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A 6-year global climatology of occurrence of upper-tropospheric ice supersaturation inferred from the Atmospheric Infrared Sounder after synergetic calibration with MOZAIC

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Atmospheric Chemistry and Physics Discussions 2 2 3 1 Correspondence to: N. Lamquin (nicolas.lamquin@lmd.polytechnique.fr) Published by Copernicus Publications on behalf of the European Geosciences Union. | 12889 Discussion Paper Received: 9 September 2010 – Accepted: 7 April 2011 – Published: 27 April 2011 | Laboratoire de Météorologie Dynamique, UMR8539, CNRS/IPSL – Ecole Polytechnique, Palaiseau, France 2 Deutsches Zentrum für Luft- und Raumfahrt, Oberpfaffenhofen, Germany 3 Forschungzentrum Jülich, Institut für Chemie der belasteten Atmosphäre (ICG2), Jülich, Germany Discussion Paper 1 ACPD 11, 12889–12947, 2011 Ice supersaturation from the Atmospheric InfraRed Sounder N. Lamquin et al. Title Page Abstract Introduction Conclusions References Tables Figures ◭ ◮ ◭ ◮ Back Close | 1 N. Lamquin , C. J. Stubenrauch , K. Gierens , U. Burkhardt , and H. Smit Discussion Paper A 6-year global climatology of occurrence of upper-tropospheric ice supersaturation inferred from the Atmospheric Infrared Sounder after synergetic calibration with MOZAIC | This discussion paper is/has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP if available. Discussion Paper Atmos. Chem. Phys. Discuss., 11, 12889–12947, 2011 www.atmos-chem-phys-discuss.net/11/12889/2011/ doi:10.5194/acpd-11-12889-2011 © Author(s) 2011. CC Attribution 3.0 License. Full Screen / Esc Printer-friendly Version Interactive Discussion 5 Discussion Paper | 12890 | 25 Ice supersaturation (or “ISS”, relative humidity with respect to ice larger than 100%) is a prerequisite for the nucleation of cirrus clouds (e.g. Haag et al., 2003) and for the persistence of condensation trails (Schumann, 1996). Few climate models have included Discussion Paper 1 Introduction ACPD 11, 12889–12947, 2011 Ice supersaturation from the Atmospheric InfraRed Sounder N. Lamquin et al. Title Page Abstract Introduction Conclusions References Tables Figures ◭ ◮ ◭ ◮ Back Close | 20 Discussion Paper 15 | 10 Ice supersaturation in the upper troposphere is a complex and important issue for the understanding of cirrus cloud formation. Infrared sounders have the ability to provide cloud properties and atmospheric profiles of temperature and humidity. On the other hand, they suffer from coarse vertical resolution, especially in the upper troposphere and therefore are unable to detect shallow ice supersaturated layers. We have used data from the Measurements of OZone and water vapour by AIrbus in-service airCraft experiment (MOZAIC) in combination with Atmospheric InfraRed Sounder (AIRS) relative humidity measurements and cloud properties to develop a calibration method for an estimation of occurrence frequencies of ice supersaturation. This method first determines the occurrence probability of ice supersaturation, detected by MOZAIC, as a function of the relative humidity determined by AIRS. The occurrence probability function is then applied to AIRS data, independently of the MOZAIC data, to provide a global climatology of upper-tropospheric ice supersaturation occurrence. Our climatology is then related to high cloud occurrence from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and compared to ice supersaturation occurrence statistics from MOZAIC alone. Finally it is compared to model climatologies of ice supersaturation from the Integrated Forecast System (IFS) of the European Centre for Medium-Range Weather Forecasts (ECMWF) and from the European Centre HAmburg Model (ECHAM). All the comparisons show good agreements when considering the limitations of each instrument and model. This study highlights the benefits of multiinstrumental synergies for the investigation of upper tropospheric ice supersaturation. Discussion Paper Abstract Full Screen / Esc Printer-friendly Version Interactive Discussion 12891 | Discussion Paper | Discussion Paper 25 ACPD 11, 12889–12947, 2011 Ice supersaturation from the Atmospheric InfraRed Sounder N. Lamquin et al. Title Page Abstract Introduction Conclusions References Tables Figures ◭ ◮ ◭ ◮ Back Close | 20 Discussion Paper 15 | 10 Discussion Paper 5 a parametrization of supersaturation despite the growing necessity of a better representation of ice cloud formation processes (Waliser et al., 2009). While radiosounding and in situ measurements provide measurements of relative humidity at a