Urbanization influences the local climate by changing the natural surface energy balance affecting the regional temperature field. One of the best-known and widely studied phenomenon is the canopy layer urban heat island (CL-UHI) which is found in cities of all sizes. Specifically, night-time temperatures are often higher in urban areas than in the surrounding rural areas. The CL-UHI characteristics differ between cities, within a city and with time of the day and the season. Climate change induced warming in cities is similar to that experienced in rural areas, but modified by the CL-UHI.

The CL-UHI is an additional heat burden on top of background anthropogenic warming, and therefore an increasing focus of urban planners. Given this development, and in response to the request of the 18th World Meteorological Congress (Resolutions 32 and 61), experts from WMO GAW (Global Atmosphere Watch) Urban Research Meteorology and Environment (GURME) initiated in 2020 an expert team inviting more than 30 world-wide experts to contribute to a guidance on measuring, modelling and monitoring the CL-UHI [1]. Topics include a clear definition of the CL-UHI and clarifications of what it is not, causes of the CL-UHI (e.g. meteorological and morphological influences), methods to assess the CL-UHI intensity (measurements, modelling approaches) as well as CL-UHI application examples. The guidance also explains why the CL-UHI mitigation is only part of an answer to reduce urban heat problems. The guidance will serve as a useful reference for meteorologists, climatologists, meteorological administrative staff, and others interested in the CL-UHI.

[1] WMO (2023): Guidance on Measuring, Modelling and Monitoring the Canopy Layer Urban Heat Island (CL-UHI).

K.H. Schlünzen, S. Grimmond, A. Baklanov (edts.), World Meteorological Organisation, WEATHER CLIMATE WATER. 2023 edition. WMO-No. 1292, pp.88.
https://library.wmo.int/doc_num.php?explnum_id=11537 last used 11.04.2023

How to cite: Schlünzen, K. H., Grimmond, S., Baklanov, A., Martilli, A., Masson, V., Miao, S., Ren, C., Roth, M., and Stewart, I.: A new guidance on measuring, modelling and monitoring the canopy layer urban heat island, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-240, https://doi.org/10.5194/ems2023-240, 2023.

The urban heat island (UHI) is a well-known effect where the temperature is higher in a city compared to a rural area, defined as the temperature difference between an urban and a rural location. This is a challenging phenomenon because it exacerbates the heat stress on human health in addition to the on-going global warming. It is therefore important to understand temporal changes in the UHI effect in a warming climate. To examine the UHI effect intensity and variability, we use 40 years (1980-2019) of observational data (daily maximum, minimum, and mean temperature) from the Global Summary of the Day (GSOD), consisting of about 1000 stations of varying temporal extend, spanning the Middle East and North Africa (MENA) region where a faster warming rate has occurred than the other regions globally.

The challenge in using data with such spatial and temporal extend is the need to allow for heterogeneities between each of the two stations used to define an urban-rural pair. For instance, one has to allow for the distance between the pair, elevation differences, spatial changes in urbanization as well as the distance from the coast. Here a new method is proposed based on flexible statistical methods (Generalized Additive Models –GAMs) to quantify the temporal trend in the UHI effect while allowing for the aforementioned characteristics using regression splines of appropriately defined variables.

A composition of high-resolution satellite geospatial information related to urbanisation properties and population data was utilized from the Global Human Settlement (GHSL-SMOD), in order to characterise the stations in terms of their urbanization type. This was also used to quantify changes in the extend of urbanisation in an area surrounding the rural stations. Results indicate a consistently upward trend of the UHI effect, particularly at night time (Tmin), across all four seasons.

How to cite: Tzyrkalli, A., Lazoglou, G., Constantinidou, K., Economou, T., and Hadjinicolaou, P.: Quantification of the Urban Heat Island effect using paired station data in the Middle East and North Africa region, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-13, https://doi.org/10.5194/ems2023-13, 2023.

Recently, the nexus between urban microclimate, outdoor and indoor thermal comfort, the following linked urban energy demands, and the corresponding CO₂ emissions footprint has garnered significant attention from both the scientific community and individuals responsible for decision making. The need to establish a low-carbon society and reduce human impact on the environment requires the consideration of potential environmental consequences associated with urban form changes in cities, particularly in relation to planning and development strategies. The World Urban Database and Access Portal Tools (WUDAPT) collects information on the physical geographies of urban areas worldwide for the benefit of the scientific community. This study proposes a novel methodology on how to translate geographically-based information through the Local Climate Zone (LCZ) classification, into a complete gridded numerical information for atmospheric numerical modeling or multi-resolution post-treatment. This is done so that numerical modelers will be able to make use of and capitalize on the vast amount of data that is available to them. In order to examine the relationship between the urban form and the CO₂ emissions footprint, we used the Metropolitan London area as a case study. In addition, the Principal Component Analysis was used to investigate the connection between the type of urban development and the amount of CO₂ emissions. The key conclusion of our analysis suggests that sparser arrangement of buildings, as indicated by lower λ⁠_p values, is associated with a decrease in CO⁠₂ emissions. Moreover, the potential of this study lies in utilizing the materiality of individual buildings and their corresponding energy requirements to achieve energy efficiency, which aligns with the objectives of WUDAPT Level 1 and 2.

How to cite: Mouzourides, P., Eleftheriou, A., Kyprianou, A., Ching, J., and Neophytou, M.: Exploring spatial heterogeneity for land use and local climate zones interactions using multi-resolution analysis, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-635, https://doi.org/10.5194/ems2023-635, 2023.

The expansion of urban areas significantly modulates the local climate in cities. In this regard, in the last few decades, there has been a non-negligible increase in the urban areas and the urban population of Türkiye. This study aims to assess the impact of increasing urbanization on the current warming trend which is highly dominated by human-induced climate change. The findings of this study are substantial for sustainable urban planning and future climate studies using temperature observation data. The urban-minus-rural (UMR) method, which has been widely used in urban heat island (UHI) studies, is applied to determine the effect of urbanization on temperature change. In the UMR method, in order to detect the urbanization effect more precisely, the meteorological stations should be properly classified into urban stations and rural stations that have been used as reference stations. In previous studies conducted in Türkiye to determine the impact of urbanization on the warming trend, station classification was done with population data. However, population information does not provide direct information about the extent of urban areas around the stations. Thus, the CORINE (Coordination of Information on the Environment) dataset from 1990 to 2018 was used to directly determine land cover information around the stations. Compared to average temperatures and maximum temperatures, minimum temperatures are more sensitive to the urban heat island effect. Therefore, the daily minimum temperature data of the stations in Türkiye between 1980 and 2022 was used as temperature data. The determination of the change in urban areas around the station was done by placing circular buffers on each station. The correlation coefficient between the change in the urban area within the buffer placed over the stations and the temperature trend of the stations was examined with increasing buffer radii. The radius where the urbanization effect is most pronounced was determined to be 8 km. As a result, statistically significant trends were detected in urban stations in the specified period interval; also, these stations showed a large urbanization effect and urbanization contribution, reaching 0.57°C per decade and 85%, respectively.

How to cite: Türkmen, D. E. and Önol, B.: The Contribution of Urbanization to the Current Temperature Trend in Türkiye, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-341, https://doi.org/10.5194/ems2023-341, 2023.

In this research, we outline the main thermo-hygrometric characteristics of local climate zones (LCZs) identified in four of the largest cities in north-eastern Romania (Iași, Bacău, Botoșani, and Suceava), which together have a population of over 1 million inhabitants. The urban structure of these cities could be considered typical for medium size cities in Eastern Europe, being characterized by their recent development, with residential and industrial areas developed intensively in the communist period, followed nowadays by the conversion of decaying industrial areas in commercial units and a new phase of largely unorganized residential expansion.

