Cooling ranges for urban heat mitigation: continuous cooling effects along the edges of small greenspaces

2021 ◽  
Author(s):  
Jonghoon Park ◽  
Jun-Hyun Kim ◽  
Wonmin Sohn ◽  
Ming-Han Li
Keyword(s):  
Continuous Cooling ◽  
Urban Heat ◽  
Cooling Effects

scholarly journals Effect of Urban Heat Island and Global Warming Countermeasures on Heat Release and Carbon Dioxide Emissions from a Detached House

Atmosphere ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 572
Author(s):  
Daisuke Narumi ◽  
Ronnen Levinson ◽  
Yoshiyuki Shimoda
Keyword(s):  
Carbon Dioxide ◽  
Global Warming ◽  
Heat Release ◽  
Urban Heat Island ◽  
Co2 Emissions ◽  
Heat Island ◽  
Sensible Heat ◽  
Heating Season ◽  
Urban Heat ◽  
Cooling Effects

Urban air temperature rises induced by the urban heat island (UHIE) effect or by global warming (GW) can be beneficial in winter but detrimental in summer. The SCIENCE-Outdoor model was used to simulate changes to sensible heat release and CO2 emissions from buildings yielded by four UHIE countermeasures and five GW countermeasures. This model can evaluate the thermal condition of building envelope surfaces, both inside and outside. The results showed that water-consuming UHIE countermeasures such as evaporative space cooling and roof water showering provided positive effects (decreasing sensible heat release and CO2 emissions related to space conditioning) in summer. Additionally, they had no negative (unwanted cooling) effects in winter since they can be turned off in the heating season. Roof greening can provide the greatest space- conditioning CO2 emissions reductions among four UHIE countermeasures, and it reduces the amount of heat release slightly in the heating season. Since the effect on reducing carbon dioxide (CO2) emissions by UHIE countermeasures is not very significant, it is desirable to introduce GW countermeasures in order to reduce CO2 emissions. The significance of this study is that it constructed the new simulation model SCIENCE-Outdoor and applied it to show the influence of countermeasures upon both heat release and CO2 emissions.

scholarly journals A Study on the cooling effects of the park dispersions applied in PUD

2018 ◽  
Vol 57 ◽  
pp. 04002
Author(s):  
Yi-Cheng Chiang ◽  
Hong-Yun Lin
Keyword(s):  
High Temperature ◽  
Urban Heat Island ◽  
Urban Heat Island Effect ◽  
Heat Island ◽  
Vicious Cycle ◽  
Island Effect ◽  
Urban Heat ◽  
Cooling Effects ◽  
Research Studies

Urban heat-island effect causes the vicious cycle of city high temperature. The collocation of green park space can effectively cool down the heat of city. This research studies the cooling effects of the park dispersion by simulations of PUD projects. In this study, 3 different schemes were developed and simulated by CFD software. The results show that the more disperse the parks are, the lower the site temperatures.

scholarly journals A Numerical Study on Mitigation Strategies of Urban Heat Islands in a Tropical Megacity: A Case Study in Kaohsiung City, Taiwan

2020 ◽  
Vol 12 (10) ◽  
pp. 3952 ◽  
Author(s):  
Jou-Man Huang ◽  
Liang-Chun Chen
Keyword(s):  
Thermal Environment ◽  
Numerical Study ◽  
Mitigation Strategies ◽  
Comfort Level ◽  
Tropical Region ◽  
Permeable Pavement ◽  
Coverage Ratio ◽  
Urban Heat ◽  
Cooling Effects

