Artykuły w czasopismach na temat „Ocean bottom – Remote-sensing maps”
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1
Frezzotti, Massimo. "Glaciological study in Terra Nova Bay, Antarctica, inferred from remote sensing analysis". Annals of Glaciology 17 (1993): 63–71. http://dx.doi.org/10.1017/s0260305500012623.
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Analysis of satellite images (Landsat 1 MSS, 4 TM and SPOT 1 XS), of U.S. Navy aerial photographs (TMA) and of U.S.G.S. maps has made it possible to assess a number of parameters relating to the surface dynamics (between 1956 and 1990) of eight ice tongues and of two ice shelves in the Terra Nova Bay area. The study shows that between 1960–63 and 1972–73 there was a decided decrease in the areas of some of the tongues and shelves: −53 km2 for the Aviator Glacier Tongue and −124 km2 for the Nansen Ice Sheet. On the other hand, the areas generally increased in the period 1972–73 to 1988. An exception to this situation is the small Hells Gate ice shelf whose area diminished by 1.15 km2 between 1956–57 and 1988. The calculated surface velocity of the ice tongues shows that they increase from the grounding line to their outer limit. Values of longitudinal strain rate generally increase from the grounding line to just after the start of the ice tongue, after which they diminsh proceeding towards its outer limit. Integration of the areal values with radio-echo sounding data has enabled the ice discharges of the southern flow of the David Glacier (12km3a−1) and of the Aviator Glacier Tongue (0.62 km3 a−1) to be calculated. Furthermore, on the basis of the data available, basal melting values of between 25 cm a−1 and 100 cm a−1 are deduced for these two ice tongues, and bottom freezing values of 20 cm a−1 for the Drygalski Ice Tongue. Different spectral responses of the glacial areas have made it possible to discriminate ablation areas from those of accumulation and to differentiate various typologies of ice (glacier ice, melt lake ice, and sea ice formed at the ice shelf-ocean interface).
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Frezzotti, Massimo. "Glaciological study in Terra Nova Bay, Antarctica, inferred from remote sensing analysis". Annals of Glaciology 17 (1993): 63–71. http://dx.doi.org/10.3189/s0260305500012623.
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Analysis of satellite images (Landsat 1 MSS, 4 TM and SPOT 1 XS), of U.S. Navy aerial photographs (TMA) and of U.S.G.S. maps has made it possible to assess a number of parameters relating to the surface dynamics (between 1956 and 1990) of eight ice tongues and of two ice shelves in the Terra Nova Bay area. The study shows that between 1960–63 and 1972–73 there was a decided decrease in the areas of some of the tongues and shelves: −53 km2 for the Aviator Glacier Tongue and −124 km2 for the Nansen Ice Sheet. On the other hand, the areas generally increased in the period 1972–73 to 1988. An exception to this situation is the small Hells Gate ice shelf whose area diminished by 1.15 km2 between 1956–57 and 1988. The calculated surface velocity of the ice tongues shows that they increase from the grounding line to their outer limit. Values of longitudinal strain rate generally increase from the grounding line to just after the start of the ice tongue, after which they diminsh proceeding towards its outer limit. Integration of the areal values with radio-echo sounding data has enabled the ice discharges of the southern flow of the David Glacier (12km3a−1) and of the Aviator Glacier Tongue (0.62 km3 a−1) to be calculated. Furthermore, on the basis of the data available, basal melting values of between 25 cm a−1 and 100 cm a−1 are deduced for these two ice tongues, and bottom freezing values of 20 cm a−1 for the Drygalski Ice Tongue. Different spectral responses of the glacial areas have made it possible to discriminate ablation areas from those of accumulation and to differentiate various typologies of ice (glacier ice, melt lake ice, and sea ice formed at the ice shelf-ocean interface).