We used the LCZ Generator to assess local climate zones in these cities, resulting in the identification of eight LCZs, with the largest extension being specific to compact midrise and open midrise, covering approximately 40% of the cities' surface. The accuracy of the LCZ delimitation ranges from 0.80 to 0.90.

We described the thermo-hygrometric features within the identified LCZs using in-situ observations, mobile measurements, and LANDSAT LST products. We used 30 in-situ observation points for air temperature and humidity with hourly temporal resolution to describe the major features of LCZs. We also made two mobile measurements monthly between May 2022 and April 2023 for each city, during clear sky conditions, in the early morning and the first part of the night, in order to spatially cover the diversity of LCZs. The thermo-hygrometric profile of LCZs was completed with LANDSAT LST data analyzed for 1983-2021, enabling a multiannual trend analysis of the two main LCZs in the analyzed cities. 

We grouped the study results by advective and radiative conditions using a Self-Organizing Maps method for atmospheric circulation. We also explored the thermo-hygrometric features of the two main LCZs using EUROCORDEX data for 2025-2100. The main output of this analysis indicates that the magnitude of changes identified in either moderate or extreme climate scenarios overwhelms the differences observed nowadays between the current conditions imposed by each local climate zone.

The results of this study synthesize the progress made in assessing urban climate conditions in the cities of North-Eastern Romania, in the framework of UCLAR project, and are intended to serve as a basis for mitigation policies to be developed by local and regional stakeholders for the sustainable development of these cities in the actual context of climate change. 

Acknowledgement: This work was supported by a grant of the Ministry of Research, Innovation and Digitization, CNCS - UEFISCDI, project number PN-III-P1-1.1-TE-2021-0882, within PNCDI III. 

How to cite: Sfica, L., Ichim, P., Crețu, C.-S., Amihaesei, V.-A., Bistricean, P.-I., Hritac, R., Irasoc, A., and Mihaila, D.: Thermo-hygrometric characteristics of Local Climate Zones (LCZs) in the primary urban areas of north-eastern Romania investigated through multivariate tools, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-291, https://doi.org/10.5194/ems2023-291, 2023.

How to cite: Canton, J. and Dipankar, A.: Analysis of the Swiss urban climate over the past five years, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-144, https://doi.org/10.5194/ems2023-144, 2023.

Studying urban climate in cold climate cities is essential for understanding the implications for urban sustainability. Recent research has found that urban areas in high northern latitudes experience intense and persistent positive temperature anomalies, known as urban heat islands (UHI). Heat accumulation from year to year creates a cumulative UHI effect that fundamentally changes the environment and soil properties, affecting vegetation productivity and the length of the growing season. The warmer urban climate has significant implications for the urban economy, environment, and human health, particularly in light of global climate change in the cold climate regions. This study analyzes land surface temperature data in the seven largest cities in the European Arctic, ranging in population from 50,000 to nearly 300,000 and spanning four countries and three bioclimatic zones. The results indicate persistent temperature anomalies every season in the 1–5 ◦C range, with the largest city, Murmansk (Russia), showing the highest values. The study also finds a strong inverse relationship between surface UHI intensity and temporal variability. The more substantial the surface UHI, the more stable it is and the lower its temporal variability. We found no general direction of surface UHI change in the long term. The study also suggests that compact and dense urban infrastructure has a more significant impact than the geographical setting of the city on UHI. Understanding the intensity and variability of UHI in these regions is crucial for developing sustainable urban planning and management strategies to mitigate the negative impacts of UHI on the environment and human health.

How to cite: Miles, V., Esau, I., and Miles, M.: Understanding Cold Climate Cities: Implications for Urban Sustainability, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-544, https://doi.org/10.5194/ems2023-544, 2023.

Urban areas are becoming more vulnerable with their growth and an increasing number of heatwaves caused by anthropogenic climate change. Differences in the surface structure, such as between green spaces and sealed surfaces, cause differences in surface energy budget due to the different heat storage capacity, resulting in a high inner-city air temperature variability.

Initial conditions of NWP models do not accurately represent air temperatures in urban areas, since official (WMO) ground weather stations are typically located in city outskirts where air temperatures are lower than in the city center. Hence, the urban heat island effect is not fully resolved in NWP models which results in an underestimation of urban air temperatures. Since the urban air temperature variability occurs on a micro-scale, state-of-the art NWP models, with resolution in the order of a few km, are not able to resolve the air temperature field.

This study focuses on the development of the meteoblue city-climate model (mCCM), a dynamic statistical downscaling model which was developed to resolve the urban heat island effect and the small-scale air temperature variability in urban areas.

The mCCM is based on a high-resolution model domain with 10 m horizontal resolution and trained on air temperature data from measurement networks. These networks are operated by the municipality or based on crowdsourcing and help understanding the air temperature variability and dynamics in an urban environment. To resolve the differences in the surface energy budget, surface texture parameters are derived from the polar-orbiting, high-resolution satellites Sentinel-2 and Landsat 8. Further improvement is achieved with the parameterization of the coefficients of the statistical model, which depend on the prevailing meteorological conditions. The trained model is then fully driven by meso-scale NWP models and thus independent of any air temperature measurements, which allows a direct forecast of high-resolution air temperatures in urban environments.

Through statistical downscaling, the mCCM can resolve the urban heat island effect and the inner-city air temperature variability, reducing the bias to almost 0 K. Implementing the parameterization, the model considers dynamic processes which makes the model sensitive to different meteorological conditions and further reduces the hourly MAE by at least 25 % compared to NWP models.

The mCCM allows more reliable and location-specific air temperature forecasts in cities for the upcoming six days for areas where vulnerable groups live, such as hospitals, kindergartens, or schools. The approach helps decision-makers to improve the heat wave management in their cities and allows data-driven decisions.

How to cite: Bader, N., Schlögl, S., and Gutbrod, K.: High-resolution air temperature forecast for urban heat wave management, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-379, https://doi.org/10.5194/ems2023-379, 2023.

The newly developed Parallelized Large-Eddy Simulation Model for Urban Applications (PALM-4U) has been applied for the city of Vienna to simulate thermal conditions in urban environment and to evaluate its performance using different modelling configurations as well as variable spatial scales.

Model simulations were carried out for a representative clear-sky heat day in August 2022 for the entire city of Vienna with a spatial resolution of 20 m and for a selected residential area in the city with a spatial resolution varying between 1 and 10 m. The data related to geographical information and urban structures are based on high-resolution GIS data provided by the city of Vienna, including multi-purpose area map, street tree cadastre, digital elevation and surface model, which were combined with the national land cover data (Land Information System Austria - LISA) to account for the unresolved vegetation and Open Street Map to include building properties in surrounding areas of the city. Selected model configurations enable evaluation of model performance both on micro-scale taking into account variable building types, resolved vegetation and detailed surface properties as well as on city-scale including interaction with regional weather conditions and complex terrain.

The results for hourly air temperature were compared with the conventional weather stations of the national weather service and the city of Vienna. In addition, quality-controlled data from more than 1000 citizen weather stations from the company Netatmo available in Vienna were used to compare differences in temperature variability and spatial patterns. The results show high intra-urban variability during daytime, but distinct spatial pattern during the night.

In order to evaluate the temperature variations on micro-scale, a measurement campaign at the headquarter of the Austrian weather service using 25 low-cost weather stations equipped with LoRaWAN Dragino LHT65 sensors was conducted. The stations were positioned in the vicinity of different artificial and natural surfaces (e.g. grass, parking lot, street) and structures (e.g. concrete and green roof) and the retrieved data were used to evaluate temperature variations in the high-resolution model setup. Both, measurements and the model results, show high variability in air temperature during daytime and higher temperatures near building structures than vegetation. Due to extremely dry conditions, natural surfaces, such as free soil or low grass show high daytime temperatures as well.    