In recent years, with the rapid increase in global warming and urbanization, urban heat island effects (UHI) have become an important environmental issue. Taiwan is no exception, with previous studies demonstrating serious UHIs in megacities. Although existing UHI research has utilized computer simulations to analyze improvement scenarios, there are few cooling strategy studies in actual blocks of Taiwan. Therefore, this study selected a block of a megacity in a tropical region of Taiwan as a case study by ENVI-met. Five improvement strategies were tested and compared to the current situation (B0): (1) Case C1 changed to permeable pavement, (2) Case C2 increased the green coverage ratio (GCR) of the street to 60%, (3) Case C3 changed to permeable pavement and increased the GCR in the street to 60%, (4) Case C4 changed to permeable pavement, increased the GCR in the street to 60%, and increased the GCR in the parks to 80%, and (5) Case C5 changed to permeable pavement, increased GCR in the street to 60% and parks to 80%, and set the GCR on the roof of public buildings to 100%. The results showed that the average temperature of the current thermal environment is 36.0 °C, with the comfort level described as very hot. Among the five improvement schemes, C5 had the greatest effect, cooling the area by an average of 2.00 °C. Further analysis of the relationship between the different GCRs of streets (SGCR) and the cooling effects revealed that for every 10% increase in the SGCR, the temperature of the pedestrian layer was reduced by 0.15 °C.

Remotely sensing the cooling effects of city scale efforts to reduce urban heat island

2012 ◽  
Vol 49 ◽  
pp. 348-358 ◽  
Author(s):  
Christopher W. Mackey ◽  
Xuhui Lee ◽  
Ronald B. Smith
Keyword(s):  
Urban Heat Island ◽  
Heat Island ◽  
Urban Heat ◽  
Cooling Effects

scholarly journals Time-Series Analysis Reveals Intensified Urban Heat Island Effects but without Significant Urban Warming

2019 ◽  
Vol 11 (19) ◽  
pp. 2229 ◽  
Author(s):  
Jia Wang ◽  
Weiqi Zhou ◽  
Jing Wang
Keyword(s):  
Time Series ◽  
Urban Heat Island ◽  
Urban Areas ◽  
Temporal Trends ◽  
Heat Island ◽  
Entire Study ◽  
Urban Warming ◽  
Urban Heat ◽  
Surface Urban Heat Island ◽  
Cooling Effects

Numerous studies have shown an increased surface urban heat island intensity (SUHII) in many cities with urban expansion. Few studies, however, have investigated whether such intensification is mainly caused by urban warming, the cooling of surrounding nonurban regions, or the different rates of warming/cooling between urban and nonurban areas. This study aims to fill that gap using Beijing, China, as a case study. We first examined the temporal trends of SUHII in Beijing and then compared the magnitude of the land surface temperature (LST) trend in urban and nonurban areas. We further detected the temporal trend of LST (TrendLST) at the pixel level and explored its linkage to the temporal trends of EVI (TrendEVI) and NDBI (TrendNDBI). We used MODIS data from 2000 to 2015. We found that (1) SUHII significantly increased from 4.35 °C to 6.02 °C, showing an intensified surface urban heat island (SUHI) effect, with an annual increase rate of 0.13 °C in summer during the daytime and 0.04 °C in summer at night. In addition, the intensification of SUHII was more prominent in new urban areas (NUA). (2) The intensified SUHII, however, was largely caused by substantial cooling effects in nonurban areas (NoUA), not substantial warming in urban areas. (3) Spatially, there were large spatial variations in significant warming and cooling spots over the entire study area, which were related to TrendNDBI and TrendEVI. TrendNDBI significantly affected TrendLST in a positive way, while the TrendEVI had a significant positive effect (p = 0.023) on TrendLST only when EVI had an increasing trend. Our study underscores the importance of quantifying and comparing the changes in LST in both urban and nonurban areas when investigating changes in SUHII using time-series trend analysis. Such analysis can provide insights into promoting city-based urban heat mitigation strategies which focused on both urban and nonurban areas.

scholarly journals Increasing Evapotranspiration on Extensive Green Roofs by Changing Substrate Depths, Construction, and Additional Irrigation

Buildings ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 173 ◽  
Author(s):  
Daniel Kaiser ◽  
Manfred Köhler ◽  
Marco Schmidt ◽  
Fiona Wolff
Keyword(s):  
Green Roof ◽  
Green Roofs ◽  
Urban Environments ◽  
Normal Green ◽  
University Of Applied Sciences ◽  
Daily Evapotranspiration ◽  
Urban Heat ◽  
Cooling Effects ◽  
Cool Summer ◽  
The University

