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Ozone and NO<sub><i>x</i></sub> chemistry in the eastern US: evaluation of CMAQ/CB05 with satellite (OMI) data

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Atmos. Chem. Phys., 15, 10965–10982, 2015 www.atmos-chem-phys.net/15/10965/2015/ doi:10.5194/acp-15-10965-2015 © Author(s) 2015. CC Attribution 3.0 License. Ozone and NOx chemistry in the eastern US: evaluation of CMAQ/CB05 with satellite (OMI) data T. P. Canty1, L. Hembeck1, T. P. Vinciguerra1, D. C. Anderson1, D. L. Goldberg1, S. F. Carpenter1, D. J. Allen1, C. P. Loughner2,3, R. J. Salawitch1,2,4, and R. R. Dickerson1 1Department of Atmospheric and Oceanic Science, University of Maryland, College Park, MD, USA 2Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD, USA 3NASA Goddard Space Flight Center, Greenbelt, MD, USA 4Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, USA Correspondence to: T. P. Canty (tcanty@atmos.umd.edu) Received: 6 December 2014 – Published in Atmos. Chem. Phys. Discuss.: 17 February 2015 Revised: 13 August 2015 – Accepted: 19 August 2015 – Published: 2 October 2015 Abstract. Regulatory air quality models, such as the Community Multiscale Air Quality model (CMAQ), are used by federal and state agencies to guide policy decisions that determine how to best achieve adherence with National Ambient Air Quality Standards for surface ozone. We use observations of ozone and its important precursor NO2 to test the representation of the photochemistry and emission of ozone precursors within CMAQ. Observations of tropospheric column NO2 from the Ozone Monitoring Instrument (OMI), retrieved by two independent groups, show that the model overestimates urban NO2 and underestimates rural NO2 under all conditions examined for July and August 2011 in the US Northeast. The overestimate of the urban to rural ratio of tropospheric column NO2 for this baseline run of CMAQ (CB05 mechanism, mobile NOx emissions from the National Emissions Inventory; isoprene emissions from MEGAN v2.04) suggests this model may underestimate the importance of interstate transport of NOx. This CMAQ simulation leads to a considerable overestimate of the 2-month average of 8 h daily maximum surface ozone in the US Northeast, as well as an overestimate of 8 h ozone at AQS sites during days when the state of Maryland experienced NAAQS exceedances. We have implemented three changes within CMAQ motivated by OMI NO2 as well as aircraft observations obtained in July 2011 during the NASA DISCOVER-AQ campaign: (a) the modeled lifetime of organic nitrates within CB05 has been reduced by a factor of 10, (b) emissions of NOx from mobile sources has been reduced by a factor of 2, and (c) isoprene emissions have been reduced by using MEGAN v2.10 rather than v2.04. Compared to the baseline simulation, the CMAQ run using all three of these changes leads to considerably better simulation of column NO2 in both urban and rural areas, better agreement with the 2-month average of daily 8 h maximum ozone in the US Northeast, fewer number of false positives of an ozone exceedance throughout the domain, as well as an unbiased simulation of surface ozone at groundbased AQS sites in Maryland that experienced an ozone exceedance during July and August 2007. These modifications to CMAQ may provide a framework for use in studies focused on achieving future adherence to specific air quality standards for surface ozone by reducing emission of NOx from various anthropogenic sectors. 1 Introduction The spatial scale of tropospheric ozone production is of enormous consequence, especially for the eastern US where cross-state transport of air pollutants is a major policy concern (EPA vs. EME, 2014). As early as the 1980’s (Logan, 1989), analysis of measurements indicated that surface ozone episodes covered areas approaching 106 km2. Numerous observational studies have demonstrated the westerly transport of ozone and its precursors and the impact of upwind emissions that lead to high concentrations of surface ozone in the eastern United States (Brent et al., 2013; Hains et al., 2008; He et al., 2014, 2013a, b; Ryan et al., 1998; Taubman et al., 2004, 2006). Dramatic improvements in air quality have been Published by Copernicus Publications on behalf of the European Geosciences Union. 