Radiative Transfer Model 3.0 integrated into the PALM model system 6.0

Krč, Pavel; Resler, Jaroslav; Sühring, Matthias; Schubert, Sebastian; Salim, Mohamed; Fuka, Vladimír

doi:10.5194/gmd-14-3095-2021

Cited by 40 publications

(26 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The RTM within PALM 6.0 system models the major shortwave (SW) and longwave (LW) radiative processes inside the UCL (Krč et al, 2021;Krč, 2019). In particular, it calculates the SW and LW irradiance received by all surfaces in the domain from the sky according to their orientation.…”

Section: Radiative Transfer Modelmentioning

confidence: 99%

“…The RRTMG provides both the direct SW radiation flux and the diffuse downwelling SW and LW fluxes at this height. The recent development of the PALM model allows for a twoway coupling between the radiation model, the RRTMG in this case, and the RTM (Krč et al, 2021). For instance, the incoming SW and LW radiation fluxes from the RRTMG are used as inputs to the RTM so that all the RTPs are calculated and provided to the impeded models (e.g.…”

Section: Radiation Model and Couplingmentioning

confidence: 99%

“…Those major RTPs exist in the commonly used UCMs. It is worth here mentioning that this study does not engage with validating the RTM of the Parallelized Large-eddy Simulation Model (PALM) against observations, which is the scope of other studies (Krč et al, 2021;Krč, 2019;Resler et al, 2017Resler et al, , 2021.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Importance of radiative transfer processes in urban climate models: a study based on the PALM 6.0 model system

et al. 2022

Self Cite

View full text Add to dashboard Cite

Abstract. Including radiative transfer processes within the urban canopy layer into microscale urban climate models (UCMs) is essential to obtain realistic model results. These processes include the interaction of buildings and vegetation with shortwave and longwave radiation, thermal emission, and radiation reflections. They contribute differently to the radiation budget of urban surfaces. Each process requires different computational resources and physical data for the urban elements. This study investigates how much detail modellers should include to parameterize radiative transfer in microscale building-resolving UCMs. To that end, we introduce a stepwise parameterization method to the Parallelized Large-eddy Simulation Model (PALM) system 6.0 to quantify individually the effects of the main radiative transfer processes on the radiation budget and on the flow field. We quantify numerical simulations of both simple and realistic urban configurations to identify the major and the minor effects of radiative transfer processes on the radiation budget. The study shows that processes such as surface and vegetation interaction with shortwave and longwave radiation will have major effects, while a process such as multiple reflections will have minor effects. The study also shows that radiative transfer processes within the canopy layer implicitly affect the incoming radiation since the radiative transfer model is coupled to the radiation model. The flow field changes considerably in response to the radiative transfer processes included in the model. The study identified those processes which are essentially needed to assure acceptable quality of the flow field. These processes are receiving radiation from atmosphere based on the sky-view factors, interaction of urban vegetation with radiation, radiative transfer among urban surfaces, and considering at least single reflection of radiation. Omitting any of these processes may lead to high uncertainties in the model results.

show abstract

Section: Radiative Transfer Modelmentioning

confidence: 99%

Section: Radiation Model and Couplingmentioning

confidence: 99%

See 1 more Smart Citation

Importance of radiative transfer processes in urban climate models: a study based on the PALM 6.0 model system

et al. 2022

Self Cite

View full text Add to dashboard Cite

show abstract

“…However, even though this accelerates the development of turbulence in the LES, it still requires sufficiently large fetch distances for the turbulence to be spatially fully developed. Lee et al (2018) pointed out that an insufficiently developed turbulent flow can bias results in urban boundary layer simulations. Hence, in order to assess how the turbulent flow develops within the model domain, Fig.…”

Section: Spatial Development Of the Urban Boundary Layermentioning

confidence: 99%

Validation of the PALM model system 6.0 in a real urban environment: a case study in Dejvice, Prague, the Czech Republic

