Evaluation of high-resolution GRAMM–GRAL (v15.12/v14.8) NO<sub><i>x</i></sub> simulations over the city of Zürich, Switzerland

Abstract

Abstract. Hourly NO x concentrations were simulated for the city of Zürich, Switzerland, at 10 m resolution for the years 2013-2014. The simulations were generated with the nested mesoscale meteorology and micro-scale dispersion model system GRAMM-GRAL (versions v15.12 and v14.8) by applying a catalogue-based approach. This approach was specifically designed to enable long-term city-wide buildingresolving simulations with affordable computation costs. It relies on a discrete set of possible weather situations and corresponding steady-state flow and dispersion patterns that are pre-computed and then matched hourly with actual meteorological observations. The modelling system was comprehensively evaluated using eight sites continuously monitoring NO x concentrations and 65 passive samplers measuring NO 2 concentrations on a 2-weekly basis all over the city. The system was demonstrated to fulfil the European Commission standards for air pollution modelling at nearly all sites. The average spatial distribution was very well represented, despite a general tendency to overestimate the observed concentrations, possibly due to a crude representation of trafficinduced turbulence and to underestimated dispersion in the vicinity of buildings. The temporal variability of concentrations explained by varying emissions and weather situations was accurately reproduced on different timescales. The seasonal cycle of concentrations, mostly driven by stronger vertical dispersion in summer than in winter, was very well captured in the 2-year simulation period. Short-term events, such as episodes of particularly high and low concentrations, were detected in most cases by the system, although some unrealistic pollution peaks were occasionally generated, pointing at some limitations of the steady-state approximation.The different patterns of the diurnal cycle of concentrations observed in the city were generally well captured as well. The evaluation confirmed the adequacy of the cataloguebased approach in the context of city-scale air pollution modelling. The ability to reproduce not only the spatial gradients but also the hourly temporal variability over multiple years makes the model system particularly suitable for investigating individualized air pollution exposure in the city.

Graz Lagrangian Model (GRAL) for Pollutants Tracking and Estimating Sources Partial Contributions to Atmospheric Pollution in Highly Urbanized Areas

“…Unfortunately, the state air quality report contains too little data for a matching analysis of simulated and observed values. An attempt to check the model to FAIRMODE (Forum for air quality modeling in Europe) [65,66] criteria compliance similar to the authors at [26] was made. However, due to the low number of observed values per monitoring station (from 1 to 6), the results are not relevant to the FAIRMODE methodology.…”

“…The objectives of the current research were to assess the pollutants concentrations and determine the contributions of the main groups of sources to Krasnoyarsk's atmosphere, concerning the regional specifics. Based on the research results in [26][27][28], which demonstrates the advantages of Lagrangian models for complex landscapes and communities, the Graz Mesoscale Model (GRAMM)/Graz Lagrangian model (GRAL) methodology [29] was used to simulate the pollutants dispersion from the sources (industry, heat-generating facilities, transport, and private households). A computational experiment was carried out based on the real meteorological parameters for the particular period (the eve of the 2019 Winter Universiade [30]).…”

TRAFAIR: Understanding Traffic Flow to Improve Air Quality

“…By comparing simulated concentration obtained with the applications of PMSS model and a full CDF model well adapted for the planetary boundary layer, final concentration differ in general by 3-5% [15], [16]. Instead, for the GRAL model the temporal correlations between simulation and observation pollutant concentrations are generally in the range 0.5-0.8 at hourly scale and 0.7-0.9 at daily scale [17].…”

Development of the Mesoscale Model GRAMM-SCI: Evaluation of Simulated Highly-Resolved Flow Fields in an Alpine and Pre-Alpine Region

“…This led to the development of socalled wind-field libraries established for a single calendar year (e.g., [1]), whereby the horizontal resolution is 200 m in the current library for the reference year 2015. Examples for wind-field libraries for varying purposes are reported for instance in [2][3][4][5], or [6]. The development of the mesoscale model GRAMM-SCI (Graz Mesoscale Model-Scientific) aims at providing such wind fields in highly complex terrain with a horizontal resolution below 1000 m. GRAMM-SCI ( [7,8]) is a new branch of the model GRAMM, which has been further developed to make use of ERA5 (ECMWF Reanalysis 5th Generation) reanalysis data issued by the European Centre for Medium-Range Weather Forecasts (ECMWF, [9]).…”