10966 T. P. Canty et al.: Ozone and NOx chemistry in the eastern US observed due to reductions in the emission of ozone precursors (Butler et al., 2011; Fiore et al., 1998; Gego et al., 2007; He et al., 2013b; Marufu et al., 2004; Walsh et al., 2008). Numerical simulations of ozone show a dependence on NOx (NO + NO2) concentrations, but do not always capture the regional nature of photochemical smog events nor the strength of the response to NOx emission controls (Fujita et al., 2013; Gilliland et al., 2008; Godowitch et al., 2008a, b; Hogrefe et al., 2011; Pollack et al., 2013; Wilson et al., 2012; Yegorova et al., 2011; Zhou et al., 2013). Recognizing that long-range transport affects local compliance of federally mandated standards, the EPA enacted the Cross State Air Pollution Rule (CSAPR) http://www.epa.gov/crossstaterule which reduces the emissions of ozone precursors from power plants. Phase 1 of the CSAPR emissions budgets is scheduled for implementation in 2015. The Community Multiscale Air Quality model (CMAQ) is used extensively for regulatory purposes (Byun and Schere, 2006). State Implementation Plans (SIPs) quantify future emission reductions that will bring nonattainment areas into compliance with the National Ambient Air Quality Standard (NAAQS) for surface ozone. The recommendations submitted in the SIPs are based on analysis of output from air quality models such as CMAQ that simulate meteorology and the nonlinearities inherent in tropospheric ozone chemistry. Oxides of nitrogen play a controlling role in ozone production in the eastern US and comparison of monitor records with CMAQ output suggests that this model overestimates NOx concentrations in urban areas, but underestimates NOx in rural areas (Castellanos et al., 2011). The overestimate of NOx in urban areas, coupled with the underestimate in rural areas, means CMAQ may keep NOx too closely confined to source regions, thereby underestimating the interstate transport of ozone precursors. Such disagreement may stem from the complicated nature of NOx emissions, recycling, and removal though proper representation of dynamics (e.g. vertical mixing) may also play a role. Organo-nitrate compounds can act as reservoirs or sinks for NOx and have received substantial attention for many years (Atlas, 1988; Beaver et al., 2012; Day et al., 2003; Farmer et al., 2006; Lockwood et al., 2010; Neff et al., 2002; Perring et al., 2013, 2010, 2009; Xie et al., 2013). The production and loss mechanisms that govern the concentrations of organo-nitrate species are largely simplified in most air quality models. Ground-based and aircraft measurements of ozone and its precursors provide important constraints on the concentrations of trace gasses and can be used to validate model output. However, these data are geographically limited. In contrast, satellites provide a measure of the spatial variation of these species over a much larger domain. In this study, we investigate the regional representation of NO2 in CMAQ by comparing model output to satellite observations from the Ozone Monitoring Instrument (OMI) (e.g., Boersma et al., 2011; Bucsela et al., 2013) during July and August 2007. Modifications to the chemical mechanism and emissions inventories used by the model are suggested to improve agreement between model and observations. More relevant to policy makers is the ability of air quality models to reproduce surface ozone. We extend our analysis to include comparisons between model output and ozone observed at ground-based stations. The model domain for this study is the eastern United States (i.e., most of the states eastward of the Mississippi river), a region that has been the focus of intense SIP modeling efforts by midAtlantic states and for which detailed emissions inventories and meteorological fields are readily available. 2 Data description: OMI satellite OMI is one of four instruments onboard the NASA Aura satellite, now in its tenth year http://aura.gsfc.nasa.gov/. The satellite is in a sun synchronous orbit, providing OMI with a daytime overpass at ∼ 13:40 local time (LT). NO2 columns are retrieved using differential optical absorption spectroscopy (DOAS) in the 405–465 nm range. There are two operational retrievals of tropospheric column NO2 based on radiances measured by OMI; the Derivation of OMI tropospheric NO2 (DOMINO) product (Boersma et al., 2007, 2011) provided by the Royal Netherlands Meteorological Institute (KNMI) and the NASA Goddard Space Flight Center (GSFC) product (Bucsela et al., 2013). Retrievals of tropospheric column NO2 (hereafter, column NO2) from OMI are available for the width of the atmosphere observed along the viewing track (or swath) of