3
Arnold, S. R., D. V. Spracklen, J. Williams, N. Yassaa, J. Sciare, B. Bonsang, V. Gros i in. "Evaluation of the global oceanic isoprene source and its impacts on marine organic carbon aerosol". Atmospheric Chemistry and Physics Discussions 8, nr 4 (27.08.2008): 16445–71. http://dx.doi.org/10.5194/acpd-8-16445-2008.
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Abstract. We have combined the first satellite maps of the global distribution of phytoplankton functional type and new measurements of phytoplankton-specific isoprene productivities, with available remote marine isoprene observations and a global model, to evaluate our understanding of the marine isoprene source and its impacts on organic aerosol abundances. Using satellite products to scale up data on phytoplankton-specific isoprene productivity to the global oceans, we infer a mean "bottom-up" oceanic isoprene emission of 0.31±0.08 (1 σ) Tg/yr. By minimising the mean bias between the model and isoprene observations in the marine atmosphere remote from the continents, we produce a "top-down" oceanic isoprene source estimate of 1.9 Tg/yr. We suggest our reliance on limited atmospheric isoprene data, and limited knowledge of isoprene productivity across the broad range of phytoplankton communities in the oceans as contributors to this difference between the two estimates. Inclusion of secondary organic aerosol (SOA) production from oceanic isoprene in the model with a 2% yield produces small contributions (0.01–1.6%) to observed organic carbon (OC) aerosol mass at three remote marine sites in the Northern and Southern Hemispheres. In addition, we find the seasonal cycle of the isoprene SOA source is out of phase with the observed cycle in OC in the remote Southern Ocean. Based on these findings we suggest an insignificant role for isoprene in modulating remote marine aerosol abundances, giving further support to a recently postulated primary OC source in the remote marine atmosphere.
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de Lavergne, Casimir, Gurvan Madec, Julien Le Sommer, A. J. George Nurser i Alberto C. Naveira Garabato. "On the Consumption of Antarctic Bottom Water in the Abyssal Ocean". Journal of Physical Oceanography 46, nr 2 (luty 2016): 635–61. http://dx.doi.org/10.1175/jpo-d-14-0201.1.
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AbstractThe abyssal ocean is primarily filled by cold, dense waters formed around Antarctica and collectively referred to as Antarctic Bottom Water (AABW). At steady state, AABW must be consumed in the ocean interior at the same rate it is produced, but how and where this consumption is achieved remains poorly understood. Here, estimates of abyssal water mass transformation by geothermal heating and parameterized internal wave–driven mixing are presented. This study uses maps of the energy input to internal waves by tidal and geostrophic motions interacting with topography combined with assumptions about the distribution of energy dissipation to evaluate dianeutral transports induced by breaking internal tides and lee waves. Geothermal transformation is assessed based on a map of geothermal heat fluxes. Under the hypotheses underlying the constructed climatologies of buoyancy fluxes, the authors calculate that locally dissipating internal tides and geothermal heating contribute, respectively, about 8 and 5 Sverdrups (Sv; 1 Sv ≡ 106 m3 s−1) of AABW consumption (upwelling), mostly north of 30°S. In contrast, parameterized lee wave–driven mixing causes significant transformation only in the Southern Ocean, where it forms about 3 Sv of AABW, decreasing the mean density but enhancing the northward flow of abyssal waters. The possible role of remotely dissipating internal tides in complementing AABW consumption is explored based on idealized distributions of mixing energy. Depending mostly on the chosen vertical structure, such mixing could drive 1 to 28 Sv of additional AABW upwelling, highlighting the need to better constrain the spatial distribution of remote dissipation. Though they carry large uncertainties, these climatological transformation estimates shed light on the qualitative functioning and key unknowns of the diabatic overturning.
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Hofmann, Andreas F., Peter M. Walz, Hans Thomas, Edward T. Peltzer i Peter G. Brewer. "High-Resolution Topography-Following Chemical Mapping of Ocean Hypoxia by Use of an Autonomous Underwater Vehicle: The Santa Monica Basin Example". Journal of Atmospheric and Oceanic Technology 30, nr 11 (1.11.2013): 2630–46. http://dx.doi.org/10.1175/jtech-d-12-00249.1.