et al. 2021

Self Cite

View full text Add to dashboard Cite

Abstract. In recent years, the PALM 6.0 modelling system has been rapidly developing its capability to simulate physical processes within urban environments. Some examples in this regard are energy-balance solvers for building and land surfaces, a radiative transfer model to account for multiple reflections and shading, a plant-canopy model to consider the effects of plants on flow (thermo)dynamics, and a chemistry transport model to enable simulation of air quality. This study provides a thorough evaluation of modelled meteorological, air chemistry, and ground and wall-surface quantities against dedicated in situ measurements taken in an urban environment in Dejvice, Prague, the Czech Republic. Measurements included monitoring of air quality and meteorology in street canyons, surface temperature scanning with infrared cameras, and monitoring of wall heat fluxes. Large-eddy simulations (LES) using the PALM model driven by boundary conditions obtained from a mesoscale model were performed for multiple days within two summer and three winter episodes characterized by different atmospheric conditions. For the simulated episodes, the resulting temperature, wind speed, and chemical compound concentrations within street canyons show a realistic representation of the observed state, except that the LES did not adequately capture night-time cooling near the surface for certain meteorological conditions. In some situations, insufficient turbulent mixing was modelled, resulting in higher near-surface concentrations. At most of the evaluation points, the simulated surface temperature reproduces the observed surface temperature reasonably well for both absolute and daily amplitude values. However, especially for the winter episodes and for modern buildings with multilayer walls, the heat transfer through walls is not well captured in some cases, leading to discrepancies between the modelled and observed wall-surface temperature. Furthermore, the study corroborates model dependency on the accuracy of the input data. In particular, the temperatures of surfaces affected by nearby trees strongly depend on the spatial distribution of the leaf area density, land surface temperatures at grass surfaces strongly depend on the initial soil moisture, wall-surface temperatures depend on the correct setting of wall material parameters, and concentrations depend on detailed information on spatial distribution of emissions, all of which are often unavailable at sufficient accuracy. The study also points out some current model limitations, particularly the implications of representing topography and complex heterogeneous facades on a discrete Cartesian grid, and glass facades that are not fully represented in terms of radiative processes. Our findings are able to validate the representation of physical processes in PALM while also pointing out specific shortcomings. This will help to build a baseline for future developments of the model and improvements of simulations of physical processes in an urban environment.

show abstract

“…It was validated against wind-tunnel and lidar observations in Kanani et al (2014). The PCM furthermore interacts with radiation (absorption, transmission, reflections) and provides volume sources of sensible and latent heat that enter the prognostic equations of potential temperature and mixing ratio, respectively (Krč et al 2021). The PCM is currently not coupled with the LSM but assumes that water availability is always sufficient for transpiration.…”

Section: Set-up Of Land-surface Model and Plant-canopy Model Simulationsmentioning

confidence: 99%

How Does the Choice of the Lower Boundary Conditions in Large-Eddy Simulations Affect the Development of Dispersive Fluxes Near the Surface?

Wanner

Roo

Sühring

et al. 2021

Boundary-Layer Meteorol

Self Cite

View full text Add to dashboard Cite

Large-eddy simulations (LES) are an important tool for investigating the longstanding energy-balance-closure problem, as they provide continuous, spatially-distributed information about turbulent flow at a high temporal resolution. Former LES studies reproduced an energy-balance gap similar to the observations in the field typically amounting to 10–30% for heights on the order of 100 m in convective boundary layers even above homogeneous surfaces. The underestimation is caused by dispersive fluxes associated with large-scale turbulent organized structures that are not captured by single-tower measurements. However, the gap typically vanishes near the surface, i.e. at typical eddy-covariance measurement heights below 20 m, contrary to the findings from field measurements. In this study, we aim to find a LES set-up that can represent the correct magnitude of the energy-balance gap close to the surface. Therefore, we use a nested two-way coupled LES, with a fine grid that allows us to resolve fluxes and atmospheric structures at typical eddy-covariance measurement heights of 20 m. Under different stability regimes we compare three different options for lower boundary conditions featuring grassland and forest surfaces, i.e. (1) prescribed surface fluxes, (2) a land-surface model, and (3) a land-surface model in combination with a resolved canopy. We show that the use of prescribed surface fluxes and a land-surface model yields similar dispersive heat fluxes that are very small near the vegetation top for both grassland and forest surfaces. However, with the resolved forest canopy, dispersive heat fluxes are clearly larger, which we explain by a clear impact of the resolved canopy on the relationship between variance and flux–variance similarity functions.

show abstract

Radiative Transfer Model 3.0 integrated into the PALM model system 6.0

Cited by 40 publications

References 38 publications

Importance of radiative transfer processes in urban climate models: a study based on the PALM 6.0 model system

Importance of radiative transfer processes in urban climate models: a study based on the PALM 6.0 model system

Validation of the PALM model system 6.0 in a real urban environment: a case study in Dejvice, Prague, the Czech Republic

How Does the Choice of the Lower Boundary Conditions in Large-Eddy Simulations Affect the Development of Dispersive Fluxes Near the Surface?

Contact Info

Product

Resources

About