EVALUATION OF THE SEASONAL NIGHTTIME LST-AIR TEMPERATURE DISCREPANCIES AND THEIR RELATION TO LOCAL CLIMATE ZONES (LCZ) IN STRASBOURG

More and more uses and applications are being given to local climate zone (LCZ) maps, which describe the structure of the urban and semi-urban areas. Among others, it is worth highlighting its use in studies of urban heat islands (UHI), sustainability and urban energy balance. Even if the classes are well described in the literature, it is difficult to estimate the general precision of these classification maps because the classification is highly dependent of the urban typology of the city under study. However, LCZ maps represent a reference in the field of urban climatology. This research work aims to make use of these maps to explain the strong influence of LCZ classes on land surface temperature (LST) and, consequently, on air temperature (AT). This kind of investigations will help us to explain the outliers observed in previous work between LST and AT at specific locations in the city of Strasbourg for the period 2012–2019. The LST data were obtained from the thermal infrared data of both ASTER (with 90-m spatial resolution and 16-days temporal resolution) and MODIS satellite (with 1-km spatial resolution and daily revisit period). The reference ATs were obtained from different field measurement provided by a huge network of meteorological stations distributed in the city of Strasbourg. The comparison of measured ATs and remote LSTs provide the opportunity to thoroughly evaluate the relationship between these two parameters both during the day and night, for different land covers and for different times of the year. Finally, UHI maps of Strasbourg for every season are presented.

Pathways for climate change adaptation in urban areas - first results from field measurements and ENVI-met modeling

<p>In the context of climate change, more frequent and intensive exposure to heat stress is observed and predicted for many cities worldwide. Urban climatological studies in recent decades have shown significant positive trends in the number of hot days. As heat stress poses a considerable health risk, adaptation measures need to be developed. Against this background, the research study aims to measure and model the urban microclimate of a 15 ha study area in Cologne. A network of IButtons and Netatmo weather stations with ultrasonic anemometers is used to measure temperature, humidity and wind speed/direction for assessing the climate character of the study area. The low cost sensors are calibrated against built up research grade meteorological stations. Utilizing low cost sensors also provides opportunities to activate citizens in microclimate research and to foster participation in mitigating climate change effects. The measurement network is set up as transects along street corridors and is used to a) identify the local climatic impacts of different surface types, vegetation areas and building structures, and b) to later calibrate and validate the ENVI-met model. Processes affecting the urban energy balance and microclimate are identified focussing particularly on source areas of excessive heat. Effects of urban green infrastructures are analysed with regard to their mitigation potential for heat stress, water demand for evapotranspiration, and their potential to modify the partitioning of the radiation balance into sensible heat and latent heat flux. We will use the validated ENVI-met model to simulate various adaptation scenarios and climate change scenarios. Adaptation measures will comprise changes in surface (e.g. urban water bodies and vegetation areas), facade/roof greenings or cooling materials. Climate projections until 2099 will be used with ENVI-met by downscaling meteorological data using the Statistical DownScaling Model (SDSM) and assuming the HadCM3 future emission scenarios.</p>

Large Scale Exploitation of Satellite Data for the Assessment of Urban Surface Temperatures

<p>The rate at which global climate change is happening is arguably the most pressing environmental challenge of the century and it affects our cities. Temperature is one of the most important parameters in climate monitoring and Earth Observation (EO) systems and the advances in remote sensing science increase the opportunities for monitoring the surface temperature from space. The EO4UTEMP project examines the exploitation of EO data for monitoring the urban surface temperature (UST). Large variations in surface temperatures can be observed within a couple of hours, particularly when referring to urban surfaces. The geometric, radiative, thermal, and aerodynamic properties of the urban surface are unique and exert particularly strong control on the surface temperature. EO satellites provide excellent means for mapping the land surface temperature, but the particular properties of the urban surface and the unique urban geometry in combination with the trade-off between temporal and spatial resolution of the current satellite missions impose the development of new sophisticated surface temperature retrieval methods particularly designed for urban areas. EO4TEMP develops a novel UST algorithm exploiting multi-temporal, multi-sensor, multi-resolution EO data, to be validated with in-situ measurements in urban sites and to be applied to Sentinel-3 and Sentinel-2 data. Therefore, EO4UTEMP will provide an advanced methodology for deriving frequent UST estimations at local scale (100 m), capable of resolving the diurnal variation of UST and contribute to the study of the urban energy balance.</p>

Sensitivity study of urban energy balance to albedo, emissivity and heat capacity in Seoul Metropolitan Area

<p>As urban populations increase, urban heat island effect is enhanced and urban heat stress and air pollutant concentrations increase. Sensitivity experiments of changing the albedo, emissivity, and heat capacity of urban facets can provide information to mitigate the heat island effect and allow the model to study urban climate more accurately. Experiments on sensitivity of the surface energy balance of albedo, emissivity and heat capacity in the metropolitan area of ​​Seoul were conducted using Met-Office-Reading Urban Surface Exchange Scheme (MORUSES) of Unified Model Local Data Assimilation and Prediction (UM LDAPS) model. The analysis period is a heat wave period from July 15 to 21, 2018, which is a clear day without cloud and precipitation. Comparing 1.5-m temperature of AWS data, it overestimated about 0.5-2K in the model. If the albedo decreases, the net radiation, storage heat, sensible heat and ground heat fluxes increase after sunrise. Storage heat becomes negative in the afternoon, and sensible heat is positive during the night. When the albedo decreases, the air temperature increases. As the emission rate decreases, the air temperature increases as storage heat decreases and sensible, latent and geothermal heat increases, which is more intense at night than during the day. When heat capacity decreases, sensible and ground heat increase during the day, storage heat decreases, and vice versa at night. Air temperature increases during midday when solar radiation is strong and decreases elsewhere. Considering that the LDAPS-MORUSES model underestimates the air temperature, albedo and emission rates can be reduced to achieve more accuracy.</p><p>Acknowledgement: This research was supported by the Korea Meteorological Administration’s National Institute of Meteorological Sciences "Development of Biomechanical Meteorological Technology" (1365003004).</p>

