Detecting volcanic sulfur dioxide plumes in the Northern Hemisphere using the Brewer spectrophotometer, other networks, and satellite observations

This paper demonstrates that SO 2 columnar amounts have significantly increased following the five largest volcanic eruptions of the past decade in the Northern Hemisphere. A strong positive signal was detected by all the existing networks either ground based (Brewer, EARLINET, AirBase) or from satellites (OMI, GOME-2). The study particularly examines the adequacy of the existing Brewer network to detect SO 2 plumes of volcanic origin in comparison to other networks and satellite platforms. The comparison with OMI and 45 GOME-2 SO 2 space-borne retrievals shows statistically significant agreement between the Brewer network data and the collocated satellite overpasses. It is shown that the Brewer instrument is capable of detecting significant columnar SO 2 increases following large volcanic eruptions, when SO 2 levels rise well above the instrumental noise of daily observations, estimated to be of the order of 2 DU. A model exercise from the MACC project shows that the large increases of SO 2 over Europe following the Bárðarbunga eruption in Iceland were not caused by local sources or ship emissions but are clearly linked to the eruption. We propose that by combining Brewer data with that from other networks and satellites, a useful tool aided by trajectory analyses and modeling could be created which can be used to forecast high SO 2 values both at ground level and in air flight corridors following future eruptions

Metastable superpositions of ortho- and para-Helium states

We analyze superpositions of ortho- and para-Helium states, considering the possible existence of stationary and metastable states in the system. In particular, the metastable superposition of 1s2s ortho and para states seems to be accessible to experimental scrutiny

A major star formation region in the receding tip of the stellar Galactic bar. II. Supplementary information and evidence that the bar is not the same structure as the triaxial bulge previouly reported

This paper is the second part of Garzon et al. (1997: ApJ 491, L31) in which we presented an outline of the analysis of 60 spectra from a follow-up program to the Two Micron Galactic Survey (TMGS) project in the l=27 deg., b=0 deg. area. In this second part, we present a more detailed explanation of the analysis as well a library of the spectra for more complete information for each of the 60 stars, and further discussions on the implications for the structure of the Galaxy. This region contains a prominent excess in the flux distribution and star counts previously observed in several spectral ranges, notably in the TMGS. More than 50% of the spectra of the stars detected with m_K<5.0 mag, within a very high confidence level, correspond to stars of luminosity class I, and a significant proportion of the remainder are very late giants which must also be rapidly evolving. We make the case, using all the available evidence, that we are observing a region at the nearer end of the Galactic bar, where the Scutum spiral arm breaks away, and that this is powerful evidence for the presence of the bar. Alternative explanations do not give nearly such a satisfactory account of the observations. The space localization of one and, a fortiori, of both ends of the bar allows us to infer a position angle for the bar of around 75 deg. with respect to the Sun-Galactic centre line. The angle is different from that given by other authors for the bar and this, we think, is because they refer to the triaxial bulge and not to the bar as detected here.Comment: 21 pages, 1 table, 9 figures, accepted in A

Intercomparison of spectroradiometers and Sun photometers for the determination of the aerosol optical depth during the VELETA-2002 field campaign

[ 1] In July 2002 the VELETA-2002 field campaign was held in Sierra Nevada ( Granada) in the south of Spain. The main objectives of this field campaign were the study of the influence of elevation and atmospheric aerosols on measured UV radiation. In the first stage of the field campaign, a common calibration and intercomparison between Licor-1800 spectroradiometers and Cimel-318 Sun photometers was performed in order to assess the quality of the measurements from the whole campaign. The intercomparison of the Licor spectroradiometers showed, for both direct and global irradiances, that when the comparisons were restricted to the visible part of the spectrum the deviations were within the instruments' nominal accuracies which allows us to rely on these instruments for measuring physical properties of aerosols at the different measurement stations. A simultaneous calibration on AOD data was performed for the Cimel-318 Sun photometers. When a common calibration and methodology was applied, the deviation was lowered to much less than 0.01 for AOD. At the same time an intercomparison has been made between the AOD values given by the spectroradiometers and the Sun photometers, with deviations obtained from 0.01 to 0.03 for the AOD in the visible range, depending on the channel. In the UVA range, the AOD uncertainty was estimated to be around 0.02 and 0.05 for Cimel and Licor respectively. In general the experimental differences were in agreement with this uncertainty estimation. In the UVB range the AOD measurements should not be used due to maximum instrumental uncertainties

Sensitivity of a distributed temperature-radiation index melt model based on AWS observations and surface energy balance fluxes, Hurd Peninsula glaciers, Livingston Island, Antarctica