Urban environments are characterized by dense development and paved ground with reduced evapotranspiration rates. These areas store sensible and latent heat, providing the base for typical urban heat island effects. Green roof installations are one possible strategy to reintroduce evaporative surfaces into cities. If green roofs are irrigated, they can contribute to urban water management and evapotranspiration can be enhanced. As part of two research projects, lysimeter measurements were used to determine the real evapotranspiration rates on the research roof of the University of Applied Sciences in Neubrandenburg, Germany. In this paper, we address the results from 2017, a humid and cool summer, and 2018, a century summer with the highest temperatures and dryness over a long period of time, measured in Northeast Germany. The lysimeter measurements varied between the normal green roof layer (variation of extensive green roof constructions) and a special construction with an extra retention layer and damming. The results show that the average daily evapotranspiration rates can be enhanced from 3 to 5 L/m2/day under optimized conditions. A second test on a real green roof with irrigation was used to explain the cooling effects of the surface above a café building in Berlin.

On the Mechanism of Thunderstorm Downdrafts

1943 ◽  
Vol 24 (2) ◽  
pp. 54-59
Author(s):  
Henry G. Kaplan
Keyword(s):  
Specific Heat ◽  
Heavy Precipitation ◽  
The Other ◽  
Original Position ◽  
Continuous Cooling ◽  
Close Relationship ◽  
Two Factors ◽  
Cooling Effects ◽  
Heat Of Evaporation ◽  
The One

Synopsis If a unit of air starts to descend in a region of the atmosphere characterized by a lepse rate between dry and saturated adiabatic, it becomes warmer than its surroundings and tends to return to its original position. Yet, in air where such a vertical temperature distribution exists, violent downdrafts are observed after the onset of a thunderstorm. Continuous cooling of the descending units of air by water and ice hydrometeors keeps them colder than the surrounding air. Thus a downdraft is maintained. The cooling can be divided into several factors. The most important is the heat of vaporization of the heavy precipitation falling with or through the descending units. The precipitation keeps the downdraft practically saturated; so that a plot of the path of a descending unit of air on an adiabatic chart will follow a saturation adiabat. The factor of next importance is the specific heat of the tremendous quantities of water and ice accompanying or passing through each unit of descending air. Although the ratio of heat of evaporation to specific heat of water is about five hundred to one, the specific heat factor is a more important cooling agent than this indicates. For, in estimating the relative cooling effects of these two factors one must remember that in descending from one level to another, an air parcel can only evaporate a limited amount of water. On the other hand the quantity of liquid and solid water involved in the specific heat transfer has no limitations. The third factor, the one which does not have, the continuous cooling properties of the other two but is of tremendous importance in the regions where the downdraft acquires above freezing temperatures, is the melting of ice hydrometeors. Large quantities of melting ice tend to give the unit isothermal descent characteristics, rapidly increasing the area on the adiabatic chart between a plotting of this descent and the plotting of the original atmospheric sounding. In other words, this melting causes a large acceleration in descent. Falling raindrops and ice hydrometeors, by compressing air ahead of them and rarefying air behind them, contribute to the downward motion of air. This factor, although not great, may be instrumental in initiating downdrafts. The sum of these effects, each one having an importance depending on particular conditions, makes up the downdraft characteristics. Downdrafts having a greater horizontal component than the accompanying precipitation, may leave the precipitation zone and continue to descend dry adiabatically until they acquire the same temperature (or better, the same density characteristics) of the surrounding air. Those leaving the precipitation at a low level may reach the earth as a cool wind unaccompanied by rain. The understanding of the necessarily close relationship between thunderstorm downdrafts and precipitation should be of valuable aid to pilots flying in thunderstorm areas.

scholarly journals Quantifying the effect of waterways and green areas on the surface temperature

2017 ◽  
Vol 39 (1) ◽  
pp. 89 ◽  
Author(s):  
Elis Dener Lima Alves
Keyword(s):  
Surface Temperature ◽  
Temporal Variability ◽  
Urban Heat Islands ◽  
Landsat 8 ◽  
Natural Area ◽  
Heat Islands ◽  
Green Areas ◽  
Urban Heat ◽  
Cooling Effects ◽  
The Relationship