How to cite: Zuvela-Aloise, M., Hahn, C., and Hollosi, B.: Evaluation of the urban climate model PALM-4U with conventional and non-conventional monitoring data for a case study Vienna, Austria, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-205, https://doi.org/10.5194/ems2023-205, 2023.

The high-density building environment and complex, heterogeneous landscape in Hong Kong result in significant spatial variability of local temperatures, winds and other weather elements down to the street level.  To enhance meteorological observation and forecasting services, the Hong Kong Observatory (HKO) has been actively developing an urban-scale weather observing network in recent years through in-house efforts and collaboration with local communities.  In this presentation, a novel real-time monitoring network, based on economical sensors deployed at various sites within the urban areas, providing basic temperature and relative humidity measurements will be introduced.  They are found to provide useful data for analyses of daily temperature variations in urban areas under very hot or prolonged heat stress episodes.  The new observations offer indispensable meteorological information and reference for studies of urban micro-climate and the impact of heat stress on public health or activities.  The data of the urban-scale weather monitoring network are then utilized to generate location-specific hourly forecasts of air temperatures and relative humidity for the next nine days through post-processing of downscaled forecasts from the global NWP models.  It is found that the mean absolute errors of daily minimum and maximum temperature forecasts at the urban-scale monitoring network stations are generally within 2 degrees Celsius in the next 5 days.   The real-time forecast products have been launched to public since mid-2022 on HKO’s Automatic Regional Weather Forecast web portal.   The automatic urban-scale forecast shows useful information for the public and serves as potential early alert for communities to get prepared for potential heat stress brought by the very hot weather in the next few days.  The methodology and recent development of the forecast products will be presented, including artificial intelligence technique to consider different meteorological factors for improving forecast of daily minimum and maximum temperatures, as well as machine learning methods to generate urban-scale forecasts under different weather regimes.

How to cite: Kwok, Y., Lau, S. P., Wong, W., and Lee, O. S.: Development of Real-time Urban-scale Weather Monitoring Network and Experimental Hourly Temperature Forecasts in Hong Kong, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-369, https://doi.org/10.5194/ems2023-369, 2023.

Urban areas are particularly affected by climate change effects such as heat or droughts. The high percentage of dark and impervious surfaces leads to high radiation absorption and low evaporative cooling. Negative consequences for urban dwellers will significantly increase in future due to a higher frequency of extreme heat and drought events. At the same time, the high demand for new infrastructure and housing results in an increasing trend of sealed surfaces which is expected to continue in the next decades in many European agglomerations. To reconcile the requirements for climate change adaptation and urban development, strategies are needed to improve infiltration and evapotranspiration as well as decrease shortwave radiation absorption. Unsealed areas can 1) increase surface albedo in contrast to sealed asphalt or concrete roads and pavements, and 2) allow for bare-soil evaporation or evapotranspiration if vegetated, and thus increase latent heat flux and simultaneously reduce sensible heat flux. Furthermore, unsealed urban soils contribute keeping the water in the system of a city for longer time periods. This can reduce flooding and drought effects and improve the urban microclimate through more and longer-lasting evapotranspiration from unsealed soil water storages. Adaptation potentials and thermal effects of unsealing measures depend on many factors such as their size, structure or physical surface properties. The implementation of new unsealed areas is largely limited by urban structural constraints, development and traffic usage. Thus, adaptation potentials of different unsealing approaches must be assessed based on the given local conditions to achieve the best possible cooling effects during heat and droughts. Our study aims to investigate the effects of unsealing surfaces on the urban microclimate using scenario analyses. The high-resolution physically-based 3D ENVI-met model was used for a densely-developed residential research area in Cologne/Germany. The model simulations are driven by our local meteorological measurements and validated using our dense microclimate sensor network within the study area. To evaluate the potentials of various unsealing strategies on air temperature, permeable surfaces are parameterized and implemented in the setup model domain according to the given spatial constraints of the study area. Based on a simulation of the current sealed status quo, three unsealing scenarios are assessed: 1) natural bare-soil unsealings in traffic-free areas, 2) vegetated lawn unsealings in traffic-free areas, as well as 3) usage compatible unsealing measures in private spaces and low-traffic areas (courtyards, little frequented side streets, parking areas) by implementing grass grid pavers, while all main roads remain sealed. The model simulation results of the current situation are compared to the unsealing scenarios with respect to changes in the simulated air temperature. Significant differences were identified. These findings have important implications for urban planning aiming to mitigate future heat stress, droughts, flooding and improve thermal comfort. 

How to cite: Eingrüber, N., Domm, A., Korres, W., Löhnert, U., and Schneider, K.: Climate change adaption potentials of unsealing strategies in cities – An assessment during heat and drought events based on microclimatic simulations, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-525, https://doi.org/10.5194/ems2023-525, 2023.

Cities play a fundamental role in climate at local to regional scales through modification of heat and moisture fluxes, as well as affecting local atmospheric chemistry and composition, alongside air-pollution dispersion. Vice versa, regional climate change impacts urban areas and is expected to increasingly affect cities and their citizens in the upcoming decades. To assess the impact of cities and urban structures on weather, climate, and air quality, a modeling approach is commonly used and the inclusion of urban parameterization in land-surface interactions is of primary importance to capture the urban effects properly. This is especially important when going to higher resolution, which is a common trend in the operational weather forecast, air-quality prediction as well as regional climate modeling. As the most of population is living in the cities and the share is increasing, we need a proper description of urban processes to assess impacts within the cities and the effectiveness of adaptation and mitigation options applied in cities in connection with climate change as well as the urban heat island itself. This is critical in connection to extreme events, for instance, heat waves with extremely high temperatures exacerbated by the urban heat island effect, in particular during night-time, with significant consequences for human health. In the City of Prague, this can achieve about 4-5°C.

This is studied in the local project PERUN in very high resolution (convection-permitting) to localize climate change scenarios for the City of Prague. The potential of such simulations for urban heat island adaptation and/or mitigation options assessment and planning is studied within the project IMPETUS4CHANGE, where the City of Prague is one of the so-called Demonstrator City, where proof of concept will be evaluated. Connection to the air quality interaction is considered as well.

How to cite: Halenka, T., Belda, M., Huszar, P., Karlicky, J., and Dhib, S.: Climate Change Scenarios and Prediction Localization for City of Prague, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-618, https://doi.org/10.5194/ems2023-618, 2023.

We use analogues of atmospheric patterns to investigate changes in the three most devastating Acqua Alta (flooding) events in the lagoon of Venice associated with intense Mediterranean cyclones occurred in 1966, 2018 and 2019. Our results provide evidence that changes in atmospheric circulation, although not necessarily anthropogenically driven only, are linked to the severity of these events. We also evaluate the cost and benefit of the MoSE system, which was designed to protect against flooding. Our analysis shows that the MoSE has already provided protection against analogues of the most extreme events, which occurred in 1966, while for 2018 and 2019 events our analysis is non-conclusive because of the lack of analogues situations of those events.  These findings have significant implications for the future of Venice and other coastal cities facing similar challenges from rising sea levels due to extreme events. Our study represents one of the first examples that goes beyond identifying the circulation drivers of extreme events to quantifying the changes and their impacts. The framework we presented is general and can be applied to other case studies. However, our study also has limitations, including the limited database of sea-level for the past, the limited analogues used, and the fact that we did not use climate models. Despite these limitations, our study provides important insights into the attribution and impacts of extreme events, which are crucial for developing effective mitigation and adaptation strategies. We hope that our work will inspire future research and inform policymakers in their efforts to reduce the risks associated with extreme events.

