Urban structures increase turbulence within the atmospheric boundary layer (ABL) due to increased surface roughness and create channel effects within the urban canopy that cannot be fully captured by a single measurement technique. Furthermore, operational measurements within urban structures are difficult due to limited space and nearby objects.

Doppler lidars are a preferred remote sensing tool for observing the wind profile in the ABL, but they miss either the urban canopy or the upper ABL. Pulsed Doppler lidars (PDL) are typically sensitive enough to reach the top of the ABL, but they leave an unobserved gap in the lower 50 m and cannot reliably resolve wind gradients within the lowest range gates. Continuous wave Doppler lidars (CDL) are typically limited to a maximum height of 200 m because the range is achieved by focusing the beam. To observe the entire wind profile from the surface to the top of the ABL, we deploy a PDL and a CDL in combination. For retrieving vertical 3D wind profiles, both lidars perform conical scans (VAD) around a vertical axis with a narrow 10° zenith angle, which reduces the diverting of the beams and separation of the measuring volumes along the scan. This also allows for measurements in complex terrains with obstacles like high buildings and trees.

We present measurements of the 3D wind profile obtained with a combination of PDL and CDL. Both lidars are in very good agreement with mast measurements. Results from measurements in a street canyon at an urban site (Hamburg) are presented.

How to cite: Burgemeister, F., Markmann, P., Kirtzel, H.-J., and Peters, G.: 3D wind profiling from the surface to the top of the urban boundary layer with Doppler lidars, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-685, https://doi.org/10.5194/icuc12-685, 2025.

The roughness length (z₀) and displacement height (z_d) are essential surface-layer parameters in numerical models (e.g., weather, climate, wall-modeled LES, etc.). Approaches to estimating these parameters for heterogeneous urban environments can be separated into three broad groups: rule-of-thumb, morphometric, and anemometric methods. This work evaluates the consistency of z₀ and z_d values estimated using methods from each of these groups, including examining the impacts of urban vegetation. The analysis uses data from two eddy-covariance flux towers (AmeriFlux US-INg and US-INc) in Indianapolis, IN. US-INg sits between a major highway and a vegetated suburban neighborhood, while US-INc sits over a network of intersecting highways surrounded by buildings of various shapes and sizes. Results show significant discrepancies in estimated z₀ and z_d values depending on the choice of method and the consideration of urban vegetation. In addition, no parameters estimated using any method can be used by existing similarity theories to reproduce observed surface-layer flux-profile relationships. These results are consistent with previous observational and modeling studies in urban areas, suggesting limitations in applying similarity theories to urban environments. Specifically, existing similarity theories underestimate integral velocity and length scales, and the degree of underestimation depends on stability conditions. For unstable conditions, accounting for the anisotropy of surface-layer turbulence helps reduce the biases between similarity theories and observations. Future work is needed to identify the cause of such biases for near-neutral conditions.

How to cite: Horne, J., Pan, Y., and Davis, K.: Estimating and evaluating roughness length and displacement height in heterogeneous urban environments, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-322, https://doi.org/10.5194/icuc12-322, 2025.

Accurate estimates of atmospheric boundary layer (BL) height, structure, as well as dynamics, are in important ingredient of numerical model evaluation processes. The BL structure and height are essential physical drivers for transport processes in horizontal and vertical directions, with direct implications for air-quality, climate action management assessments like source attribution and concentration thresholds. Between summer 2022 and spring 2023 we conducted an observational campaign in Zurich, Switzerland as part of the ICOS-Cities project (Pilot Applications in Urban Landscapes - Towards integrated city observatories for greenhouse gases). In this study we demonstrate the dynamics of BL height by utilizing vertical profile measurements from a pulsed Doppler Wind Lidar system as well as radiometric temperature measurements. We computed diagnostics on low-level jets, temperature inversion heights, shear layers, turbulent layers and aerosol gradients. Additionally, we used a continuous-wave Doppler Wind Lidar system to obtain data within the urban canopy layer and compared it to wind measurements obtained from co-located sonic anemometry at 100 meters above ground level. We found good agreement between the different measurement systems in general, with certain sectors being directly affected by building wake effects. We use this data to demonstrate the complexity of real-world meteorology in urban, orographically influenced environments and discuss, how the methodology of estimating BL properties affects the results obtained, highlighting opportunities and limitations of remote sensing systems in urban environments.

How to cite: Holst, C. C., Lan, C., Ponomarev, N., Hervo, M., Brunner, D., Emmenegger, L., and Mauder, M.: Urban boundary layer structure dynamics derived from remote sensing profile measurements in Zurich, Switzerland, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-787, https://doi.org/10.5194/icuc12-787, 2025.

Doppler wind lidars (DWL) offer high-resolution wind profile measurements valuable for understanding atmospheric boundary layer (ABL) dynamics and provide novel means of studying modifications of airflow over urban areas. Here six ground-based DWL, deployed in a multi-institutional effort along a 40 km transect  through the centre of the metropolitan area of Paris (France), are used to retrieve simultaneous horizontal wind speed and direction through the entire ABL. Data between different DWL systems are harmonized and quality controlled. The DWL dataset is evaluated using in-situ measurements from Eiffel Tower and radiosondes. Based on this unique dataset, we explore for different forcing weather conditions how vertical wind profiles are affected and modified by roughness and thermal effects of a large built-up area. For strong synoptic forcing along the transect, we find generally a near-surface wind reduction over the built-up city centre associated with an anti-clockwise turning of the wind direction and a subsequent acceleration downwind. For clear-sky and weak synoptic conditions more complex wind profiles emerge. This unique, spatially dense, open dataset is providing an assimilation or evaluation dataset for high-resolution weather, climate, inverse and air pollution models that resolve city-scale processes.

How to cite: Christen, A., Morrison, W., Grimmond, S., Cespedes, J., Claxton, B., Drouin, M.-A., Dupont, J.-C., Faucheux, A., Haeffelin, M., Holst, C., Kotthaus, S., McGregor, J., Masson, V., Price, J., and Zeeman, M.: Modifications of boundary layer wind profiles across the urban area of Paris measured using a transect of six ground-based doppler wind lidars, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-758, https://doi.org/10.5194/icuc12-758, 2025.

The Urban Boundary Layer (UBL) is characterized by higher temperatures and weaker airflow than its rural counterpart. This unique microclimate drives the formation of the Urban Heat Island (UHI) effect, which exacerbates the urban heat risks, particularly at night when the human body requires rest. Despite extensive research on the canopy layer UHI, the impact of mesoscale Atmospheric Boundary Layer (ABL) dynamics on the UHI intensity remains poorly understood. 

