A one-year data set for the year 2015 of near-surface air temperature (T$T$), crowdsourced from ‘Netatmo’ citizen weather stations (CWS) in Berlin, Germany, and surroundings was analysed. The CWS ...data set, which has been quality-checked and filtered in a previous study, consists of T$T$ measurements from several hundred CWS. It was investigated (1) how CWS are distributed among urban and rural environments, as represented by ‘local climate zones’ (LCZ), (2) how LCZ are characterised in T$T$ along the annual cycle and concerning intra-LCZ T$T$ variability, and (3) if significant T$T$ differences between LCZ (ΔT$\Delta T$) can be detected with CWS data. Further, it was investigated how the results from CWS compare to reference data from standard meteorological measurement stations. It can be shown that all ‘urban’ LCZ are covered by CWS, but only few CWS are located in ‘natural’ LCZ (e.g. forests or urban parks). CWS data along the annual cycle show generally good agreement to reference data, though for some LCZ monthly means between both data sets differ up to 1 K. Intra-LCZ T$T$ variability is particularly large during night-time. Statistically significant ΔT$\Delta T$ can be detected with CWS data between various LCZ pairs, particularly for structurally dissimilar LCZ, and the results are in agreement with existing literature on LCZ or the urban heat island. Furthermore, annual mean ΔT$\Delta T$ in CWS data agree well with reference data, thus showing the potential of CWS data for long-term studies. Several challenges related to crowdsourced CWS data need further investigation, namely missing meta data, the non-standard measurement locations, the imbalanced availability in time and space, and potentials to combine CWS and reference data to benefit from the main advantages of both, i.e., the large number of stations and the high quality of data, respectively.
This open access book presents a catalogue of over one thousand indicators which can be used by cities' public administrators to monitor and evaluate social innovation action plans to support ...people-centred, collaborative or co-designed solutions to lower carbon emissions. Indicators are clustered according to a framework of social innovation solutions for climate neutrality at city level, developed by merging top-down academic knowledge with bottom-up pragmatic case studies. There is currently limited guidance on how to embed social innovations in their cities’ action plans with the aim of reaching climate neutrality, and on how to assess the progress and impacts of such people-centred projects in cities. The book addresses this gap and is thus relevant for scholars in the field of policy-making and design, as well as cities’ transition teams, policymakers and consultants. Based on the work developed within the EU-funded project NetZeroCities, intervention logics are provided for each of the ten categories of action, with related indicators clustered by category and evaluation criteria (effectiveness, efficiency, relevance, replicability, and scalability). Guidelines to implement the framework support city administrators in defining steps they need to follow to apply the indicators to their local case, making social innovation a crucial lever for accelerating systemic transformation.
The Guangdong-Hong Kong-Macao Greater Bay Area (GBA) is one of the regions with the fastest urbanization process in China in the past 4 decades. The urbanization process of the GBA is still ongoing ...and the meteorological observation resource in the region is rich, making the GBA an ideal testbed for the study of urban climate. In the past decades, the studies on the urban climate in the GBA has been quite active. The topics of these studies can be categorized into 3 topics: (1) urban climate characteristics and variations in the GBA, including significant increase in average temperature, decrease in relative humidity and average wind speed, and more frequent extreme precipitation; (2) challenges brought by urban climate change to GBA, such as the meteorological conditions affecting the atmospheric environment have become more complex, the health risk of urban residents has increased, the risk of urban flash flood and waterlogging has increased, and the demand for urban energy consumption has also increased significantly; (3) technologies and strategies to mitigate and adapt to urban climate change in GBA, including the optimization of urban wind environment, the regulation of urban thermal environment and the response technology of urban flood disaster.
•Urbanization made Guangdong-Hong Kong-Macau Greater Bay Area (GBA) hotter, drier and increased the intensity of rainstorms.•Challenges induced by climate change in GBA are in environment, health, public safety and energy.•Urban climate researches help GBA to adapt to climate change.
If we are to achieve climate change targets, transport systems need to transform. This article is concerned with the prospects of challenging the regime of automobility in urban areas. It employs a ...governmentality framework, alongside theories of automobility, in order to analyse mobility governmentalities in Gothenburg, Sweden. Gothenburg is an interesting case in the context of reducing car use given its identity as a ‘car city.’ Despite this, Gothenburg has high ambitions in terms of reducing car traffic. Reaching these goals are however associated with challenges: prognoses predict a continued increase in car traffic, and political acceptance is viewed as an obstacle. The article’s findings are based on semi-structured interviews with public officials and stakeholders, zooming in on (1) conflicting spatialities and temporalities (2) competing logics of circulation and pace and (3) mobility imaginaries of the (im)possible. We argue that while there are new logics entering urban mobility governmentalities as an effect of the climate transition, their possibilities to affect material change are confined because the movement and circulation of ‘people and things,’ ultimately represented by the private car, are closely tied to the way that freedom is exercised, understood and manifested in contemporary liberal societies.
