9/19/2022 URBAN CLIMATOLOGY Part 1. Motivation to study urban climates, objectives, historical overview Department of Geography Petr Dobrovolný Outline 1. Motivation to study urban climates, historical overview 2. Main factors controlling urban climate (UC), UC scales, layers, energy balance 3. The climate of Brno as an example (data, methods, main outcomes) 4. Urban heat Island (UHI), UHI types, atmospheric UHI, UHI intensity 5. Urban Remote Sensing, surface UHI 6. Precipitation in urban areas 7. Spatio-temporal variability of other meteorological elements in urban areas 8. Local climate zones 9. Urban Climate Modelling 10. Urban adaptation to climate change 1 Paper to read Urban Climate 10 (2014) 479-489 Contents lists available al ScienceDired Urban Climate journal homepage: www.elsevier.com/lacate/uclim Urban climatology: History, status and prospects ^c™SMari Gerald Mills School of Geography, Planning & Environmental Policy, UCD, Dublin, Itvland https://is.muni.cz/auth/el/sci/podzim2022/ZX601/um/67875456/01 Mills 2014.pdf 1.1 Objective Climate in urban areas differ from that of rural areas due to process of urbanization. _ Manhattan-Mannahatta: on right is a reconstruction of Manhattan Island circa 1609 (called "Mannahatta"), as compared to today, based on historical landscape ecology and map data. • First phase of urbanization (initiated by the industrial revolution) • Second phase (uncontrolled development in less-developed countries) • As for climate, urbanization means ... • Problem of sustainability 1.1 Objective • Most meteorological elements and climatological characteristics have specific features of their spatial and temporal variability in urbanized areas • However, typical spatiotemporal variability of urban climate in individual cities is formed as a superposition of natural and anthropogenic factors atmosph Urban biosphi Urban hydrosphere pedo- and lithosphere Oke et al., 2017, Urban Climates ) Cambridge University Press 2017 Built system The biophysical components of an urban ecosystem. They include all aspects of the pre-urban natural environment subsequently modified by the introduction of built infrastructure Urban climate = natural climate variability + urban forced climate variability 1.1 Objective • Specific features of urban climate may strongly affect economic activities, infrastructure functioning, quality of life, etc. goods Oke et al., 2017, Urban Climates © Cambridge University Press 2017 The representation of the inputs to, and outputs from, an urban ecosystem (concept of urban metabolism). 1.1 Objective Urban climatology objective is to study: a) How cites impact climate b) How climate impacts cities and their dwellers Built-up areas create specific category of local climate - urban climate 10H Regional scale Bourikas, 2016 The peculiarities of the urban climate can be studied at the level of the mesoclimate, local climate or microclimate categories 1.2 Urban Climate co 10J 1 10' 10° 10° 10B Climate categories: The hierarchy of climate scales from global to regional to meso-scale to local to ] micro-scale 10 mm 1 in 1 km 1,000 km Oke etai, 2017, Urban Climates Characteristic horizontal distance scale (in) For local climate it is typical that the processes in the lower layers of the atmosphere are significantly shaped by the radiation, thermal, aerodynamic, and moisture properties of active surfaces. 1.2 Urban Climate concept Active surface - transition between the atmosphere and the lithosphere or hydrosphere (surface of soil, water, vegetation, roads, roofs of houses, etc.), on which radiation energy is reflected and/or transformed into other types of energy (primarily heat). In cities, active surfaces create complicated hierarchy: Urban region a u 10 City (bulit up area) Neighbourhood (LCZ) Block Canyon Element Facet 1 AntfrrapBgirric full i . 1 I LMkH Ml Active surface influences atmospheric processes in the boundary layer of the atmosphere through its physical and chemical properties (relief height, orientation, albedo, thermal conductivity, humidity, soil composition and structure, vegetation, ...). 1.3 Motivation Over the last 200 years, the global population has increased sevenfold and the fraction of the people living in urban areas increased from 3% to 50% (UN, 2015) SMART, green and climate neutral cities Regenerative and prosperous urban economies Equitable, engaged and empowered communities Connected, healthy and climate friendly lifestyles Urban sustainability ©https:/Avww2.helsinki.fi 1.3 Motivation Importance of urban climate studies increase in recent decades due to global climate change Europe - 2018 surface temperature anomaly relative to 1981 2010 1 0.5 °C o -0.5 -1 -1.5 - ll .. ll......Ill III II 1954 1959 19S4 1969 1974 1979 1984 1989 1994 1999 2004 2009 2014 G*a»=a Cecmwf 0 European surface air temperature anomaly for annual averages from 1950 to 2018, relative to the annual average for the period 1981-2010. Data source: ERA5 (dark blue and red, starting 1979) and E-OBS (light blue and yellow). Credit: Copernicus Climate Change Service (C3S)/ECMWF/KNMI. 1.3 Motivation It is very probable that the frequency and intensity of hydrometeorological extremes will be higher in the near future New Scientist European heatwave caused 35,000 deaths Heat wave in the western Europe: temperature differences between July 2003 and July 2001 http://earthobservatory.nasa.gov/NaturalHazards Annual number of tropical days (a), tropical nights (b), number (c) and intensity (d) of heat waves in Brno, airport station in the 1961-2020 period • Higher heat load and higher extremity of weather and climate may negatively influence living conditions in urban areas with the direct impact to quality of life and health of population • Better know/ledge of causes and mechanisms that form urban climate are necessary for the mitigation of negative impacts and for the realization of adaptation strategies_ 1.4 History Antiquity, middle ages Bad quality of air in the cities, air pollution Luke Howard (1772-1864) The Climate of London (1833) A comparison between the air temperature observations by Luke Howard (solid) against those made by the Royal Society within London (broken). Source: Howard (1833). 1.4 History • 21th century • concept of Local Climate Zones • urban climate modelling (WRF, MUKLIMO_3D, ENVIMET) • realisation of adaptation and mitigation measures • www. urban-climate, org/ Urban Climate Change Research Network • http://uccrn.org/ 1.4 Future prospects • 'Reducing solitudes' in urban climatology • Improving scientific knowledge (the urban effect on precipitation) • To overcome the paucity of information on the rapidly growing cities of the less prosperous regions • Rapid advances in sensor technologies, problem of appropriate measurement devices and methods • More realistic descriptions of land cover; better characterization of the city structure: material properties, geometry, and functions (traffic) Development of models (physical, numerical) • Concept urban - rural is regionally different and mostly pays for mid-latitudes; rural mostly does not mean natural but managed natural 1.5 Definitions Oke (2006) described the evolution of urban climatology using eight modes of investigation or practice: • Conceptualisation • Theorisation • Field observation • Modelling • Model evaluation • Application in urban design and planning • Impact assessment (post-implementation) • Policy development and modification. 1.5 Definitions Urban climatology is concerned with the study of the climate effect of urban areas and the application of the knowledge acquired to the better planning and design of cities. Descriptive climatology Despite the accumulation of evidence (e.g. on the urban air temperature effect), much of it was specific to particular places and used distinct methods that made generalisations difficult. ATu-R(max) = 2.96 log P-6.41 Physical climatology Adopts a quantitative and systematic approach to research. Its the most common expression was formulation of the surface energy balance in cities. Q* = Qh + Q.e + Qg The research focus was shifted from describing effects (responses) to seeking their cause (processes). 1.6 Final remarks and questions 1. Why it is important to study urban climates? 2. What are the main objectives of urban climatology 3. What do you know about history of urban meteorology and climatology? 4. Characterize urban climate within the scale of climate categories 5. What is the difference between "descriptive" and "physical" urban climatology? 6. What are the main topics of urban climatology in the near future?