The mesoscale Low-Level Jet (LLJ) is a common nocturnal ABL phenomenon that influences the transport of moisture, atmospheric pollutants, and heat. However, experimental evidence of LLJ interactions with the UBL is still scarce, leaving a gap in understanding its impact on UHI development. Hence, this work presents a novel wind and turbulence data set that provides insights into the links between these two phenomena.

This study quantifies the interactions between mesoscale LLJs and the UBL in the Paris region (France) using two years of Doppler Wind Lidar (DWL) observations at urban and suburban sites. Results show that LLJs are frequent in summer, with characteristics varying by wind direction. Clear interactions between the LLJ and the UBL are identified. The mechanical vertical mixing generated by the LLJ influences the UHI intensity, while the urban buoyancy can increase the LLJ core height for certain conditions. In addition, the three-dimensional variability of the LLJ and its interaction with the topography and atmospheric stability is assessed through numerical simulations.

These findings highlight the role of ABL dynamics and mesoscale flows in modifying the near-surface processes of the UBL, i.e., UHI intensity and evolution. They also emphasize the impact of turbulent mixing on heat distribution and public health.

How to cite: Céspedes, J., Kotthaus, S., Toupoint, C., Thobois, L., Nagel, T., Lemonsu, A., Masson, V., and Haeffelin, M.: Summertime nocturnal Low-Level Jet in Paris and its interactions with urban heat and topography, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-902, https://doi.org/10.5194/icuc12-902, 2025.

Greening cities is one solution that local authorities are using in order to reduce residents' exposure to heat, which is a major public health issue for urban populations. Urban green spaces, known to be cool spots, are an integral part of local adaptation strategies. For example, Paris' 2024-2030 Climate Plan aims to create 300 ha of additional green space by 2050. Detailed knowledge of green spaces cooling potential and variability factors likely to influence it is needed to plan effective adaptation strategies. This is one of the aims of the PANAME measurement campaign in which an experimental set-up combining in situ surface measurements and vertical profiling of the surface layer using quadcopter drones and soundings has been deployed to measure meteorological variables in five contrasting parisian green spaces and their surrounding built-up areas along summer 2023.

The night-time near-surface cooling capacity of the green spaces relative to their surrounding built-up area has been calculated for different nocturnal vertical turbulent mixing in the urban canopy layer. For nights of low turbulent mixing, often associated with the highest daily temperatures, urban parks cool by several degrees compared with built-up areas, with differences depending on their size and vegetation. A small wooded garden square has a greater cooling capacity than a large grassy esplanade, illustrating the importance of tree cover, even for parks of less than 1 ha, in adapting cities.

For low turbulent mixing nights, the park cooling also often extends vertically over several tens of meters, where a local inversion is found. This stable park layer is not vertically constrained by the buildings surrounding the green space as it can possibly extend higher. It is also only little influenced by the green space size as it is found similarly above urban park of 15ha and garden square of less than 1ha.

How to cite: Nagel, T., Lemonsu, A., Masson, V., Goret, M., Roberts, G., Haeffelin, M., Ribaud, J.-F., Rivollet, M., Havu, M., Wurtz, J., Capo, J., Garrouste, O., de Munck, C., Kotthaus, S., Dupont, J.-C., Wallois, S., and Dumas, G.: Investigation of urban park cooling efficiency during summer inParis with drones, sondes, and ground measurements, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-938, https://doi.org/10.5194/icuc12-938, 2025.

Micro-climate conditions and air quality in the urban environment are strongly influenced by anthropogenic activities and local characteristics of the surface canopy. However, larger-scale flow dynamics also have an important impact on surface-atmosphere exchange processes and their spatio-temporal variations. While “background weather conditions” may to some extent be described through rather general categories (e.g. clear sky; low wind speed), the latter rarely portray the complexity of relevant dynamics and limit investigations of process-understanding. To better characterise the joint implications of synoptic-scale (or regional-scale) dynamics and surface-driven processes, a better monitoring of transport processes and atmospheric stratification across the urban atmospheric boundary layer is required.

Thanks to advances in atmospheric ground-based remote sensing technology and product development, vertical profiles of different key variables (wind, temperature, aerosol) are increasingly gathered by distributed sensor networks across urban areas. In the Paris Region (France), a dense monitoring network is being developed by the PANAME initiative, including a network of remote sensing instruments. Here we exploit observations from Doppler wind lidars (DWL) and microwave radiometers (MWR) to derive high-resolution data of wind, turbulence and air temperature throughout the vertical extent of the atmospheric boundary layer. The continuous profile observations in suburban and urban settings allow for a detailed mapping of atmospheric stability and dynamic mixing. Comparing a range of indicators (lapse rate, bulk Richardson number, vertical velocity variance, wind shear, mixed-layer height) and their spatial and temporal variations, it is shown that the diurnal evolution of the urban boundary layer and its vertical structure can effectively be monitored continuously.

Highlighting the importance of atmospheric boundary layer dynamics and atmospheric stratification for street level micro-climates and ventilation, the work suggests that such processes should be better incorporated in the assessment and mitigation of e.g. heat-risk or air pollution episodes.

How to cite: Kotthaus, S., Haeffelin, M., Céspedes, J., Van Hove, M., Hersent, M., Bastin, S., Ribaud, J.-F., Dupont, J.-C., Faucheux, A., Drouin, M.-A., Martinet, P., Fathalli, M., and Lemonsu, A.: Atmospheric stability and transport processes in the urban boundary layer from ground-based remote sensing profile observations , 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-900, https://doi.org/10.5194/icuc12-900, 2025.

A process-based understanding of urban atmospheric boundary layer (ABL) dynamics and surface-atmosphere feedback is central to improving the modelling and forecasting of weather, air quality, and thermal comfort, particularly in densely populated urban areas. The year-long urbisphere-Paris measurement campaign generated extensive in-situ and remotely sensed observations of the ABL. Seven Vaisala CL61 automated lidar-ceilometers (ALC) were operated on a 120 km transect along the predominant wind direction (SSW-NNE), from the rural periphery both up- and downwind of central Paris. The high signal-to-noise ratio CL61 observations are used to derive mixed layer height (MLH).  We find significant changes in MLH between locations along the transect that exceed inter-CL61 differences. 

