Oriol Jorba

Cluster analysis of 4 day back trajectories arriving in the Barcelona Area (Spain) from 1997 to 2002

A cluster algorithm was implemented to analyze the backward trajectories arriving in the Barcelona area (BCN), located at the eastern coast of the Iberian Peninsula. Five years of 4-day kinematic back trajectories, computed with version 4 of the Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT), were clustered and classified in groups of similar length and curvature. To describe better the tropospheric circulations at BCN, backward trajectories arriving at 5500, 3000, and 1500 m above sea level were analyzed. The main transport patterns are identified at 5500 m: westerly flows (49% of the total situations), northwesterly flows (17%), southwesterly flows (20%), and regional recirculations over Europe and the Mediterranean Sea (15%). An annual distribution of the transport patterns is described. During the summertime, moderate westerlies (19%) and southwesterlies (13%) in the middle troposphere, slow westerlies (11%) and southwesterlies (10%) at 3000 m, and regional recirculations (29%) at 1500 m characterize the BCN long-range transport. This general pattern varies during wintertime, with more westerlies at 5500 m and an increase of northern and northwestern situations at 1500 m. A large number of situations with decoupling between the lower and middle troposphere are observed when combining 5500- and 1500-m cluster results. Interannual variability is discussed, and the influence of the North Atlantic Oscillation phase is captured by winter average regime patterns.

An annual assessment of air quality with the CALIOPE modeling system over Spain.

The CALIOPE project, funded by the Spanish Ministry of the Environment, aims at establishing an air quality forecasting system for Spain. With this goal, CALIOPE modeling system was developed and applied with high resolution (4km×4km, 1h) using the HERMES emission model (including emissions of resuspended particles from paved roads) specifically built up for Spain. The present study provides an evaluation and the assessment of the modeling system, coupling WRF-ARW/HERMES/CMAQ/BSC-DREAM8b for a full-year simulation in 2004 over Spain. The evaluation focuses on the capability of the model to reproduce the temporal and spatial distribution of gas phase species (NO(2), O(3), and SO(2)) and particulate matter (PM10) against ground-based measurements from the Spanish air quality monitoring network. The evaluation of the modeling results on an hourly basis shows a strong dependency of the performance of the model on the type of environment (urban, suburban and rural) and the dominant emission sources (traffic, industrial, and background). The O(3) chemistry is best represented in summer, when mean hourly variability and high peaks are generally well reproduced. The mean normalized error and bias meet the recommendations proposed by the United States Environmental Protection Agency (US-EPA) and the European regulations. Modeled O(3) shows higher performance for urban than for rural stations, especially at traffic stations in large cities, since stations influenced by traffic emissions (i.e., high-NO(x) environments) are better characterized with a more pronounced daily variability. NO(x)/O(3) chemistry is better represented under non-limited-NO(2) regimes. SO(2) is mainly produced from isolated point sources (power generation and transformation industries) which generate large plumes of high SO(2) concentration affecting the air quality on a local to national scale where the meteorological pattern is crucial. The contribution of mineral dust from the Sahara desert through the BSC-DREAM8b model helps to satisfactorily reproduce episodic high PM10 concentration peaks at background stations. The model assessment indicates that one of the main air quality-related problems in Spain is the high level of O(3). A quarter of the Iberian Peninsula shows more than 30days exceeding the value 120μgm(-3) for the maximum 8-h O(3) concentration as a consequence of the transport of O(3) precursors downwind to/from the Madrid and Barcelona metropolitan areas, and industrial areas and cities in the Mediterranean coast.

Using NOAA AVHRR and SPOT VGT data to estimate surface parameters: application to a mesoscale meteorological model

The mesoscale numerical weather prediction model MM5, the 5th generation Pennsylvania State University/NCAR Mesoscale Model, uses a global land-use map to set the physical parameters on the surface characteristics to model the soil-atmosphere processes. These parameters are albedo, emissivity, thermal inertia, roughness length and soil moisture. A new estimation of soil parameters is done for the north-east of the Iberian Peninsula from an AVHRR data set of year 2000. The new values are introduced into MM5 via a new land-use map, the recent NATLAN 2000-CORINE land-use map, in order to incorporate the last decade land-cover changes. The model is tested with the original and the CORINE land-use map to evaluate the sensitivity to land-use changes and new physical soil parameters definition. Results show clear local differences in some meteorological variables as wind fields or updraft movements, but comparisons with ground measurements do not lead to a clear improvement in the model general performance.

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.

Effects of sources and meteorology on particulate matter in the Western Mediterranean Basin: An overview of the DAURE campaign