high vertical resolution (Spichtinger et al., 2003a; Krämer et al., 2009), continuous and global observations are only achievable from satellite measurements which, in turn, suffer from a limited vertical resolution. For example, Kahn et al. (2008) and Lamquin et al. (2008) have shown that cirrus clouds have generally a smaller vertical extent (about 2 km) than the AIRS vertical resolution (>3 km in the upper troposphere, Maddy and Barnet, 2008) and that relative humidity (RHi) inside cirrus clouds is difficult to determine since clear parts of the profile, over or under the clouds, are taken into account in its computation. In addition, the radiances used for the retrieval of atmospheric temperature and water vapour profiles are cloud cleared (Chahine et al., 2006) and therefore these RHi profiles correspond more to the atmosphere around the clouds. Thus RHi distributions in the presence of cirrus clouds show dry biases when compared to in situ measurements and model parametrizations (e.g. Lamquin et al., 2009). Ice supersaturation (RHi > 100%) occurs over even thinner portions of the atmosphere (about 500 m according to Spichtinger et al., 2003a), it is thus even harder to detect by satellites (e.g. Gierens et al., 2004). As a consequence, its global frequency of occurrence is underestimated if a threshold of 100% is used (Gettelman et al., 2006a). Therefore, Stubenrauch and Schumann (2005) have taken the coarse vertical resolution of TOVS data into account by adjusting the threshold to 70%. We now propose a more sophisticated method based on the construction of an a priori knowledge of the occurrence probability of ice supersaturation inside a vertical pressure layer as a function of the AIRS relative humidity (from now onwards termed “RHiA ”) computed over this vertical pressure layer. Section 2 presents AIRS and MOZAIC datasets. Section 3 presents relationships inferred from the collocation of AIRS and MOZAIC as well as the calibration method. This method is then employed in Sect. 4, independently of the MOZAIC data, to build Full Screen / Esc Printer-friendly Version Interactive Discussion 10 Discussion Paper | 12892 | 25 Discussion Paper 20 ACPD 11, 12889–12947, 2011 Ice supersaturation from the Atmospheric InfraRed Sounder N. Lamquin et al. Title Page Abstract Introduction Conclusions References Tables Figures ◭ ◮ ◭ ◮ Back Close | 15 On board the NASA Aqua satellite, AIRS provides very high resolution measurements of Earth emitted radiation in three spectral bands from 3.74 to 15.40 µm, using 2378 channels. Observations exist at 01:30 and 13:30 local time since May 2002. The spatial resolution of these measurements is 13.5 km at nadir. Nine AIRS measurements (3×3) correspond to one footprint of the Advanced Microwave Sounder Unit (AMSU) within which atmospheric profiles of temperature T and specific humidity q are retrieved from cloud-cleared AIRS radiances at a spatial resolution of about 40 km at nadir (Chahine et al., 2006). AIRS level 2 (L2) standard products include temperature at 28 pressure levels from 0.1 hPa to the surface and water vapour mixing ratios w within 14 pressure layers from 50 hPa to the surface (Susskind et al., 2003, 2006). We investigate ISS occurrence within the 6 standard pressure layers 100–150, 150–200, 200–250, 250– 300, 300–400, and 400–500 hPa. These layers are about 2 km thick. Version 5 of AIRS L2 data provide quality flags for each atmospheric profile (Susskind et al., 2006; Tobin et al., 2006). We derive relative humidity “RHiA ” as in Lamquin et al. (2009) from profiles of best and good quality using the conditions Qual H2O 6= 2 and PGood > 600 hPa. These correspond to about 70% of all situations. Discussion Paper 2.1 AIRS data, quality and vertical resolution | 2 Data handling Discussion Paper 5 a climatology of ice supersaturation from the AIRS data only. Our climatology is first related to high cloud statistics from CALIOP and is evaluated with the ice supersaturation climatology determined with MOZAIC data over regions of air traffic. Then we compare it to model climatologies from ECMWF and ECHAM4. Data other than AIRS and MOZAIC are shortly introduced before each comparison in Sect. 4 because the relevance of the extracted parameters then appears in a more comprehensible manner. Full Screen / Esc Printer-friendly Version Interactive Discussion Discussion Paper | The MOZAIC experiment (Marenco et al., 1998) gathered concentrations of ozone and water vapour mainly in the upper troposphere/lower stratosphere (UTLS) region from 12893 | 2.2 MOZAIC data Discussion Paper 25 ACPD 11, 