Pedro Jiménez

Comparison of photochemical mechanisms for air quality modeling

Abstract Photochemical mechanisms are a critical module of air quality models. In the past 20 years, several mechanisms have been developed to study the chemistry of the troposphere. This work compares several state-of-the-science photochemical mechanisms (including LCC, CBM-IV, RADM2, EMEP, RACM, SAPRC99, and CACM which have never been compared before in other studies). Concise descriptions of the chemical schemes are included. The main difference among existing mechanisms is the lumping technique used to classify organic compounds into surrogate groups. First, box model calculations are conducted to highlight the features that lead to differences in the modeled behaviors of photochemical pollutants and their precursors. Results indicate that most chemical schemes yield similar ozone concentrations. Nevertheless, there are significant discrepancies, mainly in predicted concentration of HNO 3 , HO 2 and total PAN among model simulations. Finally, the sources of the discrepancy are identified.

Urban photochemical pollution in the Iberian Peninsula: Lisbon and Barcelona airsheds.

Abstract Numerical simulations with photochemical transport models were independently performed for two domains situated in the Iberian Peninsula covering the Lisbon and Barcelona airsheds. Although the days chosen for simulation of the two cities are not the same, the synoptic situations in both cases, known as typical summertime situations, were similar, which allowed the development of typical mesoscale circulations, such as sea breezes and mountain and valley winds dominated by the Azores anticyclone. Emission inventories for the two areas were developed. The O3 concentrations recorded in both cities have a similar level. Nevertheless, Ox values in Barcelona are higher than in Lisbon, which may, at a first glance, indicate an apparently more oxidant atmosphere in Barcelona. Photochemical modeling for the two cities has shown that the behavior of the circulatory patterns in both urban areas is rather different, which mainly has to do with the different strengths of the sea breeze and the topography, inducing an important offshore vertical layered dimension of pollutant transport in Barcelona versus an important inland horizontal transport in Lisbon.

Multiscale modeling of air pollutants dynamics in the northwestern Mediterranean basin during a typical summertime episode

[1]xa0The complex behavior of photochemical pollutants in the northwestern Mediterranean basin (NWMB) is conditioned by the superposition of circulations of different scale and the pattern of emissions. Therefore a new approach to the modeling of air quality in the NWMB has been adopted by combining the global climate-chemistry model ECHAM5/MESSy and the regional modeling system MM5-EMICAT2000-CMAQ to analyze the high levels of photochemical air pollution during a typical summertime episode. We show that this combination of models is well suited to address the range of scales involved. The complexity of the area requires the application of high spatial and temporal resolution (2 km and 1 hour) modeling to cover local to regional interactions. We address the local and large-scale processes controlling tropospheric ozone in the NWMB, notably emissions and photochemistry, convective and advective transport, deposition processes, and stratosphere-troposphere exchange. The simulation results indicate that the ozone buildup largely results from local photochemical production, which strongly exceeds the removal rates through transport and deposition. The contribution by advective transport is limited, associated with the stagnant meteorological conditions. In the lower troposphere, local recirculation systems are of key importance. The strength of the land-sea breeze circulation and thermally or mechanically driven convection over the complex orography of the eastern Iberian coast can induce vertical transport and the layering of air pollution.

Ozone response to precursor controls in very complex terrains: Use of photochemical indicators to assess O3-NOx-VOC sensitivity in the northeastern Iberian Peninsula

[1]xa0The kinetics of ozone (O3) chemistry and its two main precursors, nitrogen oxides (NOx) and volatile organic compounds (VOC), represents an important field of uncertainty in atmospheric chemistry and photochemical modeling. This uncertainty affects the design of control strategies to reduce tropospheric O3 production. The effect of controlling ozone precursors on sensitivity regimes was evaluated by performing simulations with MM5-EMICAT2000-CMAQ model to represent O3 formation in the northeastern Iberian Peninsula with baseline emission rates for VOC and NOx, and reducing anthropogenic VOC and NOx emissions on a 35%. Three different scenarios were considered in order to assess chemical sensitivity in urban, industrial, and background domains. Areas downwind of the city of Barcelona benefit from NOx reductions (reduction of 10 ppb in ground-level O3), while the same reduction causes an important increment of O3 in Barcelona (9 ppb) and the area downwind of Tarragona (18 ppb), with a high industrial influence. The city of Barcelona benefits from VOC reductions (10 ppb of O3) as well as the industrial zone of Alcover (20 ppb). The rest of the domain is practically insensitive to VOC reductions. Diverse photochemical species derived from the air quality model were used as indicators in order to establish the chemical sensitivity regime existing in the areas, analyzing whether O3 values reacted consistently to similar changes in emissions. Results showed that NOy (total reactive nitrogen) and O3/NOy are the indicators involving a lower uncertainty when assessing sensitivity, according to the narrow transition regime between NOx- and VOC-sensitive chemistry and the low uncertainty observed. Indicators performed better in VOC-sensitive than in NOx-sensitive domains. H2O2- and HNO3- derived indicators entailed higher uncertainties since transition regimes between NOx and VOC sensitivity covered a wide range. The extent of reaction also performed as a good indicator to separate NOx- and VOC-sensitive regimes. This sensitivity analysis provides a tool for establishing hypothetical control policies for O3 precursor emissions through a comparison of simulated correlation between the species.

An Interval NLPV Parity Equations Approach for Fault Detection and Isolation of a Wind Farm

In this paper, the problem of fault diagnosis of a wind farm is addressed using interval nonlinear parameter-varying (NLPV) parity equations. Fault detection is based on the use of parity equations assuming unknown but bounded description of the noise and modeling errors. The fault detection test is based on checking the consistency between the measurements and the model, by finding if the formers are inside the interval prediction bounds. The fault isolation algorithm is based on analyzing the observed fault signatures online and matching them with the theoretical ones obtained using structural analysis. Finally, the proposed approach is tested using the wind farm benchmark proposed in the context of the wind farm fault-detection-and-isolation/fault-tolerant-control competition.