With along-transect wind, the observed ABL is modified as air moves into, across, and beyond the metropolitan area. To understand surface-atmosphere feedbacks, the differences in MLH between urban and rural locations along the transect are explained with differences in turbulent heat fluxes measured by multiple eddy-covariance towers at contrasting urban, peri-urban and rural sites along the transect.

Spatiotemporal differences in MLH are analysed for different synoptic conditions. During typical clear–sky summer days an elevated MLH over both the urban area and downwind in comparison to upwind. MLH differences are most pronounced in afternoon/evening, with a maximum difference of 12 % for upwind vs urban/downwind. Over the city, the MLH grows earlier and faster, and collapses later than upwind. MLH growth and collapse at downwind sites varies with increasing distance from the city. At the most remote downwind site, MLH growth rates are similar to upwind sites, but evening collapse is even later than at the urban sites, suggesting that excess buoyancy is advected downwind.

How to cite: Looschelders, D., Christen, A., Grimmond, S., Kotthaus, S., Bignotti, L., Dupont, J.-C., Haeffelin, M., Hilland, R., Loubet, B., Morrison, W., and Zeeman, M.: Spatial variations in mixed-layer height along a rural-urban transect in Paris in relation to surface heat fluxes, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-636, https://doi.org/10.5194/icuc12-636, 2025.

The dynamics of the Atmospheric Boundary Layer (ABL) play a crucial role for the transport of heat, moisture, and pollutants within urban environments. In this study, we use long-term observations from ground-based remote sensing to examine indicators of ABL dynamics for multiple cities in Europe. Two independent methods are employed to monitor the Mixed Layer Height (MLH): (1) aerosol-based layer detection using observations from automatic lidars and ceilometers (ALC) and (2) turbulence-based layer detection that exploits profiles of the vertical velocity variance obtained from Doppler wind lidar (DWL) measurements. We compare aerosol-derived layer heights at the European scale and layer heights from both methods at a suburban and an urban site in the Paris region.

While the general agreement of the layer results obtained with these two approaches gives  confidence to the automatic MLH detection, a detailed comparison provides valuable insights into the relationship between instantaneous mixing and aerosol vertical transport. We present an extensive analysis of MLH variability across diurnal to seasonal timescales as well as spatial variations at European and regional scales. Particular attention is given to the morning evolution of the MLH, examining its dependence on nocturnal atmospheric stratification and the presence and characteristics of the Low-Level Jet (LLJ). By integrating high-resolution lidar observations with advanced analysis of mixing processes, this work contributes to a better understanding of urban climate dynamics and provides a framework for studying the interactions between the city and boundary layer processes. 

The study is linked to the RI-URBANS project and the European Research Infrastructure ACTRIS, the ABL testbed project implemented at AERIS with support of the European COST Action PROBE, and the PANAME initiative in the Paris Region (France).

How to cite: Van Hove, M., Kotthaus, S., Adam, M., Apituley, A., Cespedes, J., Bouffies-Cloche, S., De Haij, M., Drouin, M.-A., Dupont, J.-C., Faucheux, A., Gouveia, D., Hersent, M., Laplace, C., Miladi, L., O'Connor, E., Ollier, R., Pirloaga, R., Trules, J., and Haeffelin, M.: Variations in urban boundary layer height at regional and European scales from lidar network observations, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-903, https://doi.org/10.5194/icuc12-903, 2025.

How to cite: Fenner, D., Christen, A., Grimmond, S., Kotthaus, S., Meier, F., and Zeeman, M.: Year-round urban modifications and urban-plume effects of the mixed-layer height, boundary-layer clouds, and fog revealed by a ceilometer network in Berlin, Germany, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-425, https://doi.org/10.5194/icuc12-425, 2025.

The urban surface interacts differently with the overlying atmosphere compared to natural surfaces, resulting in phenomena such as the urban heat island and the urban breeze. Water availability is a key factor governing the energy exchange between the surface and the atmosphere. Evaporation diverts energy from heating the air and requires both energy and water. However, few studies explicitly focus on this coupling between the surface energy and water balance.

Here, both observations and models are used to explore how water influences the urban climate by bridging these balances. Water storage serves as the source of evaporation during dry periods, but estimating its capacity is challenging due to its fragmented nature. Eddy-covariance observations from 14 cities reveal the recession after rainfall, providing insights into how much water is stored. Water storage capacity appears to be significantly lower in cities than in natural areas.

Focusing on a single city, we link neighborhood-scale evaporation dynamics to patch-scale observations and conceptual models. Eddy-covariance footprint modeling enables this connection by accounting for the dynamic surface cover composition. Large-eddy simulations demonstrate that this composition is highly sensitive to the location of the eddy-covariance measurements. These same observations are often used to evaluate urban land surface models. Despite the inherent link between the water and energy balance, urban land surface models do not simulate evaporation more accurately when they include improved water balance representations. This discrepancy may be explained by human modeling error or differences in model components beyond the water balance. Enhancing the water balance could involve ensuring water balance closure and revising the runoff parameterization.

As water is directly relevant to the urban climate, urban water management must consider its effects on energy exchange. This knowledge has the potential to contribute to the creation of more livable cities.

How to cite: Jongen, H., Steeneveld, G.-J., Grimmond, S., Lipson, M., Meier, F., Vulova, S., and Teuling, R.: Bridging balances: water and energy in the urban climate, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-36, https://doi.org/10.5194/icuc12-36, 2025.

Ultrasonic anemometers have been the cornerstone in observing momentum, heat and scalar fluxes near the surface. Urban life, between tall and dense buildings has raised questions about the usefulness of flux observations at the surface. The strict regulations for weather stations misrepresent the effects of the urban environment. Therefore, we are faced with the conundrum of how to take flux measurements higher up in the urban canopy, where the effect of the quasi-surface urban parameters are still representative to the atmospheric boundary layer processes. While vertical soundings with gradient methods and aerial observations can give us flux measurements, they are almost always too far from the urban environment both horizontally and vertically.

A series of experiments combining mobile and stationary observations employing sonic-anemometer-equipped bicycle and drone were conducted. Along an urban river, a bicycle is used in a one-dimensional path to assess the quality of the flux measurements of a moving observer compared with two static observers. A drone was flown in three-dimensional (3D) space to observe 3D turbulent fluxes. Taylor’s hypothesis of frozen turbulence is what provides insight into vertical transport. This research investigates the extent to which Taylor’s hypothesis, within reason, holds true for a moving observer, while also assessing the departure from ground truth and the possibility of correcting these signals.