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Abstract This paper reports on the execution of a combined chemical sensing/high-resolution terrain-following autonomous underwater vehicle (AUV) survey to explore the fine structure and functional boundaries of the Santa Monica Basin suboxic zone and its relationship to topography. An AUV mapping vehicle is used in a novel configuration—combining the mapping vehicle tail section, with precision inertial navigation and acoustic communications systems, with CTD/O2, NO3 sensing, and Gulper water sampling systems. The challenge was to perform a long-distance near-bottom physical/chemical survey in deep water without any intermediate surfacing to disrupt the survey or require the vehicle to surface in areas of heavy ship traffic. Some 210 km of AUV cruise track at ≈10 m above bottom were accomplished during a 3-day survey. The dissolved oxygen concentration [O2] data are combined with temperature T, salinity S, and hydrostatic pressure P to produce maps of oxygen partial pressure pO2 that help define the limits at which the oceanic supply of O2 can match the O2 demands required to sustain various forms of marine life. The chemical NO3 sensing was included to define the critical pO2 boundary at which NO3 reduction occurs. The combination of a high-resolution terrain-following AUV with chemical sensors is important for a diverse array of investigations, including the study of vent sites, and for locating the source of chemical signals originating from the seafloor. The hypoxic basin example here permits better discrimination between general climate/circulation controls on hypoxia and more specific point-source-driven processes.
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Specht, Cezary, Emilian Świtalski i Mariusz Specht. "Application of an Autonomous/Unmanned Survey Vessel (ASV/USV) in Bathymetric Measurements". Polish Maritime Research 24, nr 3 (1.09.2017): 36–44. http://dx.doi.org/10.1515/pomr-2017-0088.
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AbstractThe accuracy of bathymetric maps, especially in the coastal zone, is very important from the point of view of safety of navigation and transport. Due to the continuous change in shape of the seabed, these maps are fast becoming outdated for precise navigation. Therefore, it is necessary to perform periodical bathymetric measurements to keep them updated on a current basis. At present, none of the institutions in Poland (maritime offices, Hydrographic Office of the Polish Navy) which are responsible for implementation of this type of measurements has at their disposal a hydrographic vessel capable of carrying out measurements for shallow waters (at depths below 1 m). This results in emergence of large areas for which no measurement data have been obtained and, consequently, the maps in the coastal zones are rather unreliable.The article presents the concept of bathymetric measurements for shallow waters with the use of an autonomous, unmanned survey vessel (ASV/USV). For this purpose, the authors modernized a typical ASV/USV unit with standard radio remote control system to the fully autonomous mode. As part of the modernization, the route planning software was created. The developed software works based on, alternatively, GNSS measurements of the coastline, or satellite images. The system was supplemented by an own autopilot (adapted for flying drones). Moreover, the method of controlling electric motors was changed thanks to the use of own electronic circuit.The modernized ASV/USV measuring system was verified by performing bathymetric measurements of the retention reservoir in Gdansk, Poland. Then, the obtained measurement data were used to create a digital bottom model and a bathymetric map of the reservoir.
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Wason, Haneet, Felix Oghenekohwo i Felix J. Herrmann. "Low-cost time-lapse seismic with distributed compressive sensing — Part 2: Impact on repeatability". GEOPHYSICS 82, nr 3 (1.05.2017): P15—P30. http://dx.doi.org/10.1190/geo2016-0252.1.