the instrument. OMI tropospheric column NO2 is calculated by subtracting the stratospheric signal from the observations of total column NO2. The method of determining the stratospheric component varies between the GSFC and DOMINO product and is explained in Bucsela et al. (2013) and Boersma et al. (2007), respectively. GSFC assumes that total column NO2 over regions with little expected tropospheric influence represents the stratospheric column. This field of stratospheric column NO2 is interpolated over nearby regions of high surface pollution and removed from the total column NO2 retrieval to determine tropospheric column NO2. For the DOMINO product, data assimilation of OMI slant columns with the TM4 model (Tracer Model version 4, van Noije et al., 2006) determines the stratospheric subtraction. These level 2 (L2) observations do not occur on a regularly spaced grid. For a more meaningful comparison between satellite retrievals and model output, we generate level 3 (L3) products on a 0.25 × 0.25 (latitude, longitude) grid for both observed and calculated column NO2. Column NO2 from OMI is weighted based on satellite viewing angle using the formulation of Bucsela et al. (2013). These same weights are applied to column NO2 from CMAQ to assure a meaningful comparison. Column NO2 measurements are only considered for the gridding procedure when solar zenith angle is less than 85 and effective cloud fraction (Acarreta et al., 2004) is Atmos. Chem. Phys., 15, 10965–10982, 2015 www.atmos-chem-phys.net/15/10965/2015/ T. P. Canty et al.: Ozone and NOx chemistry in the eastern US 10967 less than 30 %. Observations are only considered valid and used for our analysis if the flag “xtrackqualityflag”, provided in the data files for both retrievals, is equal to zero. This flag indicates which OMI data products can be used in a manner that minimizes the influence of the row anomaly along the observing swath (see http://www.knmi.nl/omi/ research/product/rowanomaly-background.php for more information). Summary quality flags, also provided in the data files, provide quality assurance that at least 50 % of the tropospheric column is determined by observed information. In our study, retrievals are only used when this flag also equals zero. Comparison with model output is facilitated through the use of averaging kernels (DOMINO) or scattering weights (GSFC). No uncertainties are provided explicitly for the averaging kernels or scattering weights. Instead, the DOMINO retrieval team provides uncertainties (“VCDTropErrorUsingAVKernel”) that account for errors in both the NO2 column and the averaging kernel. The precision in the GSFC NO2 product is provided in the variable “ColumnAmountNO2TropStd”. We use these uncertainties as the defacto way of comparing the two different retrievals of column NO2 to model output of this quantity. The production of ozone in our region of study is NOxlimited for nearly all of the domain. An analysis of satellite observations acquired in 2005 to 2007 shows that ozone production is VOC-limited for only a small part of New York City, with the rest of the domain being NOx-limited (Duncan et al., 2010). Hence, the general focus of this manuscript is on model representation of nitrogen oxides. The results of this study may not be applicable to regions where production of ozone is VOC dominant, which occurs primarily in rural regions such as the so-called isoprene volcano of the Ozarks (Carlton and Baker, 2011) or regions of intense hydrocarbon processing such as Houston, Texas (Li et al., 2007). 3 Model description For this analysis we use the Community Multiscale Air Quality (CMAQ) modeling system version 4.7.1 (https://www. cmascenter.org/cmaq/). This model has been used extensively by states that are members of the Ozone Transport Commission (OTC) in preparation for the 2015 ozone SIP call. For this analysis, CMAQ simulations were performed for the Eastern US with a 12 km×12 km horizontal resolution and a 34 layer (σ coordinate) vertical grid from the surface to ∼ 20 km with hourly output. CMAQ does not include stratospheric processes so the upper layers of the model atmosphere should not be used for research purposes. The analysis presented here is limited to altitudes below the tropopause. Simulated meteorology is driven by output from the Weather Research Forecasting (WRF v3.1.1) model for year 2007 and processed for use in CMAQ by the Meteorological Chemistry Interface Processor (MCIP). Emissions inventories for year 2007 were