How to cite: Makedonas, A., Inagaki, A., and Kanda, M.: Mobile Urban Turbulent Flux Measurements, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-560, https://doi.org/10.5194/icuc12-560, 2025.

The concentration of humans in cities has led to various environmental issues such as the urban heat island effect, urban rain island effect, and substantial emissions of greenhouse gases. Flux observations can provide valuable insights into urban surface-atmosphere interactions, which would help mitigate these environmental problems. In this study, we choose a typical middle-rise campus in a hot and humid city, i.e., Wuhan in central China, an international wetland city, as our test bed. To the best of our knowledge, there is a lack of relevant research in Wuhan. Therefore, we deployed the first EC tower with a height of 10m on the top of a 22.1-meter-high building. This study systematically investigates urban land-atmosphere exchanges using datasets from the EC tower, including air temperature, humidity, wind velocity, carbon dioxide flux, net radiation(Q*), sensible(Q_H) and latent(Q_E) heat fluxes, etc., as well as anthropogenic activity data, such as traffic scheme and building energy consumption. First, we used typical analytical footprint models proposed by Kljun et al. and Kormann & Meixner to analyze the diurnal and seasonal changes in the flux source area. Second, anthropogenic heat flux(Q_F) was simulated using a large-scale urban energy model(i.e., LUCY), while storage heat flux(Q_S) was estimated through an objective hysteresis model (OHM). Then, we conducted an energy balance closure analysis.  Finally, we analyzed the spatiotemporal evolution patterns of urban heat, moisture, and carbon fluxes to further our understanding of two fundamental questions: (1) how will anthropogenic and biospheric contributors influence urban heat, moisture, and carbon fluxes? (2) how will meteorological factors affect urban heat, moisture, and carbon fluxes? The objective of this study is to provide a scientific basis and decision-making insights for promoting sustainable urban development.

How to cite: Zhou, Z. and Song, J.: Investigating urban land-atmosphere exchanges of heat, moisture, and carbon via eddy covariance measurements, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-197, https://doi.org/10.5194/icuc12-197, 2025.

Observations of turbulent heat and momentum fluxes over urban landscapes are crucial for understanding urban climate processes and for evaluating urban meteorological models. These observations are particularly valuable for the verification and calibration of urban canopy models, which aim to parameterize such fluxes in weather and climate models. However, collecting these data requires the installation and maintenance of eddy-covariance masts situated above roof level, making such efforts financially and labor-intensive, and consequently rare. For instance, the recent large-scale international project Urban Plumber managed to gather data from only 20 urban masts worldwide (Lipson et al., 2022б https://doi.org/10.5194/essd-14-5157-2022). Notably, this dataset lacks sites in cold climate cities, particularly those within continental temperate and subarctic regions.

In this context, we present initial insights into the turbulent heat and momentum fluxes over the city of Tomsk in Western Siberia, facilitated by a new regional network of eddy-covariance masts entitled Tomskfluxnet. This network has been under development since 2022 and currently comprises two urban masts located in built environments of different types, along with several rural sites around the city, enabling an analysis of urban-rural differences in turbulent fluxes. Measurements are conducted using Russian-made sonic anemometers AMK-4, developed by the Institute of Monitoring of Climatic and Ecological Systems in Tomsk. Preliminary analysis of three years of data indicates that heat and momentum fluxes in the city significantly exceed background values—by tens of percent, and in some cases several times—during both summer and winter seasons. Notably, during winter, the monthly mean sensible heat flux exceeds 50 W/m² over the city, contrasting sharply with near-zero rural values.

The study was supported by Russian Science Foundation Project no. 24-17-00155.

How to cite: Varentsov, M., Telminov, A., Kobzev, A., Kapustin, S., Drozd, I., Pashkin, A., and Repina, I.: Turbulent fluxes over a cold climate city in Siberia: insights from a new flux tower network, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-1021, https://doi.org/10.5194/icuc12-1021, 2025.

The urban boundary layer is generally warmer, richer in aerosols, and experiences an increased frequency of convective clouds. Consequently, incoming shortwave and longwave radiation fluxes are expected to be modified over and possibly also downwind of cities. Previous field studies have attempted to quantify this effect, but were limited to urban-rural station-pairs. However, a two-station approach makes it difficult to disentangle regional patterns, urban and plume effects. To more comprehensively isolate urban effects and assess whether there are detectable influences by the thermal and aerosol plume of a large city on incoming radiative fluxes in the downwind area, we established a 10 station network with actively ventilated thermopile pyranometers and pyrgeometers in the Paris metropolitan area. Stations were operated to measure global (GHI) and longwave hemispherical irradiance (LHI) between April 2023 and March 2024. With three sites in the built-up area (on roofs) and seven in a ring 55±7 km from Paris city centre, representative background upwind and downwind locations are sampled. Five sites had sun trackers to quantify diffuse and direct shortwave irradiance. Radiometers were calibrated side-by-side and tested regularly using a roving master calibration system during field operations.

Despite inherent spatio-temporal variability, we find that for all-sky weather conditions, total GHI is reduced over the city, by about 3% in summer and 1 % in winter (average -10 W m-2 at 12:00). During clear-sky midday conditions, decreased direct and increased diffuse irradiance over the city are observed. LHI is elevated over the city, particularly during evenings (average +5 W m-2 at 20:00, differences up to +30 W m-2 during clear sky conditions). There is limited evidence from individual cases at 50 km downwind when LHI is elevated compared to upwind. 

How to cite: Christen, A., Morrison, W., Hilland, R., Antaluca, E., Badosa, J., Grimmond, S., Haeffelin, M., Legain, D., Looschelders, D., Masson, V., and Zeeman, M.: Urban boundary layer effects on incoming shortwave and longwave fluxes over and downwind of Paris, France, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-1053, https://doi.org/10.5194/icuc12-1053, 2025.

In-situ measurements in cities are crucial for studying the physical processes that occur within them, which impact on key aspects such as the increased temperatures in the city centre compared to their rural surroundings, as well as air quality. It is widely known that meteorology plays a significant role in the daily fluctuations of pollutants, especially those variables related to atmospheric dispersion. Furthermore, these measurements are essential for the accurate evaluation of numerical simulations carried out in urban environments.