•Stormwater management practices help to adapt to extreme rainfall events.•Green roofs, rain gardens and porous pavement are helpful to cope with heavy rains.•Creation of living space can be combined ...with water resilient planning.•Compaction by additional storeys with green roofs preferable over extra buildings.•Reduction of climate change impact of heavy rainfall with nature-based solutions.
The demand for living space is rising in growing cities. To restrict urban expansion in the outskirts, a common strategy is to densify existing neighbourhoods. Densification implies the increase of water impervious area which increases the vulnerability to flooding during extreme precipitation events. Sustainable urban drainage systems are considered as a strategy to handle stormwater runoff locally and thus relieve the sewage system. This study investigates the combined quantitative hydrological impact of densification and sustainable stormwater management measures in a residential neighbourhood in Munich, Germany. The living-lab approach pursues the application of nature-based solutions in a real planning case to achieve positive climate effects while densifying the neighbourhood. The study is based on single event simulations of three return periods with the physically based software PCSWMM. The events are implemented for both current and climate change precipitation intensities of the RCP 8.5 projection for 2040–2069. Three scenarios are implemented: a status quo, a business as usual scenario (additional buildings without compensation measures) and a best-case scenario (one additional floor with green roofs disconnected from the sewers in combination with rain gardens and porous pavements on the land parcels). The comparison between the different scenarios focuses on three main aspects of the water balance, namely, infiltration, runoff and storage. The results show that measures for sustainable stormwater management are crucial elements to cope with an increasing number of heavy precipitation events due to climate change. The best-case scenario significantly outperforms the other two concerning water infiltration, surface runoff and storage. Most notably is the impact of climate change projection rainfall intensities for 2040–2069. The outcomes for these intensities clearly show the positive impact of sustainable water-sensitive design. The results demonstrate that it is in fact possible to enhance the water balance and gain new living space simultaneously if a sustainable urban planning strategy is implemented that includes future-oriented stormwater management.
Paucity of information on Urban Canopy Parameters (UCPs) is considered as one of the major reason behind limited urban climate research and modelling in developing region of Asia, Africa, and Latin ...America. UCPs define those characteristics of urban built form which have direct or indirect influence on urban climate. Most of the studies in developed world have utilized 3-Dimension (3D) Geographic Information System (GIS) database either developed from ground survey or Remotely Sensed (RS) data such as Aerial Photographs, Airborne Light Detection and Ranging (LiDAR) and high-resolution Interferometric Synthetic Aperture Radar (InSAR) data for retrieval of UCPs. However, non-existence of 3D GIS database and limited availability of above RS datasets in developing region necessitates to employ widely available low-cost alternative datasets for retrieval of UCPs. Hence, this study focuses on retrieval of UCPs by employing Very High Resolution Satellite (VHRS) optical stereo data, which has repeat availability, low cost and extensive coverage, in a highly dense and complex urban environment with a challenging composite climate like Delhi, India. A novel methodology for extraction of gridded UCPs from VHRS optical stereo data has been developed in this study to overcome the limitation of extraction of individual building footprint in dense and compact urban built-up. The validation of key UCPs such as building height (Mean error, Root Mean Square Error (RMSE) and Mean Absolute Error <1 m in all height groups), Building Surface Area (Accuracy 84.27%) and Sky View Factor (RMSE = 0.046 and correlation = 0.94) with ground measurements has displayed reasonable accuracies. Hence, the study demonstrates successfully the use of VHRS optical satellite stereo data for generation of gridded UCPs in a highly heterogeneous and dense urban built-up environment. The developed approach is globally replicable in any city of any country.
Summertime (June–August 2015) radiative and turbulent heat fluxes were measured concurrently at two sites (urban and suburban) in Beijing. The urban site has slightly lower incoming and outgoing ...shortwave radiation, lower atmospheric transmissivity and a lower surface albedo than the suburban site. Both sites receive similar incoming longwave radiation. Although the suburban site had larger daytime outgoing longwave radiation (L↑), differences in the daily mean L↑ values are small, as the urban site has higher nocturnal L↑. Overall, both the midday and daily mean net all‐wave radiation (Q*) for the two sites are nearly equal. However, there are significant differences between the sites in the surface energy partitioning. The urban site has smaller turbulent sensible heat (Q
H) (21–25% of Q* midday–daily) and latent heat (Q
E) fluxes (21–45% of Q*). Whereas, the suburban proportions of Q* are Q
H 32–32% and Q
E 39–66%. The daily (midday) mean Bowen ratio (Q
H/Q
E) was 0.56 and 0.49 (0.98 and 0.83) for the urban and suburban sites, respectively. These values are low compared with other urban and suburban areas with similar or larger fractions of vegetated cover. Likely, these are caused by the widespread external water use for road cleaning/wetting, greenbelts, and air conditioners. Our suburban site has quite different land cover to most previous suburban studies as crop irrigation supplements rainfall. These results are important in enhancing our understanding of surface–atmosphere energy exchanges in Chinese cities and can aid the development and evaluation of urban climate models and inform urban planning strategies in the context of rapid global urbanization and climate change.