Influence of initial and boundary conditions for ozone modeling in very complex terrains: A case study in the northeastern Iberian Peninsula

Initial (IC) and boundary conditions (BC) are required in order to solve the set of stiff differential equations included in air quality models. In this work, the influences of IC-BC are analyzed in the northeastern Iberian Peninsula (NEIP) by applying MM5-EMICAT2000-CMAQ. A multiscale-nested configuration has been used to generate the IC-BC. The wider domain (D1) covers an area of 1392x1104km^2 centered in the Iberian Peninsula. Domain 2 (D2) covers an area of 272x272km^2 in the NEIP (D2) with high spatial and temporal resolution. The information related to BC has been supplied to D2 through one-way nesting. Different scenarios were considered (base case, increments of +50% in ozone (O3) IC, +50% in O3 BC, +50% in O3 precursors IC, +50% in O3 precursors BC and clean BC). The impacts of the IC on a site decrease with simulation time. Focusing on the conditions within the PBL, a 48-h spin-up time is sufficient to reduce the impact factor of IC to 10% or less for O3 since the influence of pervasive local emissions. The influences of BC are more important for areas near domain boundaries, especially in areas where the contribution of O3 precursors is due to a short-medium range transport.

Influence of high-model grid resolution on photochemical modelling in very complex terrains

The study of photochemical pollution in very complex terrains, such as the Northeastern Iberian Peninsula (NEIP), is primarily influenced by local topography. This kind of study demands a high spatial resolution. In order to illustrate the influence of the grid resolution on tropospheric ozone levels, several simulations were carried out with MM5-EMICAT2000-CMAQ model using horizontal resolutions ranging from 8, 4 and 2 km and with 6 or 16 vertical layers during an episode of photochemical pollution (13–16 August 2000). High resolutions lead to improve discrete and categorical statistical parameters when evaluating the model against meteorological and air quality data. Results show that coarser grids tend to present a homogeneous and smoothened behaviour of wind flows. Also, results do not manage to describe the particularities of the circulations of the region. Coarser simulations underestimate maximum ozone levels since the grid resolution highly influences the formation and loss processes of ozone.

An Evaluation of the Performance of the CHIMERE Model over Spain Using Meteorology from MM5 and WRF Models

The presence of high pollution levels in the atmosphere can produce damages to human health and ecosystems. Because of this reason, the prediction of air pollutant concentration is important to prevent any potential damage. Chemistry-transport models constitute a useful tool to quantify the presence of pollutants in the atmosphere. Input information, such as meteorology and emissions, has a strong influence on model results. Many research activities are focused on trying to reduce errors affecting input information. In this paper we have applied the CHIMERE photochemical model to simulate ozone, NO2 and SO2 in Spain for two sets of meteorological fields obtained with the MM5 and WRF meteorological models. An evaluation of the performance of the CHIMERE model for both meteorological data sets is presented. Very similar air pollutant concentrations were found for the three pollutants and for the two sets of meteorological information.

Control of ozone precursors in a complex industrial terrain by using multiscale-nested air quality models with fine spatial resolution (1 km2).

Abstract The location of the northeastern Iberian Peninsula (NEIP) in the northwestern Mediterranean basin, the presence of the Pyrenees mountain range (with altitudes >3000 m), and the influence of the Mediterranean Sea and the large valley canalization of Ebro river induce an extremely complicated structure for the dispersion of photochemical pollutants. Air pollution studies in very complex terrains such as the NEIP require high-resolution modeling for resolving the very complex dynamics of flows. To deal with the influence of larger-scale transport, however, high-resolution models have to be nested in larger models to generate appropriate initial and boundary conditions for the finer resolution domains. This article shows the results obtained through the utilization of the MM5-EMICAT2000-CMAQ multiscale-nested air quality model relating the sensitivity regimes for ozone (O3)-nitrogen oxides (NOx)-volatile organic compounds (VOCs) in an area of high geographical complexity, like the industrial area of Tarragona, located in the NEIP. The model was applied with fine temporal (one-hour) and spatial resolution (cells of 24 km, 2 km, and 1 km) to represent the chemistry and transport of tropospheric O3 and other photochemical species with respect to different hypothetical scenarios of emission controls and to quantify the influence of different emission sources in the area. Results indicate that O3 chemistry in the industrial domain of Tarragona is strongly sensitive to VOCs; the higher percentages of reduction for ground-level O3 are achieved when reducing by 25% the emissions of industrial VOCs. On the contrary, reductions in the industrial emissions of NOx contribute to a strong increase in hourly peak levels of O3. At the same time, the contribution of on-road traffic and biogenic emissions to ground-level O3 concentrations in the area is negligible with respect to the pervasive weight of industrial sources. This analysis provides an assessment of the effectiveness of different policies for the control of emission of precursors by comparing the modeled results for different scenarios.

Fault Diagnosis of a Wind Farm using Interval Parity Equations

Abstract In this paper, the problem of fault diagnosis of a wind farm is addressed using interval parity equations. Fault detection is based on the use of parity equations and unknown but bounded description of the noise and modeling errors. The fault detection test is based on checking the consistency between the measurements and the model by finding if the formers are inside the interval prediction bounds. The fault isolation algorithm is based on analyzing the observed fault signatures on-line, and matching them with the theoretical ones obtained using structural analysis. Finally, the proposed approach is tested using the wind farm benchmark proposed in the context of the wind farm FDI/FTC competition.