We use an automatic weather station and surface mass balance dataset spanning four melt seasons collected on Hurd Peninsula Glaciers, South Shetland Islands, to investigate the point surface energy balance, to determine the absolute and relative contribution of the various energy fluxes acting on the glacier surface and to estimate the sensitivity of melt to ambient temperature changes. Long-wave incoming radiation is the main energy source for melt, while short-wave radiation is the most important flux controlling the variation of both seasonal and daily mean surface energy balance. Short-wave and long-wave radiation fluxes do, in general, balance each other, resulting in a high correspondence between daily mean net radiation flux and available melt energy flux. We calibrate a distributed melt model driven by air temperature and an expression for the incoming short-wave radiation. The model is calibrated with the data from one of the melt seasons and validated with the data of the three remaining seasons. The model results deviate at most 140 mm w.e. from the corresponding observations using the glaciological method. The model is very sensitive to changes in ambient temperature: a 0.5 ◦ C increase results in 56 % higher melt rates

Entanglement of unstable atoms: modifications of the emission properties

We analyse the influence of entanglement on the emission properties of atoms. To this end, first, we propose a scheme for the preparation of a pair of entangled Helium atoms, one in the ortho and the other in the para spin configuration. We discuss a realistic scenario for this process, based in the double ionization of He by intense laser fields. These states are used to analyse disentanglement and the role of entanglement in the spontaneous emission from the pair. In particular, we show that the decaying rate of an entangled atom is different from that in a product state, modifying the temporal emission distribution and lifetime of the atoms.Comment: Accepted in JP

Identical two-particle interferometry in diffraction gratings

We study diffraction and interference of indistinguishable particles. We consider some examples where the wavefunctions and detection probabilities can be evaluated in an analytical way. The diffraction pattern of a two-particle system shows notorious differences for the cases of bosons, fermions and distinguishable particles. In the example of near-field interferometry, the exchange effects for two-fermion systems lead to the existence of planes at which the probability of double detection is null. We also discuss the relation with the approach to systems of identical particles based on correlation functions. In particular, we shall see that these functions reflect, as in noise interferometry, the underlying periodic structure of the diffraction grating

Primavera i canvi climàtic

L’escalfament observat a les illes balears els darrers trenta o quaranta anys, com a conseqüència del canvi climàtic, és més del doble del que s’observa a escala planetària. aquest escalfament presenta, a més, una gran estacionalitat. Concretament, a l’observatori de l’aeroport de palma l’escalfament és bastant feble a ple hivern, però presenta un índex màxim exagerat a la primavera i al principi de l’estiu (abril, maig i juny). el desequilibri radiatiu produït per la intensificació de l’efecte hivernacle no és suficient per explicar un escalfament tan important en aquesta època. hi ha d’haver algun mecanisme meteorològic addicional. per tal d’esbrinar a quin mecanisme meteorològic addicional correspon aquest escalfament exagerat, hem analitzat la dinàmica dels mesos de maig i juny entre el 1973 i el 2009, mitjançant les reanàlisis de ncep/ncar, a més d’alguns índexs de teleconnexió i alguns aspectes complementaris del temps local. el resultat és que el gran escalfament observat al maig i juny a les illes balears, a mallorca concretament, està associat amb un augment del predomini de l’anticicló subtropical en aquesta època, la qual cosa significa que és la prolongació de l’estiu dinàmic cap a la primavera. aquest fet, que és compatible amb la coneguda migració cap al nord del camí de les pertorbacions ciclòniques, seria un fet transitori, que de cara al futur s’hauria de desaccelerar, per permetre el desplaçament cap a ple estiu de l’escalfament màxim, tal com indiquen els escenaris climàtics construïts. el sosteniment d’un escalfament tan gran a la primavera no és compatible amb els escenaris climàtics disponibles

L’estudi de la tramuntana: de J. M. Jansà al PYREX

La tramuntana és el vent dominant a Menorca i un dels més importants de la Mediterrània occidental. També és el responsable de la majoria dels temporals d’aquesta zona. J. M. Jansà va ésser un dels primers meteoròlegs que es va dedicar a estudiar aquest vent. Entre les seves contribucions cal destacar la climatologia del vent en altura i un minuciós estudi sobre la tramuntana a l’illa de Menorca. En aquest article es repassen la contribució de J. M. Jansà al coneixement de la tramuntana, així com els recents resultats que sobre aquest vent s’han obtingut de l’experiment PYREX

Meteorologia mediterrània: de Josep M. Jansà a avui

Josep Maria Jansà va poder ser considerat, d’alguna manera, profeta de la meteorologia mediterrània, entesa com una meteorologia singular i específica. Una apropiada selecció d’escrits seus permet reconstruir la visió global d’aquesta meteorologia que va edificar Jansà. En aquest treball es confronta aquesta visió amb els coneixements que actualment tenim sobre la meteorologia mediterrània. El resultat de la comparació ens diu que la visió de Jansà va ser prou encertada i avançada, de manera que es pot considerar globalment vigent, tot i que hi ha hagut alguns desplaçaments quant al nivell de prioritat dels temes i que algunes idees puntuals no resisteixen la crítica actual. En canvi, algunes de les propostes de Jansà encara són un camí obert de recerca, que convé explorar amb més detall per poder millorar el coneixement actual sobre la meteorologia mediterrània