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Irregular or off-the-grid spatial sampling of sources and receivers is inevitable in field seismic acquisitions. Consequently, time-lapse surveys become particularly expensive because current practices aim to replicate densely sampled surveys for monitoring changes occurring in the reservoir due to hydrocarbon production. We have determined that under certain circumstances, high-quality prestack data can be obtained from cheap randomized subsampled measurements that are observed from nonreplicated surveys. We extend our time-jittered marine acquisition to time-lapse surveys by designing acquisition on irregular spatial grids that render simultaneous, subsampled, and irregular measurements. Using the fact that different time-lapse data share information and that nonreplicated surveys add information when prestack data are recovered jointly, we recover periodic densely sampled and colocated prestack data by adapting the recovery method to incorporate a regularization operator that maps traces from an irregular spatial grid to a regular periodic grid. The recovery method is, therefore, a combined operation of regularization, interpolation (estimating missing fine-grid traces from subsampled coarse-grid data), and source separation (unraveling overlapping shot records). By relaxing the insistence on replicability between surveys, we find that recovery of the time-lapse difference shows little variability for realistic field scenarios of slightly nonreplicated surveys that suffer from unavoidable natural deviations in spatial sampling of shots (or receivers) and pragmatic compressed-sensing-based nonreplicated surveys when compared with the “ideal” scenario of exact replicability between surveys. Moreover, the recovered densely sampled prestack baseline and monitor data improve significantly when the acquisitions are not replicated, and hence they can serve as input to extract poststack attributes used to compute time-lapse differences. Our observations are based on experiments conducted for an ocean-bottom cable survey acquired with time-jittered continuous recording assuming source equalization (or the same source signature) for the time-lapse surveys and no changes in wave heights, water column velocities or temperature, and salinity profiles.
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Bunchuk, A. V., i A. N. Ivakin. "Remote acoustic sensing of manganese nodules on the ocean bottom". Journal of the Acoustical Society of America 95, nr 5 (maj 1994): 2802–3. http://dx.doi.org/10.1121/1.409758.
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Greene, Chad A., i Preston S. Wilson. "Toward passive acoustic remote sensing of ocean‐bottom gas seeps." Journal of the Acoustical Society of America 127, nr 3 (marzec 2010): 1938. http://dx.doi.org/10.1121/1.3384877.
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Reichstetter, Martina, Peter Fearns, Scarla Weeks, Lachlan McKinna, Chris Roelfsema i Miles Furnas. "Bottom Reflectance in Ocean Color Satellite Remote Sensing for Coral Reef Environments". Remote Sensing 7, nr 12 (9.12.2015): 16756–77. http://dx.doi.org/10.3390/rs71215852.
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Savelyev, Ivan, William Miller, Mark Sletten, Geoffrey Smith, Dana Savidge, Glendon Frick, Steven Menk i in. "Airborne Remote Sensing of the Upper Ocean Turbulence during CASPER-East". Remote Sensing 10, nr 8 (4.08.2018): 1224. http://dx.doi.org/10.3390/rs10081224.
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This study takes on the challenge of resolving upper ocean surface currents with a suite of airborne remote sensing methodologies, simultaneously imaging the ocean surface in visible, infrared, and microwave bands. A series of flights were conducted over an air-sea interaction supersite established 63 km offshore by a large multi-platform CASPER-East experiment. The supersite was equipped with a range of in situ instruments resolving air-sea interface and underwater properties, of which a bottom-mounted acoustic Doppler current profiler was used extensively in this paper for the purposes of airborne current retrieval validation and interpretation. A series of water-tracing dye releases took place in coordination with aircraft overpasses, enabling dye plume velocimetry over 100 m to 10 km spatial scales. Similar scales were resolved by a Multichannel Synthetic Aperture Radar, which resolved a swath of instantaneous surface velocities (wave and current) with 10 m resolution and 5 cm/s accuracy. Details of the skin temperature variability imprinted by the upper ocean turbulence were revealed in 1–14,000 m range of spatial scales by a mid-wave infrared camera. Combined, these methodologies provide a unique insight into the complex spatial structure of the upper ocean turbulence on a previously under-resolved range of spatial scales from meters to kilometers. However, much attention in this paper is dedicated to quantifying and understanding uncertainties and ambiguities associated with these remote sensing methodologies, especially regarding the smallest resolvable turbulent scales and reference depths of retrieved currents.