developed by the Mid-Atlantic Regional Air Management Association, Inc. (MARAMA) specifically for use in OTC modeling efforts. Biogenic emissions were estimated using the Model of Emissions of Gases and Aerosols in Nature (MEGAN v2.04) (Guenther et al., 2006). Emissions from on-road mobile sources were developed using the Motor Vehicle Emission Simulator (MOVES) (USEPA, 2010) while off–road emissions were supplied by the National Mobile Inventory Model (NMIM) (USEPA, 2005). Emissions due to aircraft are included in the inventories based on take-off and landing data for individual airports. Emission inventories and WRF/MCIP meteorology are merged and gridded using the Sparse Matrix Operator Kernel Emissions (SMOKE v3.1, https://www.cmascenter.org/smoke/) model to generate timevarying, three dimensional CMAQ ready emission fields. CMAQv4.7.1 uses the 2005 Carbon Bond (CB05) chemical mechanism (Yarwood et al., 2005). Though there is a more recent version of the Carbon Bond chemical mechanism (CB6) it is not available for use in publicly available versions of CMAQ as of the submission of this manuscript. We have added lightning-generated NOx (LNOx ), assuming an NOx production rate of 500 moles flash−1, to the merged emissions files following the parameterization described in Allen et al. (2012). The production of LNOx is correlated to lightning flashes observed by the National Lightning Detection network (NLDN), which records cloud to ground flashes (CG). The amount of intercloud lightning (IC) is calculated based on a climatological IC / CG ratio (Boccippio et al., 2001). In general, the amount of NOx supplied by lightning is much smaller than anthropogenic sources, especially in urban areas. This may not necessarily be true in the future as further pollution control measures are enacted to reduce the emissions of NOx from power plants, vehicles, etc. Neglecting LNOx may result in modeled NOx being biased low, especially in rural regions where NOx levels are already much lower than in urban regions. Modeled tropospheric column NO2 is calculated by integrating the CMAQ NO2 profiles from the surface to the level of the tropopause provided by either the DOMINO or GSFC retrieval teams. Model output at the hour closest to the OMI overpass time are convolved with the air mass factors and averaging kernels (DOMINO) or scattering weights (GSFC) appropriate for the two satellite retrievals. We interpolate the CMAQ output to the pressure grid of the averaging kernel/scattering weight. The DOMINO tropospheric averaging kernel is calculated by taking the product of the averaging kernel and the ratio of the air mass factor to the tropospheric air mass factor (Boersma et al., 2011). CMAQ output is multiplied by the tropospheric averaging kernel and then integrated over pressure. In a similar fashion, GSFC scattering weights are applied to the model profiles of NO2 to generate CMAQ tropospheric column NO2 for direct comparison with the GSFC tropospheric NO2 product (Bucsela et al., 2013; Lamsal et al., 2014). www.atmos-chem-phys.net/15/10965/2015/ Atmos. Chem. Phys., 15, 10965–10982, 2015 10968 T. P. Canty et al.: Ozone and NOx chemistry in the eastern US Figure 1. Average OMI tropospheric column NO2 observations for July and August 2007 for both the DOMINO (left) and GSFC (middle) retrievals. The level 2 swath data for both retrievals have been screened, weighted based on viewing angle and gridded onto a 0.25 × 0.25 lat/lon grid. Only observations where cloud fraction is less than 30 % are used in the gridding process. Both data sets indicate that the highest levels of tropospheric NO2 occur over urban regions. A scatter plot of DOMINO vs. GSFC observations (right) indicates that the DOMINO retrieval is roughly 20 % higher, on average, than the GSFC satellite product. Error bars indicate the uncertainty in the satellite retrievals. Only those model grid points closest to the center of each pixel along the satellite swath are considered. To generate a model L3 gridded product, CMAQ output at each model grid cell is only used if the co-located satellite retrieval satisfies the quality flags and cloud fraction limits described above (i.e., we only use those CMAQ points where the closest satellite retrieval is also considered “valid”). CMAQ output is screened and gridded in an identical fashion as the respective OMI retrievals, to generate model L3 products (one for the DOMINO retrieval, the other for the GSFC retrieval) appropriate for comparison to the equilibrium