How to cite: Faranda, D., Alberti, T., and Coppola, E.: Attributing Venice Acqua Alta events to a changing climate and evaluating the efficacy of MoSE adaptation strategy, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-26, https://doi.org/10.5194/ems2023-26, 2023.

Urbanization significantly alters a region's land surface properties, which in turn modifies the surface energy balance, having an impact on the climate at the local, regional, and global levels. In particular, urban areas experience higher temperatures compared to their rural surroundings which in combination with humidity have an effect on the quality of the citizens’ lives. Wet-bulb temperature (WBT) is an essential and widely used metric to assess the effects of humid heat. A WBT of 35◦C is considered to be the survivability limit, and prolonged exposure beyond this value could be deadly even for the fittest of humans. The region of eastern Mediterranean and the Middle East (EMME) is highly susceptible to high WBT values, especially in densely populated areas, where humid heat events with WBT≥35◦ C are projected by the end of this century. It is therefore crucial to assess the projected levels of humid heat over this particular area.

This work uses the Weather Research and Forecasting (WRF) model to simulate climate over the EMME coupled with the bulk urban parametrization and NoahMP land surface scheme. The simulations are performed at 4 km horizontal resolution for a recent past (2000-2004) and a future (2056-2060) period driven by the Representative Concentration Pathway (RCP) RCP 8.5. The aim of this study is to investigate how the simulated minimum, minimum and wet bulb temperatures are projected to change in the future during the summer period over the EMME region and, more specifically, over eleven cities located in the region of interest. The simulated summer climatologies of the two periods of time of the maximum and minimum temperatures are derived from hourly timeseries, which are then to calculate the WBT using also the relative humidity by the model output.

How to cite: Constantinidou, K. and Hadjinicolaou, P.: How thermally comfortable are cities in the EMME region simulated to be in the future?, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-381, https://doi.org/10.5194/ems2023-381, 2023.

Due to climate change and urbanization, the world's population is increasingly exposed to extreme heat, posing a threat to public health. Despite people spending ~90% of their time indoors, heat effects in buildings have been studied far less than outdoor heat island effects. This study aims to observe, understand and model the behaviour of indoor air temperatures (T_in) during summer heat. As a proof of concept, we present and analyse up to 27 years of individual T_in timeseries of seven citizen weather stations (CWS) across the Netherlands. First, we find that typically T_in increases slower, but also cools down slower than T_out with a lag difference of ~130 minutes in the diurnal cycle. We demonstrate that nocturnal indoor human thermal comfort (HTC) can be worse than outdoor HTC even for days after a heatwave.

Second, to model T_in behaviour, we simulate six-hour changes in T_in behaviour with a physics-based statistical model by Vant-Hull et al. (2018) that has an outdoor conduction, indoor conduction and solar transfer component. Preliminary results of this computationally-fast model for each of the seven houses are promising, showing on average a R-squared of 0.74 and a root mean squared error of 0.13 K. Third, we are also interested in how T_in may evolve due to climate change. We study this by converting the T_in measurements to 2050 and 2085 values based on the Royal Netherlands Meteorological Institute 2014 climate scenarios.

Finally, in the next research step, we will scale up our proof-of-concept analyses to 100 indoor CWS placed in Amsterdam. The participating households receive a CWS for three years to measure their indoor climate – temperature, relative humidity, CO₂ concentrations – in the bedroom and living room. Based on our insights, we will make recommendations for climate-sensitive urban design to reduce indoor heat stress.

How to cite: Peerlings, E., van Esch, M., Poolman, H. R., and Steeneveld, G.-J.: Heatwave impacts on urban indoor air temperature assessed through citizen science observations in the Netherlands, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-389, https://doi.org/10.5194/ems2023-389, 2023.

 
Reconstruction of Emissions from Pottery Kilns in the Roman Period

Clemens Drüe (1), Michael Herdick (2) and Holger Schaaff (2) 

1) Universität Trier, Umweltmeteorologie / environmental meteorology, Trier, Germany (druee@uni-trier.de)
2) Leibniz-Zentrum für Archäologie (LEIZA), Mainz and Mayen, Germany

Thanks to modern filtering techniques, the loading of exhaust gases from industrial plants in Europe has been steadily decreasing over the last sixty years. Prior to that, emissions had been steadily increasing since the Middle Ages. Although the effects of industrial metal production in ancient Rome and China can be traced worldwide, most emissions before the modern era were negligible on a global scale. On a regional or local scale, however, pollution may have been severe, as historical sources suggest. Given the complete lack of data, however, it is not clear a priori whether the small size and production volume of the historical industry or the lack of pollution control combined with the high number of small sources is the predominant factor.

Roman pottery kilns provide a rare opportunity to shed light on this question. Experimental studies in reconstructed kilns of the Leibniz Center for Archaeology in Mayen, Germany, provide data on productivity and fuel consumption in this important industry. Such pottery kilns were located throughout the Roman Empire. However, production in Mayen, Germany, was of particular importance because of the high thermal shock resistance of the goods produced. 
Another important pottery production place was in and around Herforst (municipality of Speicher) near Trier. Recent studies have suggested that there existed  more than 200 roman potteries. This makes it one of the largest known industrial areas of antiquity.

We have used these experimental data to predict one year's emissions. Based on the resulting source strengths, we simulated the pollutant load using AUSTAL, Germany's regulatory model for emission forecasting.  Various kilns in different locations in and around the city of Mayen as well as several of the scattered kilns in the Roman industrial area near Herforst were simulated. Initial results show a strong dependence on night-time weather conditions and suggest that air pollution was not negligible and may have influenced the potteries' choice of location.

How to cite: Drüe, C., Michael, H., and Holger, S.: Reconstruction of Emissions from Pottery Kilns in the Roman Period, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-49, https://doi.org/10.5194/ems2023-49, 2023.

How to cite: McGrory, M., Hertwig, D., Lo Piano, S., Ramirez-Mendiola, J. L., Smith, S. T., Paskin, M., Liu, Y., and Grimmond, S.: Dynamic Anthropogenic actiVities and feedback to Emissions (DAVE): – An agent based model for heat and exposure to other anthropogenic emissions, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-147, https://doi.org/10.5194/ems2023-147, 2023.

Methane, a potent greenhouse gas with a relatively short atmospheric lifetime and the potential for rapid, targeted abatement, is gaining importance for near-term climate action.

Despite that Urban Areas cover <2% of the Earth’s surface, they are responsible for either anthropogenic or natural a large fraction of CH₄ emissions from different types of sources. Urban Areas are responsible for a large fraction of GHG emissions (30 to 40% of global anthropogenic emissions), including methane from the different types of sources.

Usually, urban studies are generally focused on gas leaks from natural gas networks, domestic networks, combustion systems, landfills, wastewater (sewer systems) and road transport.

However, CH₄ emissions have a high degree of uncertainty and aquatic systems in Urban Areas are generally neglected in the literature. Also, the Romanian national GHG inventory does not report Urban Areas emissions of CH₄.

Our study is a preliminary identification of urban sources for CH₄ emissions in Cluj-Napoca, the second most populous city in Romania, based on a simple detection of gas leaks, CH₄ content in aquatic systems.

Tunable Diode Laser Absorption Spectroscopy (TDLAS) with resolution of 0.1 ppmv were used to determine the atmospheric concentrations of gas at different points of potential sources of CH₄ around the city. Also, gas from water samples was analyzed via head-space extraction and the CH4 laser sensor of TDLAS.

This study has revealed that more than 76% of the natural gas distribution points and more than 39% sewer man-holes have values higher than the estimated background. All water samples are almost over-saturated with CH₄, which means that the aquatic ecosystems represent a potential source of CH₄ fluxes into the atmosphere.

These results indicate that flux measurements and sources attribution of CH₄ are required for further investigation of all CH₄-bearing systems.

