1,721,060 research outputs found
Influence of the Alps on two troughs affecting WRF forecasts of convection in the Po Valley during HyMeX
No full textTwo Intensive Observation Periods (IOPs) from the HYdrological cycle in Mediterranean Experiment (HyMeX) have been studied here. IOP6 and IOP13 were dedicated to the documentation of heavy precipitation events over target areas in northern Italy. In both cases convection in the Po Valley was also observed, but in each case there was a distinct difference in the ability to reproduce the observations by most of the models available during the campaign. In particular the WRF model was able to reproduce correctly IOP13, whereas it failed in maintaining the squall line moving west to east along the Po Valley during IOP6. A parallel analysis of the two events highlights differences in the dynamics that are critical in determining conditions favorable for convection along the Po Valley. A basic difference is that the trough in IOP6 produced much stronger downslope winds in the lee of the Alpine barrier than it did in IOP13. A comparison with observations from different sources allowed the identification of the models overestimation of the zonal wind in the Po Valley as the main cause of convection suppression during IOP6. Sensitivity tests to the planetary boundary layer (PBL) parameterization show similar results for most of the WRF PBL schemes. However, an improvement in the wind forecast is produced if the Bougeault-Lacarrére scheme is used, thus restoring realistic conditions along the Po Valley that allow for a better simulation of the convective system in IOP6
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
On the accuracy of integrated water vapor observations and the potential for mitigating electromagnetic path delay error in InSAR
No full textA field campaign was carried out in the framework of the Mitigation of Electromagnetic Transmission errors induced by Atmospheric Water Vapour Effects (METAWAVE) project sponsored by the European Space Agency (ESA) to investigate the accuracy of currently available sources of atmospheric columnar integrated water vapor measurements. The METAWAVE campaign took place in Rome, Italy, for the 2-week period from 19 September to 4 October 2008. The collected dataset includes observations from ground-based microwave radiometers and Global Positioning System (GPS) receivers, from meteorological numerical model analysis and predictions, from balloon-borne in-situ radiosoundings, as well as from spaceborne infrared radiometers. These different sources of integrated water vapor (IWV) observations have been analyzed and compared to quantify the accuracy and investigate the potential for mitigating IWV-related electromagnetic path delay errors in Interferometric Synthetic Aperture Radar (InSAR) imaging. The results, which include a triple collocation analysis accounting for errors inherently present in every IWV measurements, are valid not only to InSAR but also to any other application involving water vapor sensing. The present analysis concludes that the requirements for mitigating the effects of turbulent water vapor component into InSAR are significantly higher than the accuracy of the instruments analyzed here. Nonetheless, information on the IWV vertical stratification from satellite observations, numerical models, and GPS receivers may provide valuable aid to suppress the long spatial wavelength (>20 km) component of the atmospheric delay, and thus significantly improve the performances of InSAR phase unwrapping techniques
The CETEMPS Hydro-Meteorological chain during HyMex
No full textThe Cetemps Hydrological model has been offline coupled with WRF-ARW and MM5 models in order to estimate the possibility of flood occurrence. CHyM is a distributed grid based hydrological model implementing an explicit parameterization of different physical processes contributing to hydrological cycle, the model can be forced with temperature and precipitation scenarios predicted by MM5 or WRF model. In addition this model implements the calculus of two different alarm indexes providing a map of the segments of hydrological network where floods are more likely to occur. The WRF simulations are characterized by two domains running independently. The larger domain covers Europe with a horizontal resolution of 12 km using as analysis the ECMWF model, instead, the inner one covers Italy with a grid spacing of 3 km using as boundary and initial conditions the output from the low resolution simulation. CHyM alarm maps are described and the results for cases study occurred during HyMeX campaign are shown (IOP4, IOP18 and IOP19). The three events, characterized by precipitation producing flash flood and/or an increase of the rivers level, are used to this purpose. Heavy precipitation occurred over Central Italy (CI) and North East Italy (NEI) during these events: the rainfall maxima reached more than 150 mm/24h producing floods over Marche and Abruzzo, during IOP4; 120-140mm/24hr were reached in the south side of Lazio region during IOP18, whereas 350mm/24h were accumulated during IOP19 in the NEI. Emphasis is given to the possibility of coupling WRF and CHYM model providing an effective tool for operational flood alert mapping. Moreover, a comparison with the maps obtained forcing CHyM with MM5 is performed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Water vapour distribution at urban scale using high-resolution numerical weather model and spaceborne SAR interferometric data
No full textThe local distribution of water vapour in the urban area of Rome has been studied using both a high resolution mesoscale model (MM5) and Earth Remote Sensing-1 (ERS-1) satellite radar data. Interferometric Synthetic Aperture Radar (InSAR) techniques, after the removal of all other geometric effects, estimate excess path length variation between two different SAR acquisitions (Atmospheric Phase Screen: APS). APS are strictly related to the variations of the water vapour content along the radar line of sight. To the aim of assessing the MM5 ability to reproduce the gross features of the Integrated Water Vapour (IWV) spatial distribution, as a first step ECMWF IWV has been used as benchmark against which the high resolution MM5 model and InSAR APS maps have been compared. As a following step, the high resolution IWV MM5 maps have been compared with both InSAR and surface meteorological data. The results show that the high resolution IWV model maps compare well with the InSAR ones. Support to this finding is obtained by semivariogram analysis that clearly shows good agreement beside from a model bias
Misure ed analisi delle concentrazioni di ozono troposferico a L’Aquila
No full textLe variazioni orare e giornaliere di ozono superficiale sono state analizzate insieme al radon ed ai parametri meteorologici per studiare i relativi meccanismi di controllo. Le misure in Italia centrale riguardano gli anni 2004 e 2005, e mostrano un ruolo importante del trasporto nella variabilità di concentrazione nell'ozono. L'analisi basata sulle back-trajectory indica che il luogo è influenzato dalle masse d'aria che provengono dall'ovest al settore di nordest in circa 74% dei giorni, suggerendo che la L' Aquila potrebbe essere considerata un luogo di background per l’ozono. L'ipotesi di sito di background è, inoltre supportata dai valori piuttosto bassi delle seguenti quantità dell'ozono: massimo delle medie mensili (39 ppbv, luglio), dalla mediana annuale dei dati orari (ppbv 29) e della media annuale dei massimi orari (ppbv 49). Soltanto in 6 casi in due anni di osservazioni si sono registrati valori di ozono superiore ai 90ppbv 90, comunque mai superiore a 100ppbv. Il modello di regressione riproduce l'ozono misurato con in 67% delle osservazioni orare e 74% dei dati di media giornaliere qui il modello include le informazioni dai seguenti parametri meteorologici: temperatura, umidità relativa, velocità di vento orizzontale e direzione, radiazione solare e concentrazione nel radon. Un tracciante come il radon descrive i cambiamenti dinamici della bassa atmosfera ed ha un ruolo significativo nel miglioramento del modello di previsione dell'ozono, particolarmente per le osservazioni orare e per la componente sinottica. Nel primo caso (osservazioni orarie), l'inclusione dei dati del radon migliora le prestazioni del modello di regressione da 5% (62% - 67%); nell’ultimo caso (componente sinottica), l'accuratezza del modello aumenta di 3% (78% - 81%)
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