value of MeCpG steps (,+14 deg.) [31,44]. In comparison, methylation has a significantly lower stability cost when happening at major groove positions, such as 211 and 21 base pair from dyad (mutations 9 and 12), where the roll of the nucleosome bound conformation (+10 deg.) is more compatible with the equilibrium geometry of MeCpG steps. The nucleosome destabilizing effect of cytosine methylation increases with the number of methylated cytosines, following the same position dependence as the single methylations. The multiple-methylation case reveals that each major groove meth- PLOS Computational Biology | www.ploscompbiol.org 3 November 2013 | Volume 9 | Issue 11 | e1003354 DNA Methylation and Nucleosome Positioning ylation destabilizes the nucleosome by around 1 kJ/mol (close to the average estimate of 2 kJ/mol obtained for from individual methylation studies), while each minor groove methylation destabilizes it by up to 5 kJ/mol (average free energy as single mutation is around 6 kJ/mol). This energetic position-dependence is the reverse of what was observed in a recent FRET/SAXS study [30]. The differences can be attributed to the use of different ionic conditions and different sequences: a modified Widom-601 sequence of 157 bp, which already contains multiple CpG steps in mixed orientations, and which could assume different positioning due to the introduction of new CpG steps and by effect of the methylation. The analysis of our trajectories reveals a larger root mean square deviation (RMSD) and fluctuation (RMSF; see Figures S2– S3 in Text S1) for the methylated nucleosomes, but failed to detect any systematic change in DNA geometry or in intermolecular DNA-histone energy related to methylation (Fig. S1B, S1C, S4–S6 in Text S1). The hydrophobic effect should favor orientation of the methyl group out from the solvent but this effect alone is not likely to justify the positional dependent stability changes in Figure 2, as the differential solvation of the methyl groups in the bound and unbound states is only in the order of a fraction of a water molecule (Figure S5 in Text S1). We find however, a reasonable correlation between methylation-induced changes in hydrogen bond and stacking interactions of the bases and the change in nucleosome stability (see Figure S6 in Text S1). This finding suggests that methylation-induced nucleosome destabilization is related to the poorer ability of methylated DNA to fit into the required conformation for DNA in a nucleosome. Changes in the elastic deformation energy between methylated and un-methylated DNA correlate with nucleosomal differential binding free energies To further analyze the idea that methylation-induced nucleosome destabilization is connected to a worse fit of methylated DNA into the required nucleosome-bound conformation, we computed the elastic energy of the nucleosomal DNA using a harmonic deformation method [36,37,44]. This method provides a rough estimate of the energy required to deform a DNA fiber to adopt the super helical conformation in the nucleosome (full details in Suppl. Information Text S1). As shown in Figure 2, there is an evident correlation between the increase that methylation produces in the elastic deformation energy (DDE def.) and the free energy variation (DDG bind.) computed from MD/TI calculations. Clearly, methylation increases the stiffness of the CpG step [31], raising the energy cost required to wrap DNA around the histone octamers. This extra energy cost will be smaller in regions of high positive roll (naked DNA MeCpG steps have a higher roll than CpG steps [31]) than in regions of high negative roll. Thus, simple elastic considerations explain why methylation is better tolerated when the DNA faces the histones through the major groove (where positive roll is required) that when it faces histones through the minor groove (where negative roll is required). Nucleosome methylation can give rise to nucleosome repositioning We have established that methylation affects the wrapping of DNA in nucleosomes, but how does this translate into chromatin structure? As noted above, accumulation of minor groove methylations strongly destabilizes the nucleosome, and could trigger nucleosome unfolding, or notable changes in positioning or phasing of DNA around the histone core. While accumulation of methylations might be well tolerated if placed in favorable positions, accumulation in unfavorable positions would destabilize the nucleosome, which might trigger changes in