Basics for the operationalization of the new urban climate model PALM-4U

Abstract. As most of the population lives in urban environments, the simulation of the urban climate has become a key problem in the framework of the climate change impact assessment. However, the high computational power required by these simulations is a severe limitation. Here we present a study on the performance of a Urban Climate Model (UrbClim), designed to be several orders of magnitude faster than a full-fledge mesoscale model. The simulations are validated with station data and with land surface temperature observations retrieved by satellites. To explore the advantages of using a simple model like UrbClim, the results are compared with a simulation carried out with a state-of-the-art mesoscale model, the Weather Research and Forecasting model, using an Urban Canopy model. The effect of using different driving data is explored too, by using both relatively low resolution reanalysis data (70 km) and a higher resolution forecast model (15 km). The results show that, generally, the performance of the simple model is comparable to or better than the mesoscale model. The exception are the winds and the day-to-day correlation in the reanalysis driven run, but these problems disappear when taking the boundary conditions from the higher resolution forecast model.

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Modelling rain heterogeneities within an urban neighbourhood

10.5194/egusphere-egu21-7806 ◽

2021 ◽

Author(s):

Karolin S. Ferner ◽

K. Heinke Schlünzen ◽

Marita Boettcher

Keyword(s):

Wind Speed ◽

Urban Areas ◽

Climate Model ◽

Numerical Models ◽

Urban Climate ◽

Cloud Microphysics ◽

In Situ Measurements ◽

Small Scale ◽

Atmospheric Processes

Urbanisation locally modifies the regional climate: an urban climate develops. For example, the average wind speed in cities is reduced, while the gustiness is increased. Buildings induce vertical winds, which influence the falling of rain. All these processes lead to heterogeneous patterns of rain at ground and on building surfaces. The small-scale spatial rain heterogeneities may cause discomfort for people. Moreover, non-uniform wetting of buildings affects their hydrothermal performance and durability of their facades.Measuring rain heterogeneities between buildings is, however, nearly impossible. Building induced wind gusts negatively influence the representativeness of in-situ measurements, especially in densely urbanised areas. Weather radars are usually too coarse and, more importantly, require an unobstructed view over the domain and thus do not measure ground precipitation in urban areas. Consequently, researchers turn to numerical modelling in order to investigate small-scale precipitation heterogeneities between buildings.In building science, numerical models are used to investigate rain heterogeneities typically focussing on single buildings and vertical facades. Only few studies were performed for more than a single building or with inclusion of atmospheric processes such as radiation or condensation. In meteorology, increasing computational power now allows the use of small-scale obstacle-resolving models resolving atmospheric processes while covering neighbourhoods.In order to assess rain heterogeneities between buildings we extended the micro-scale and obstacle-resolving transport- and stream model MITRAS (Salim et al. 2019). The same cloud microphysics parameterisation as in its mesoscale sister model METRAS (Schl&#252;nzen et al., 2018) was applied and boundary conditions for cloud and rain water content at obstacle surfaces were introduced. MITRAS results are checked for plausibility using radar and in-situ measurements (Ferner et al., 2021). To our knowledge MITRAS is the first numerical urban climate model that includes rain and simulates corresponding processes.Model simulations were initialised for various wind speeds and mesoscale rain rates to assess their influence on the heterogeneity of falling rain in a domain of 1.9 x 1.7 km&#178; around Hamburg City Hall. We investigated how wind speed or mesoscale rain rate influence the precipitation patterns at ground and at roof level. Based on these results we assessed the height dependence of precipitation. First analyses show that higher buildings receive more rain on their roofs than lower buildings; the results will be presented in detail in our talk.Ferner, K.S., Boettcher, M., Schl&#252;nzen, K.H. (2021): Modelling the heterogeneity of rain in an urban neighbourhood. Publication in preparationSalim, M.H., Schl&#252;nzen, K.H., Grawe, D., Boettcher, M., Gierisch, A.M.U., Fock B.H. (2018): The microscale obstacle-resolving meteorological model MITRAS v2.0: model theory. Geosci. Model Dev., 11, 3427&#8211;3445, https://doi.org/10.5194/gmd-11-3427-2018.Schl&#252;nzen, K.H., Boettcher, M., Fock, B.H., Gierisch, A.M.U., Grawe, D., and Salim, M. (2018): Scientific Documentation of the Multiscale Model System M-SYS. Meteorological Institute, Universit&#228;t Hamburg. MEMI Technical Report 4

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Innovative urban climate model PALM-4U as a support tool for municipal climate adaptation strategies.

