Asimilacija podataka o temperaturi i salinitetu u jadranskom regionalnom modelu

Temperature and salinity data collected during the October 2002 - October 2003 period have been assimilated into a version of the Princeton Ocean Model implemented over the entire Adriatic Sea. The scheme used is SOFA (System for Ocean Forecast and Analysis, DE MEY & BENKIRAN, 2002) and this is the first coastal application of this scheme. The CTD data were collected in 4 coastal areas (Emilia-Romagna coastal strip, the Gulf of Trieste, the Rovinj and Pelješac-Vis-Drvenik coastal strips) while temperature profiles were acquired with XBT in the southern Adriatic Sea deep ocean areas. The analysis skill scores are examined in order to evaluate the assimilation performance. The results of the assimilation are first compared with independent analyses of satellite Sea Surface Temperature (SST) and it is found that assimilation of profiles improves the SST model estimate. Furthermore, the Root Mean Square (RMS) difference between model and temperature and salinity profiles before data insertion is analysed. The range of RMS temperature error is less than 1 0C for the entire area and decreases with time, indicating a positive impact of the assimilation. The RMS of salinity is less than 1 psu and it also shows a decreasing trend during the assimilation period.Podaci temperature i saliniteta, prikupljeni u razdoblju listopad 2002. - listopad 2003., su asimilirani u Princeton oceanski model koji je primijenjen na cijeli Jadran. Upotrijebljena shema je bila SOFA (Sys-tem for Ocean Forecast and Analysis, DE MEY & BENKIRAN, 2002), što je prva primjena ove sheme na obalno more. CTD podaci su prikupljeni na četiri obalna područja (obalni pojas Emilia–Romagna, Tršćanski zaljev, obalno područje kod Rovinja i obalno područje Pelješac-Vis-Drvenik) dok su podaci XBT-a prikupljeni u dubokim područjima južnog Jadrana. Ispitane su modelske analize, kako bi se procijenila uspješnost asimilacije. Rezultati asimilacije su najprije uspoređeni s nezavisnim analizama površinske tem-perature mora (SST) iz satelita te je nađeno da asimilacija profila poboljšava procjenu površinske tempera-ture iz modela. Nadalje je analiziran kvadratni korjen razlike (RMS) između modela te profila temperature i saliniteta prije uključivanja podataka. Raspon RMS pogreške temperature je ispod 1 0C na čitavom području i opada s vremenom, ukazujući na pozitivni utjecaj asimilacije. RMS razlika saliniteta je ispod 1 psu i pokazu-je trend opadanja za vrijeme razdoblja asimilacije