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Gao, Jay. "Bathymetric mapping by means of remote sensing: methods, accuracy and limitations". Progress in Physical Geography: Earth and Environment 33, nr 1 (luty 2009): 103–16. http://dx.doi.org/10.1177/0309133309105657.
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Bathymetry has been traditionally charted via shipboard echo sounding. Alhough able to generate accurate depth measurements at points or along transects, this method is constrained by its high operating cost, inefficiency, and inapplicability to shallow waters. By comparison, remote sensing methods offer more flexible, efficient and cost-effective means of mapping bathymetry over broad areas. Remote sensing of bathymetry falls into two broad categories: non-imaging and imaging methods. The non-imaging method (as typified by LiDAR) is able to produce accurate bathymetric information over clear waters at a depth up to 70 m. However, this method is limited by the coarse bathymetric sampling interval and high cost. The imaging method can be implemented either analytically or empirically, or by a combination of both. Analytical or semi-analytical implementation is based on the manner of light transmission in water. It requires inputs of a number of parameters related to the properties of the atmosphere, water column, and bottom material. Thus, it is rather complex and difficult to use. By comparison, empirical implementation is much simpler and requires the input of fewer parameters. Both implementations can produce fine-detailed bathymetric maps over extensive turbid coastal and inland lake waters quickly, even though concurrent depth samples are essential. The detectable depth is usually limited to 20 m. The accuracy of the retrieved bathymetry varies with water depth, with the accuracy substantially lower at a depth beyond 12 m. Other influential factors include water turbidity and bottom materials, as well as image properties.
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Niroumand-Jadidi, Milad, Nima Pahlevan i Alfonso Vitti. "Mapping Substrate Types and Compositions in Shallow Streams". Remote Sensing 11, nr 3 (29.01.2019): 262. http://dx.doi.org/10.3390/rs11030262.
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Remote sensing of riverbed compositions could enable advances in hydro-morphological and habitat modeling. Substrate mapping in fluvial systems has not received as much attention as in nearshore, optically shallow inland, and coastal waters. As finer spatial-resolution image data become more available, a need emerges to expand research on the remote sensing of riverbed composition. For instance, research to date has primarily been based on spectral reflectance data from above the water surface without accounting for attenuation by the water-column. This study analyzes the impacts of water-column correction for substrate mapping in shallow fluvial systems (depth < 1 m). To do so, we performed three different experiments: (a) analyzing spectroscopic measurements in a hydraulic laboratory setting, (b) simulating water-leaving radiances under various optical scenarios, and (c) evaluating the potential to map bottom composition from a WorldView-3 (WV3) image of a river in Northern Italy. Following the retrieval of depth and diffuse attenuation coefficient ( K d ), bottom reflectances were estimated using a water-column correction method. The results indicated significant enhancements in streambed maps based on bottom reflectances relative to maps produced from above-water spectra. Accounting for deep-water reflectance, embedded in the water-column correction, was demonstrated to have the greatest impact on the retrieval of bottom reflectance in NIR bands, when the water column is relatively thick (>0.5 m) and/or when the water is turbid. We also found that the WV3’s red-edge band (i.e., 724 nm) considerably improved the characterization of submerged aquatic vegetation (SAV) densities from either above-water or retrieved bottom spectra. This study further demonstrated the feasibility of mapping SAV density classes from a WV3 image of the Sarca River in Italy by retrieving the bottom reflectances.
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Umbert, Marta, Sebastien Guimbard, Joaquim Ballabrera Poy i Antonio Turiel. "Synergy between Ocean Variables: Remotely Sensed Surface Temperature and Chlorophyll Concentration Coherence". Remote Sensing 12, nr 7 (3.04.2020): 1153. http://dx.doi.org/10.3390/rs12071153.
