Urban climatology is the study of

urban climate The climate in urban areas differs from that in neighboring rural areas, as a result of urban development. Urbanization greatly changes the form of the landscape, and also produces changes in an area's air. The study of urban climate is urban clima ...

. It is a branch of

climatology Climatology (from Greek , ''klima'', "place, zone"; and , ''-logia'') or climate science is the scientific study of Earth's climate, typically defined as weather conditions averaged over a period of at least 30 years. This modern field of study ...

that concerns interactions between

urban Urban means "related to a city". In that sense, the term may refer to: * Urban area, geographical area distinct from rural areas * Urban culture, the culture of towns and cities Urban may also refer to: General * Urban (name), a list of people ...

areas and the atmosphere, the effects they have on one another, and the varying spatial and temporal scales at which these processes (and responses) occur.

History

Luke Howard Luke Howard, (28 November 1772 – 21 March 1864) was a British manufacturing chemist and an amateur meteorologist with broad interests in science. His lasting contribution to science is a nomenclature system for clouds, which he proposed i ...

is considered to have established urban climatology with his book ''The Climate of London'', which contained continuous daily observations from 1801 to 1841 of

wind direction Wind direction is generally reported by the direction from which it originates. For example, a ''north'' or ''northerly'' wind blows from the north to the south. The exceptions are onshore winds (blowing onto the shore from the water) and offsho ...

atmospheric pressure Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1013.25 millibars, ...

, maximum

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measurement, measured with a thermometer. Thermometers are calibrated in various Conversion of units of temperature, temp ...

, and

rain Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water ...

fall. Urban climatology came about as a methodology for studying the results of industrialization and

urbanization Urbanization (or urbanisation) refers to the population shift from rural to urban areas, the corresponding decrease in the proportion of people living in rural areas, and the ways in which societies adapt to this change. It is predominantly t ...

. Constructing cities changes the physical environment and alters energy, moisture, and motion regimes near the surface. Most of these alterations can be traced to causal factors such as

air pollution Air pollution is the contamination of air due to the presence of substances in the atmosphere that are harmful to the health of humans and other living beings, or cause damage to the climate or to materials. There are many different typ ...

; anthropogenic sources of heat; surface

waterproofing Waterproofing is the process of making an object or structure waterproof or water-resistant so that it remains relatively unaffected by water or resisting the ingress of water under specified conditions. Such items may be used in wet environme ...

; thermal properties of the surface materials; and morphology of the surface and its specific three-dimensional geometry—building spacing, height, orientation, vegetative layering, and the overall dimensions and geography of these elements. Other factors are relief, proximity to water bodies, size of the city, population density, and land-use distributions.

Influential factors

Several factors influence the urban

climate Climate is the long-term weather pattern in an area, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologi ...

, including city size, the morphology of the city, land-use configuration, and the geographic setting (such as relief, elevation, and regional climate). Some of the differences between urban and rural climates include

air quality Air pollution is the contamination of air due to the presence of substances in the atmosphere that are harmful to the health of humans and other living beings, or cause damage to the climate or to materials. There are many different types ...

wind Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few ho ...

patterns, and changes in rainfall patterns, but one of the most studied is the

urban heat island An urban heat island (UHI) is an urban or metropolitan area that is significantly warmer than its surrounding rural areas due to human activities. The temperature difference is usually larger at night than during the day, and is most apparen ...

(UHI) effect.

Temperature and urban heat island effect

Urban environments, and slightly downwind, are typically warmer than their surroundings, as documented over a century ago by Howard. Urban areas are islands or spots on the broader scale compared with more rural surrounding land. The spatial distribution of temperatures occurs in tandem with temporal changes, which are both causally related to anthropogenic sources. The urban environment has two atmosphere layers, besides the

planetary boundary layer In meteorology, the planetary boundary layer (PBL), also known as the atmospheric boundary layer (ABL) or peplosphere, is the lowest part of the atmosphere and its behaviour is directly influenced by its contact with a planetary surface. On Ear ...