chromatin structure. Chromatin could in fact react in two different ways in response to significant levels of methylation in unfavorable positions: i) the DNA could either detach from the histone core, leading to nucleosome eviction or nucleosome repositioning, or ii) the DNA could rotate around the histone core, changing its phase to place MeCpG steps in favorable positions. Both effects are anticipated to alter DNA accessibility and impact gene expression regulation. The sub-microsecond time scale of our MD trajectories of methylated DNAs bound to nucleosomes is not large enough to capture these effects, but clear trends are visible in cases of multiple mutations occurring in unfavorable positions, where unmethylated and methylated DNA sequences are out of phase by around 28 degrees (Figure S7 in Text S1). Due to this repositioning, large or small, DNA could move and the nucleosome structure could assume a more compact and distorted conformation, as detected by Lee and Lee [29], or a slightly open conformation as found in Jimenez-Useche et al. [30]. Using the harmonic deformation method, we additionally predicted the change in stability induced by cytosine methylation for millions of different nucleosomal DNA sequences. Consistently with our calculations, we used two extreme scenarios to prepare our DNA sequences (see Fig. 3): i) all positions where the minor grooves contact the histone core are occupied by CpG steps, and ii) all positions where the major grooves contact the histone core are occupied by CpG steps. We then computed the elastic energy required to wrap the DNA around the histone proteins in unmethylated and methylated states, and, as expected, observed that methylation disfavors DNA wrapping (Figure 3A). We have rescaled the elastic energy differences with a factor of 0.23 to match the DDG prediction in figure 2B. In agreement with the rest of our results, our analysis confirms that the effect of methylation is position-dependent. In fact, the overall difference between the two extreme methylation scenarios (all-in-minor vs all-in-major) is larger than 60 kJ/mol, the average difference being around 15 kJ/ mol. We have also computed the elastic energy differences for a million sequences with CpG/MeCpG steps positioned at all possible intermediate locations with respect to the position (figure 3B). The large differences between the extreme cases can induce rotations of DNA around the histone core, shifting its phase to allow the placement of the methylated CpG steps facing the histones through the major groove. It is illustrative to compare the magnitude of CpG methylation penalty with sequence dependent differences. Since there are roughly 1.5e88 possible 147 base pairs long sequence combinations (i.e., (4n+4(n/2))/2, n = 147), it is unfeasible to calculate all the possible sequence effects. However, using our elastic model we can provide a range of values based on a reasonably large number of samples. If we consider all possible nucleosomal sequences in the yeast genome (around 12 Mbp), the energy difference between the best and the worst sequence that could form a nucleosome is 0.7 kj/mol per base (a minimum of 1 kJ/mol and maximum of around 1.7 kJ/mol per base, the first best and the last worst sequences are displayed in Table S3 in Text S1). We repeated the same calculation for one million random sequences and we obtained equivalent results. Placing one CpG step every helical turn gives an average energetic difference between minor groove and major groove methylation of 15 kJ/ mol, which translates into ,0.5 kJ/mol per methyl group, 2 kJ/ mol per base for the largest effects. Considering that not all nucleosome base pair steps are likely to be CpG steps, we can conclude that the balance between the destabilization due to CpG methylation and sequence repositioning will depend on the PLOS Computational Biology | www.ploscompbiol.org 4 November 2013 | Volume 9 | Issue 11 | e1003354 DNA Methylation and Nucleosome Positioning Figure 3. Methylated and non-methylated DNA elastic deformation energies. (A) Distribution of deformation energies for 147 bplong random DNA sequences with CpG steps positioned every 10 base steps (one helical turn) in minor (red and dark red) and major (light and dark blue) grooves respectively. The energy values were rescaled by the slope of a best-fit straight line of figure 2, which is 0.23, to por la lectura a través de la lectura de la prensa. La educación en los medios las fuerzas dispersas en función