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The similarity of mesoscale and submesoscale features observed in different ocean scalars indicates that they undergo some common non-linear processes. As a result of quasi-2D turbulence, complicated patterns of filaments, meanders, and eddies are recognized in remote sensing images. A data fusion method used to improve the quality of one ocean variable using another variable as a template is used here as an extrapolation technique to improve the coverage of daily Aqua MODIS Level-3 chlorophyll maps by using MODIS SST maps as a template. The local correspondence of SST and Chl-a multifractal singularities is granted due to the existence of a common cascade process which makes it possible to use SST data to infer Chl-a concentration where data are lacking. The quality of the inference of Level-4 Chl-a maps is assessed by simulating artificial clouds and comparing reconstructed and original data.
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Buckingham, Michael J. "Remote sensing of the ocean bottom using the vertical directionality of the ambient noise in the water column". Journal of the Acoustical Society of America 85, S1 (maj 1989): S105. http://dx.doi.org/10.1121/1.2026621.
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Holden, Heather, i Ellsworth LeDrew. "The scientific issues surrounding remote detection of submerged coral ecosystems". Progress in Physical Geography: Earth and Environment 22, nr 2 (czerwiec 1998): 190–221. http://dx.doi.org/10.1177/030913339802200203.
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According to the 1993 colloquium on the ‘Global status of coral reefs', our understanding of the global role of coral reefs is inadequate. To increase our understanding, an accurate large-scale mapping and monitoring programme is necessary. Historically, coastal zones have been mapped using traditional surveying tools such as topographic maps, nautical charts, existing aerial photographs and direct observations. Although less expensive than digital imagery, exclusive use of these traditional tools may not be practical for monitoring large or remote coral reef ecosystems accurately. Researchers are attempting to develop an adequate coral reef mapping system based on digital remote sensing, but are impeded by issues such as effects of the intervening water column and spectral distinction of bottom types. The two variables discussed, which will contribute to our understanding of the global role of coral reefs, are: 1) remote sensing of submerged coral reefs in general; and 2) remote sensing of coral bleaching in particular. A summary of radiative transfer theory is presented and case studies of attempts at mapping remotely the geographic extent and health of submerged ecosystems, as well as a discussion of the remote estimation of water depth and quality. Problems in the translation and delivery of information to the end user are presented, and possible solutions suggested.
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Wang, Hao-Yu, i Jyh-Ching Juang. "Retrieval of Ocean Wind Speed Using Super-Resolution Delay-Doppler Maps". Remote Sensing 12, nr 6 (12.03.2020): 916. http://dx.doi.org/10.3390/rs12060916.
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The use of reflected Global Navigation Satellite System (GNSS) signals has shown to be effective for some remote sensing applications. In a GNSS Reflectometry (GNSS-R) system, a set of delay-Doppler maps (DDMs) related to scattered GNSS signals is formed and serves as a measurement of ocean wind speed and roughness. The design of the DDM receiver involves a trade-off between computation/communication complexity and the effectiveness of data retrieval. A fine-resolution DDM reveals more information in data retrieval while consuming more resources in terms of onboard processing and downlinking. As a result, existing missions typically use a compressed or low-resolution DDM as a data product, and a high-resolution DDM is processed for special purposes such as calibration. In this paper, a deep learning, super resolution algorithm is developed to construct a high-resolution DDM based on a low-resolution DDM. This may potentially enhance the data retrieval results with no impact on the instrument design. The proposed method is applied to process the DDM products disseminated by the Cyclone GNSS (CYGNSS) and the effectiveness of wind speed retrieval is demonstrated.
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Roy, Shovonlal, Trevor Platt i Shubha Sathyendranath. "Modelling the time-evolution of phytoplankton size spectra from satellite remote sensing". ICES Journal of Marine Science 68, nr 4 (17.12.2010): 719–28. http://dx.doi.org/10.1093/icesjms/fsq176.