ALGORITHM OF COMPLEX URBAN METEOROLOGICAL ASSESSMENT

Determining the main patterns influencing the formation of urban meteorological transformations in cities, establishing mechanisms of interaction between components of the urban environment, development of methods, approaches, and preparation of algorithms for obtaining objective information about the urban environment are very important and urgent tasks which determine the development of urban meteorology as a science and have important practical significance. The aim of this work is the development of the algorithm of complex urban meteorological assessment for objective identification of transformations in the atmospheric environment of big cities. The methodological basis of the research is the concept of interaction of urban meteorological components of the city. The results of the latest meteorological studies of urban areas are systematized in this work. It is shown the close relationships between the urban meteorological components (microclimate, bioclimate, air pollution, and climate change and vulnerability to it) and their significant influence on the formation of each other. The necessity of the development of a complex urban meteorological assessment algorithm is substantiated and such an algorithm is offered. The algorithm consists of four basic stages and one which can be realized optionally. The assessment of microclimatic features of separate sites of the territory should be carried out at the first stage. The second stage of the assessment should be the study of the specific urban bioclimate, as the UHI existence, wind speed reduction and associated changes in urban energy balance within the city lead to the formation of specific bioclimatic conditions in urban areas. The third stage of the assessment should be devoted to the evaluation of air pollution levels in the urban environment. The city’s climate change vulnerability assessment should be done at the fourth stage. Features of realization of each stage are described in detail.

Assessment of Local Climate Zone Classification Maps of Cities in China and Feasible Refinements

Local climate zone (LCZ) maps that describe the urban surface structure and cover with consistency and comparability across cities are gaining applications in studies of urban heat waves, sustainable urbanization and urban energy balance. Following the standard World Urban Database and Access Portal Tools (WUDAPT) method, we generated LCZ maps for over 20 individual cities and 3 major economic regions in China. Based on the confusion matrices constructed by manual comparison between the predicted classes and ground truths, we highlight the following: (1) notable variation in overall accuracies (i.e., 60%–89%) among cities were observed, which was mainly due to class incompleteness and distinct proportions of natural landscapes; (2) building classes in selected cities were poorly classified in general, with a mean accuracy of 48%; (3) the sparsely built class (i.e., LCZ 9), which is rare in the selected Chinese cities, had the lowest classification accuracy (32% on average), and the class of low plants had the widest accuracy range. The findings indicate that the standard WUDAPT method alone is insufficient for generating LCZ products that demonstrate practical value, especially for built-up areas in China, and the misclassification is largely caused by the lack of building height data. This result is confirmed by a refinement test, in which the urban DEM retrieved from Sentinel-1 data with radar interferometry technique was used. The study shows a detailed and comprehensive assessment of applying the WUDAPT method in China and a feasible refinement strategy to improve the classification accuracy, especially for the built-up types of LCZ. The study could serve as a useful reference for generating quality-ensured LCZ maps. This study also examines and explores the relationship between socio-economic status and LCZ products, which is essential for further implementations.

Green Roofs and Greenpass

The United Nations have identified climate change as the greatest threat to human life. As current research shows, urban areas are more vulnerable to climate change than rural areas. Numerous people are affected by climate change in their daily life, health and well-being. The need to react is undisputed and has led to numerous guidelines and directives for urban climate adaptation. Plants are commonly mentioned and recommended as one key to urban climate adaptation. Due to shading of open space and building surfaces, as well as evapotranspiration, plants reduce the energy load on the urban fabric and increase thermal comfort and climate resilience amongst many other ecosystem services. Plants, therefore, are described as green infrastructure (GI), because of the beneficial effects they provide. Extensive green roofs are often discussed regarding their impact on thermal comfort for pedestrians and physical properties of buildings. By means of Stadslab2050 project Elief Playhouse in Antwerp, Belgium, a single-story building in the courtyard of a perimeter block, the effects of different extensive green roof designs (A and B) on the microclimate, human comfort at ground and roof level, as well as building physics are analyzed and compared to the actual roofing (bitumen membrane) as the Status Quo variant. For the analyses and evaluation of the different designs the innovative Green Performance Assessment System (GREENPASS®) method has been chosen. The planning tool combines spatial and volumetric analyses with complex 3D microclimate simulations to calculate key performance indicators such as thermal comfort score, thermal storage score, thermal load score, run-off and carbon sequestration. Complementary maps and graphs are compiled. Overall, the chosen method allows to understand, compare and optimize project designs and performance. The results for the Elief Playhouse show that the implementation of green roofs serves a slight contribution to the urban energy balance but a huge impact on the building and humans. Variant B with entire greening performs better in all considered indicators, than the less greened design Variant A and the actual Status Quo. Variant B will probably bring a greater cost/benefit than Variant A and is thus recommended.