In situ measurements of the attenuation of high-frequency sonar pulses in sea water

1964 ◽  
Vol 11 (3) ◽  
pp. 498
Keyword(s):  
High Frequency ◽  
Sea Water ◽  
In Situ Measurements

scholarly journals Long-term, high frequency in situ measurements of intertidal mussel bed temperatures using biomimetic sensors

2016 ◽  
Vol 3 (1) ◽  
Author(s):  
Brian Helmuth ◽  
Francis Choi ◽  
Allison Matzelle ◽  
Jessica L. Torossian ◽  
Scott L. Morello ◽  
...  
Keyword(s):  
High Frequency ◽  
In Situ Measurements ◽  
Mussel Bed ◽  
Intertidal Mussel

Environmental influences on historical monuments: a multi-analytical characterization of degradation materials

2020 ◽  
Author(s):  
Joao Pedro Veiga ◽  
Fernanda Carvalho ◽  
Hugo Aguas ◽  
Giampiero Montesperelli ◽  
Elissavet Kavoulaki ◽  
...  
Keyword(s):  
Sea Water ◽  
Science And Technology ◽  
In Situ Measurements ◽  
Ex Situ ◽  
The European Union ◽  
Horizon 2020 ◽  
Surrounding Environment ◽  
Supporting Material ◽  
Salt Efflorescence

<div> <p>The Minoan Palace of Knossos and the Venetian coastal fortress “Rocca a mare” (Koules), located in Heraklion, Crete, Greece, are two important monuments for the history of mankind particularly vulnerable to environmental conditions, since they are located in an island subjected to strong variations in humidity and, as in the case of the Venetian fortress, in direct contact with sea water. In this type of surrounding environment, the formation of salt efflorescence as well as various other soluble salts crusts is a common situation. They occur according to the existing solubilization and crystallization conditions and can happen either in exterior or interior areas of the monuments. Their presence may stimulate further degradation, either due to the chemical dissolution of the substrate materials or due to the mechanical actions created by the formation of crystals, which may result in the decay of the substrate.</p> <p>A set of samples from both monuments were analysed using various laboratory (ex-situ) analytical methods such as optical microscopy (OM), X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), Raman spectroscopy and Laser-Induced Breakdown Spectroscopy (LIBS). In-situ measurements using portable Raman and LIBS instruments were also performed. The comparative results from ex-situ analysis and in-situ measurements will be presented with emphasis to the chemical composition of the crusts and their origin. Results indicate that observed stalactites and salt efflorescence are directly related to the type of supporting material and the conditions of the surrounding environment. In general, the formation of crusts and salts are due to processes of alteration of the supporting material while the high impact of sea salt on the formation of the efflorescence at the Venetian coastal fortress was also confirmed.</p> <p> </p> <p>[1] This work was supported by the European Union’s Framework Programme for Research and Innovation HORIZON 2020 under Grant Agreement 700395 project HERACLES.</p> <p>Acknowledgment to the Portuguese Foundation for Science and Technology (FCT) UID/EAT/00729/2013 and EAT/00729-3 by FEDER funds through the COMPETE 2020 Programme and National Funds through FCT—Portuguese Foundation for Science and Technology under the project number POCI-01-0145-FEDER-007688, Reference UID/CTM/50025/2013 NOVA.ID.FCT, and the PhD Scholarship SFRH/BD/145308/2019.</p> </div>

scholarly journals In situ measurements of the direct-current conductivity of Antarctic Sea ice: implications for airborne electromagnetic Sounding of Sea-ice thickness

2006 ◽  
Vol 44 ◽  
pp. 217-223 ◽  
Author(s):  
J.E. Reid ◽  
A. Pfaffling ◽  
A.P. Worby ◽  
J.R. Bishop
Keyword(s):  
Sea Ice ◽  
Direct Current ◽  
Sea Water ◽  
Vertical Direction ◽  
In Situ Measurements ◽  
Ice Thickness ◽  
Sea Ice Thickness ◽  
Antarctic Sea Ice ◽  
Direct Current Conductivity

AbstractAirborne, Ship-borne and Surface low-frequency electromagnetic (EM) methods have become widely applied to measure Sea-ice thickness. EM responses measured over Sea ice depend mainly on the Sea-water conductivity and on the height of the Sensor above the Sea-ice–sea-water interface, but may be Sensitive to the Sea-ice conductivity at high excitation frequencies. We have conducted in Situ measurements of direct-current conductivity of Sea ice using Standard geophysical geoelectrical methods. Sea-ice thickness estimated from the geoelectrical Sounding data was found to be consistently underestimated due to the pronounced vertical-to-horizontal conductivity anisotropy present in level Sea ice. At five Sites, it was possible to determine the approximate horizontal and vertical conductivities from the Sounding data. The average horizontal conductivity was found to be 0.017 Sm–1, and that in the vertical direction to be 9–12 times higher. EM measurements over level Sea ice are Sensitive only to the horizontal conductivity. Numerical modelling has Shown that the assumption of zero Sea-ice conductivity in interpretation of airborne EM data results in a negligible error in interpreted thickness for typical level Antarctic Sea ice.

