10/10/2022 URBAN CLIMATOLOGY 4. Urban heat Island, UHI types, atmospheric UHI, UHI intensity Paper to read https://is.muni.cz/auth/el/sci/podzim2022/ZX601/um/67875456/04_UHI_BasicsCompendium.pdf 1 4.1 Urban Heat Island concept Urban Heat Island Profile Rural Commercial Urban Suburban _ : Residential Residential Suburban Residential D™ntoWn Park http://weather.msfcnasa.gov/urban/urban heat island.html) Simplified model - role of natural and anthropogenic factors? 4.2 Types of UHI městská mezní vrstva vrstva 'j1 městského , 'venkovská mezní zápoje vrstva venkov What variables are measured? 1. Atmospheric Boundary layer Urban Heat Island 2. Atmospheric Canopy Layer Urban Heat Island 3. Surface Urban Heat Island 4. Subsurface Urban Heat Island (Oke et al., 2017) UHI profiles Surface Temperatur? (Day) AirTemperature {Day) Surface Temperature (Night) AirTemperature [Night) £ NIGHT ■- a. --A ■L_,- r Rural Suburban Pond Warehouse Urban Downtown Urban Park Suburban Rural or Industrial Residential Residential Reducing Urban Heat Islands: Compendium of Strategies and (Voogt 2000) UHI types characteristic Table 1: Basic Characteristics of Surface and Atmospheric Urban Heat Islands (UHls)4 Feature Surface UHI Atmospheric UHI Temporal Development • Present at all times of the day and night • Most intense during the day and in the summer ■ May be small or non-existent during the day ■ Most intense at night or predawn and in the winter Peak Intensity (Most intense UHI conditions) • More spatial and temporal variation: ■ Day: 18 to 27°F (10 to 15T) ■ Night: 9to 18"F (S to I0°C) • Less variation: ■ Day: -1.8 to 5.4°F (-1 to3°C) ■ Night: 12.6 to 21.6°F (7 to 12°Q Typical Identification Method • Indirect measurement: ■ Remote sensing • Direct measurement: ■ Fixed weather stations ■ Mobile traverses Typical Depiction • Thermal image • Isotherm map • Temperature graph Reducing Urban Heat Islands: Compendium of Strategies and (Voogt 2000) UHI intensity (ATu„r) i i i i i i i iii "v Sunset Sunrise f S ■ \\l 3 (a) \ iN \i \ Urban Ol O. \ \ £ i-h_ '< J Intensity -\ C / -> Heat Isla ^ -1 1 1 ' 1 1 1 1 ill 1 1 12 IS 24 06 12 Time Conceptual Drawing of the Diurnal Evolution of the Urban Heat Island during Calm and Clear Conditions (modified from Oke, 1982) UHI intensity and weather types -2 -1 . i 2 1 4 - ' -2.2,,. A 1 Nocturnal UHI intensity in London durinf the radiation-driven (a) and advection-driven (b) weather Oke et al.r 2017, Urban Climates © Cambridge University Press 2017 UHI intensity for heat wave days (HW) and non-HW days (NHW) during the summer months (JJA season) of the 2011-2020 period at Brno BISK station. Vertical lines are mean UHIIs, and their differences express the heat magnitude (HM). UHI intensity (ATu.r) The size of the city forms the intensity of UHI in general The size of the city can be characterized via number of inhabitants There is a relation between maximum UHI intensity (UHImax) and number of dwellers(P) (van Hove et al. 2011): UHImax = 2,93 log P- 11,95 For Brno (P = 380 ths.) UHImax = 4,4 °C How we can estimate UHI intensity depending on available data? 4.3 Measuring the UHI effect • „Point" measurements - standard meteorological stations • „Point" measurements - special-purpose automatic stations • Mobile measurements • Urban remote sensing • Urban climate and UHI intensity modelling All types of measurements also involve three different components that are hardly to quantify (Lowry 1977): 1. the „backgound" climate 2. the effects of local climate (topoclimate) 3. the effect of local urbanization Where are the spatial limits of the urban effect? 10/10/2022 UHI Intensity in Brno Mean daily variations of summer air temperature at urban (AA) and rural (P) stations during clear and calm days in Brno region (left) and daily variation of urban heat island intensity (AT); UHI intensity is expressed as a difference between mean air temperature at urban and rural stations (right] 6 Spatial distribution of meteorological stations in Brno area (a) and their characteristics: Elevation (NV), density of buildings (DENS), and amount of vegetation (NDVI) (b) Figure * Total length of meets (further Tlafj calculated far a regular grid (300 x 30O «n> In fígiví $ Gerxitr of btfľftfngí IK) (further firWjJ calculated far a rea.o)ar grid 1.30Q x 300 m) in the figure i tiarmoYued difference Vegetal Intlex (further MOVi} es an irrditatof ri(r„j,-,:,; :n:ii ,-i;jr;r in Hjr.u n.va Temperature deviation [°C] H_I_I_^^^H 1 -0,5 D 0,5 1 15 2 2,5 _ hranice katastrálního území města Brna T=f(NDVI) Spatial distribution of mean daily air temperature (Tavg), temperature minimum (Tmin) and intensity of UHI (AT) in Brno area during clear and calm days in summer; air temperatures are expressed as deviations from mean temperature of the study area (c) 10/10/2022 AUHI - mobile measurements -L-- Design of measuring routes (a), air temperature profile along measurement routes (b) and typical spatial distribution of air temperature in central part of Brno in early night hours; air temperature is expressed as deviation (dT) from mean value of the study area and is typical for clear and calm weather during summer (c) AUHI - from mobile measurements to maps 8 SUHI - remote sensing (a) Spatial variability of LST values within the Brno region; LST derived from Landsat thermal imagery acquired on 15 June 2006. (b) Intensity of surface UHI in Brno region defined as the difference between urban (M) and rural areas (P); LSTs UHI consequences • UHI impacts may be direct and indirect, negative effects prevail in general • Diurnal Temperature Range is smaller in cities • Higher air pollution reduce nighttime cooling, both factors increase a discomfort for city dwellers • Increased temperatures during summer in cities amplify energy demand for air conditioning. • Higher surface temperatures can heat storm water runoff with negative effect of various water ecosystems (thermal pollution) • Impacts to plants through changes in phenology may be ambiguous (beginning and end of individual phases of the growing cycle 4.4 UHI and recent global warming gj; r Brno area 2010s A paper by AAcKitrick & Michaels (2004) concludes that half of the global warming trend from 1980 to 2002 is caused by Urban Heat Island. UHI and recent global warming Urban and rural regions show the same warming trend. Rural Stations - old (Jones el al.J Rural stations - new?Li et al.) Urban slations - o|d [Jones et a|.> - Urban stations - rtevj (Li etal.l All-^itiur-^-China - [Li) ■ Land-box dala - CRLITE! Anomaly (°C) time series relative to the 1961 to 1990 mean of the full US Historical Climatology Network (USHCN) data (red), the USHCN data without the 16% of the stations with populations of over 30,000 within 6 km in the year 2000 (blue), and the 16% of the stations with populations over 30,000 (green). The full USHCN set minus the set without the urban stations is shown in magenta. Source IPCC 2007 Parker (2004, 2006) noted that warming trends in night minimum temperatures over the 1950-2000 period were not enhanced on calm nights, which would be the time most likely to be affected by urban warming. UHI and recent global warming CISTEMP v4 Annual Trend 1979-2019 Temperature change