Tamir G. Reisin

COST 732 in practice: the MUST model evaluation exercise

The aim of this paper is to describe the use of a general methodology tailored to the evaluation of micro-scale meteorological models applied to flow and dispersion simulations in urban areas. This methodology, developed within COST 732, has been tested through a large modelling exercise involving many groups across Europe. The major test case used is the Mock Urban Setting Test (MUST) experiment representing an idealised urban area. It is emphasised that a full model evaluation is problem-dependent and requires several activities including a statistical validation that requires a careful choice of the metrics for the comparison with measurements.

Comparison of atmospheric modelling systems simulating the flow, turbulence and dispersion at the microscale within obstacles

Three different modelling techniques to simulate the pollutant dispersion in the atmosphere at the microscale and in presence of obstacles are evaluated and compared. The Eulerian and Lagrangian approaches are discussed, using RAMS6.0 and MicroSpray models respectively. Both prognostic and diagnostic modelling systems are considered for the meteorology as input to the Lagrangian model, their differences and performances are investigated. An experiment from the Mock Urban Setting Test field campaign observed dataset, measured within an idealized urban roughness, is used as reference for the comparison. A case in neutral conditions was chosen among the available ones. The predicted mean flow, turbulence and concentration fields are analysed on the basis of the observed data. The performances of the different modelling approaches are compared and their specific characteristics are addressed. Given the same flow and turbulence input fields, the quality of the Lagrangian particle model is found to be overall comparable to the full-Eulerian approach. The diagnostic approach for the meteorology shows a worse agreement with observations than the prognostic approach but still providing, in a much shorter simulation time, fields that are suitable and reliable for driving the dispersion model.

Application of a modified version of RAMS model to simulate the flow and turbulence in the presence of buildings: the MUST COST732 exercise

A modified version of the atmospheric model RAMS6.0 is used to simulate the flow in the MUST experiment, within the framework of the COST732 Action. A standard version of the k-e turbulence closure model and its renormalisation group version, RNG k-e, were implemented in the model. Simulations were performed to test the suitability of using the model to reproduce the flow and turbulence in the presence of buildings in a complex configuration. Wind speed and turbulent kinetic energy profiles from measurements and simulations with different turbulence schemes were compared. Preliminary results emphasise the difference between the different turbulence schemes.

Evaluation of Air Pollution Models for Their Use in Emergency Response Tools in Built Environments: The ‘Michelstadt’ Case Study in COST ES1006 ACTION

The first results of a model validation test case, carried out in the research context of the COST ES1006 Action, are outlined and discussed. The validation exercise was established with an application-oriented approach, devoted to the investigation of the modeling performances in the emergency-response framework.

Development and Application of MicroRMS Modelling System to Simulate the Flow, Turbulence and Dispersion in the Presence of Buildings

A modelling system for the simulation of the flow and dispersion from the mesoscale down to the urban microscale is under development. This modelling system is a microscale version of the regional off-line system RMS (RAMS-MIRS-SPRAY) — MicroRMS. A modified version of RAMS6.0 is used, in which a Cartesian grid and the ADaptive Aperture method are implemented for defining the presence of buildings in arbitrarily steep topography and where alternative versions of the k-e turbulence closure model were incorporated. After RAMS, the Lagrangian stochastic dispersion model MicroSPRAY is applied, specially devoted to simulate accidental gaseous releases at microscales, including the presence of obstacles and buildings. At present, the efforts are focused on the development of a micro-version of the interface code MIRS, calculating the surface and boundary layers’ parameters and the Lagrangian variables. The first step in the project was to harmonize the treatment of buildings between RAM6.0 and MicroSPRAY approaches. Here we present the first tests of MicroRMS prototype, applied to the MUST exercise of Cost732 Action, a flow and dispersion field test carried out in the Great Basin Desert (USA) in 2001, where 120 standard containers were set up in a regular array of obstacles.

Evaluation, Improvement and Guidance for the Use of Local-Scale Emergency Prediction and Response Tools for Airborne Hazards in Built Environments. Cost Action ES100 – A European Experience

Releases of hazardous agents, such as in a RDD event, in complex built environments pose a tremendous challenge to emergency first responders and authorities in charge due to casualties potentially involved and the significant environmental impact. Air motions in built-up areas are very complex and adequate modelling tools have to be applied properly in order to predict the dispersion of hazardous materials with sufficient accuracy within a very short time. Different types of tools are applied; however, it is not always clear the advantages and limitations of individual models and approaches. Therefore, it is of an exceptional interest to compile a detailed inventory of the different models and methodologies currently in use, to characterize their performance and to establish strategies for their improvement. The Action is a first cross-community initiative to join, to coordinate and to harmonize European efforts for a substantial improvement in the implementation of local-scale emergency response tools.

Comparison of RAMS, RMS and MSS Modelling Systems for High Resolution Simulations in Presence of Obstacles for the MUST Field Experiment

The goal of this work is to investigate, compare and evaluate three different modelling approaches to describe pollutant dispersion at the microscale and in presence of obstacles. The observed data used as reference for the comparison are those of the Mock Urban Setting Test (MUST) field campaign, providing flow and dispersion data measured within an idealized urban roughness. A case in neutral conditions was chosen.