Urban weather generation: the intercomparison of three emerging models

<p>Cities modify the background climate through the surface-atmosphere interaction. This modification is function of urban design features, such as the configuration of buildings and the amount of vegetation. Compared to the undisturbed climate of the region, the climate of cities is characterized by higher temperature and lower wind speed. This modification is especially pronounce in dense urban areas. The climate modification of cities is not static, but varies in space and time. The spatial variations are governed by land use and built form differences, as well as by the presence or absence of green and blue infrastructures. Due to the spatial complexity of cities and the general lack of urban weather station networks in most places, the amount of available urban weather data is limited. As a consequence, planners, engineers and public health professionals can only approximate the climate impact of built environments in their respective fields.</p><p>Over the past years, several numerical simulation models have emerged that are able to model the influence of built areas on the atmosphere at the local scale and thus, deliver urban weather data for an area of interest. The aim of this study is to assess the performance of three numerical models with an ability to predict site-specific urban air temperature. The evaluated models are the Urban Weather Generator (UWG), the Vertical City Weather Generator (VCWG) and the Surface Urban Energy and Water Balance Scheme (SUEWS). Although the models differ in their scopes, modeling approaches and applications, they all derive the urban weather data from rural observations considering the land use and built form characteristics of the site.</p><p>The models are evaluated against air temperature measurements from the dense, 13<span><sup>th</sup></span> District of Budapest (Hungary). The field measurement utilized simple air temperature and relative humidity loggers placed in non-aspirated solar radiation screens at four shaded sites. The two week measurement period encompassed a five-day-long anticyclonic period with clear sky and low wind speed.<strong> </strong>Preliminary results indicate a good general agreement between modeled and observed values with root mean square error below or at 2ºC and index of agreement between 0.92-0.96. During the anticyclonic period most models slightly overestimate the daily maximum and underestimated the daily minimum urban air temperature.</p>

How We Got Here: Producing Climate Inequity and Vulnerability to Urban Weather Extremes

This collected volume is intentionally future-oriented; it is authored by a team of interdisciplinary scientists and practitioners who collaborate to translate research findings into networked adaptive practices that we hope will protect urban communities against the impacts of extreme weather. While future-oriented, we cannot protect future generations against urban weather extremes without understanding the historical processes through which these existential and ethical crises came about. This chapter describes how economic and political institutions produced the climate crisis in ways that also constitute a humanitarian crisis, inscribing climate inequity into the urban built environment and institutions. It offers reflections on ways in which this history must be wrestled with in the context of equitable and resilient urban futures.

AIR-TEMPERATURE SINGULARITIES AND DIFFERENCES BETWEEN INTRA- AND EXTRA-URBAN WEATHER STATIONS. CASE STUDY: BUCHAREST-FILARET AND BUCHAREST-BĂNEASA

It is already a well-known fact that air-temperature is the most important climatic factor of differentiation between intra- and extra-urban areas, mainly due to the characteristics of the underlying active surface. Bucharest town-area is no exception to the rule. Ranking as Romania’s largest city, its air-temperature singularities and differences account for the most important example expressing the role that the artificial ground layer may play in the creation of specific urban climates. The thermal differences as well as singularities between the Bucharest town-area (Bucharest-Filaret) and its surroundings (Bucharest-Băneasa) are analyzed by means of multiple air-temperature parameters: hourly measurements (01, 07, 13 and 19 hrs.), daily, monthly, yearly values of maximum, average and minimum means, over a 30 year period (1981-2010). Besides, the analysis of some air-temperature singularities or records highlight the clear differences of air heating processes, mostly due to the different interaction patterns between solar radiation and the underlying active layer, at local scales. However, in general, although the intra-urban areas should keep warmer in summer and cooler in winter, the cooling effects seem to still remain lower in the city because of the greater artificial heat input that is being added to the built-in environment.

Opportunistic weather sensors: an Amsterdam case study of private weather stations, commercial microwave links and smartphones

<p>Several opportunistic sensors (private weather stations, commercial microwave links and smartphones) are employed to obtain weather information and successfully monitor urban weather events. The ongoing urbanisation and climate change urges further understanding and monitoring of weather in cities. Two case studies during a 17-day period over the Amsterdam metropolitan area, the Netherlands, are used to illustrate the potential and limitations of hydrometeorological monitoring using non-traditional and opportunistic sensors. We employ three types of opportunistic sensing networks to monitor six important environmental variables: (1) air temperature estimates from smartphone batteries and personal weather stations; (2) rainfall from commercial microwave links and personal weather stations; (3) solar radiation from smartphones; (4) wind speed from personal weather stations; (5) air pressure from smartphones and personal weather stations; (6) humidity from personal weather stations. These observations are compared to dedicated, traditional observations where possible, although such networks are typically sparse in urban areas. First we show that the passage of a front can be successfully monitored using data from several types of non-traditional sensors in a complementary fashion. Also we demonstrate the added value of opportunistic measurements in quantifying the Urban Heat Island (UHI) effect during a hot episode. The UHI can be clearly determined from personal weather stations, though UHI values tend to be high compared to records from a traditional network. Overall, this study illustrates the enormous potential for hydrometeorological monitoring in urban areas using non-traditional and opportunistic sensing networks.</p>

From Urban Air Quality Forecasting and Information Systems to Integrated Urban Hydrometeorology, Climate and Environment Systems and Services for Smart Cities