This work will present data from four intensive measurement field campaigns carried out in Madrid, Spain, during the years 2020 and 2021, both in winter and summer, near two public buildings (a university and a hospital). The results obtained from various instruments will be provided, offering a comprehensive analysis of the meteorological conditions observed during the campaigns, including both synoptic and local factors. The specific meteorological conditions of each campaign were linked to the pollutant concentrations observed in the area. Additionally, turbulent measurements obtained from sonic anemometers installed at different locations will be considered.

In this sense, the winter 2020 field campaign included a particularly stable period during which turbulence typically decreased in the evening, leading to the highest observed NO₂ concentrations during the four field campaigns. However, under these stable conditions, thermally-driven winds were also observed later at night, enhancing pollutant dispersion and leading to a reduction in pollutants concentration. The interaction between turbulence and pollutant levels will be further analysed, focusing on the role of the different dynamic processes in the evolution of NO₂ concentrations. Understanding these interactions is essential for improving urban air quality and assessing the impact of meteorological factors on pollution dynamics.

How to cite: Sastre, M., Román-Cascón, C., Ortiz-Corral, P., Carbone, J., Cicuéndez, V., Sánchez, B., Martilli, A., Artíñano, B., Gómez-Moreno, F. J., Díaz-Ramiro, E., Alonso-Blanco, E., Narros, A., Borge, R., and Yagüe, C.: Impact of turbulence and meteorological conditions on air quality in Madrid (Spain) analysed through field measurement campaigns, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-519, https://doi.org/10.5194/icuc12-519, 2025.

Although the UHI has been widely investigated, UHI studies on cities in mountainous regions are limited. Previous studies have shown that mountainous cities in hot climates have unique environmental characteristics and relatively cool temperatures. Rapid urbanization followed by urban and global warming has begun to take a toll on the climatic conditions of these cities. Understanding the mechanism of the UHI in mountainous cities is challenging science due to the complex relationship between urban structure, urban landscape, varied topography and elevation.

The study aimed to monitor the formation of the Urban Heat Island (UHI) effect in Jerusalem, a city situated in a Mediterranean mountainous region near a desert frontier. The research sought to investigate the various landscape factors influencing spatial temperature variations, considering aspects such as landscape characteristics, local topo-climatic conditions, and elevation. Given the impact of complex urban topography on atmospheric conditions, the study aimed to identify systematic correlations between these factors and UHI intensity.

The methodological approach is an integrative one which includes multiple methods: Firstly, a Local Climate Zone (LCZ) classification. Secondly, meteorological observation data was collected based on official meteorological stations in and around Jerusalem. Thirdly, synoptic and atmospheric conditions are being studied using a semi-objective synoptic classification and meteorologic and statistical tools.

Our findings demonstrate a strong correlation between synoptic conditions and the intensity of the urban heat island (UHI) in the Jerusalem mountains, governed by complex topographic influences and localized meteorological processes. During stable summer nights, UHI intensity can reach up to 6°C due to thermal inversions but may also be negligible, in accordance with the Israeli summer paradox. Unlike typical UHI dynamics, our results indicate that UHI in this region is more pronounced in summer than winter.

How to cite: Goldberg, A. and Potchter, O.: The Urban Heat Island of a Mountainous Mediterranean City with a Desert Frontier; The Case of Jerusalem, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-633, https://doi.org/10.5194/icuc12-633, 2025.

Climate change poses escalating risks to urban populations, particularly in tropical regions where vulnerability is projected to rise, as highlighted in the IPCC's Sixth Assessment Report. Among these risks, the Urban Heat Island (UHI) effect—marked by elevated temperatures in urban areas relative to their rural surroundings—is amplified by  urban densification. However, research on UHIs and their impacts remains limited in tropical settings, especially on small islands where unique climatic and geographic conditions exacerbate the issue.

This study delivers the first detailed analysis of urban overheating impacts at the district scale on Reunion Island. Using a network of low-tech environmental sensors, we conducted high-resolution in situ measurements of key atmospheric variables, including air temperature, relative humidity, wind speed, and solar radiation. These microscale observations allowed for a precise assessment of the spatial variability of heat within the urban fabric and enabled the calculation of thermal comfort indices to fully capture the effects of urban overheating.

Preliminary results show that despite its modest population of approximately 850,000, Reunion Island exhibits a significant UHI effect, with temperature differentials exceeding 2°C between urban and rural areas. Furthermore, shading plays a critical role in mitigating heat stress, as evidenced by differences in the Universal Thermal Climate Index of up to 5°C between shaded and unshaded zones within the same neighborhood. These findings highlight the importance of incorporating shading, vegetation, and optimized urban morphology to enhance outdoor thermal comfort in tropical climates.

By demonstrating the value of in situ environmental observations in understanding urban overheating challenges, this study provides actionable insights for policymakers and urban planners. It underscores the importance of targeted mitigation strategies, such as increasing vegetation coverage and promoting natural ventilation, to reduce the impacts of UHIs in tropical island urban environments.

How to cite: Lefevre, A., Malet-Damour, B., Boyer, H., and Rivière, G.: In-situ observations for analyzing urban overheating in tropical island contexts: A case study from Reunion Island, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-79, https://doi.org/10.5194/icuc12-79, 2025.

The TRAMS (Temperature Rome bus ATAC Monitoring System) experiment aims to study the temperature field across the city of Rome and its surroundings with the fine spatial resolution of individual streets. This is achieved through temperature measurements collected by microsensors (MetroTracker) mounted on the roofs of buses operated by ATAC, Rome’s main public transportation agency. These sensors continuously record temperature and other parameters as the buses travel through the city. The data enable an in-depth analysis of the city's microclimatic variations, influenced by urban morphology, including tree-lined and non-tree-lined streets, urban canyons, proximity to parks and water courses, and other factors. This information is crucial for urban planning, public health, and environmental management, especially in the context of increasing heat events and their implications for urban populations. A comprehensive analysis of these data has allowed us to investigate the spatiotemporal dynamics of the urban heat island (UHI) and the cooling effect of roadside trees. The results reveal a diurnal cycle of UHI intensity consistent with findings from previous studies, with nighttime peaks reaching up to 5°C. Additionally, a significant inverse correlation is observed between tree density and daytime temperatures, with areas of high tree density averaging approximately 1°C lower temperatures.

How to cite: Cecilia, A., Marinelli, L., Conidi, A., Casasanta, G., Conte, M., Petenko, I., Iurato, J., and Argentini, S.: The Temperature Rome bus ATAC Monitoring System (TRAMS), 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-779, https://doi.org/10.5194/icuc12-779, 2025.

