R. Stern

Comparison of five eulerian air pollution forecasting systems for the summer of 1999 using the German ozone monitoring data

Eulerian state-of-the-art air pollution forecasting systems on the European scale are operated routinely by several countries in Europe. DWD and FUB, both Germany, NERI, Denmark, NILU, Norway, and SMHI, Sweden, operate some of these systems. To apply such modeling systems, e.g. for regulatory purposes according to new EU directives, an evaluation and comparison of the model systems is fundamental in order to assess their reliability. One step in this direction is presented in this study: The model forecasts from all five systems have been compared to measurements of ground level ozone in Germany. The outstanding point in this investigation is the availability of a huge amount of data – from forecasts by the different model systems and from observations. This allows for a thorough interpretation of the findings and assures the significance of the observed features. Data from more than 300 measurement stations for a 5-month period (May–September 1999) of the German monitoring networks have been used in this comparison. Different spatial and temporal statistical parameters were applied in the evaluation. Generally, it was found that the most comprehensive models gave the best results. However, the less comprehensive and computational cheaper models also produced good results. The extensive comparison made it possible to point out weak points in the different models and to describe the individual model behavior for a full summer period in a climatological sense. The comparison also gave valuable information for an assessment of individual measurement stations and complete monitoring networks in terms of the representativeness of the observation data.

Comparison of model results obtained with several european regional air quality models

An intercomparison study has been performed with four photo-oxidant dispersion models (EMEP, EURAD, LOTOS and REM3) which are currently capable of performing photo-oxidant formation calculations over larger path of Europe. The models, in principle, were run in the mode in which they are normally used, with their own input data and process descriptions. No attempt has been made to harmonize the input data. The study focused on the simulation of a six day episode (31 July-5 August, 1990) with relatively high observed ozone levels over northwest and central Europe (up to 140 ppbv) and which ended by a frontal passage. The study was mainly restricted to an analysis of the behaviour at four receptor sites across the centre of each modelling domain. Differences in yearly averaged anthropogenic emissions are in the order of 10% only. However, episode specific hourly emissions, both anthropogenic and biogenic, show much larger differences. Here up to 40% differences for anthropogenic emissions are found for central Europe while biogenic emissions differ even up to a factor 2-3. The meteorological data base for all models is created from the synoptic measurement network by different techniques. This can result in quite different model inputs as e.g. the value of the mixing height or trajectories. Other model inputs, e.g. dry deposition velocities or photolysis frequencies, show much closer agreements than expected from their derivation through different parameterizations. Model performance for the regional scale could only be observed for ozone. In central Europe, the large-scale ozone patterns are quite similar for all models. Here the temporal evolution at some receptor sites shows also a reasonable agreement with observations. However, in case a multi-component evaluation is possible it can be expected that differences between models can be revealed to a greater detail than was possible here. The model responses to emission reductions show substantial differences although the direction of the responses generally agree. The most complex model (EURAD) has the most pronounced response to anthropogenic emission reductions. The treatment of the biogenic emissions can have a large impact on scenario simulations.

Is regional air quality model diversity representative of uncertainty for ozone simulation

We examine whether seven state-of-the-art European regional air quality models provide daily ensembles of predicted ozone maxima that encompass observations. Using tools borrowed from the evaluation of ensemble weather forecasting, we analyze statistics of simulated ensembles of ozone daily maxima over an entire summer season. Although the model ensemble overestimates ozone, the distribution of simulated concentrations is representative of the uncertainty. The spread of simulations is due to random fluctuations resulting from differences in model formulations and input data, but also to the spread between individual model systematic biases. The ensemble average skill increases as the spread decreases. The skill of the ensemble in giving probabilistic predictions of threshold exceedances is also demonstrated. These results allow for optimism about the ability of this ensemble to simulate the uncertainty of the impact of emission control scenarios.

Data Assimilation for Ctm Based on Optimum Interpolation and Kalman Filter

The aim of this paper is to compare the performance of two data assimilation schemes for the Eulerian chemistry transport model REM/CALGRID. Optimum Interpolation (OI) and Kaiman Filtering (KF) have been applied to assimilate hourly O3 and NO2 observations in a model run for July 2001. The comparison comprises the structure of the obtained model error covariances and the analysed concentration fields. In addition, an example of an assessment of model parameters such as turbulent exchange coefficients by means of the Kaiman filter is given.

Long term evaluation of the ozone forecast by an Eulerian model

Abstract The regional chemistry transport model REM3 has been applied operationally to forecast ozone since 1997 at the FU - Berlin. Within a forecast system REM3 is utilized to predict the large scale ozone situation in Central Europe. The paper gives an overview about the application of the model and assess the model performance with respect to the objective of the model application.

