R. San José

Prediction of ozone levels in London using the MM5-CMAQ modelling system

Air pollution in urban areas has important implications for health and environmental management. Consequently, various methodologies have been developed for its assessment. Traditionally, simple approaches such as the box model or the Gaussian plume have been used to assess urban air quality. The use of Eulerian grid models, which provide a more realistic and comprehensive description of the urban atmosphere, has been increasing over the past few years. This paper reports on the use of the MM5-CMAQ modelling system to predict hourly ozone levels over London, UK. This work represents the first application of MM5-CMAQ in the UK for predicting air pollution levels in London. Domain resolutions of 9km, 3km and 1km (innermost) have been employed for this study. Summer periods in July and August 2002 have been simulated and the predicted results have been compared to several urban background stations across London. Input data for emissions have been derived from the UK National Emissions inventory and from the outputs of the EMIMO emission model. The CBM-IV chemical scheme has been used to simulate the atmospheric reactions for ozone. The model performance has been evaluated with measured data through a range of statistical measures. Although, the MM5-CMAQ model reproduces the ozone temporal trends it was not able to simulate the peak magnitudes consistently. Furthermore, for nighttime the model overestimated the ozone concentrations. The paper discusses the model performance and reasons for these discrepancies in terms of the various input data including emissions and meteorological parameters.

Air Quality Modeling

Air pollution modeling (APM) is being developed and used in order to better understand, investigate, assess, and regulate the quality of the atmospheric environment and the distribution of toxic pollutants which are often used in ecotoxicology. Atmospheric models are also used to assess the impact of air pollutants on human health. In this respect, APM covers a very complex and interdisciplinary scientific area, where aspects of environmental policy and decision making mix together with aspects like remote sensing, land-use impact, initial and boundary conditions, data assimilation techniques, chemical schemes, comparison methods between data measured and data modeled, computational efficiency and performance, coupling with the meteorology, long-range transport impact on local air pollution, new satellite data assimilation techniques, real-time and forecasting air quality modeling and sensitivity analysis, and many others. APM has progressed significantly during the last two decades, attracting the interest of various research groups and initiatives worldwide. It covers all aspects related to the life cycle of pollutants, starting from their emission or ‘production’ within the atmosphere, and ending with their impacts on man and the ecosystem. This field of science is interested to describe the generation, transportation, dispersion, physical and chemical transformation, and the impact of various categories of substances that are identified and classified as air pollutants via the environmental legal framework and the scientific community. It should be noted that air pollution is very much related to meteorological fields, since the atmosphere is governed by the general fluid mechanics laws described by the Navier–Stokes equation system, while progress in computer performance during the last decades has substantially impelled the research on air quality modeling in a parallel way. This contribution focuses on providing a general overview of the state of the art on air quality modeling, from the point of view of the ‘user community’, that is, policy makers, urban planners, environmental managers, etc. It also tries to bring to the discussion key questions concerning the air quality modeling success in usage, such as: identification of uncertainties in emission inventories and meteorological fields, capability of simulating pollutants like urban aerosols, the next-generation developments in models to answer new scientific questions, etc.

A modelling study of an extraordinary night time ozone episode over Madrid domain

AbstractDuring the early morning hours on April 29, 2000, a time series of ozone observations from several stations showed that a uniqueand exceptional ozone episode occurred in Madrid city and surrounding areas, whereby monitoring stations reported ozoneconcentrations up to 1190 mg/m 3 . In order to investigate this phenomenon, two different air quality modeling approaches are usedhere:U The FLEXTRA trajectory model was initially used, suggesting that an intrusion of stratospheric air occurred over the Madridarea and brought stratospheric air down to 1000e2000 m AGL. The local circulation system, not resolved by the FLEXTRAtrajectories, subsequently brought some of this stratospheric air to the surface. However, the maximum ozone concentrationthat could be explained by this process is much less than the observed one.U The OPANA Air Quality Modeling System was also employed to study air quality over the Madrid community and citydomains. Results suggested that the main wind direction returned to Madrid after 180( wind change direction 1 to 2 h beforethe ‘‘episode’’, bringing back ozone generated the day before (typical weekend day with high traffic density). On the other hand,convergence of winds along the South-West North-East axis over the Madrid community showed an important correspondencewith the sequence of observations.Preliminary conclusions show that the exceptional meteorological conditions on such a night could be reason for the occurrenceof high values. Additional technical circumstances (such as technical incidences in some monitoring stations) also suggest that someinstruments did not work properly under these high concentrations and, thus, real ozone concentrations may have been lower thanthose measured. 2004 Elsevier Ltd. All rights reserved.