(PBL) outside and extending well above the city: (1) The urban boundary layer is due to the spatially integrated heat and moisture exchanges between the city and its overlying air. (2) The surface of the city corresponds to the level of the urban canopy layer. Fluxes across this plane comprise those from individual units, such as roofs, canyon tops, trees, lawns, and roads, integrated over larger land-use divisions (for example, suburbs). The urban heat island effect has been a major focus of urban climatological studies, and in general the effect the urban environment has on local meteorological conditions. These are sometimes measured by micronets or

mesonet In meteorology and climatology, a mesonet, portmanteau of mesoscale network, is a network of automated weather and, often, environmental monitoring stations designed to observe mesoscale meteorological phenomena and/or microclimates. Dry lin ...

s, as well as by Earth observation satellites.

Pollution

The field also includes the topics of

, radiation fluxes,

microclimate A microclimate (or micro-climate) is a local set of atmospheric conditions that differ from those in the surrounding areas, often with a slight difference but sometimes with a substantial one. The term may refer to areas as small as a few squ ...

s and even issues traditionally associated with architectural design and engineering, such as

wind engineering Wind engineering is a subset of mechanical engineering, structural engineering, meteorology, and applied physics that analyzes the effects of wind in the natural and the built environment and studies the possible damage, inconvenience or benefits ...

. Causes and effects of pollution as understood through urban climatology are becoming more important for

urban planning Urban planning, also known as town planning, city planning, regional planning, or rural planning, is a technical and political process that is focused on the development and design of land use and the built environment, including air, water, ...

Precipitation

Changes in winds and

convection Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the conve ...

patterns over and around cities impacts

precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...

. Contributing factors are believed to be urban heat island, heightened surface roughness, and increased aerosol concentration.

Climate change

Urban climatology is strongly linked to research surrounding

global warming In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...

. As centers for socioeconomic activities, cities produce large amounts of greenhouse gases (GHGs), most notably CO₂ as a consequence of human activities such as transport, development, waste related to heating and cooling requirements etc. Globally, cities are expected to grow into the 21st century (and beyond) - as they grow and develop the landscapes in which they inhabit will change so too will the atmosphere resting above them, increasing emissions of GHGs thus contributing to the global

greenhouse effect The greenhouse effect is a process that occurs when energy from a planet's host star goes through the planet's atmosphere and heats the planet's surface, but greenhouse gases in the atmosphere prevent some of the heat from returning directly ...

. Finally, many cities are vulnerable to the projected

consequences of climate change The effects of climate change impact the physical environment, ecosystems and human societies. The environmental effects of climate change are broad and far-reaching. They affect the water cycle, oceans, sea and land ice ( glaciers), sea le ...

(

sea level rise Globally, sea levels are rising due to human-caused climate change. Between 1901 and 2018, the globally averaged sea level rose by , or 1–2 mm per year on average.IPCC, 2019Summary for Policymakers InIPCC Special Report on the Ocean and Cry ...

, changes in temperature, precipitation, storm frequency) as most develop on or near coastlines, nearly all produce distinct urban heat islands and atmospheric pollution: as areas in which there is concentrated human habitation these effects potentially will have the largest and most dramatic impact (e.g. the 2003 European heat wave that especially deadly in France) and thus are a major focus for urban climatology.

Spatial planning and public health

Urban climatology impacts decision-making for municipal planning and policy in regards to

pollution Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the ...

, extreme

heat In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary. A thermodynamic system does not ''contain'' heat. Nevertheless, the term is ...

events, and stormwater modeling.Yen, Ben Chie. "Urban Stormwater Modeling and Simulation." Bulletin of the American Meteorological Society Apr. 1995: 564+. Academic OneFile. Web. 11 Nov. 2014.

References

External links

Urban climatology: History, status and prospects
at ScienceDirect {{DEFAULTSORT:Urban Climatology Regional climate effects Climatology Physical geography Urbanization