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Semedo A.,Escola Naval CINAV | Semedo A.,University of Lisbon | Soares P.M.M.,University of Lisbon | Lima D.C.A.,University of Lisbon | And 4 more authors.
Global and Planetary Change | Year: 2016

Coastal low-level jets (CLLJ) are low tropospheric coast-parallel wind features, confined to the marine atmospheric boundary layer, which lay on the east flank of the semi-permanent sub-tropical high-pressure systems, in the mid-latitudes, along equator-ward eastern boundary currents. Coastal jets are of utmost relevance to the regional climate, through their impact on the along coast sea surface temperature, driving the upwelling of cold deep nutrient-rich waters, and by having a decisive impact on the aridity of the mid-latitude western coastal areas. Here the impact of a warmer climate in the CLLJ climate is investigated, through a 2-member ensemble of EC-Earth CMIP5 simulations of future climate, following the RCP8.5 greenhouse gases emissions scenario. Besides the projected changes of the CLLJ, towards the end of the 21st century, the future characteristics of the coastal jets are also presented. No common feature of projected changes in the seven identified CLLJ areas was identified. The Iberian Peninsula and the Oman coastal jets are the ones that presented the highest differences, compared to present climate: highest projected increases in frequency of occurrence, as well as highest projected increases in jet strength (wind speed at the jet height) and jet height. This study presents a step forward towards a larger ensemble of CLLJ projections, required to better assess robustness and uncertainty of potential future climate change. © 2015. Source


Semedo A.,Escola Naval CINAV | Semedo A.,Uppsala University | Semedo A.,University of Lisbon | Vettor R.,University of Lisbon | And 6 more authors.
Ocean Dynamics | Year: 2014

A detailed climatology of wind sea and swell waves in the Nordic Seas (North Sea, Norwegian Sea, and Barents Sea), based on the high-resolution reanalysis NORA10, developed by the Norwegian Meteorological Institute, is presented. The higher resolution of the wind forcing fields, and the wave model (10 km in both cases), along with the inclusion of the bottom effect, allowed a better description of the wind sea and swell features, compared to previous global studies. The spatial patterns of the swell-dominated regional wave fields are shown to be different from the open ocean, due to coastal geometry, fetch dimensions, and island sheltering. Nevertheless, swell waves are still more prevalent and carry more energy in the Nordic Seas, with the exception of the North Sea. The influence of the North Atlantic Oscillation on the winter regional wind sea and swell patterns is also presented. The analysis of the decadal trends of wind sea and swell heights during the NORA10 period (1958–2001) shows that the long-term trends of the total significant wave height (SWH) in the Nordic Seas are mostly due to swell and to the wave propagation effect. © 2014, Springer-Verlag Berlin Heidelberg. Source


Correia F.,CINAV Inesc ID | Santos J.,Escola Naval CINAV | Mesquita P.,Escola Naval CINAV
Maritime Engineering and Technology - Proceedings of 1st International Conference on Maritime Technology and Engineering, MARTECH 2011 | Year: 2012

The design of a naval communication system can be done using the Mobile Ad hoc Network working concept (MANET), enhanced with the capability to communicate with the command and control centres ashore.Actually the Portuguese Navy has the capability to communicate between the land based command centres and the ships, and between ships. However, the communication technology used in ship-to-ship link set bounds to the serviceswhich are required for the command and control procedures. The use of a naval MANET enhanced with the capacity to link the ships at sea with the command and control centres ashore will extend the network services to a greater number of ships. This document presents a case study about the usability of a MANET by a naval force. In this study was considered different classes of routing protocols and several models for the Transmission Control Protocol (TCP). In this scope, it is done a performance comparison between the routing protocols with the TCP models under study. The results were achieved through simulation using different naval scenarios. © 2012 Taylor & Francis Group, London. Source

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