How to cite: Hmoudah, M., Baciu, C., and Pop, C.: Potential Sources of Methane Emissions in Urban Areas, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-652, https://doi.org/10.5194/ems2023-652, 2023.

Heatwaves are increasing in both intensity and frequency every year. In urban areas, the urban heat island (UHI) effect exacerbates this impact, with significant consequences for city dwellers and urban ecosystem functions. This work evaluated the impact of urbanization on thermal comfort in Turin, a city in the North-West region of Italy bordered by the Alps to the west and hills up to 600m high to the east. Two numerical simulations were performed: one representing a real-case urban scenario and another idealized simulation where all urban surfaces were replaced with dense forest. The real-case scenario used weather research and forecast models (WRF) with a multilayer urban canopy model (MLUCM) and was simulated over a heatwave (HW) period in June 2019. High-resolution urban land use/land cover data was taken from local climate zone (LCZ) maps provided by the World Urban Database and Access Portal Tools (WUDAPT) repository. The simulation was validated with data from ARPA meteorological stations located in the region. The lower root mean squared error of air temperature and higher index of agreement showed that the simulation was in good agreement with observational data. Results from both simulations were used to study the effect of urbanization on UHI phenomena by comparing the real case with the ideal simulation where no urban area was present. The study revealed that urbanization had the greatest impact on UHI during nighttime, with a maximum deviation of 5°C, while its effect was less during mid-day, with a maximum deviation of 1.2°C. Furthermore, an average temperature increase of 3°C was found in the city center due to urbanization compared to the idealized simulation.

Keywords
Urban heat island (UHI), WRF/MLUCM, heatwave (HW), Urban Microclimate

How to cite: Pauly, L., Ferrero, E., and Canonico, M.: Evaluating the Impact of Urbanization on Thermal Comfort in Turin: A Numerical Simulation Study, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-62, https://doi.org/10.5194/ems2023-62, 2023.

The proportion of the world’s population living in cities has increased from 37% to 56% over the last 50 years, and it is expected to continue rising further to 60% by 2030 (UN, 2022). As an essential part of this evolution, urban land cover has expanded rapidly. It is well established that urbanization reduces the vegetated cover and modifies surfaces properties altering the surface-atmosphere interactions compared to rural areas. Therefore, analyzing the impact of the past changes in urban land cover contributes to understand the potential risks that urban residents might face considering the future urban grown and the expected rising of air temperatures, as this has adverse impacts on human health, livelihoods, and key infrastructure.

Our objective is to examine the impact of Madrid's urban growth in the last 50 years (1970-2020) on local climate. A modeling study is carried out using the Weather Research and Forecasting (WRF) model, where land use and land cover have been modified according to each decade's urban expansion from 1970 to 2020. Two representative scenarios of extreme meteorological conditions are selected for this study: a period of intense heatwave during the summer season and a short period of strongly stable atmospheric conditions in winter. In areas where the urban fraction increased significantly, the model results reveal an increase of 1-2 ºC in 2 m air temperatures during the day and approximately 4-6 ºC at night in summer. In contrast, smaller differences are obtained at night for the winter period, probably due to the presence of thermally driven buoyancy flows generated during the night under stable conditions. The current results also indicate how these changes from non-urban to urban land cover over time have altered the surface energy balance system in Madrid over the last 50 years. And in turn, it reveals the relative contribution of urbanization and anthropogenic heat emissions to the warmer temperatures observed in cities compared to rural areas.

How to cite: Carbone, J., Sánchez, B., Román-Cascón, C., Yagüe, C., and Martilli, A.: How has the urban development of Madrid affected the local climate? Analysis ofthe last 50 years, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-16, https://doi.org/10.5194/ems2023-16, 2023.

The Eastern Mediterranean and Middle East (EMME) region is an exceptionally thermally vulnerable area, projected to suffer from frequent and severe heat waves in the coming decades. Process-based numerical simulations of the urban climate can provide a cost-effective assessment of urban overheating with greater spatial and temporal resolution than in-situ observations. High-resolution numerical simulations are crucial to assess the impacts of climate change on the urban thermal environment in cities. In this study, the Weather Research and Forecasting (WRF) model was used to dynamically downscale the regional scale (12km) to the local scale (1km) and thus derive high-resolution data for the 2m air temperature and land surface temperature over Nicosia, Cyprus which is located in the EMME region. The simulation was driven by the ERA5 re-analysis, over a three-year period. The WRF model was coupled with the Single Layer Urban Canopy Model (SLUCM) parameterization for a better representation of the urban characteristics of Nicosia. Detailed information on the urban form was inserted into the model through the creation of the Local Climate Zones classification scheme. An evaluation of the simulation results with observation data was performed in terms of annual, monthly, and seasonal values as well as of the capability of the model to identify the urban heat island effect. Following, simulated land surface temperature and spatial patterns were compared with observations from different satellites over Nicosia. Finally, air and surface urban heat island intensity and diurnal dynamics were evaluated using in-situ measurements, reanalysis data, WRF simulations, and remotely sensed thermal observations.

How to cite: Koutroumanou-Kontosi, K., Cartalis, C., Hadjinicolaou, P., Constantinidou, K., and Agathangelidis, I.: Modelling and Evaluating the Urban Thermal Environment of Nicosia through the Combined Use of WRF and Satellite Observations, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-531, https://doi.org/10.5194/ems2023-531, 2023.

How to cite: Vurro, G., Constantinidou, K., and Hadjinicolaou, P.: Evaluation of WRF model PBL schemes for highly resolved WRF-BEP/BEM simulations over Nicosia urban area, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-14, https://doi.org/10.5194/ems2023-14, 2023.

The increase in the resolution of atmospheric models for numerical weather prediction and climate simulations allows for a more accurate description of the physical processes at urban scale. Furthermore, a common trend is occurring in most countries: the number of people living in towns keeps on growing remarkably, therefore it becomes increasingly important to study the living conditions in urban or metropolitan areas under demographic and climate change.

In these scenarios, the interest in properly modelling the physical processes in urban areas has gained wide attention in the research community. In particular, the convection-permitting atmospheric models, associated with urban parameterizations, are able to resolve the heterogeneity of cities with applications to heat stress assessment and the development of urban climate adaptation and mitigation strategies. In this perspective, a bulk urban canopy parameterization, TERRA_URB, has been developed for the multi-layer land surface scheme of the COSMO regional atmospheric model. This parameterization has already demonstrated to be able to accurately describe the overall properties of urban areas and to correctly reproduce the prominent urban meteorological characteristics for different European cities. Thus, in the framework of the transition from the COSMO model to the new Icosahedral Nonhydrostatic (ICON) Weather and Climate regional model, TERRA_URB needs to be implemented in ICON.

In this work, we present the results for TERRA_URB in ICON-LAM (the limited area model version), for some cities of the Italian peninsula at a mesh size of 2 km. At this stage of the implementation, although further investigations in calibration and in the use of more realistic urban canopy parameters are needed, the preliminary results are really encouraging, since some urban key features are already properly represented, such as urban heat island and urban dry island phenomena. The comparison of these results with available observations is promising. Therefore, this work provides strong evidences regarding the added value of TERRA_URB to ICON in modelling the complex urban canopy interaction processes with the atmosphere.

How to cite: Campanale, A., Adinolfi, M., Raffa, M., Mercogliano, P., and Schulz, J.-P.: A new urban parameterization for the ICON atmospheric model: first results over Italy, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-461, https://doi.org/10.5194/ems2023-461, 2023.