On the Variability in the Onset of the Norwegian Coastal Current

2018 ◽  
Vol 48 (3) ◽  
pp. 723-738 ◽  
Author(s):  
Kai Håkon Christensen ◽  
Ann Kristin Sperrevik ◽  
Göran Broström
Keyword(s):  
Remote Sensing ◽  
High Frequency ◽  
Conceptual Models ◽  
Sea Water ◽  
Surface Current ◽  
Wind Forcing ◽  
Coastal Current ◽  
Norwegian Coastal Current ◽  
Forcing Mechanisms

AbstractA high-resolution reanalysis of the circulation in the Kattegat and Skagerrak is used to investigate the mechanisms that control the variability in the onset of the Norwegian Coastal Current. In the reanalysis, the authors have used all available in situ and remote sensing observations of salinity and temperature and use surface current observations from two coastal high-frequency radars that were ideally placed to monitor the exchange between the two basins. This study finds a strong correlation between the variability in the wind forcing in the Skagerrak and the transport in the Norwegian Coastal Current through the Torungen–Hirtshals section. Two cases with winds into and out of the Skagerrak are studied in more detail, and the results suggest asymmetries in the forcing mechanisms. For winds out of the Skagerrak, strong outflows of Baltic Sea Water associated with a deflection of the Kattegat–Skagerrak Front may disrupt local processes in the Skagerrak, which is not accounted for in previously published conceptual models for the variability of the coastal currents in this region.

scholarly journals Remote Sensing of Ice Conditions in the Southeastern Baltic Sea and in the Curonian Lagoon and Validation of SAR-Based Ice Thickness Products

2020 ◽  
Vol 12 (22) ◽  
pp. 3754
Author(s):  
Igor E. Kozlov ◽  
Elena V. Krek ◽  
Andrey G. Kostianoy ◽  
Inga Dailidienė
Keyword(s):  
Sea Water ◽  
Temporal Analysis ◽  
In Situ Measurements ◽  
Curonian Lagoon ◽  
Ice Thickness ◽  
Finnish Meteorological Institute ◽  
Ice Conditions ◽  
Ice Regime ◽  
Sar Data

Here we analyze ice conditions in the Southeastern Baltic (SEB) Sea and in the Curonian Lagoon (CL) using spaceborne synthetic aperture radar (SAR) data combined with in-situ measurements from coastal stations during four winter seasons between 2009–2013. As shown, the ice conditions in the SEB and in the CL are strongly varying from year to year and do not always correlate with each other. In the SEB, ice cover may form only within 5–15 km band along the coast or spread up to 100 km offshore covering almost the entire region. The mean ice season duration here is 45 days. The CL is almost fully ice-covered every year apart of its northern part subjected to sea water inflow and active shipping. The ice regime is also more stable here, however, it also possesses multiple periods of partial melting and re-freezing. In this study we also perform a validation of three SAR-based ice thickness products (Envisat ASAR 0.5-km and 1-km, and RADARSAT-2 0.5-km) produced by the Finnish Meteorological Institute versus in-situ measurements in the CL. As shown, all satellite products perform rather well for the periods of gradual ice thickness growth. When the ice thickness grows rapidly, all products underestimate the observed values by 10–20 cm (20–50%). The best results were obtained for the RADARSAT-2 ice thickness product with the highest R2 value (0.68) and the root mean square error around 8 cm. The results of the study clearly show that multi-mission SAR data are very useful for spatial and temporal analysis of the ice regime in coastal waters and semi-enclosed shallow water bodies where the number of field observations is insufficient or lacking.

scholarly journals A five year record of high-frequency in situ measurements of non-methane hydrocarbons at Mace Head, Ireland

2011 ◽  
Vol 4 (5) ◽  
pp. 955-964 ◽  
Author(s):  
A. Grant ◽  
E. L. Yates ◽  
P. G. Simmonds ◽  
R. G. Derwent ◽  
A. J. Manning ◽  
...  
Keyword(s):  
High Frequency ◽  
Temporal Trends ◽  
Kendall Test ◽  
In Situ Measurements ◽  
Baseline Data ◽  
Seasonal Cycles ◽  
Air Masses ◽  
Northern Hemispheric ◽  
Eastern Edge

Abstract. Continuous high-frequency in situ measurements of a range of non-methane hydrocarbons have been made at Mace Head since January 2005. Mace Head is a background Northern Hemispheric site situated on the eastern edge of the Atlantic. Five year measurements (2005–2009) of six C2–C5 non-methane hydrocarbons have been separated into baseline Northern Hemispheric and European polluted air masses, among other sectors. Seasonal cycles in baseline Northern Hemispheric air masses and European polluted air masses arriving at Mace Head have been studied. Baseline air masses show a broad summer minima between June and September for shorter lived species, longer lived species show summer minima in July/August. All species displayed a winter maxima in February. European air masses showed baseline elevated mole fractions for all non-methane hydrocarbons. Largest elevations (of up to 360 ppt for ethane maxima) from baseline data were observed in winter maxima, with smaller elevations observed during the summer. Analysis of temporal trends using the Mann-Kendall test showed small (<6 % yr−1) but statistically significant decreases in the butanes and i-pentane between 2005 and 2009 in European air. No significant trends were found for any species in baseline air.

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