de los soportes mediáticos y orientarse más hacia la educación en medios que al dominio adquiere pleno derecho y entidad en la sección sexta titulada «competencias sociales y cívi- técnico de los aparatos. cas» que indica que «los alum- nos deberán ser capaces de juz- gar y tendrán espíritu crítico, lo que supone ser educados en los las programaciones oficiales, ya que, a lo largo de un medios y tener conciencia de su lugar y de su influencia estudio de los textos, los documentalistas del CLEMI en la sociedad». han podido señalar más de una centena de referencias a la educación de los medios en el seno de disciplinas 4. Un entorno positivo como el francés, la historia, la geografía, las lenguas, Si nos atenemos a las cifras, el panorama de la las artes plásticas : trabajos sobre las portadas de educación en medios es muy positivo. Una gran ope- prensa, reflexiones sobre temas mediáticos, análisis de ración de visibilidad como la «Semana de la prensa y publicidad, análisis de imágenes desde todos los ángu- de los medios en la escuela», coordinada por el CLE- los, reflexión sobre las noticias en los países europeos, MI, confirma año tras año, después de 17 convocato- información y opinión rias, el atractivo que ejerce sobre los profesores y los Esta presencia se constata desde la escuela mater- alumnos. Concebida como una gran operación de nal (2 a 6 años) donde, por ejemplo, se le pregunta a complementariedad entre la escuela y los profesiona- los niños más pequeños si saben diferenciar entre un les de los medios, alrededor del aprendizaje ciudada- periódico, un libro, un catálogo, a través de activida- no de la comunicación mediática, este evento moviliza des sensoriales, si saben para qué sirve un cartel, un durante toda una semana un porcentaje elevado de periódico, un cuaderno, un ordenador si son capa- centros escolares que representan un potencial de 4,3 ces de reconocer y distinguir imágenes de origen y de millones de alumnos (cifras de 2006). Basada en el naturaleza distintas. Podríamos continuar con más voluntariado, la semana permite desarrollar activida- ejemplos en todos los niveles de enseñanza y práctica- des más o menos ambiciosas centradas en la introduc- Páginas 43-48 ción de los medios en la vida de la escuela a través de la instalación de kioscos, organización de debates con profesionales y la confección por parte de los alumnos de documentos difundidos en los medios profesionales. Es la ocasión de dar un empujón a la educación en medios y de disfrutarlos. Los medios –un millar en 2006– se asocian de maneras diversas ofreciendo ejemplares de periódicos, acceso a noticias o a imágenes, proponiendo encuentros, permitiendo intervenir a los jóvenes en sus ondas o en sus columnas Esta operación da luz al trabajo de la educación en medios y moviliza a los diferentes participantes en el proyecto. 5. La formación de los docentes La formación es uno de los pilares principales de la educación en los medios. Su función es indispensable ya que no se trata de una disciplina, sino de una enseñanza que se hace sobre la base del voluntariado y del compromiso personal. Se trata de convencer, de mostrar, de interactuar. En primer lugar es necesario incluirla en la formación continua de los docentes, cuyo volumen se ha incrementado desde 1981 con la aparición de una verdadera política de formación continua de personal. Es difícil dar una imagen completa del volumen y del público, pero si nos atenemos a las cifras del CLEMI, hay más de 24.000 profesores que han asistido y se han involucrado durante 2004-05. 5.1. La formación continua En la mayoría de los casos, los profesores reciben su formación en contextos cercanos a su centro de trabajo, o incluso en este mismo. Después de una política centrada en la oferta que hacían los formadores, se valora más positivamente la demanda por parte del profesorado, ya que sólo así será verdaderamente fructífera. Los cursos de formación se repartieron en varias categorías: desde los formatos más tradicionales (cursos, debates, animaciones), hasta actividades de asesoramiento y de acompañamiento, y por supuesto los coloquios que permiten un trabajo en profundidad ya que van acompañados de expertos investigadores y profesionales. Citemos, por ejemplo en 2005, los coloquios del CLEMI-Toulouse sobre el cine documental o el del CLEMI-Dijon sobre «Políticos y medios: ¿connivencia?». Estos coloquios, que forman parte de un trabajo pedagógico regular, reagrupan a los diferentes participantes regionales y nacionales