12889–12947, 2011 Ice supersaturation from the Atmospheric InfraRed Sounder N. Lamquin et al. Title Page Abstract Introduction Conclusions References Tables Figures ◭ ◮ ◭ ◮ Back Close | 20 Discussion Paper 15 | 10 Discussion Paper 5 Humidity measurements for which the water vapour content is lower than 10– 20 ppmv are below the nominal instrument sensitivity and are subject to a higher uncertainty (Gettelman et al., 2004). By comparing AIRS and Microwave Limb Sounder (MLS) products Fetzer et al. (2008) show that AIRS moisture data at altitudes higher than 200 hPa may lead to misleading results. As a consequence, RHiA may not be fully exploitable at pressure levels higher than 200 hPa. However, Montoux et al. (2009) suggest that these data can be used even though they are less precise. We decide to include these data as the results at such altitudes (pressure layers 100–150 an 150– 200 hPa) are indicative. Nevertheless, caution warnings recall the reader’s attention throughout the analysis. We also use cloud properties retrieved at LMD (Stubenrauch et al., 2010) for each AIRS footprint at the spatial scale of about 13.5 km. This global cloud climatology, covering the period from 2003 to 2008, provides cloud pressure pcld and emissivity ǫcld thus allowing a distinction between clear skies, low, middle, and high cloudiness. In addition, high clouds are further distinguished according to cloud emissivity, as high opaque clouds (ǫcld > 0.95), cirrus (0.95 > ǫcld > 0.5) and thin cirrus (0.5 > ǫcld ). Their global coverage is about 2%, 11% and 9%, respectively. However, considering only situations with atmospheric profiles retrieved with good quality, their fractions change to about 0%, 5% and 10%, respectively. Combining all seasons, Table 1 shows these statistics (for high clouds and for other situations) separately for good quality data and for any data. The statistics are made globally, for tropics only and for northern midlatitudes only. Therefore, high clouds for which AIRS provides atmospheric profiles of good quality consist of all thin cirrus and of half of the cirrus category. In the following, we use the general term “cirrus”, including both categories, with exception of Sect. 3.4, where we distinguish between both categories. Full Screen / Esc Printer-friendly Version Interactive Discussion 12894 | Discussion Paper | Discussion Paper 25 ACPD 11, 12889–12947, 2011 Ice supersaturation from the Atmospheric InfraRed Sounder N. Lamquin et al. Title Page Abstract Introduction Conclusions References Tables Figures ◭ ◮ ◭ ◮ Back Close | 20 Discussion Paper 15 | 10 Discussion Paper 5 measurements aboard commercial airplanes over the period August 1994–December 2007. The accuracy of the water vapour measurements is an asset for locally detecting ice supersaturation in the UTLS (Gierens et al., 1999). However, this database only covers the main flight routes of European airliners involved in the project (Marenco et al., 1998), and it is impossible to obtain a global coverage. In addition, the small amount of aircraft equipped with probing sondes as well as the randomness and the seasonal variability of flight destinations induce a nonuniform spatial and temporal representation. Figure 1 highlights this fact for upper tropospheric data (pM < 500 hPa, where pM stands for the flight altitude) over the period 2002–2007. The top figure shows the fraction of measurements, in a 5 × 5 grid, taken in summer compared to the statistics including winter and summer for each latitude/longitude. The very large variability indicates that these data will sometimes include more statistics from winter measurements (over the Arctic for example) or from summer measurements (over Russia for example). Moreover, statistics in each grid box are not sampled within regular time steps. To illustrate this, the bottom figure of Fig. 1 shows the average interval (in days) between overpasses for each grid box. Except on very common routes, such as the NorthAtlantic Flight Corridor, overpasses are not obtained on a daily basis. Rather, about 5 days are necessary for further overpasses of a region, which is very sparse for accurate statistics. 