10.5194/egusphere-egu21-12563 ◽

2021 ◽

Author(s):

Antonina Kriuger ◽

Alexander Reinbold ◽

Martina Schubert-Frisius ◽

Jörg Cortekar

Keyword(s):

Climate Change ◽

High Performance ◽

Climate Model ◽

Urban Climate ◽

Performance Model ◽

Practical Implementation ◽

Adaptation Measures ◽

Funding Program ◽

The Impact ◽

Comfort Indices

Cities are particularly vulnerable to climate change. At the same time, cities change slowly. Accordingly, preparatory measures to adapt to climate change have to be taken urgently. High-performance urban climate models with various applications can form the basis for prospective planning decisions, however, as of today no such model exists that can be easily applied outside of the scientific community. Therefore, the funding program Urban Climate Under Change [UC]2 aims to further develop the new urban climate model PALM-4U (Parallelized Large-Eddy Simulation Model for Urban Applications) into a practice-oriented and user-friendly product that meets the needs of municipalities and other practical users in addition to scientific research.Specifically, the high-performance model PALM-4U allows simulation of entire large cities comprising the area over 1.000 km2 with a grid size of down to few meters. One of our goals within the project ProPolis is to design and test the practical implementation of PALM-4U in standard and innovative application fields which include thermal comfort (indices like PT, PET, UTCI), cold air balance (source areas, reach and others), local wind comfort (indices derived from medium winds and gusts) as well as dispersion of pollutants.In close cooperation with our practice partners, we explore the potential of PALM-4U to support the urban planning processes in each specific application setting. Additionally, with development of the fit for purpose graphic user interface, manuals and trainings we aim to enable practitioners to apply the model for their individual planning questions and adaptation measures.In our presentation, we will show an application case of PALM-4U in a major German city. We will investigate the effect of a planned development area on the local climate and the impact of different climate change adaptation measures (such as extensive vs. intensive green roofs). The comparative simulations of the current state and planning scenarios with integrated green and blue infrastructure should provide arguments for the municipal decision making in consideration of climate change aspects in a densely built-up environment, e.g. urban heat stress.

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Development of a new urban climate model based on the model PALM – Project overview, planned work, and first achievements

Meteorologische Zeitschrift ◽

10.1127/metz/2019/0909 ◽

2019 ◽

Vol 28 (2) ◽

pp. 105-119 ◽

Cited By ~ 15

Author(s):

Björn Maronga ◽

Günter Gross ◽

Siegfried Raasch ◽

Sabine Banzhaf ◽

Renate Forkel ◽

...

Keyword(s):

Climate Model ◽

Urban Climate ◽

Model Based

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Heat load assessment in Central European cities using an urban climate model and observational monitoring data

Energy and Buildings ◽

10.1016/j.enbuild.2019.07.023 ◽

2019 ◽

Vol 201 ◽

pp. 53-69 ◽

Cited By ~ 9

Author(s):

Anita Bokwa ◽

Jan Geletič ◽

Michal Lehnert ◽

Maja Žuvela-Aloise ◽

Brigitta Hollósi ◽

...

Keyword(s):

Heat Load ◽

Climate Model ◽

Urban Climate ◽

Monitoring Data ◽

Central European ◽

European Cities

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Estimation of the energy demand for air conditioning using the outdoor temperature distribution calculated by the urban climate model.