alrededor de grandes temas de la educación en medios y permiten generar nuevos conocimientos de aproximación y una profundización. Páginas 43-48 Hay otro tipo de formación original que se viene desarrollando desde hace menos tiempo, a través de cursos profesionales, como por ejemplo, en el Festival Internacional de Foto-periodismo «Visa para la imagen», en Perpignan. La formación se consolida en el curso, da acceso a las exposiciones, a las conferencias de profesionales y a los grandes debates, pero añade además propuestas pedagógicas y reflexiones didácticas destinadas a los docentes. Estas nuevas modalidades de formación son también consecuencia del agotamiento de la formación tradicional en las regiones. Los contenidos más frecuentes en formación continua conciernen tanto a los temas más clásicos como a los cambios que se están llevando a cabo en las prácticas mediáticas. Así encontramos distintas tendencias para 2004-05: La imagen desde el ángulo de la producción de imágenes animadas, el análisis de la imagen de la información o las imágenes del J.T. La prensa escrita y el periódico escolar. Internet y la información en línea. Medios y educación de los medios. 5.2 La formación inicial La formación inicial está aun en un grado muy ini- cial. El hecho de que la educación en medios no sea una disciplina impide su presencia en los IUFM (Institutos Universitarios de Formación de Maestros) que dan una prioridad absoluta a la didáctica de las disciplinas. En 2003, alrededor de 1.400 cursillistas sobre un total de 30.000 participaron en un momento u otro de un módulo de educación en medios. Estos módulos se ofrecen en función del interés que ese formador encuentra puntualmente y forman parte a menudo de varias disciplinas: documentación, letras, historia-geografía Estamos aún lejos de una política concertada en este dominio. La optativa «Cine-audiovisual» ha entrado desde hace muy poco tiempo en algunos IUFM destinada a obtener un certificado de enseñanza de la opción audiovisual y cine. Internet tiene cabida también en los cursos de formación inicial, recientemente con la aparición de un certificado informático y de Internet para los docentes, dirigido más a constatar competencias personales que a valorar una aptitud para enseñarlos. 6. ¿Y el futuro? El problema del futuro se plantea una vez más por la irrupción de nuevas técnicas y nuevos soportes. La difusión acelerada de lo digital replantea hoy muchas cuestiones relativas a prácticas mediáticas. Muchos Comunicar, 28, 2007 47 Comunicar, 28, 2007 Enrique Martínez-Salanova '2007 para Comunicar 48 trabajos que llevan el rótulo de la educación en medios solicitan una revisión ya que los conceptos cambian. La metodología elaborada en el marco de la educación en medios parece incluso permitir la inclinación de la sociedad de la información hacia una sociedad del conocimiento, como defiende la UNESCO. En Francia, se necesitaría unir las fuerzas dispersas en función de los soportes mediáticos y orientarse más hacia la educación en medios que al dominio técnico de los aparatos. Los avances recientes en el reconocimiento de estos contenidos y las competencias que supondrían podrían permitirlo. Referencias CLEMI/ACADEMIE DE BORDEAUX (Ed.) (2003): Parcours médias au collège: approches disciplinaires et transdisciplinaires. Aquitaine, Sceren-CRDP. GONNET, J. (2001): Education aux médias. Les controverses fécondes. Paris, Hachette Education/CNDP. SAVINO, J.; MARMIESSE, C. et BENSA, F. (2005): L’éducation aux médias de la maternelle au lycée. Direction de l’Enseignement Scolaire. Paris, Ministère de l’Education Nationale, Sceren/CNDP, Témoigner. BEVORT, E. et FREMONT, P. (2001): Médias, violence et education. Paris, CNDP, Actes et rapports pour l’éducation. – www.clemi.org: fiches pédagogiques, rapports et liens avec les pages régionales/académiques. – www.ac-nancy-metz.fr/cinemav/quai.html: Le site «Quai des images» est dédié à l’enseignement du cinéma et de l’audiovisuel. – www.france5.fr/education: la rubrique «Côté profs» a une entrée «education aux médias». – www.educaunet.org: Programme européen d’éducation aux risques liés à Internet. dResedfeleexliobnuetsacón Páginas 43-48
Ozone and NO<sub><i>x</i></sub> chemistry in the eastern US: evaluation of CMAQ/CB05 with satellite (OMI) data
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Ozone and NO<sub><i>x</i></sub> chemistry in the eastern US: evaluation of CMAQ/CB05 with satellite (OMI) data

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