<p>This presentation is analysing a modern evolution in research and development from specific urban air quality systems to multi-hazard and integrated urban weather, environment and climate systems and services and provides an overview of joint results of large EU FP FUMAPEX, MEGAPOLI, EuMetChem and MarcoPolo projects and international WMO GURME and IUS teams. </p><p>Urban air pollution is still one of the key environmental issues for many cities around the world. A number of recent and previous international studies have been initiated to explore these issues. In particular relevant experience from several European projects will be demonstrated. MEGAPOLI studies aimed to assess the impacts of megacities and large air-pollution hotspots on local, regional and global air quality; to quantify feedback mechanisms linking megacity air quality, local and regional climates, and global climate change; and to develop improved tools for predicting air pollution levels in megacities (doi:10.5194/asr-4-115-2010). FUMAPEX developed for the first time an integrated system encompassing emissions, urban meteorology and population exposure for urban air pollution episode forecasting, the assessment of urban air quality and health effects, and for emergency preparedness issues for urban areas (UAQIFS: Urban Air Quality Forecasting and Information System; doi.org/10.5194/acp-6-2005-2006; doi.org/10.5194/acp-7-855-2007).</p><p>While important advances have been made, new interdisciplinary research studies are needed to increase our understanding of the interactions between emissions, air quality, and regional and global climates. Studies need to address both basic and applied research and bridge the spatial and temporal scales connecting local emissions, air quality and weather with climate and global atmospheric chemistry. WMO has established the Global Atmosphere Watch (GAW) Urban Research Meteorology and Environment (GURME) project which provides an important research contribution to the integrated urban services.</p><p>Most of the disasters affecting urban areas are of a hydro-meteorological nature and these have increased due to climate change. Cities are also responsible not only for air pollution emissions, but also for generating up to 70% of GHG emissions that drive large scale climate change. Thus, there is a strong feedback between contributions of cities to environmental health, climate change and the impacts of climate change on cities and these phases of the problem should not be considered separately. There is a critical need to consider the problem in a complex manner with interactions of climate change and disaster risk reduction for urban areas (doi:10.1016/j.atmosenv.2015.11.059, doi.org/10.1016/j.uclim.2017.05.004).</p><p>WMO is promoting safe, healthy and resilient cities through the development of Integrated Urban Weather, Environment and Climate Services (IUS). The aim is to build urban services that meet the special needs of cities through a combination of dense observation networks, high-resolution forecasts, multi-hazard early warning systems, disaster management plans and climate services. This approach gives cities the tools they need to reduce emissions, build thriving and resilient communities and implement the UN Sustainable Development Goals. The Guidance on IUS, developed by a WMO inter-programme working group, documents and shares the good practices that will allow countries and cities to improve the resilience of urban areas to a great variety of natural and other hazards (https://library.wmo.int/doc_num.php?explnum_id=9903).</p>

A Building Retrofit and Sensitivity Analysis in an Automatically Calibrated Model Considering the Urban Heat Island Effect in Abu Dhabi, UAE

Villas are a very common building typology in Abu Dhabi. Due to its preponderance in residential areas, studying how to effectively reduce energy demand for this type of building is critical for Abu Dhabi, and many similar cities in the region. This study aims to show the impact of proposed energy efficiency measures on a villa using a calibrated model and to demonstrate that to be accurate, the model must be driven using urban weather data instead of rural weather data due to the significance of the urban heat island effect. Available data for this case study includes construction properties, on-site (urban) weather data, occupancy-related loads and schedules and rural weather data. Four main steps were followed, weather data customisation combining urban and rural weather variables, model calibration using a genetic algorithm-based tool and simulating retrofit strategies. We created a calibrated model for electricity demand during 2016–2017 with a 4% normalized mean bias error and an 11% coefficient of variation of the mean square error. Changing from none to all retrofit strategies results in a 34% reduction in annual energy consumption. According to the calibrated model, increased urban temperatures cause a 7.1% increase in total energy consumption.

Validation of UWG and ENVI-Met Models in an Abu Dhabi District, Based on Site Measurements

The city of Abu Dhabi is growing every year in population, urban extent and energy demand. This research focuses on the application of two simulation programs to estimate changes in urban climate associated with continued development in Abu Dhabi: The Urban Weather Generator (UWG) and ENVI-met. Simulation with these two software packages are validated with the site data measured in downtown Abu Dhabi. A comparison analysis (in the different seasons) between the rural data, the simulation output, and the site measurements shows the variations of the UHI in this Middle Eastern city and the potential of the validated tools. The main aims of this study are: (a) to make a seasonal validation of the UWG for the city of Abu Dhabi (referring to urban-rural available data). The tool was previously validated for a year (no seasonal division) for Abu Dhabi, Toulouse, Basel, Singapore, Rome and Barcelona. The simulations are based on the 2016 version of the Urban Weather Generator. The analysis is separated into three main seasons (instead of the full year): winter, spring, summer. (b) To make a seasonal validation and improve the second tool evaluated in this study, ENVI-met 4.0. The software can simulate urban temperature, humidity and wind speed. Guides are proposed for the enhancement of the accuracy of both estimation procedures. Referring to the results, UWG tends to overestimate the canyon temperature during the summer and has a more realistic estimation on the winter season. ENVI-met has better estimations of temperatures during the summer season compared to UWG. Finally, the UWG weather file contributes a more detailed energy model on a mesoscale model. It considers the seasonal effect and shows the impact of the climate on profiling the UHI phenomena. ENVI-met needs improvement in calculating the anthropogenic heat and in calculation of the mean radiant temperature.