Fluxes of ammonia over oilseed rape: Overview of the EXAMINE experiment

An integrated field experiment was organized as part of the EC EXAMINE project to quantify surface–atmosphere fluxes of ammonia (NH3). Fluxes of NH3, NH4+ aerosol, HNO3 and HCl were measured using the gradient method with several continuous and batch sampling systems. Within-canopy NH3 was determined to quantify the contribution of leaf cuticles, sub-stomatal apoplastic (intercellular) fluids and other sources and sinks to net fluxes. The campaign included the first field measurements of apoplastic pH and [NH4+], providing independent estimates of the stomatal compensation point (χs) for comparison with micrometeorological results. The latter also compared fluxes before and after cutting. Under the clean conditions of the experiment, [NH3][HNO3] and [NH3][HCl] were much less than values required for aerosol formation, while the NH4+ aerosol size distribution indicated that aerosol evaporation would be much slower than the time-scale of turbulent exchange. Nevertheless, the measurements suggest that aerosol production/growth as well as formation of HCl may have occurred within the canopy. Apoplastic [NH4+] and pH of leaves showed no diurnal patterns, with the main control on χs being the temperature dependence of the solubility equilibria. Fluxes of NH3 were bi-directional (−200 to 620 ng m−2 s−1), with deposition generally occurring when the canopy was wet and emission when it was dry, particularly during the day. Nocturnal emissions indicated a non-stomatal NH3 source, while daytime emissions were larger than indicated by the apoplastic estimates of χs. The within-canopy data, together with an inverse Lagrangian source–sink analysis, showed decomposing litter to be a significant NH3 source, explaining nocturnal NH3 emissions and larger emissions following cutting. Daytime net fluxes were controlled by the top part of the canopy, due to χs for siliques apparently being larger than for leaves. The measurements have been used to develop multi-layer resistance models of NH3 exchange. A 3-layer ‘foliage–litter–silique model’ provides a detailed mechanistic treatment of the component fluxes, while a 2-layer ‘foliage–litter model’ is better suited to generalization in atmospheric transport models. Application of the new models should help improve estimates of regional atmospheric ammonia budgets.

On the Use of MRF/AVN Global Information to Improve the Operational Air Quality Model OPANA

Operational air quality models have become an important tool to assist the decision makers in European Environmental Offices at different levels: cities, regional and state. Because of the important advance on computing capabilities during the last few years the possibility of incorporating the complex research and academic mesoscale air quality models under routine operational basis has become a reality. OPANA model is the operational version of the research model ANA (Atmospheric mesoscale Numerical pollution model for regional and urban Areas). This model is a limited area model (mesoscale beta) and the capability to extend the prediction horizon is limited unless proper boundary conditions are provided during long simulations. In this contribution we show how AVN/MRF (NOAA) vertical numerical meteorological soundings are incorporated to the OPANA system by using JAVA technology. This new feature helps to keep the air quality model into medium power workstations and the performance is improved accordingly. This technology avoids running mesoscale models over larger areas (continental scale) to accordingly increase the forecasting temporal horizon.

The evaluation of the air quality impact of an incinerator by using MM5-CMAQ-EMIMO modeling system : North of Spain case study

The use of sophisticated air pollution modeling systems to evaluate the impact of different industrial plant emissions is currently done in an extensive way. MM5-CMAQ (PSU/NCAR and EPA, USA) is one of the most applicable air quality modeling systems to evaluate those impacts. In this contribution we present the methodology and results obtained when applying the MM5-CMAQ air quality modeling system for evaluating the potential impact of an incinerator in San Sebastián (Basque Country, Spain). We have used the EMIMO (UPM, Spain) emission model to simulate the emissions from biogenic and anthropogenic sources including traffic and tertiary sector sources. The study includes the air quality impact of a highway located near the incinerator named A8 and 6 industrial plants which already exist. The impact study has been compared with the results obtained from this highway impact and the 6 industrial plants which are normally operating during the last 30 years. The system has been prepared to simulate also Cadmium, Arsenic, Nickel, Lead and Benzo(a)pyrene air quality impacts. The PCDD/F air concentrations have been determined for the 16 toxic dioxins and furans as determined in the bibliography. The criteria pollutants such as CO, NOx, SO(2), PM(10) and O(3) have also been determined according to the different EU Directives which limit the values of such a pollutants for different periods of time.