DAURE (Determination of the Sources of Atmospheric Aerosols in Urban and Rural Environments in the Western Mediterranean) was a multidisciplinary international field campaign aimed at investigating the sources and meteorological controls of particulate matter in the Western Mediterranean Basin (WMB). Measurements were simultaneously performed at an urban-coastal (Barcelona, BCN) and a rural-elevated (Montseny, MSY) site pair in NE Spain during winter and summer. State-of-the-art methods such as 14C analysis, proton-transfer reaction mass spectrometry, and high-resolution aerosol mass spectrometry were applied for the first time in the WMB as part of DAURE. WMB regional pollution episodes were associated with high concentrations of inorganic and organic species formed during the transport to inland areas and built up at regional scales. Winter pollutants accumulation depended on the degree of regional stagnation of an air mass under anticyclonic conditions and the planetary boundary layer height. In summer, regional recirculation and biogenic secondary organic aerosols (SOA) formation mainly determined the regional pollutant concentrations. The contribution from fossil sources to organic carbon (OC) and elemental carbon (EC) and hydrocarbon-like organic aerosol concentrations were higher at BCN compared with MSY due to traffic emissions. The relative contribution of nonfossil OC was higher at MSY especially in summer due to biogenic emissions. The fossil OC/EC ratio at MSY was twice the corresponding ratio at BCN indicating that a substantial fraction of fossil OC was due to fossil SOA. In winter, BCN cooking emissions were identified as an important source of modern carbon in primary organic aerosol.

Effect of High-Resolution Meteorological Forcing on Nearshore Wave and Current Model Performance

Accurate representation of wind forcing and mean sea level pressure is important for modeling waves and surges. This is especially important for complex coastal zone areas. The Weather Research and Forecasting (WRF) model has been run at 12-, 4-, and 1.33-km resolutionfor a storm event over the Irish Sea. The outputs were used to force the coupled hydrodynamic and the Proudman Oceanographic Laboratory Coastal Ocean Modeling System (POLCOMS)‐Wave Model (WAM) and the effect on storm surge and waves has been assessed. An improvement was observed in the WRF model pressure and wind speed when moving from 12- to 4-km resolution with errors in wind speed decreasing more than 10% on average. When moving from 4 to 1.33km no further significant improvement was observed. The atmospheric model results at 12 and 4km were then applied to the ocean model. Wave direction was seen to improve with increased ocean model resolution,andhigher-resolutionforcingwasfoundtogenerallyincreasethewaveheightovertheIrishSeaby up to 40cm in places. Improved clustering of wave direction was observed when 4-km meteorological forcing was used. Large differences were seen in the coastal zone because of the improved representation of the coastline and, in turn, the atmospheric boundary layer. The combination of high-resolution atmospheric forcing and a coupled wave‐surge model gave the best result.

Simulations of moist convection by a variational multiscale stabilized finite element method

A variational multiscale stabilized finite element scheme is presented for the solution of moist atmospheric flows. The fully compressible Euler equations are coupled to a system of three advection equations that model the transport of water quantities in the atmosphere. A Kessler-type parametrization of microphysical processes of warm rain is used. Because analytic solutions to this problem are not available, the model is assessed by comparison with similar simulations presented in the literature. The metrics for evaluation are the intensity and spatial distribution of the storm, its duration, the location of precipitation, and water accumulation at different grid resolutions. The current model is able to capture the principal features of two-dimensional convective storms and orographic clouds at the grid scales typical of mesoscale atmospheric simulations.

A variational multiscale stabilized finite element method for the solution of the Euler equations of nonhydrostatic stratified flows

We present a compressible version of the variational multiscale stabilization (VMS) method applied to the finite element (FE) solution of the Euler equations for nonhydrostatic stratified flows. This paper is meant to verify how the algorithm performs when solving problems in the framework of nonhydrostatic atmospheric dynamics. This effort is justified by the previously observed good performance of VMS and by the advantages that a compact Galerkin formulation offers on massively parallel architectures - a paradigm for both computational fluid dynamics (CFD) and numerical weather prediction (NWP) practitioners. We also propose a simple technique to construct a well-balanced approximation of the dominant hydrostatics that, if not properly discretized, may cause unacceptable vertical oscillations. This is a relevant problem in NWP, especially in the proximity of steep topography. To evaluate the performance of the method for stratified environments, six standard 2D and two 3D test cases are selected. Of these, two admit a semi-analytic solution, while the remaining six are non-steady and non-linear thermal problems with dominant buoyancy effects that challenge the algorithm in terms of stability.

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.

Assessment of Kalman filter bias-adjustment technique to improve the simulation of ground-level ozone over Spain

The CALIOPE air quality modelling system has been used to diagnose ground level O(3) concentration for the year 2004, over the Iberian Peninsula. We investigate the improvement in the simulation of daily O(3) maximum by the use of a post-processing such as the Kalman filter bias-adjustment technique. The Kalman filter bias-adjustment technique is a recursive algorithm to optimally estimate bias-adjustment terms from previous measurements and model results. The bias-adjustment technique improved the simulation of daily O(3) maximum for the entire year and the all the stations considered over the whole domain. The corrected simulation presents improvements in statistical indicators such as correlation, root mean square error, mean bias, and gross error. After the post-processing the exceedances of O(3) concentration limits, as established by the European Directive 2008/50/CE, are better reproduced and the uncertainty of the modelling system, as established by the European Directive 2008/50/CE, is reduced from 20% to 7.5%. Such uncertainty in the model results is under the established EU limit of the 50%. Significant improvements in the O(3) timing and amplitude of the daily cycle are also observed after the post-processing. The systematic improvements in the O(3) maximum simulations suggest that the Kalman filter post-processing method is a suitable technique to reproduce accurate estimate of ground-level O(3) concentration. With this study we evince that the adjusted O(3) concentrations obtained after the post-process of the results from the CALIOPE system are a reliable means for real near time O(3) forecasts.