Urban areas with their high population density, industrial facilities and traffic account for about 70% of the world’s CO₂ emissions and thereby contribute to global climate change. In addition, the urban fabric and its qualities (albedo, heat storage, vertical extension) influence atmospheric parameters, resulting in the well-known urban heat island (UHI) effect that may influence precipitation as well as temperature. Although both effects are found worldwide, analyses of global climate model results for urban impacts on temperature and precipitation are rare.

Previous analyses of global climate model CCAM simulations for 1985-2010 have revealed UHI effects and influences of urban areas on minimum and maximum temperatures [1]. Using the same data set to derive time-zone corrected 3-hourly data, climate average global diurnal cycles of temperature and precipitation were calculated. The  UHI intensity depends on season and climate region (northern extra-tropics (NET), southern extra-tropics (SET), or tropics (TR)). The largest statistically significant UHI influences are consistently found in the evening and at night-time, in agreement with many previous studies. Signs of urban cool islands were found for a few hours per season and climate region. Influences of urban areas on precipitation varied, with increases and decreases in all climate regions and seasons. For NET (274 cities), two out of three cities show significantly increased precipitation, while for SET (39 cities) and TR (26 cities) more decreases than increases were noted. Exceptions to these general influences of urban areas on precipitation were found at several hours for all seasons. The geographic settings of the large urban areas used for these analyses might be one explanation of the different precipitation changes induced by UHI, since urban areas are not distributed evenly around the globe. The increase in precipitation seen for NET might be because these urban areas are in less warm climate regions compared to SET and TR.

[1] Katzfey J.; Schlünzen K.H.; Hoffmann P.; Thatcher M. (2020): How an Urban Parameterization Affects a High-resolution Global Climate Simulation. QJRMS, 146 (733), 3808–3829. https://doi.org/10.1002/qj.3874.

How to cite: Katzfey, J., Schlünzen, K. H., Hoffmann, P., and Thatcher, M.: Effects of urban areas on the diurnal cycle of temperature and precipitation as found in global climate simulations, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-149, https://doi.org/10.5194/ems2023-149, 2023.

In order to plan and implement appropriate adaptation measures to protect settlements, the economy and other assets from natural hazards, it is important to know the potential consequences of climate change. Accordingly, the Plan-B model region within the Rhine Valley of the west-Austrian state of Vorarlberg is supported by the KLAR! program of the Austria Climate and Energy Fund to assist with this endeavour. The region encompasses some 91,000 inhabitants, making it one of the most densely populated regions in Austria. 

The focus of this work was on a detailed climate modelling study of the Plan-B region using the microscale urban climate model MUKLIMO_3. An accurate representation within the model involved processing input data from the Copernicus high-resolution datasets such as the digital elevation model, CORINE land cover, imperviousness and tree cover density supplemented by locally available building, land cover and vegetation data. The availability of measurements from a dense network of weather stations during July 2022 allowed the model accuracy to be evaluated for two case studies, and showed good results in representing the spatial variations of the region at a resolution of 50 m.

The modelling results from MUKLIMO_3 for the historical and current climate periods show hot-spots concentrated within the built-up urban areas. In such locations, annual averages of up to 70 summer days and 27 hot days are simulated for the period 1991-2020, consistent with the observations. Conversely, in the vicinity of water bodies such as Lake Constance, within parks or areas outside the urban fabric, annual averages of about 20-30 summer days and 2-8 hot days are more typical. From 1961 to 2020 the annual numbers of summer days, hot days and tropical nights are shown to increase across the entire domain reflecting the warming trend due to climate change. 

Climate model projection data from an ensemble of EURO-CORDEX models under the emissions scenarios RCP4.5 and RCP8.5 are input to show the expected heat load changes across the region for two future time periods. When compared with the 1991-2020 period, 2041-2070 can expect local increases of up to 20 summer days and 4 hot days for RCP4.5, and 28 summer days and 9 hot days for RCP8.5. A larger disparity in the results between the scenarios is shown for the period 2071-2100, with local increases of up to 56 summer days and 35 hot days for the extreme RCP8.5 scenario simulated relative to the 1991-2020 period. These results provide important information for decision makers and urban planners on where climate change adaptation measures to reduce heat load should be planned.

How to cite: Goler, R., Hollósi, B., Kainz, A., Vergeiner, J., and Ender, G.: A climate modelling analysis of the Plan-B region in Vorarlberg, Austria, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-219, https://doi.org/10.5194/ems2023-219, 2023.

Air pollution represents the most significant environmental health risk in Europe, which significantly impacts the health of the European population, especially in urban areas. The pollutants with the most critical threat to human health in European urban areas include fine particulate matter (PM), a mixture of aerosols with an aerodynamic diameter less or equal to 2.5 μm. To better understand the composition of fine PM in any urban area of Europe, it is important to identify and quantify the sources of its components. Such knowledge can be further used to propose effective strategies for reducing this type of pollution in this urban area. One of the commonly used ways to source attribution analysis of fine PM is to use sophisticated chemical transport models that can rigorously control: (1) the evolution of primary fine PM, (2) the formation of secondary inorganic and organic fine PM from gaseous precursors and their subsequent development, and (3) aqueous aerosol chemistry (e.i., all relevant processes connected with fine PM).

In this work, we utilized an offline coupled modeling framework consisting of the Weather Research and Forecast (WRF) Model version 4.0.3 and the Comprehensive Air quality Model with Extensions (CAMx) version 7.10 on the Central European domain with a horizontal resolution of 9 km for the period covering the years 2018 and 2019 to investigate the relationships between emissions from a wide range of anthropogenic activity sectors and the total concentrations of fine PM in six large cities of this region (Berlin, Munich, Prague, Vienna, Budapest, and Warsaw) from two different approaches. First, we analyzed the contributions of emissions from anthropogenic activity sectors to the total concentrations of fine PM using the Particulate Source Apportionment Technology (PSAT) tool implemented in the used version of the CAMx model. Second, using the zero-out method, we examined the impacts of emissions from the same anthropogenic activity sectors used in the source apportionment analysis on the total concentrations of fine PM. In this case, we additionally considered a dual implementation of organic aerosol chemistry/partitioning in the CAMx model by performing two sensitivity studies determining the impacts described above, each using one of the implementations. As part of the analysis, we compared the identified contributions with the impacts and discussed cases of mutual similarity between the two approaches.

How to cite: Bartík, L., Huszár, P., Karlický, J., and Vlček, O.: Modeling the drivers of urban fine PM pollution over Central Europe: contributions and impacts of emissions from different sources, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-44, https://doi.org/10.5194/ems2023-44, 2023.

Cities play a fundamental role in climate at local to regional scales through modification of heat and moisture fluxes, as well as affecting local atmospheric chemistry and composition, alongside air-pollution dispersion. Vice versa, regional climate change impacts urban areas and is expected to increasingly affect cities and their citizens in the upcoming decades. Simultaneously, the share of the population living in urban areas is growing and is projected to reach about 70 % of the world population by 2050. This is especially critical in connection to extreme events, for instance, heat waves with extremely high temperatures exacerbated by the urban heat island effect, in particular during night-time, with significant consequences for human health.

Additionally, from the perspective of recent regional climate model development with increasing resolution down to the city scale, proper parameterization of urban processes plays an important role to understand local/regional climate change. The inclusion of the individual urban processes affecting energy balance and transport (i.e. heat, humidity, momentum fluxes, emissions) via special urban land-surface interaction parameterization of local processes becomes vital to simulate the urban effects properly. This will enable improved assessment of climate change impacts in cities and inform adaptation and/or mitigation options, as well as adequately prepare for climate-related risks (e.g. heat waves, smog conditions, etc.).

Cities are becoming one of the most vulnerable environments under climate change. Therefore, we introduced this topic to the CORDEX platform aiming to provide regional climate downscaling, within the framework of so-called flagship pilot studies on challenging issues and gaps in regional climate change knowledge. The main aims and progress of this activity will be presented, on the analysis of previous simulations available and test case studies. 