The daily (midday) mean Bowen ratio (
Q
H/Q
E) was 0.56 and 0.49 (0.98 and 0.83) for the urban and suburban sites, respectively. These values are low compared with other urban and suburban areas with similar or larger fractions of vegetated cover. Likely, these are caused by the widespread external water use for road cleaning/wetting, greenbelts, and air conditioners. At the suburban site, quite a different land cover to most suburban sites studied to date, crop irrigation supplements rainfall. Figure: Daytime (
K↓ > 5 W m−2) Bowen ratio (circle) and median 30 min daytime Bowen ratio (diamond) for each day (right hand axis) coloured by number of days since rainfall (days in legend). Daily rainfall amounts (bars) given on left‐hand axis.
Effectively addressing climate change in line with the Paris Agreement and the EU Climate Law requires the establishment of governance structures with the participation and coordination of all levels ...of government and where the local level plays a key role. This is evident with the emergence of city-to-city networks of urban policymakers and supporting initiatives such as the EU 100 Climate-Neutral and Smart Cities Mission. The purpose of this article is to demonstrate how approximately 400 European cities are shaping their governance structures to tackle the complexities of achieving climate neutrality, highlighting the key elements on which cities focus their efforts. This study analyses data collected through the Expression of Interest survey of the European Commission's 100 Climate-Neutral and Smart Cities Mission, which contains inputs directly provided by local authorities responsible for implementing climate policies. The results reveal the significant progress cities have made in adapting their governance approaches to effectively address climate challenges through for instance the institutionalisation of climate change, and the introduction of enabling and participative forms of governing with the involvement of key stakeholders in the decision-making processes. It also highlights the challenges cities face concerning climate financing and the need to unlock private investments.
•Network analysis of European cities' legal powers in climate-related sectors•Urban climate governance models necessitate continuous adjustments.•European cities face challenges when financing climate actions.•Stakeholders' collaboration is essential for urban climate transitions.
Few studies have investigated the spatial patterns of the air temperature urban heat island (AUHI) and its controlling factors. In this study, the data generated by an urban climate model were used ...to investigate the spatial variations of the AUHI across China and the underlying climate and ecological drivers. A total of 355 urban clusters were used. We performed an attribution analysis of the AUHI to elucidate the mechanisms underlying its formation. The results show that the midday AUHI is negatively correlated with climate wetness (humid: 0.34 K; semi-humid: 0.50 K; semi-arid: 0.73 K). The annual mean midnight AUHI does not show discernible spatial patterns, but is generally stronger than the midday AUHI. The urban–rural difference in convection efficiency is the largest contributor to the midday AUHI in the humid (0.32 ± 0.09 K) and the semi-arid (0.36 ± 0.11 K) climate zones. The release of anthropogenic heat from urban land is the dominant contributor to the midnight AUHI in all three climate zones. The rural vegetation density is the most important driver of the daytime and nighttime AUHI spatial variations. A spatial covariance analysis revealed that this vegetation influence is manifested mainly through its regulation of heat storage in rural land.
Urban tree planting has the potential to reduce urban heat island intensity and building energy consumption. However, the heterogeneity of cities makes it difficult to quantitatively assess the ...integrated impacts of tree planting and street layouts. Scaled outdoor experiments were conducted to investigate the influence of tree plantings on wind and thermal environments in two-dimensional (2D) north-south oriented street canyons with various aspect ratios (building height/street width, AR = H/W = 1, 2, 3; H = 1.2 m). The effects of tree species with similar leaf area index (C. kotoense, big crown; C. macrocarpa, small crown), tree planting densities (ρ = 1, 0.5), and arrangements (double-row, single-row) were considered.
Vegetation reduces pedestrian-level wind speed by 29%–70%. For ρ = 1 and single-row arrangement, C. kotoense (big crown) has a better shading effect and decreases wall and air temperature during the daytime by up to 9.4 °C and 1.2 °C, respectively. In contrast, C. macrocarpa (small crown) leads to a temperature increase at the pedestrian level. Moreover, C. kotoense raises the air and wall temperature of the upper urban canopy layer and increases the street albedo during the daytime because of the solar radiation reflected by trees. C. kotoense/C. macrocarpa produces the maximum daytime cooling/warming and nighttime warming of air temperature when H/W = 2 owing to its weaker convective heat transfer. When H/W = 3, the building shade dominates the shading cooling and tree cooling is less significant. When ρ = 1, double-row trees (C. kotoense) reduce wall and air temperatures by up to 10.0 °C and 1.0 °C during the daytime. However, reducing ρ from 1 to 0.5 weakens the capacity of daytime cooling by C. kotoense and the warming effect by C. macrocarpa. Our study quantifies the influence of tree planting and aspect ratios on the thermal environment, which can provide meaningful references for urban tree planting and produce high-quality validation data for numerical modeling.
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•Scaled outdoor experiments are tested for tree impacts in streets (H/W = 1–3, H = 1.2 m).•Tree plantings may reduce the pedestrian-level wind speed by 29%–70%.•Species with big crown get better cooling effect than small one in the daytime.•Tree planting density of ρ = 0.5 (less dense) produces higher T than ρ = 1 (denser).•Trees reduce (raise) air-wall T below (above) them due to solar shading/reflection.
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