352 grid boxes have an average time step smaller than 10 days but 273 grid boxes have an average time step larger than 10 days, 67 grid boxes attain average delays larger than 100 days. We derive relative humidity with respect to ice “RHiM ” as in Gierens et al. (1999) and only keep data of highest quality (tag “1”) with pM < 500 hPa and T < 243 K so that we avoid mixed-phase relative humidities (e.g. Pruppacher, 1994). Moreover, the same procedure as in Gierens et al. (1999) is applied to find out if measurements were taken in the lower stratosphere or in the upper troposphere. An ozone mixing ratio mO3 of 130 ppbv is used as a threshold separating troposphere (lower values) and Full Screen / Esc Printer-friendly Version Interactive Discussion 5 Discussion Paper stratosphere (higher values). We have collocated these data with the AIRS data to (1) investigate relationships between MOZAIC relative humidity and AIRS cloud properties and (2) to develop a calibration method for the detection of ice supersaturation within the AIRS data. 3 Synergy of AIRS and MOZAIC | 10 Discussion Paper | 12895 | 25 Discussion Paper 20 11, 12889–12947, 2011 Ice supersaturation from the Atmospheric InfraRed Sounder N. Lamquin et al. Title Page Abstract Introduction Conclusions References Tables Figures ◭ ◮ ◭ ◮ Back Close | 15 AIRS cloud properties are retrieved within each AIRS footprint of 13.5 km whereas RHiA is computed within the AMSU footprint of about 40 km. Therefore, we use two different collocation schemes. When combining the AIRS cloud properties with MOZAIC RHi measurements we only keep the one flight measurement which is closest to the center of the AIRS footprint and which is inside the AIRS footprint. When combining the AIRS relative humidity RHiA with MOZAIC RHi we first collect all MOZAIC single measurements located within the AMSU footprint and then choose the highest relative humidity RHiM among the collection of collocated measurements. In both cases data have to be coincident within a timeframe of 30 min. The situation is illustrated in Fig. 2 where a MOZAIC flight is crossing an AMSU footprint. A maximum of about 50 collocated MOZAIC measurements (from one flight) can reside within one AMSU footprint. The high coverage and the large amount of AIRS data between 2003 and 2007 lead to a relatively large set of statistics. Table 2 shows statistics of collocated events (one MOZAIC single measurement per AIRS footprint) in the upper troposphere (p < 500 hPa) per latitude band and per AIRS scene divided into clear sky (“clear”), low and mid-level clouds (“lmclds”, pcld > 440 hPa) and high clouds (“cirrus”, pcld < 440 hPa). In brackets we indicate the fraction of all MOZAICAIRS collocations with respect to the total number of events per latitude band and with respect to the total number of collocations. A large majority of the collocations are located outside of the tropical band, linked to the density of commercial flights. Discussion Paper 3.1 AIRS-MOZAIC collocations and statistics ACPD Full Screen / Esc Printer-friendly Version Interactive Discussion Discussion Paper | Discussion Paper 25 ACPD 11, 12889–12947, 2011 Ice supersaturation from the Atmospheric InfraRed Sounder N. Lamquin et al. Title Page Abstract Introduction Conclusions References Tables Figures ◭ ◮ ◭ ◮ Back Close | 20 Discussion Paper 15 | Figure 3 shows distributions of RHiM , separately for three scene types: cirrus, clear sky and clouds with cloud-top pressure larger than 440 hPa (low and mid-level clouds). We compare two latitude bands: northern midlatitudes 40–60 (left) and tropics 20 N– 20 S (right). For clear and lmclds situations RHiM corresponds to measurements within the 200–250 and 250–300 hPa layers. In the case of cirrus, RHiM is measured close to the cloud pressure with |pM − pcld | < 50 hPa so that the distributions begin to represent what might actually be observed inside a cirrus layer. For every situation data are only considered below the tropopause. This is ensured by the MOZAIC criterion mO3 < 130 ppbv and by the tropopause altitude provided in the AIRS L2 data. In both latitude bands the distributions for clear skies are similar to those for low and middle clouds. We observe drier upper tropospheric air in the tropics at aircraft cruise altitudes (mainly about 200–250 hPa), consistent with Fig. 4 of Gierens et al. (1999). For situations involving cirrus clouds we observe a peak frequency at 115–120% for the northern midlatitudes and around 100% for the tropics. In 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
A 6-year global climatology of occurrence of upper-tropospheric ice supersaturation inferred from the Atmospheric Infrared Sounder after synergetic calibration with MOZAIC
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A 6-year global climatology of occurrence of upper-tropospheric ice supersaturation inferred from the Atmospheric Infrared Sounder after synergetic calibration with MOZAIC

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