Studi Kinerja AODV-PNT dengan Penambahan Faktor Jumlah Node Tetangga pada VANET

VANET (Vehucular Ad hoc Network) merupakan pengembagan dari Mobile Ad hoc Network atau yang sering disebut MANET. Topologi pada VANET dapat berubah dengan cepat karena pergerakan simpul (node) sehingga topologi dapat berubah secara dinamis, selain itu terdapat permasalahan yang cukup menarik untuk diteliti pada VANET yaitu konektivitas antar simpul (node). Ada beberapa routing protokol pada MANET yang diterapkan pada VANET salah satunya adalah AODV (On-deman Distance Protocol) AODV adalah protokol reactive atau on-deman, jenis routing ini hanya akan membuat route ketika simpul sumber (source node) membutuhkannya. Routing protokol AODV dikembangkan lebih lanjut salah satunya adalah menjadi AODV-PNT (Prediction Node Trend), dengan menambahkan prediksi kecenderungan simpul dapat meningkatkan performa dalam menentukan rute yang stabil,berdasarkan nilai TWR (Total Weight of The Route). Nilai TWR memperhatikan beberapa faktor mobilitas seperti: kecepatan, percepatan, arah dan kualitas tautan (link quality) antar kendaraan. Pada penelitian ini, kami mengadopsi formula perhitungan TWR pada AODV-PNT dan juga menambahkan faktor lain yaitu jumlah node tetangga dalam menentukan nilai TWR. Dari hasil uji coba, AODV-PNT yang dimodifikasi berhasil meningkatkan nilai paket delivery ratio hingga 3,7%. Sedangkan untuk jumlah routing paket yang dihasilkan dalam simulasi, protokol AODV-PNT modifikasi menghasilkan routing paket 21% lebih banyak dibandingkan dengan protokol AODV-PNT original dan 62,4% lebih sedikit dibandingkan dengan protokol AODV original. Pada penelitian ini protokol modifikasi kami sebut dengan AODV-MNS. ===================================================================================================== VANET (Vehucular Ad hoc Network) is a development of Mobile Ad hoc Network or often called MANET. Topology in VANET can change rapidly because of the movement of node so that topology can change dynamically, besides there is problem interesting enough to be examined at VANET that is connectivity between node. There are several routing protocols on MANET that are applied to VANET one of them is AODV (On-deman Distance Protocol) AODV is a reactive or on-deman protocol, this type of routing will only create a route when the source node needs it. AODV protocol routing is further developed one of them is to become AODV-PNT (Prediction Node Trend), by adding prediction of node tendency can improve performance in determining stable route, based on TWR value (Total Weight of The Route). TWR values pay attention to several mobility factors such as speed, acceleration, direction and links quality between vehicles. In this study, we adopted the TWR calculation formula on AODV-PNT and also added another factor that is the number of neighboring nodes in determining the TWR value. From the trial results, modified AODV-PNT managed to increase the value of packet delivery ratio up to 3.7%. As for the number of routing packets generated in the simulation, the modified AODV-PNT protocol produced 21% more packet routing than the original AODV-PNT protocol and 62.4% less than the original AODV protocol. In this study the modification protocol we call AODV-MNS

Tsunami risk assessments in Messina, Sicily – Italy

Abstract. We present a first detailed tsunami risk assessment for the city of Messina where one of the most destructive tsunami inundations of the last centuries occurred in 1908. In the tsunami hazard evaluation, probabilities are calculated through a new general modular Bayesian tool for Probability Tsunami Hazard Assessment. The estimation of losses of persons and buildings takes into account data collected directly or supplied by: (i) the Italian National Institute of Statistics that provides information on the population, on buildings and on many relevant social aspects; (ii) the Italian National Territory Agency that provides updated economic values of the buildings on the basis of their typology (residential, commercial, industrial) and location (streets); and (iii) the Train and Port Authorities. For human beings, a factor of time exposition is introduced and calculated in terms of hours per day in different places (private and public) and in terms of seasons, considering that some factors like the number of tourists can vary by one order of magnitude from January to August. Since the tsunami risk is a function of the run-up levels along the coast, a variable tsunami risk zone is defined as the area along the Messina coast where tsunami inundations may occur

A Methodology for a Comprehensive Probabilistic Tsunami Hazard Assessment: Multiple Sources and Short-Term Interactions

We propose a methodological approach for a comprehensive and total probabilistic tsunami hazard assessment (TotPTHA), in which many different possible source types concur to the definition of the total tsunami hazard at given target sites. In a multi-hazard and multi-risk perspective, the approach allows us to consider all possible tsunamigenic sources (seismic events, slides, volcanic eruptions, asteroids, etc.). In this respect, we also formally introduce and discuss the treatment of interaction/cascade effects in the TotPTHA analysis and we demonstrate how the triggering events may induce significant temporary variations in short-term analysis of the tsunami hazard. In two target sites (the city of Naples and the island of Ischia in Italy) we prove the feasibility of the TotPTHA methodology in the multi-source case considering near submarine seismic sources and submarine mass failures in the study area. The TotPTHA indicated that the tsunami hazard increases significantly by considering both the potential submarine mass failures and the submarine seismic events. Finally, the importance of the source interactions is evaluated by applying a triggering seismic event that causes relevant changes in the short-term TotPTHA

Multisource Bayesian Probabilistic Tsunami Hazard Analysis for the Gulf of Naples (Italy)