The cooling effects of urban parks and green areas, which form the “Park Cool Island” (PCI) can help decrease the surface temperature and mitigate the effects of urban heat islands (UHI). Therefore, the objective of this research was to know the temporal variability of PCI intensity, as well as analyze the factors that determines it and propose an equation to predict the PCI intensity in Iporá, Goiás State, Brazil. To this purpose, the PCI intensity values were obtained using the Landsat-8 satellite (band 10), and then correlated with the NDVI and the LAI, in which proposes equations through multiple linear regression to estimate the PCI intensity. The results indicated that: 1) the greater the distance of the natural area, greater the surface temperature; 2) there is a great seasonality in PCI, in which the intensity of PCI is much higher in the spring (or close to it); 3) the relationship between NDVI and LAI variables, showed good coefficients of determination; 4) the equations for the buffer of 200 and 500 m, had low RMSE with high coefficients of determination (r2 = 0.924 and r2 = 0.957 respectively). 

Cooling Extent of Green Parks: A Case Study in Beijing

2014 ◽  
Vol 962-965 ◽  
pp. 2005-2017
Author(s):  
Wen Qi Lin ◽  
Xiang Qi Chang ◽  
Na Yan ◽  
Ting Yu
Keyword(s):  
Land Surface ◽  
Urban Heat Islands ◽  
Total Size ◽  
Heat Islands ◽  
Green Areas ◽  
Urban Heat ◽  
Cooling Effects ◽  
Higher Temperature ◽  
Lower Temperature

Cooling effects of green areas are an effective way to mitigate the urban higher temperature caused by urban heat islands. The cooling extent goes beyond a green area’s boundary and extends into its surrounding area. However, measurement of the exact cooling extent and mechanism of such effects had remained unclear. Using Landsat Enhanced Thematic Mapper Plus (ETM+) images of Beijing, we have determined the lower temperature of green cooled areas by land surface temperature, identified green areas’ cooling extents, and evaluated the relation of cooling extents to green areas’ features. Results show that the total size of extended cooled areas is larger than that of total green areas, and the cooling extents and magnitudes are statistically related to the biomass, size and shape of green areas. This study has demonstrated the calculation of cooling extents, and provided an approach to the assessment of cooling effects.

scholarly journals Scale-dependent interactions between tree canopy cover and impervious surfaces reduce daytime urban heat during summer

2019 ◽  
Vol 116 (15) ◽  
pp. 7575-7580 ◽  
Author(s):  
Carly D. Ziter ◽  
Eric J. Pedersen ◽  
Christopher J. Kucharik ◽  
Monica G. Turner
Keyword(s):  
Land Cover ◽  
Spatial Scale ◽  
Air Temperature ◽  
Canopy Cover ◽  
Impervious Surface ◽  
Tree Canopy ◽  
Impervious Surfaces ◽  
Tree Canopy Cover ◽  
Urban Heat ◽  
Cooling Effects

As cities warm and the need for climate adaptation strategies increases, a more detailed understanding of the cooling effects of land cover across a continuum of spatial scales will be necessary to guide management decisions. We asked how tree canopy cover and impervious surface cover interact to influence daytime and nighttime summer air temperature, and how effects vary with the spatial scale at which land-cover data are analyzed (10-, 30-, 60-, and 90-m radii). A bicycle-mounted measurement system was used to sample air temperature every 5 m along 10 transects (∼7 km length, sampled 3–12 times each) spanning a range of impervious and tree canopy cover (0–100%, each) in a midsized city in the Upper Midwest United States. Variability in daytime air temperature within the urban landscape averaged 3.5 °C (range, 1.1–5.7 °C). Temperature decreased nonlinearly with increasing canopy cover, with the greatest cooling when canopy cover exceeded 40%. The magnitude of daytime cooling also increased with spatial scale and was greatest at the size of a typical city block (60–90 m). Daytime air temperature increased linearly with increasing impervious cover, but the magnitude of warming was less than the cooling associated with increased canopy cover. Variation in nighttime air temperature averaged 2.1 °C (range, 1.2–3.0 °C), and temperature increased with impervious surface. Effects of canopy were limited at night; thus, reduction of impervious surfaces remains critical for reducing nighttime urban heat. Results suggest strategies for managing urban land-cover patterns to enhance resilience of cities to climate warming.

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