This study explores the urban microclimate in the historic center of Málaga, Spain, focusing on how construction materials, urban morphology, and surface characteristics influence localized temperature variations. The research was conducted between June 24 and July 5, 2024, using a Fluke TI400 thermal camera and a bicycle-mounted measurement system to capture spatially detailed thermal data. Measurements followed the Picassian route of Málaga at two critical times: 11:00 a.m. and 11:00 p.m., providing insights into both diurnal and nocturnal temperature profiles.

The analysis of thermal data from building façades and pavements identified significant temperature variations linked to material properties, façade height, and urban density. High-density areas, with limited vegetation and impermeable surfaces, retained more heat during summer nights, exacerbating the urban heat island (UHI) effect. These findings emphasize the role of urban morphology and material choices in shaping local microclimates and thermal comfort levels, particularly in Mediterranean cities like Málaga.

To mitigate these impacts, the study recommends targeted urban design interventions, including increasing vegetation, using permeable pavements, incorporating high-reflectance materials, and adding shading elements in heat-prone areas. These strategies, tailored to Málaga’s climate, aim to reduce heat stress, improve thermal comfort, and enhance urban resilience to climate change. This research contributes valuable knowledge on urban microclimate dynamics and provides a framework for sustainable urban planning in Mediterranean environments.

How to cite: Forestieri, G., Peña Acosta, M., Jato-Espino, D., and Tomatis, F.: Analysis of the Urban Microclimate in the Historic Center of Málaga: Mitigation Strategies Adapted to the Mediterranean Climate, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-181, https://doi.org/10.5194/icuc12-181, 2025.

Rapid urbanization and global warming exacerbate urban heat stress, demanding innovative approaches to understanding cities’ thermodynamics. Land Surface Temperature (LST) is an important parameter in urban overheating studies as it can be related to heat storage, which contributes to elevated air temperatures and increased thermal stress. LST is commonly derived from satellite images, but this technique is limited by cloud cover and low spatial resolution. Our study presents a novel methodology for estimating LST at the pedestrian level based on mobile monitoring integrated with fixed weather station data to drive high-resolution urban microclimate simulations and provide detailed LST. Specifically, air temperature data was gathered using a wearable system to ensure it was monitored near pedestrians. These data were integrated with air temperature registered with fixed weather stations (located above the canopy level) to obtain daily temperature profiles within the urban canyon. These values, together with a QGIS-generated 3D model of an urban area, were then used as input in the high-resolution urban modeling software ENVI-met, which provided the LST with a high spatial resolution (5m). This methodology was applied in three case studies in New York City (East Side, Financial District, and Queens), with mobile monitoring sessions conducted twice a day during the summer and fall of 2024. The modeled areas were approximately 240m × 120m to optimize the simulations. The LST estimated with the proposed framework demonstrated a strong correlation with satellite measurements, validated by GOES-16 and LANDSAT-9 data, with RMSE values ranging from 1.93K to 2.66K and uncertainty bands overlapping 88-96%. Moreover, the proposed method was effective in determining LST under all weather conditions, unlike satellite measurements. The primary contribution of this research lies in establishing a validated framework for obtaining high-resolution LST data at the pedestrian level, contributing to enhanced urban climate resilience through improved thermal monitoring.

How to cite: Cerquetelli, S., Jacoby Cureau, R., Pigliautile, I., Bonafoni, S., Ramamurthy, P., and Pisello, A. L.: A Novel Pedestrian-Level Approach to Land Surface Temperature Estimation Using Wearable Environmental Monitoring and Urban Microclimate Modeling, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-499, https://doi.org/10.5194/icuc12-499, 2025.

The City of Linz identified heat stress as a strong climate hazard for its inhabitants. To improve knowledge about local characteristics of heat stress, potential measures, and its consequences, a meteorological monitoring network, focusing on the parameter air temperature is to be implemented. The network will consist of approx. 50 monitoring stations optimally placed with respect to several requirements: (1) representative measurements for similar regions within the city area, (2) show the variety of urban microclimate conditions, (3) include strategically reasonable sites, (4) use available mountable infrastructure (masts, public buildings) and (5) represent extreme conditions within each similar region.

An innovative research design identified a set of well-suited locations for the monitoring stations, incorporating established methods and approaches in urban climate research. It considers the following elements: (i) calculation of an urban climate simulation with PALM for a typical summer day with a spatial resolution of 10 m providing the data about heat stress conditions in the city, (ii) application of the concept of Local Climate Zones (LCZ) to define similar regions in the city, (iii) consideration of locations for potential mountable infrastructure, (iv) definition of a set of criteria for sites in each LCZ (e.g. low nighttime air temperature, sun exposure).

Performing aforementioned steps confirms that PALM is well-suited for simulating entire city areas to depict local meteorological characteristics. Further, combining the concept of LCZ with PALM output provides valuable insights into the effect of small-scale difference within the same urban typology. Incorporating the local knowledge of the participating department of urban climatology and environment ensured the applicability of the gained results. The study provides an illustrative example of how city-scale urban climate simulations deliver valuable data to support practical challenges of city management, and further highlights opportunities and benefits of close cooperations between local decision-makers and research institutions.

How to cite: Schneider, M., Bügelmayer-Blaschek, M., Tötzer, T., Horak, J., Peßenteiner, S., and Acquah, C.: Supporting site selection for a meteorological monitoring network in the City of Linz (Austria) , 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-115, https://doi.org/10.5194/icuc12-115, 2025.

With two-thirds of the world's population expected to live in urban areas by 2050, the exacerbating urban heat island effect is a critical challenge, affecting thermal comfort, public health, and air quality. Urban green spaces (UGS) serve as a crucial tool for mitigating the adverse impacts of urbanisation by regulating microclimates through evapotranspiration and shading, improving air quality by reducing pollutant concentrations, and fostering biodiversity. Beyond these regulating ecosystem services (ES), different human-place concepts show that a close connection between humans and their natural environment is essential to people's well-being.