A methodology for a comprehensive probabilistic tsunami hazard analysis is presented for the major sources of tsunamis (seismic events, landslides, and volcanic activity) and preliminarily applied in the Gulf of Naples (Italy). The methodology uses both a modular procedure to evaluate the tsunami hazard and a Bayesian analysis to include the historical information of the past tsunami events. In the urn:x-wiley:jgrc:media:jgrc23818:jgrc23818-math-0001 the submarine earthquakes and the submarine mass failures are initially identified in a gridded domain and defined by a set of parameters, producing the sea floor deformations and the corresponding initial tsunami waves. Differently volcanic tsunamis generate sea surface waves caused by pyroclastic density currents from Somma‐Vesuvius. In the urn:x-wiley:jgrc:media:jgrc23818:jgrc23818-math-0002 the tsunami waves are simulated and propagated in the deep sea by a numerical model that solves the shallow water equations. In the urn:x-wiley:jgrc:media:jgrc23818:jgrc23818-math-0003 the tsunami wave heights are estimated at the coast using the urn:x-wiley:jgrc:media:jgrc23818:jgrc23818-math-0004's amplification law. The selected tsunami intensity is the wave height. In the urn:x-wiley:jgrc:media:jgrc23818:jgrc23818-math-0005 the probabilistic tsunami analysis computes the long‐term comprehensive Bayesian probabilistic tsunami hazard analysis. In the prior analysis the probabilities from the scenarios in which the tsunami parameter overcomes the selected threshold levels are combined with the spatial, temporal, and frequency‐size probabilities of occurrence of the tsunamigenic sources. The urn:x-wiley:jgrc:media:jgrc23818:jgrc23818-math-0006 probability density functions are integrated with the urn:x-wiley:jgrc:media:jgrc23818:jgrc23818-math-0007 derived from the historical information based on past tsunami data. The urn:x-wiley:jgrc:media:jgrc23818:jgrc23818-math-0008 probability density functions are evaluated to produce the hazard curves in selected sites of the Gulf of Naples. Plain Language Summary Probabilistic analyses are essential to estimate the natural hazards caused by infrequent and devastating events and to elaborate risk assessments aiming to mitigate and reduce the impact of the natural disasters on society. Probabilistic tsunami hazard analyses use procedures that trace and weight the different tsunami sources (submarine earthquakes, aerial/submarine slides, volcanic activity, meteorological events, and asteroid impacts) with varying probability of occurrence. The scope of the present methodology is the reduction of possible biases and underestimations that arise by focusing on a single tunamigenic source. The multisource probabilistic tsunami hazard analysis is applied to a real case study, the Gulf of Naples (Italy), where relevant threats due to natural events exist in a high densely populated district. The probabilistic hazard procedure takes into account multiple tsunamigenic sources in the region and provides a first‐order prioritization of the different sources in a long‐term comprehensive analysis. The methodology is based on a Bayesian approach that merges computational hazard quantification (based on source‐tsunami simulations) and past data, appropriately including in the quantification the epistemic uncertainty. For the first time a probabilistic analysis of the tsunami hazard in the region is presented taking into consideration multiple tsunamigenic sources

Tsunami hazards in the Catalan Coast, a low-intensity seismic activity area

The final publication is available at Springer via http://dx.doi.org/10.1007/s11069-017-2918-zThe potential impacts of tsunamis along the Catalan Coast (NW Mediterranean) are analysed using numerical modelling. The region is characterized by moderate to low seismic activity and by moderate- to low-magnitude earthquakes. However, the occurrence of historical strong earthquakes and the location of several active offshore faults in front of the coast suggest that the possibility of an earthquake-triggered tsunami is not negligible although of low probability. Up to five faults have been identified to generate tsunamis, being the highest associated possible seismic magnitudes of up to 7.6. Coastal flooding and port agitation are characterized using the Worst-case Credible Tsunami Scenario Analysis approach. The results show a multiple fault source contribution to tsunami hazard. The shelf dimensions and the existence of submerged canyons control the tsunami propagation. In wide shelves, waves travelling offshore may become trapped by refraction causing the wave energy to reach the coastline at some distance from the origin. The free surface water elevation increases at the head of the canyons due to the sharp depth gradients. The effects of potential tsunamis would be very harmful in low-lying coastal stretches, such as deltas, with a high population concentration, assets and infrastructures. The Ebro delta appears to be the most exposed coast, and about the 20% of the delta surface is prone to flooding due to its extremely low-lying nature. The activity at Barcelona port will be severely affected by inflow backflow current at the entrance of up to 2 m/s.Peer ReviewedPostprint (author's final draft