Accurate ozone prognostic patterns for Madrid area by using a high spatial and temporal eulerian photochemical model

The ANA Air Quality Model (ANA stands for Atmospheric Mesoscale Numerical Pollution Model for Regional and Urban Areas) has been applied over Madrid during a five day period in June, 1995. The domain is 80 × 100 km2 and the spatial resolution is 2000 m. The ANA system is driven by a meteorological model REMEST and it includes a detailed emission model for anthropogenic and biogenic sources with 250 m spatial resolution and 60 minutes temporal resolution. Different deposition processes are used such as the Wesely (1989) and Erisman et al. (1994) resistance approaches and the simple aerodynamic resistance. The photochemical processes and the general chemistry is based on the CBM-IV mechanism for the organic compounds and solved by the SMVGEAR method (CHEMA module).The model uses 14 different landuse types which are obtained by using the REMO module which uses the information provided by the LANDSAT-5 satellite image over the domain. The emission module EMIMA takes into account the point, line and area emissions over the domain. Special importance is given to the biogenic emissions which are obtained by using the satellite landuse classification for caducous, perenneal and mixed terrain. The emission module considers the EPA and CORINAIR emission factors. The results show an accurate prediction of the ozone maxima for the five days and also the general pattern of the ozone observed data. The five day simulation is characterized by a local low pressure over the Madrid Area and high pressures over Spain and West of Europe. The ozone surface patterns show the diurnal cycle and the maxima concentrations up to 140-160 ppb for suburban areas during afternoon hours. The general performance of the model is considered quite good. The computer power requirements continue to be very high for standard workstations. Future progress on parallel platforms should improve considerably the computer time requirements.

An incinerator air quality impact assessment for metals, PAH, dioxins and furans by using the MM5-CMAQ-EMIMO atmospheric modelling system: Spain case study

In this paper, we show the implementation of a modified version of MM5-CMAQ for carrying out an air quality impact analysis for installing an incinerator in the Basque Country model domain (Spain). The modified CMAQ model (EPA USA, 2004) includes Poly-Chlorinated Dibenzop-Dioxins and Dibenzo-Furans (dioxins and furans). This model represents their congeners as divided between gaseous and aerosol forms that exchange mass based on theoretical coefficients for gas to particle portioning. The emission model EMIMO ? developed by UPM ? has been adapted to incorporate the three metals and the benzo(a)pyrene according to the EMEP annual emission inventory. In addition, the PCDD/F EMEP emission inventory has been incorporated into the EMIMO model to produce proper 1 hr and 1 km ? 1 km emission PCDD/F estimation. The emissions of the projected incinerator are incorporated by using the chimney technical parameters and the limit emission values (worst-case scenario) prescribed in the Directive/2000/76/CE.

A Multi-model Case Study on Aerosol Feedbacks in Online Coupled Chemistry-Meteorology Models Within the COST Action ES1004 EuMetChem

The importance of different processes and feedbacks in online coupled chemistry-meteorology models for air quality simulations and weather prediction was investigated in COST Action ES1004 (EuMetChem). Case studies for Europe were performed with different models as a coordinated exercise for two episodes in 2010 in order to analyse the aerosol direct and indirect radiative effect and the response of different models to aerosol-radiation interactions.

Numerical modelling of 2003 summer forest fire impacts on air quality over Portugal

In 2003 Portugal faced the worst fire season ever recorded. The main purpose of this work is to evaluate the effects of the 2003 forest fires on the air quality, applying four numerical modelling systems (LOTOS-EUROS, MM5-CMAQ, WRF/chem and MM5-CHIMERE), and to compare their results with air quality data from several monitoring stations in Portugal. Forest fire emissions have been calculated taking into account the most suitable parameters for Portuguese forest/fire characteristics and the area burned by each forest fire. They were added to the anthropogenic and biogenic gridded emissions, according to the fire location and assuming a uniform fire spread and injection into the mixing layer. Simulations were performed during August 2003 regarding gaseous and particulate matter pollutants. To better evaluate the impact of forest fire emission on the air quality, a baseline simulation was performed, including the “conventional” emissions, along with a forest fire simulation, which also considered emissions from forest fires. Modelling hourly results, namely particulate matter (PM) and ozone (O3) concentration, values have been compared to measurement data at several monitoring locations. In general, the different modelling systems show a good performance, which improves when forest fire emissions are considered, particularly for the PM concentrations. The influence of the forest fire emissions in O3 formation is not so evident and needs more attention. The evaluation of the impact of forest fires on the air quality should be included in air quality assessment procedures, specifically in areas that