ENVIRONMENTAL SYSTEMS RESEARCH ◽

10.2208/proer1988.27.165 ◽

1999 ◽

Vol 27 ◽

pp. 165-170

Author(s):

Takahito UENO ◽

Manabu SHIBATA ◽

Hiroki TANIKAWA ◽

Hidefumi IMURA

Keyword(s):

Temperature Distribution ◽

Energy Demand ◽

Air Conditioning ◽

Climate Model ◽

Urban Climate ◽

Outdoor Temperature

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Does “Alpine Pumping” have an effect on the ventilation of Munich?

10.5194/egusphere-egu2020-11498 ◽

2020 ◽

Author(s):

Katrin Sedlmeier ◽

Meinolf Koßmann ◽

Kristina Winderlich ◽

Maximilian Graf ◽

Gudrun Mühlbacher

Keyword(s):

Temperature Distribution ◽

Rural Areas ◽

Natural Ventilation ◽

Climate Model ◽

Regional Climate ◽

Urban Climate ◽

Wind System ◽

Maximum Heat ◽

City Area ◽

The City

Alpine Pumping refers to a thermally driven circulation between the Alps and the Alpine foreland in southeastern Germany, which occurs regularly under clear and calm weather conditions (e.g. Lugauer and Winkler (2005)). Earlier studies suggest, that the ventilation of the city of Munich, and thus the urban temperature distribution, could be influenced by this regional wind system. The present work was conducted in a cooperation framework between the city of Munich and the German Meteorological Service. The occurrence of Alpine Pumping and its effect on the temperature distribution in the city of Munich were investigated by temporary and operational wind measurements as well as numerical simulations. The thermal wind system was simulated with the regional climate model COSMO-CLM and the characteristics of Alpine Pumping deduced from this simulation used as input for the high-resolution urban climate model MUKLIMO_3. Using a radiation-based criterion, Alpine Pumping occurs on about 60 days per year, mostly in the summer months when the heat load is highest. The wind fields of temporary measurements in the rural areas south of Munich show the expected daily cycle of the wind system, especially the southerly flow during the night, which transports cold air from the mountains into the city. An influence of the regional circulation pattern on the temperature in the city area was found in a case study with the urban climate model MUKLIMO_3. Especially at night and in the morning hours, the cooler air from the surroundings ventilates the city area. Furthermore, the model results show a spatial shift of the maximum heat island in Munich during the course of the day.The findings show, that Alpine Pumping is a rather frequent phenomenon in the study area and represents an important contribution to the natural ventilation of different areas within the city.&#160;References:LUGAUER, M., WINKLER, P., 2005: Thermal circulation in South Bavaria - climatology and synoptic aspects. Meteorologische Zeitschrift. 14, 15-13.

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Advancement in Urban Climate Modelling at Local Scale: Urban Heat Island Mitigation and Building Cooling Demand

Atmosphere ◽

10.3390/atmos11121313 ◽

2020 ◽

Vol 11 (12) ◽

pp. 1313

Author(s):

Aytaç Kubilay ◽

Jonas Allegrini ◽

Dominik Strebel ◽

Yongling Zhao ◽

Dominique Derome ◽

...

Keyword(s):

Climate Model ◽

Heat Waves ◽

Urban Climate ◽

Building Energy ◽

Urban Heat Islands ◽

Heat Island ◽

Meteorological Model ◽

Heat Islands ◽

Urban Heat ◽

Building Cooling

As cities and their population are subjected to climate change and urban heat islands, it is paramount to have the means to understand the local urban climate and propose mitigation measures, especially at neighbourhood, local and building scales. A framework is presented, where the urban climate is studied by coupling a meteorological model to a building-resolved local urban climate model, and where an urban climate model is coupled to a building energy simulation model. The urban climate model allows for studies at local scale, combining modelling of wind and buoyancy with computational fluid dynamics, radiative exchange and heat and mass transport in porous materials including evaporative cooling at street canyon and neighbourhood scale. This coupled model takes into account the hygrothermal behaviour of porous materials and vegetation subjected to variations of wetting, sun, wind, humidity and temperature. The model is driven by climate predictions from a mesoscale meteorological model including urban parametrisation. Building energy demand, such as cooling demand during heat waves, can be evaluated. This integrated approach not only allows for the design of adapted buildings, but also urban environments that can mitigate the negative effects of future climate change and increased urban heat islands. Mitigation solutions for urban heat island effect and heat waves, including vegetation, evaporative cooling pavements and neighbourhood morphology, are assessed in terms of pedestrian comfort and building (cooling) energy consumption.