However, there is a paucity of research on how these ES vary across different UGS and under various meteorological conditions. This study, funded by the German Research Foundation under contract 471909988, aims to provide a climatological characterisation of six different UGS in Augsburg, Germany. These include an urban park, a mixed forest, a beech-dominated forest, a pine forest and a heath. A measurement network comprising 33 MX2301A HOBO loggers was established in late 2023 to quantify the climatic differences between the study sites. These ongoing stationary measurements thus cover one complete annual cycle and provide high-resolution air temperature and relative humidity data at the sub-hourly scale. The study uses, among other approaches, a two-way analysis of variance to quantify the effect of different forest characteristics on the local climatic conditions while considering large-scale weather types as an additional factor. Additionally, the study assesses the impact of seasonality, particularly summer heat stress.

This climatological characterisation of UGS provides a foundation for a more detailed analysis, incorporating thermal walks through the UGS, thereby collecting mobile climate data, human health signals and subjective perceptions. This allows for the potential determination of whether "climatic" forest types are also "human physiological" and "therapeutic" forest types.

How to cite: Simon, J., Stocker, M., Falkenrodt, L.-M., and Beck, C.: Beyond Cooling: A Comprehensive Climatological and Human Health Assessment of Augsburg‘s Urban Green Spaces, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-679, https://doi.org/10.5194/icuc12-679, 2025.

Establishing public parks in new residential suburbs is a good way to mitigate urban heat and provide green space for nature connection, social recreation and exercise. However, understanding what drives when, and by how much, a park is cooler than the surrounding built residential landscape is key to designing and managing public parks for climate change adaption.

We established a climate sensor network across three small public parks in new residential landscapes of Western Melbourne, Australia. LoRaWAN gateways and three sensor networks were established at 1.5 m to measure microclimate conditions at a human-scale within and around these three parks for five months continuously from Summer into Winter.  The driving variables of background air temperature, wind speed, wind direction and solar radiation were modelled to understand how often and under what conditions a significant PCI developed and how far the cooling benefit could extends from the park.

Daytime PCI intensity remained <1.0°C and showed a positive response to solar radiation and background air temperature of the day, and a weak negative response to increasing windspeed. In the mid-afternoon (3 pm) PCI intensity could be as great as 2.0°C.  The need to standardise how PCI phenomena are studied is discussed in light of these models and the impact of different sensor network configurations.

How to cite: Livesley, S., Woods, E., and Cheung, P. K.: IoT sensor networks at a human-scale: Understanding what drives suburban Park Cool Islands, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-584, https://doi.org/10.5194/icuc12-584, 2025.

How does urban space shape small-scale pedestrian thermal environments in the context of intense heat? To answer this research question, various mobile sensing techniques are proposed recently. However, the assessment of thermal environments at pedestrian level is complex because of physical urban heterogeneity, highly variable microclimate conditions and dynamically changing environmental factors. Therefore, high spatio-temporal resolution data is needed, which implies adapted sampling frequency, low sensor inertia and suitable data post processing methods.

In this context, this work aims to present the portable meteorological measuring prototype, Comfy’PACK (Comfort Pedestrian Assessment of CitywalKs), to improve microclimate and pedestrian thermal comfort zoning in a dynamically changing physical urban environment. The wearable device consists of air temperature, humidity, solar radiation, wind speed and mean radiant temperature sensors, a GPS and a thermal camera. The experimental site is an identified future de-sealing site in the city of Nantes (France), aiming to improve local outdoor thermal comfort. After a detailed physical characterisation of pedestrian pathways on site, mobile measures are repeated over several days, investigating transitions between different thermal ambiances.

In this work we present the prototypes’ performances and its first application to an urban case study, evaluating small scale microclimate and thermal comfort conditions for pedestrians in relation with urban heterogeneity. Thermal comfort indicators are calculated, questioning their pertinence within various thermal environmental contexts. Data mapping will allow establishing a more detailed microclimate comfort zone classification. As part of the French research project PERMEPOLIS the findings will support the methodological development of soil de-sealing strategies and identification of alternative cool walking path in the urban space.

How to cite: Stavropulos-Laffaille, X., Faurie, T., Rodler, A., Permalnaick, M., Bonetti, R., Noel, T., Berlin, S., Herpin, S., and Musy, M.: Comfy’Pack : Assessing urban microclimate conditions and outdoor thermal comfort at pedestrian scale, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-130, https://doi.org/10.5194/icuc12-130, 2025.

Amidst the warming climate, it is crucial for urban planners and policymakers to identify which adaptation strategies effectively reduce outdoor urban heat stress. To address this need, high-resolution meter-scale observations alongside numerical models are essential. However, such detailed heat stress observations are scarce, creating a gap in our ability to explore the micro-environmental effects of adaptation on heat stress and to validate the high-resolution heat stress models. This gap is addressed by conducting a dense meter-scale measurement campaign in the urban fringe of Ghent (Belgium) during a heat wave. The campaign evaluates consumer-grade portable AT-HTS01 devices against advanced Campbell meteorological stations, which measure all components of heat stress explored with wet bulb globe temperature (WBGT). Additionally, thermal infrared imaging was employed to correlate these measurements with surface temperatures. The findings demonstrate that the consumer-grade sensors closely match the accuracy of sophisticated research-grade equipment in assessing WBGT, affirming their utility in urban heat studies. The analysis highlights that building and tree shade can significantly reduce daytime WBGT by up to 5 °C, while at night, WBGT values are 0.8 °C lower over unpaved surfaces compared to paved surfaces. These insights emphasize the effectiveness of strategic urban design, such as optimized tree placement and reduced paving, in lowering heat stress and enhancing climate resilience. Besides the insights in the micro-environmental heat stress variations, the meter-scale in-situ observational data from this campaign serve as a crucial resource for validating high-resolution numerical heat stress models, such as the UrbClim-HiREx model exemplified in this study. UrbClim is a fast urban boundary layer model for long-term urban climate simulations at 100-meter resolution with a downscaling HiREx heat stress module calculating WBGT at meter-scale resolution considering individual building and tree shades.

How to cite: Hellebosch, I., Top, S., Souverijns, N., Takacs, S., De Ridder, K., and Caluwaerts, S.: Enabling Urban Climate Model Validation with Meter-Scale Heat Stress Observations, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-134, https://doi.org/10.5194/icuc12-134, 2025.

Mobile micrometeorological measurements provide insights into how environmental conditions and urban morphology interact with humans, particularly in terms of thermophysiological comfort, thermal sensation, and pleasantness. While other indirect factors may also influence thermal comfort, these are beyond the scope of this study.