How to cite: Halenka, T. and Langendijk, G.: CORDEX Flagship Pilot Study URB-RCC: Urban Environments and Regional Climate Change, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-616, https://doi.org/10.5194/ems2023-616, 2023.

The current climate change is a great challenge, especially for cities. The already elevated temperature levels rise further, hence, the urban heat island effect is intensified. To adapt adequately, it is essential to understand the climatic conditions of a city and how they might vary within the city. In the context of preventive disaster control, the state of Lower Saxony and the German Meteorological Service (DWD) work closely together. In a joint project, which took place between July 2017 and December 2020, the climate of the city of Hannover was investigated. To obtain a complete picture of the climate in the city, various measurement methods were used.  Here, we want to present the results of the tram measurements. Three regular trams from the Hannover public transport (Üstra) were equipped with measuring sensors. During their regular trips through the city, these trams collected meteorological data, specifically the air temperature on their route. These measurements enabled a comprehensive spatial resolution of meteorological data. For the evaluation, special route sections were selected that were of particular interest from a structural standpoint. These ranged from purely commercial areas to residential areas and even sparsely built green spaces. The differences (spatial temperature anomalies) between the tram data and a reference station located in the surrounding area, were evaluated. It was found that the structural characteristics along the route alone do not always have to be the cause of high or low overheating. The conditions in the immediate neighborhood also play a significant role. For example, a route section located in a green strip experiences strong overheating when the wind blows from the east, where the mostly strong overheated Nordstadt is located. On the other hand, heavily built and sealed areas can benefit from a sparsely built and greener environment when winds come from the appropriate direction.

In summary, the measurement of meteorological variables using trams is a powerful tool for analyzing the microclimate of a city. The high spatial resolution offers the possibility to investigate the climatic conditions of all city areas. This is a great advantage, as it is not always possible to install temporary measurement stations everywhere.

How to cite: Bauditz, S., Krugmann, G., Tinz, B., and Möller, T.: Results of the tram-based measurements from the Hannover urban climate project (2017 to 2020), EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-233, https://doi.org/10.5194/ems2023-233, 2023.

This study aims to identify hot and cold spots in the distribution of air temperature for the most important six cities from the north-eastern Romania (Iași, Bacău, Botoșani, Suceava, Piatra-Neamț and Vaslui), during the warm semester of the year. The analysis of hot and cold spots in the analyzed cities was conducted on data resulted from mobile measurements performed with Meteotracker (MT) mini weather station.

The mobile measurements were carried out under calm atmospheric conditions, with clear or partly cloudy skies, and moderate wind at three moments during the day (morning - before sunrise, noon, and evening - immediately after sunset). From May to September 2022, 80 mobile measurements were made summing up 160 hours of observation. The methodological approach involved conducting mobile measurements that cross both the central area of the cities and the peri-urban and rural areas that are not influenced by urban climate conditions. All mobile measurements started and ended in the same point so that the thermal gradient per minute could be calculated. For hot and cold spots identification, the global autocorrelation analysis method (Moran Index) was used. This analysis aims to identify areas with values that are much warmer (hot spots)/colder (cold spots) than those in neighbouring areas. The relationship between the identified hot and cold spots and imperviousness ratio (IMD) and morphometric conditions was also analysed for each city.

From this analysis, it can be observed that the occurrence of hot spots is more related to high IMD ratios, while cold spots are shaped mainly by topographic conditions. Moreover, hot spots - with a confidence level of 99% - are more frequent in the morning and evening in specific urban regions with IMD values greater than 80%. The analysis results could be useful for stakeholders involved in the mitigation of the urban heat island effect, helping them to identify the regions that risk to be excessively warm during summer in the city.

Acknowledgement: This work was supported by a grant of the Ministry of Research, Innovation and Digitization, CNCS - UEFISCDI, project number PN-III-P1-1.1-TE-2021-0882, within PNCDI III.

How to cite: Ichim, P., Sfîcă, L., Bistricean, P.-I., Crețu, C.-Ș., Hrițac, R., Roșu, L.-I., and Corocăescu, A.-C.: Hot and Cold spots identification through mobile measurements during warm season in main urban areas from North-Eastern Romania, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-330, https://doi.org/10.5194/ems2023-330, 2023.

How to cite: Schlögl, S., Bader, N., Reiss, A., Ströbel, B., and Gutbrod, K.: An overview of four use cases from a dense urban measurement network in Basel, Switzerland: Quality of the measurements, temperature and precipitation variability, and mitigation of urban heat island mitigation strategies., EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-370, https://doi.org/10.5194/ems2023-370, 2023.

The PurpleAir-II sensor provides low-cost in situ measurements of meteorological variables including temperature and humidity, as well as fine particulate matter (PM_2.5) in real time.  The sensors have been used in several studies investigating intracity differences in temperature and PM_2.5.  While the adoption and use of low-cost sensors has many benefits, care must be taken to ensure proper calibration and testing.  We have shown previously that the PurpleAir-II sensor has a high bias of 4-5 degrees Fahrenheit and a relative humidity bias of about -17%.  These results were obtained during a continuous measurement period from December 2022 to August 2023 in Asheville, North Carolina.  PurpleAir-II values were compared to temperature measurements with a Campbell Scientific 107 temperature probe and Vaisala HMP45C relative humidity probe.  We now have a longer data record (December 2022 – Summer 2024) spanning multiple seasonal changes and have updated our bias and error calculations.  We have also determined and applied correction factors for PurpleAir-II temperature and relative humidity measurements.  PurpleAir-II PM_2.5 concentrations were previously compared to a nearby regulatory PM_2.5 monitor maintained by the Asheville Buncombe Air Quality Agency during the same December 2022 – August 2023 measurement period.  PurpleAir-II bias exhibited concentration dependence with low bias at low concentrations and high bias at high concentrations.  We have updated bias and error calculations for PM_2.5 concentrations using the longer measurement period, and we have also determined and applied correction factors.  Finally, we describe an upcoming investigation using the PurpleAir-II sensor to measure neighborhood-scale temperature, relative humidity, and PM_2.5 in Asheville, North Carolina.  Such measurements will enable us to determine if certain populations are at greater risk for heat stress and PM_2.5 exposure.

How to cite: Couzo, E. and Godfrey, C.: PurpleAir-II sensor correction factors and its use in measuring neighborhood-scale temperature and particulate matter anomalies, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-354, https://doi.org/10.5194/ems2023-354, 2023.

Urban heat island (UHI) is a well-known phenomenon¹ that affects thermal comfort of city dwellers, building energy consumption, and city sustainability in general. The planting of urban trees has been identified as one of the most effective methods for mitigating UHI effect and improving urban microclimate. The flow characteristics of an idealized symmetric urban street canyon containing trees of varying sizes is being investigated in this study. Particle Image Velocimetry (PIV) measurements in a water channel at the Environmental Fluid Mechanics Laboratory of the University of Cyprus, were used, to investigate the combination of buoyant and inertial forces in the canyon. A non-dimensional analysis of the measurements² was conducted to quantify the competition between thermally driven and inertially driven flow in the presence of varying sizes of tree obstacles. This study aims to provide insights into the urban microclimate by examining the flow pattern, turbulence characteristics, and air exchanges between the canyon and the boundaries above. Results show that trees have a significant impact on the formation and strength of vortical flow within the canyon. Smaller trees stimulate the formation of stronger vortices, while larger trees lead to the elimination of the vortex and the existence of recirculation cells. The location of the heated surface also affects the vortex structure and elevation within the canyon. In addition, trees can reduce normalized vertical velocities, which can be restrictive to the “breathability”^3,4 of the canyon. The volumetric ventilation rate ⁵ through the roof-level opening that refers to the time flow travels one circuit inside the canyon, is of high interest in the context of pollution escape/removal from the canyon, as well as the removal of other scalars (e.g., relating to heat, thermal comfort, and ¨breathability¨ of the urban canyon). This study found that in the case of a leeward heated surface, air removal from the canyon can change to air entrainment with the increase in tree size, whereas in the case of a windward heated surface, air removal dominates regardless of tree size. The study encompasses an examination of the vertical profiles of Reynolds Stresses (RS) and the extent of Roughness SubLayer (RSL). Our findings demonstrate that the range of layers extension, spans from 1.10 H (minimum) to 1.60 H (maximum), where H represents the height of the building. Moreover, a substantial increase in the RSL extent was observed in windward heated surfaces scenarios in comparison to leeward heated surfaces. In conclusion, our study sheds light on the impact of trees on flow characteristics and air exchange in urban street canyons. The findings of this study can inform urban areas' design and improve their overall sustainability.