Curriculum vitae of the LOTOS–EUROS (v2.0) chemistry transport model

The development and application of chemistry transport models has a long tradition. Within the Netherlands the LOTOS–EUROS model has been developed by a consortium of institutes, after combining its independently developed predecessors in 2005. Recently, version 2.0 of the model was released as an open-source version. This paper presents the curriculum vitae of the model system, describing the model’s history, model philosophy, basic features and a validation with EMEP stations for the new benchmark year 2012, and presents cases with the model’s most recent and key developments. By setting the model developments in context and providing an outlook for directions for further development, the paper goes beyond the common model description. With an origin in ozone and sulfur modelling for the models LOTOS and EUROS, the application areas were gradually extended with persistent organic pollutants, reactive nitrogen, and primary and secondary particulate matter. After the combination of the models to LOTOS–EUROS in 2005, the model was further developed to include new source parametrizations (e.g. road resuspension, desert dust, wildfires), applied for operational smog forecasts in the Netherlands and Europe, and has been used for emission scenarios, source apportionment, and long-term hindcast and climate change scenarios. LOTOS–EUROS has been a front-runner in data assimilation of ground-based and satellite observations and has participated in many model intercomparison studies. The model is no longer confined to applications over Europe but is also applied to other regions of the world, e.g. China. The increasing interaction with emission experts has also contributed to the improvement of the model’s performance. The philosophy for model development has always been to use knowledge that is state of the art and proven, to keep a good balance in the level of detail of process description and accuracy of input and output, and to keep a good record on the effect of model changes using benchmarking and validation. The performance of v2.0 with respect to EMEP observations is good, with spatial correlations around 0.8 or higher for concentrations and wet deposition. Temporal correlations are around 0.5 or higher. Recent innovative applications include source apportionment and data assimilation, particle number modelling, and energy transition scenarios including corresponding land use changes as well as Saharan dust forecasting. Future developments would enable more flexibility with respect to model horizontal and vertical resolution and further detailing of model input data. Published by Copernicus Publications on behalf of the European Geosciences Union. 4146 A. M. M. Manders et al.: Curriculum vitae of the LOTOS–EUROS (v2.0) chemistry transport model This includes the use of different sources of land use characterization (roughness length and vegetation), detailing of emissions in space and time, and efficient coupling to meteorology from different meteorological models.

DATA ASSIMILATION FOR CT-MODELLING BASED ON OPTIMUM INTERPOLATION

In this work data assimilation of ground based concentration measurements into the fields of the Eulerian transport model REM3 was presented. The assimilation is based on the theoretical framework of Optimum Interpolation. Special emphasis was given to the modelling of the covariance of the background error and the variance of the observation error. An new scheme which accounts for the inhomogeneity of the concentration fields and their measurements was developed. It relies on the discrimination of air quality regimes in both the observations and the calculated fields of the model REM3. The performance of the new approach was compared with that of the “standard” homogeneous and isotropic covariance modelling. The new approach leads to more pronounced gradients in the NO2 concentrations, especially to lower concentration in rural areas, which seem to be more realistic.

An Application of the Empirical Kinetic Modeling Approach (EKMA) to the Cologne Area

The Empirical Kinetic Modeling Approach (EKMA), recently proposed by the EPA, is a method for deriving ozone-percursor relationships that can be used to design a control strategy for urban ozone reduction. The technique is based on an isopleth diagram generated by computer simulations of the chemical reactions occuring among pollutants in a well-mixed box subjected to dilution, time varying light intensity, diurnal dependence of the emissions, and background concentration levels. The performance of EKMA is discussed in an application to the Cologne area of the FRG. The lateral and vertical spatial distribution of the precursor emissions in this area strongly violates the assumption of homogeneous mixing underlying EKMA. Therefore, the applicability of EKMA for developing control strategies in the Cologne area is limited.

Impact of Special Features of Numerically Predicted and Analysed Meteorological Data on the Results of Ozone Forecast by a PBL-CTM

The Freie Universitat Berlin and IVU1 develop a complex ozone forecast system, which combines statistical and fuzzy methods with regional Eulerian transport modelling. Each method is an independent forecast tool focussing on different spatial and temporal scales. The statistically and fuzzy based forecast is locally applied, whereas the Eulerian transport model predicts the large scale development of ozone patterns. The results of the transport modelling will be used as an additional parameter for the statistical and fuzzy methods in a framework of a neuro fuzzy module. Ideally, the combination of both approaches shall improve the forecast performance (Reimer and Dlabka, 1998).

Simulation of a Photochemical Smog Episode in the Rhine-Ruhr Area with a Three Dimensional Grid Model

An advanced Eulerian photochemical dispersion model is applied to the Rhine-Ruhr area in the FRG. One of the main features of this area are the complicated wind conditions induced by the complexity of the terrain. Therefore, special emphasis is given in the preparation of the three dimensional wind field as input for the dispersion model. Two methods of wind field generation are discussed, one based on interpolation of surface winds, the other on a prognostic mesoscale model. The calculated concentrations of ozone, NO and NO2, utilizing both of the wind fields, are compared with measurements. Preliminary results are presented.