A compact mobile weather station equipped with sensors, a data logger, and GPS was developed to collect environmental data required to calculate the Universal Thermal Climate Index (UTCI) for an entire year. During the missions, 292 questionnaires on thermal sensation and pleasantness were also gathered. The study aims to assess how specific weather conditions and urban morphology influence thermophysiological comfort, thermal sensation, and pleasantness. Only the summer results used for the present abstract.

Geospatial analysis revealed that compact urban areas, namely with high urban density (UD) and represented by Local Climate Zones (LCZ) 1, 2, and 3, were associated with higher UTCI values (+-1ºC, per comparison with other urban classes), and 11 identified UTCI hotspots across five study areas. This UD impact on UTCI was particularly evident on avenues (6 hotspots). Surveys indicated lower perceived thermal comfort in compact urban areas.

Average daytime UTCI was 5.5% lower in the city compared to its rural surroundings, with inverse patterns at night (44% higher). Certain weather patterns were found to affect UTCI more significantly, and the western part of the city, near the Atlantic Ocean, exhibited lower UTCI without hotspots. However, this area was perceived as unpleasant due to higher wind speeds. In the easternmost areas by the Tagus estuary, wind direction influenced UTCI more markedly. Areas with greater biomass demonstrated lower UTCI scores.

Modelling showed that strategically planting trees could mitigate and revert a UTCI hotspot situation, as demonstrated for one study area.

How to cite: Silva, T., Matias, M., Vasconcelos, J., and Lopes, A.: Thermal comfort through climate walking technique: The experience in Lisbon , 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-82, https://doi.org/10.5194/icuc12-82, 2025.

The thermal impact of vehicle surfaces on urban climate is a critical yet understudied component, with the potential to influence local microclimates and the urban energy balance. This research quantified the thermal effects of vehicle surfaces in Lisbon, Portugal, through a combination of in situ measurements and parametric modeling. Using a compact mobile weather station equipped with precise sensors, we conducted both mobile and stationary measurements to capture detailed data on the radiative properties of vehicle surfaces. Results revealed significant variations in surface temperatures based on vehicle color. Black vehicles reached a median surface temperature of approximately 71°C, about 20°C higher than white vehicles, which had a median surface temperature of 45°C. This difference in heat absorption directly affected local air temperatures: black vehicles increased surrounding air temperatures by around 2.5°C on a summer day, while white vehicles caused a more moderate rise of 1°C. Black vehicles also exhibited the highest median net all-wave radiative balance (752.8 W/m²), while white vehicles showed much lower values (515 W/m²), illustrating darker vehicles’ greater thermal load and localized heating effects. When exposed to direct sunlight, dark grey vehicles showed the highest radiative balance values (median 680 W/m²), while white vehicles demonstrated the lowest values, confirming their reflective nature. To complement field measurements, we conducted thermal simulations using EnergyPlus integrated with Honeybee for Grasshopper. These simulations, calibrated with site-specific meteorological data, were used to assess whether the 3D EnergyPlus models could replicate real-world conditions. The results validated observed trends and deepened understanding of vehicle characteristics’ role in influencing surface and air temperatures. This study bridges the gap between empirical data and simulations, offering valuable insights for urban climate research and informing mitigation strategies to reduce urban heat island effects.

How to cite: Matias, M., Silva, T., Girotti, C., Mills, G., and Lopes, A.: Thermal Impact of Vehicles in urban canyons: Integrating Field Observations and Parametric Modelling in Lisbon., 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-25, https://doi.org/10.5194/icuc12-25, 2025.

Climate change presents significant challenges for urban areas including critical threat to citizen’s health and thermal comfort. To enable equitable transformation of urban spaces urban stakeholders increasingly adopt data-driven approaches. Within the Data2Resilience (D2R) project we designed a biometeorological observation network at city scale in Dortmund to provide near real-time data to support data-driven approaches. For the network design we considered relevant parameters, such as the urban structure represented by Local Climate Zones, the population density, relief, green and blue infrastructure, public spaces of particular interest, and among further expert knowledge. Existing guidelines on network design and metadata collection were considered to achieve comparability of the measurement data across the Dortmund city area and possible future networks in the Ruhr-Region.

To ensure long-term maintenance and uptake of data driven approaches by the city, the network was implemented in city ownership. The installation of the biometeorological measurement equipment was coordinated in close cooperation with the city administration and the Smart City Dortmund in particular. The continuation of the network will be done through integrating the network infrastructure as well as the data pipelines into the existing structure of the Dortmund city administration, streamlining management and maintenance coordination.

The D2R biometeorological observation network is designed to support equitable climate resilience efforts in Dortmund. Further the D2R network’s spatial distribution contributes to the increased representation and visibility of vulnerable and undersupplied hot spots in Dortmund. Besides the design and implementation of the network first results will be presented.

How to cite: Hüser, C., Weickhmann, L., Kittner, J., Reinhart, V., Sismanidis, P., and Bechtel, B.: Data2Resillience – Real-time biometeorological observations for thermal comfort assessment at city scale, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-1013, https://doi.org/10.5194/icuc12-1013, 2025.

Urban trees contribute to summer cooling by offering solar shading and evapotranspiration. But their relative significance is still unclear due to the challenges in directly measuring tree evapotranspiration rate or latent heat flux (Q_E) in actual urban environment. Concurrently, high-quality experimental data are still required for the validation of urban canopy model simulations. For this purpose and as a novelty, this study directly measures the tree evapotranspiration (or Q_E) and shading effects in street canyons (building height/street width, H/W=1 or 2, H=1.2m), using scaled outdoor experiment in a subtropical region, i.e. suburban Guangzhou, China, from August to October 2022. Results show that urban trees (leaf area index: 3.5) can effectively deliver surface temperature reductions beneath the tree canopies up to 5.1℃ as H/W=1 and 8.2℃ as H/W=2, while slightly raise air temperature by less than 2.0℃ above tree canopies. Energy flux comparison indicates tree shading dominates the primary cooling mechanism, with up to 97% of incoming solar radiation (800Wm^-2) intercepted, while tree evapotranspiration plays a secondary role, with a rate of less than 1.6g/min and a latent heat flux below 90Wm^-2. Additionally, trees decrease street air velocity by up to 63.6%, and increase of water vapor pressure by up to 2.77hPa.

How to cite: Wu, Z., Shi, Y., Ren, L., and Hang, J.: Scaled outdoor experiments to assess impacts of tree evapotranspiration and shading on microclimates and energy fluxes in 2D street canyons, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-170, https://doi.org/10.5194/icuc12-170, 2025.