How to cite: Alexandrou, G., Mouzourides, P., Haiwei, L., Yongling, Z., Carmeliet, J., and Neophytou, M.: Experimental investigation of the impact of tree-like obstacles on ventilation in street canyons under isothermal and different levels of non-isothermal conditions, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-89, https://doi.org/10.5194/ems2023-89, 2023.

Cities in Poland still suffer from poor air quality during winter. Most intense smog episodes, with very high PM10 and PM2.5 concentrations, occur during calm periods, with temperature inversions when the emission from residential sources with low injection height increases. Modelling results tend to underestimate those episodes, despite the good agreement with measured data during low and mid-concentration periods. While the variability of near-surface concentrations is well-known based on the fixed stations and the low-cost sensors measurements, the information on vertical distribution is limited.
As measurements with drones tend to be problematic and weather balloons measure only meteorological parameters, new approaches are being developed. In Cracow (in the past one of the cities in Poland with the worst air pollution) measurement campaign with the use of sensors installed on sightseeing, hot air balloons have been carried out in 2019 to check the impact of meteorological conditions on the thickness of the atmospheric layer with poor air quality (Sekula et al., 2021).  Helium tethered aerostat (Knap et al., 2021) with installed sensors is also used by the Polish Academy of Sciences as a measurement platform for vertical profiles in Warsaw (the capital city of Poland).
These two platforms were used for a short-period measurement campaign in the winter of 2023. The main goal of the project was to assess differences between modelled and observed vertical profiles of temperature, relative humidity, PM10 and PM2.5 in Warsaw and Cracow cities. The national air quality forecast calculated with the GEM-AQ model was evaluated. In addition, the model's capability to reproduce temperature inversion will be examined.
We will present and discuss the results of the measurement campaigns, and the comparison with the model results, in different meteorological and air quality conditions. 

How to cite: Durka, P., Struzewska, J., Kaminski, J. W., Posyniak, M., and Sekuła, P.: Vertical profiles of the temperature and particulate matter in Cracow and Warsaw cities – measurement campaigns results and the comparison with modelling results., EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-393, https://doi.org/10.5194/ems2023-393, 2023.

Since the 1980s, the atmospheric aerosol in Sao Paulo, the most populous and economically active region of Southeast Brazil, has been extensively studied to determine its composition, concentration, and health impacts. The city of São Paulo is characterized by a multi-centric urban landscape, with people usually commuting from the periphery to downtown where there are most of the jobs and opportunities. This results in congestion, large emissions from the transport sector and as a consequence, more pollutant exposure. The transport sector is responsible for 60% of the CO₂ emission. PM_2.5, an important climate pollutant is composed mainly of carbonaceous compounds, associated with the emissions by the vehicular fleet which uses biofuels (gasohol and bio-diesel). Starting in 2020, the aerosol network in Sao Paulo underwent updates to include measurements of greenhouse gases (GHGs) at five sites as part of the METROCLIMA project (www.metroclima.iag.usp.br). The primary objectives of this project are to determine the megacity's contribution to CO₂ and CH₄ emissions. Measurements of stable carbon isotopes (¹²C and ¹³C) of CO₂ and CH₄ in the atmosphere provide valuable information for identifying and quantifying the predominant sources and sinks of these gases. Continuous monitoring of d¹³C-CO in Sao Paulo has revealed changes in the contributions of significant CO₂ sources, including fossil fuels (including biofuels) and wildfires. CO₂ background concentrations were estimated for the period from 2019 to 2021, resulting in an annual increase rate of 2.5 ppm/year, which is consistent with the estimated values provided by NOAA-USA. The concentrations in the background station varied from 416.94 (9.25) to 421.82 (7.47), from 2019 to 2022. The highest concentrations were found in the morning and evening hours associated with vehicular emissions, but during the day it was possible to observe the effect of local vegetation photosynthesis in the reduction of the CO₂ concentrations.

How to cite: Andrade, M. D. F., Leonardo, N., Castelo, D., Souto-Oliveira, C., Medeiros, J. A. G., and Domingues, L. G.: From Aerosols to Greenhouse Gases: evaluating the concentrations, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-625, https://doi.org/10.5194/ems2023-625, 2023.

The record hot summer of 2018 and IPCC projections for Northern Europe have raised awareness of the impacts on human health and wellbeing resulting from heat stress in high latitude cities. This calls for adaptation strategies based on reliable, detailed and tailored climate data and information. Our research aims at co-creating, together with Swedish municipalities, a prototype visualization platform for enhancing the usability and relevance of climate information.

This study is part of the ongoing 4-year research project BRIGHT - “Advancing knowledge and tools for the adaptation of Swedish cities to heat”. We present the research methodology and preliminary results from (1) the dynamical downscaling of the urban climate, (2) field campaigns with low-cost thermohygrometers, and (3) the development and first results from a citizen sensing mobile application focusing on thermal comfort.

The downscaling of historical and future heat wave events from global (>25 km) to local scale (sub-kilometer) is carried out in two steps: first, the regional climate model HCLIM is used to dynamically downscale global data to 3 km grid spacing using two nested domains, and then the land surface model SURFEX is used to downscale the 2-m temperature to the grid spacing of 300 m. A novel procedure is proposed to speed up the initialization of HCLIM simulations, and we also apply the pseudo-global warming approach to get the boundary data under different warming levels for HCLIM. The optimized downscaling procedure significantly reduces the computing costs and improves the flexibility of simulations compared with the traditional dynamical downscaling method.

The last step in this process brings the climate signal down to the scale of the individual person. This is accomplished with the building-resolving radiation model Solweig, which provides mean radiant temperature fields over a detailed 3D digital surface model of the city.

Field campaigns are carried out in the cities of Linköping and Norrköping in the summers of 2022 and 2023. We monitor air temperature and humidity at 25 places in each city using HOBO and NetAtmo sensors. The locations were selected together with stakeholders, aiming at representing different local climate zones and places that are relevant for the municipalities (e.g. schools, elderly care facilities and new development areas). The analysis allowed us to quantify the intensity of the urban heat island and to identify the presence and effect of cool islands. We further employ a co-designed citizen sensing app to enable citizens, and in particular municipal employees working in elderly or child care institutions to provide their perception of heat and to comment on real-time sensor measurements.  The collected data will be analysed and compared to sensor measurements and model results to enhance the overall understanding of thermal comfort and heat in urban areas.

How to cite: Amorim, J. H., Aldama Campino, A., Belušić, D., Navarra, C., Neset, T.-S., Ribeiro, I., Segersson, D., Wang, F., and Wiréhn, L.: Dynamical downscaling and citizen sensing as tools in the adaptation of Swedish cities to heat, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-244, https://doi.org/10.5194/ems2023-244, 2023.