Key Terms: Urban Climate (AQA A Level Geography): Revision Note

Urban microclimates - key terms

Albedo – The reflectivity of a surface. Urban surfaces like tarmac have low albedo, meaning they absorb more heat.

Evapotranspiration – The combined process of water evaporation and plant transpiration; reduced in cities due to fewer green spaces.

Microclimate dome – A localised climate zone formed by urban buildings and human activities that differs from surrounding areas.

Pollution dome – A layer of polluted air trapped over a city, which can enhance warming and reduce air quality.

Temperature range (diurnal) – Cities typically show larger differences in temperature between day and night compared to rural areas.

Urban boundary layer – The layer of atmosphere above roof height influenced by the city as a whole.

Urban canopy layer – The layer of air below roof height, directly affected by buildings, streets, and trees.

Urban microclimate – The climate experienced in a small urban area, influenced by built form, surfaces, and human activity.

Wind patterns – Altered by urban structures; buildings can slow down, channel, or increase turbulence in wind flow.

Urban climates - key terms

Cloud cover – Often greater over cities due to pollution particles promoting cloud formation.

Fog – More common in urban areas due to increased condensation nuclei from pollution.

Photochemical smog – A form of air pollution caused by sunlight reacting with vehicle and industrial emissions.

Precipitation – Urban areas can receive more rainfall than rural areas due to enhanced uplift and air pollution.

Relative humidity – Often lower in cities because of higher temperatures and reduced vegetation.

Temperature cliffs – Sudden changes in temperature across short distances, often between green areas and urban buildings.

Temperature peak – The hottest part of a city, usually in the most densely built or industrial zones.

Temperature plateau – A uniformly warm zone often found in the commercial or residential areas of cities.

Temperature sink – Cooler urban zones such as parks and rivers where vegetation or water absorbs heat.

Thunderstorms – Increased frequency in cities due to heat and rising air promoting storm development.

Urban heat island (UHI) – The phenomenon of urban areas being warmer than surrounding rural areas, especially at night.

Urban wind – Cities typically have lower average wind speeds due to obstruction from buildings, although local gusts can be stronger in narrow streets.

Managing pollution - key terms

Air purification towers – Structures that filter and clean polluted urban air (e.g. Smog Free Tower).

Alternative fuels – Cleaner fuels like electricity, hydrogen, or LPG used to reduce vehicle emissions.

Car sharing/pooling – Reduces traffic and emissions by promoting shared vehicle use.

Catalytic converters – Fitted to vehicles to reduce harmful emissions from exhaust gases.

Congestion charge – A fee for driving in certain urban areas to reduce traffic and lower emissions.

Filters – Devices installed in factory chimneys to remove pollutants from emissions before release.

Green infrastructure – Urban design features like green roofs, walls, and gardens that help reduce heat and purify air.

Hydrogen fuel additives – Technologies that make combustion more efficient and reduce vehicle emissions.

Integrated Pollution Prevention and Control (IPPC) – A UK system requiring businesses to manage pollution through regulation and permits.

Legislation – Laws like the Clean Air Acts that limit air pollution and require emissions monitoring.

Park and ride – Facilities allowing commuters to park outside cities and use public transport to reduce urban congestion.

Pedestrianisation – Restricting vehicles from certain streets to reduce air pollution and make areas more people-friendly.

Photo-catalytic materials – Surfaces that break down air pollutants using sunlight, such as those coated in titanium dioxide.

Selective bans – Traffic control measures that temporarily restrict vehicles based on criteria (e.g. licence plate numbers).

Smog – A mix of smoke and fog intensified by pollutants and temperature inversions, harmful to health and visibility.

Tiocem – A special type of concrete with self-cleaning and pollutant-reducing properties under UV light.

Vehicle restrictions – Policies that limit the use of certain vehicles in city areas to reduce pollution levels.