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Effects of Urban Configuration on Human Thermal Conditions in a Typical Tropical African Coastal City

Advances in Meteorology ◽

10.1155/2013/549096 ◽

2013 ◽

Vol 2013 ◽

pp. 1-12 ◽

Cited By ~ 8

Author(s):

Emmanuel Lubango Ndetto ◽

Andreas Matzarakis

Keyword(s):

Thermal Comfort ◽

Climate Model ◽

Meteorological Data ◽

Urban Climate ◽

Thermal Conditions ◽

Urban Street ◽

Coastal City ◽

Human Thermal Conditions ◽

Comfort Parameters

A long-term simulation of urban climate was done using the easily available long-term meteorological data from a nearby synoptic station in a tropical coastal city of Dar es Salaam, Tanzania. The study aimed at determining the effects of buildings’ height and street orientations on human thermal conditions at pedestrian level. The urban configuration was represented by a typical urban street and a small urban park near the seaside. The simulations were conducted in the microscale applied climate model of RayMan, and results were interpreted in terms of the thermal comfort parameters of mean radiant (Tmrt) and physiologically equivalent (PET) temperatures. PET values, high as 34°C, are observed to prevail during the afternoons especially in the east-west oriented streets, and buildings’ height of 5 m has less effect on the thermal comfort. The optimal reduction ofTmrtand PET values for pedestrians was observed on the nearly north-south reoriented streets and with increased buildings’ height especially close to 100 m. Likewise, buildings close to the park enhance comfort conditions in the park through additional shadow. The study provides design implications and management of open spaces like urban parks in cities for the sake of improving thermal comfort conditions for pedestrians.

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Can local fieldwork help to represent intra-urban variability of canopy parameters relevant for tropical African climate studies?

Theoretical and Applied Climatology ◽

10.1007/s00704-021-03733-7 ◽

2021 ◽

Author(s):

Jonas Van de Walle ◽

Oscar Brousse ◽

Lien Arnalsteen ◽

Disan Byarugaba ◽

Daniel S. Ddumba ◽

...

Keyword(s):

Building Materials ◽

Climate Model ◽

Urban Climate ◽

Boreal Summer ◽

Future Research ◽

Site Specific ◽

Local Climate ◽

African Cities ◽

Climate Studies ◽

Urban Characteristics

AbstractRapid and uncontrolled urbanization in tropical Africa is increasingly leading to unprecedented socio-economical and environmental challenges in cities, particularly urban heat and climate change. The latter calls for a better representation of tropical African cities’ properties relevant for urban climate studies. Here, we demonstrate the possibility of collecting urban canopy parameters during a field campaign in the boreal summer months of 2018 for deriving a Local Climate Zone (LCZ) map and for improving the physical representation of climate-relevant urban morphological, thermal and radiative characteristics. The comparison of the resulting field-derived LCZ map with an existing map obtained from the World Urban Data and Access Portal Tool framework shows large differences. In particular, our map results in more vegetated open low-rise classes. In addition, site-specific fieldwork-derived urban characteristics are compared against the LCZ universal parameters. The latter shows that our fieldwork adds important information to the universal parameters by more specifically considering the presence of corrugated metal in the city of Kampala. This material is a typical roofing material found in densely built environments and informal settlements. It leads to lower thermal emissivity but higher thermal conductivity and capacity of buildings. To illustrate the importance of site-specific urban parameters, the newly derived site-specific urban characteristics are used as input fields to an urban parametrization scheme embedded in the regional climate model COSMO-CLM. This implementations decreases the surface temperature bias from 5.34 to 3.97 K. Based on our results, we recommend future research on tropical African cities to focus on a detailed representation of cities, with particular attention to impervious surface fraction and building materials.

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