Probability Analysis Improves Hazard Assessment

Many of the world’s natural events from earthquakes and volcanoes to tornados and landslides affect human populations. Estimating the likelihood of occurrence and frequency is an important science to help people plan and prepare for future events. An article recently published in Reviews in Geophysics, Grezio et al. [2017] (http://onlinelibrary.wiley.com/doi/10.1002/2017RG000579/full) considered one type of infrequent but often devastating natural event: tsunamis. They gave an overview of a method for analyzing and preparing for tsunamis. The editor asked one of the authors to explain more about methods of hazard analysis and recent developments in this field.Editors’ Vox Perspectives on Earth and space science: A blog from AGU’s journal editorsPublished6T. Studi di pericolosità sismica e da maremotoN/A or not JC

The dynamical controls on the antarctic circumpolar current with the use of general circulation models

Three general circulation models (FRAM, OCCAM and POP) are used in order to investigate the dynamics of the Antarctic Circumpolar Current (ACC) at the Drake Passage latitudes (ACCB) where the ACC is unbounded. In these models bottom form stress balances the wind stress in the momentum budgets. In the vorticity budgets the main balance is between wind curl and bottom pressure torque in FRAM and OCCAM. In the higher resolution model (POP) the non linear advection is one of the main terms. Whereas standing eddies mainly decelerate the flow in the ACCB, transient eddies play a different role in the three models. In the upper levels transient eddies accelerate the flow in POP and FRAM, but decelerate the flow in OCCAM. The behaviour of standing and transient eddies changes throughout the water column in the ACCB and eddies have a dragging effect on the flow below the levels where the topography starts to obstruct the flow. The crucial role of topography is investigated using a set of numerical experiments. In the coarse version of OCCAM Kerguelen Plateau is lowered and the Drake Passage Region and the Antarctic-Pacific Ridge are removed. Results from the analysis in the ACCB indicate that changing topography has a local effect. The complete investigation of the ACC dynamics is extended to the ACC Path (ACCP). The vorticity budgets show that the Drake Passage Region affects all of the ACC flow. Removing Drake Passage reduces the contributions of the bottom pressure torque to the vorticity balance and the region of Sverdrup-like balance is extended. The key role for all the ACC is played by Drake Passage but not from other topographic features.</p

Data assimilation of temperature and salinity profiles in the Adriatic Sea regional model

Temperature and salinity data collected during the October 2002- October 2003 period have been assimilated into a version of the Princeton Ocean Model implemented over the entire Adriatic Sea. The scheme used is SOFA (System for Ocean Analysis and Forecast, DE MEY & BENKIRAN, 2002) and this is the first coastal application of this scheme. The CTD data were collected in 4 coastal areas (Emilia – Romagna Coastal strip, the Gulf of Trieste, the Rovinj and Pelješac-Vis-Drvenik coastal strips) while temperature profiles were acquired with XBT in the southern Adriatic Sea deep ocean areas. The analysis skill scores are examined in order to evaluate the assimilation performance. The results of the assimilation are first compared with independent analyses of satellite Sea Surface Temperature (SST) and it is found that assimilation of profiles improves the SST model estimate. Furthermore, the Root Mean Square (RMS) difference between model and temperature and salinity profiles before data insertion is analysed. The range of RMS temperature error is less than 1 0C for the entire area and decreases with time, indicating a positive impact of the assimilation. The RMS of salinity is less than 1 psu and it also shows a decreasing trend during the assimilation period.Published149-168ope