UK coastal regions. These chilly winds are caused by convection currents. Cold air from the sea meets the warm land. The air is heated by the land, so it rises. More cold air from the sea moves in to replace it, forming a sea breeze.

    • Forests in the UK are typically cooler and less windy than surrounding areas – the trees act as a windbreak, and the solar radiation is 'filtered' by the leaves and branches.
    • Climatic differences between forests and surrounding areas can vary seasonally depending on if the trees are in leaf.

    Urban Microclimates

    Urbanisation can disrupt the surface energy balance of an area.

    The Urban Heat Island (UHI) is the phenomenon of higher temperatures and thermal discomfort in an urban area.

    What Causes the UHI?

    Constructing buildings close together contributes to the UHI. Buildings that are close together create an insulating effect, trapping heat and making the areas around a building warmer.

    The construction itself also affects the UHI. This is because of something known as 'waste heat'. Wasted energy from tools, cars, factories, and construction escapes in the form of heat. Urban areas are typically densely populated, leading to lots of waste heat in a small area.

    Areas that have a significant UHI typically experience poor water and air quality due to pollution.

    Atlanta, Georgia, experiences an extreme urban heat island effect. The metropolitan area experiences temperatures up to 10°C warmer than surrounding areas.

    Albedo

    The albedo of an urban area plays a part in the UHI.

    Albedo is the fraction of solar radiation reflected from a surface. The Earth's surface has an average albedo of 0.3.

    Darker surfaces, common in urban areas, have a lower albedo. Less heat is reflected away, so more is absorbed and stored by these surfaces. In urban areas, dark surfaces such as pavements and roofs can make up 60% of the area.

    How can the UHI be Reduced?

    Using green roofs can help reduce the UHI. The plants absorb carbon dioxide and reduce the heat of the surrounding area. A reduction in atmospheric carbon dioxide limits the greenhouse effect, slowing global warming and associated temperature increases.

    Using lighter-coloured materials increases the albedo of a surface. This will reflect more sunlight and trap less heat.


    I hope that this explains microclimates to you. These localised climates can be affected by topography, soil, vegetation and artificial structures. And now you know for next time to bring an extra layer when you go to the beach!

    Microclimates - Key takeaways

    • Microclimates are distinct, localised climates of a small-scale area, that differ from the general prevailing climate of that region.
    • Microclimates are affected by topography, soil, vegetation, and the presence of artificial structures.
    • Macroclimates are the overall climates of a large geographic area. Smaller microclimates are found within these.
    • The UK experiences four main types of microclimate: upland areas, coastal regions, forests and urban microclimates.
    • Urban areas are typically warmer than surrounding areas due to a phenomenon known as the urban heat island. This can be reduced by implementing green roofs and lighter-coloured materials.

    1. Anand Godson, Factors Affecting Microclimate, 2018

    2. Jeremy Gregory, Albedo, Climate, & Urban Heat Islands, 2018

    3. Meteorological Office, Microclimates, 2019

    4. N.V. Kobysheva, Local Climates, Environmental Structure and Function: Climate System - Volume 2, 2009

    5. NASA, Atlanta’s Urban Heat Island, 2022

    6. National Geographic, All About Climate, 2022

    7. National Geographic, Urban Heat Island, 2022

    8. National Geographic Society, The Five Major Types of Biomes, 2022

    9. Neil Campbell, Biology: A Global Approach Eleventh Edition, 2018

    10. Nyuk Hien Wong, Influence of Water Bodies on Outdoor Air Temperature in Hot and Humid Climate, ICSDC 2011: Integrating Sustainability Practices in the Construction Industry, 2012

    11. Paulina Wong, Microclimate Variation of Urban Heat in a Small Community, Procedia Environmental Science, 2016


    References

    1. Fig. 1 - Majestic Himalayas (https://unsplash.com/photos/AOs7iRbFngA) by Swapnil Vithaldas (https://unsplash.com/@swapnilv) licensed by CC0 1.0 Universal (https://creativecommons.org/publicdomain/zero/1.0/)
    Frequently Asked Questions about Microclimates

    What is an example of a microclimate?

    A forest is an example of a microclimate. Trees act as a windbreak, and solar radiation is filtered by the leaves and branches. This results in forests being cooler and less windy than their surrounding areas.

    What is a microclimate?

    A microclimate is the distinct, localised climate of a small-scale area.

    What factors affect microclimates?

    Microclimates are affected by topography, soil, vegetation and artificial structures.

    What is the importance of microclimates?

    Microclimates are important because they can support different species, contributing to the overall biodiversity of an area.

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