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Abstract Roy, S., Platt, T., and Sathyendranath, S. 2011. Modelling the time-evolution of phytoplankton size spectra from satellite remote sensing. – ICES Journal of Marine Science, 68: 719–728. A dynamic size-structured model is developed for phytoplankton and nutrients in the oceanic mixed layer and applied to extract phytoplankton biomass at discrete size fractions from remotely sensed, ocean-colour data. General relationships between cell size and biophysical processes (such as sinking, grazing, and primary production) of phytoplankton were included in the model through a bottom–up approach. Time-dependent, mixed-layer depth was used as a forcing variable, and a sequential data-assimilation scheme was implemented to derive model trajectories. From a given time-series, the method produces estimates of size-structured biomass at every observation, so estimates seasonal succession of individual phytoplankton size, derived here from remote sensing for the first time. From these estimates, normalized phytoplankton biomass size spectra over a period of 9 years were calculated for one location in the North Atlantic. Further analysis demonstrated that strong relationships exist between the seasonal trends of the estimated size spectra and the mixed-layer depth, nutrient biomass, and total chlorophyll. The results contain useful information on the time-dependent biomass flux in the pelagic ecosystem.
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Wu, Xiangbai, Xiao-Hai Yan, Young-Heon Jo i W. Timothy Liu. "Estimation of Subsurface Temperature Anomaly in the North Atlantic Using a Self-Organizing Map Neural Network". Journal of Atmospheric and Oceanic Technology 29, nr 11 (1.11.2012): 1675–88. http://dx.doi.org/10.1175/jtech-d-12-00013.1.
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Abstract A self-organizing map (SOM) neural network was developed from Argo gridded datasets in order to estimate a subsurface temperature anomaly (STA) from remote sensing data. The SOM maps were trained using anomalies of sea surface temperature (SST), height (SSH), and salinity (SSS) data from Argo gridded monthly anomaly datasets, labeled with Argo STA data from 2005 through 2010, which were then used to estimate the STAs at different depths in the North Atlantic from the sea surface data. The estimated STA maps and time series were compared with Argo STAs including independent datasets for validation. In the Gulf Stream path areas, the STA estimations from the SOM algorithm show good agreement with in situ measurements taken from the surface down to 700-m depth, with a correlation coefficient larger than 0.8. Sensitivity of the SOM, when including salinity, shows that with SSS anomaly data in the SOM training process reveal the importance of SSS information, which can improve the estimation of STA in the subtropical ocean by up to 30%. In subpolar basins, the monthly climatology SST and SSH can also help to improve the estimation by as much as 40%. The STA time series for 1993–2004 in the midlatitude North Atlantic were estimated from remote sensing SST and altimetry time series using the SOM algorithm. Limitations for the SOM algorithm and possible error sources in the estimation are briefly discussed.
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Sathyendranath, Shubha, Robert Brewin, Carsten Brockmann, Vanda Brotas, Ben Calton, Andrei Chuprin, Paolo Cipollini i in. "An Ocean-Colour Time Series for Use in Climate Studies: The Experience of the Ocean-Colour Climate Change Initiative (OC-CCI)". Sensors 19, nr 19 (3.10.2019): 4285. http://dx.doi.org/10.3390/s19194285.
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Ocean colour is recognised as an Essential Climate Variable (ECV) by the Global Climate Observing System (GCOS); and spectrally-resolved water-leaving radiances (or remote-sensing reflectances) in the visible domain, and chlorophyll-a concentration are identified as required ECV products. Time series of the products at the global scale and at high spatial resolution, derived from ocean-colour data, are key to studying the dynamics of phytoplankton at seasonal and inter-annual scales; their role in marine biogeochemistry; the global carbon cycle; the modulation of how phytoplankton distribute solar-induced heat in the upper layers of the ocean; and the response of the marine ecosystem to climate variability and change. However, generating a long time series of these products from ocean-colour data is not a trivial task: algorithms that are best suited for climate studies have to be selected from a number that are available for atmospheric correction of the satellite signal and for retrieval of chlorophyll-a concentration; since satellites have a finite life span, data from multiple sensors have to be merged to create a single time series, and any uncorrected inter-sensor biases could introduce artefacts in the series, e.g., different sensors monitor radiances at different wavebands such that producing a consistent time series of reflectances is not straightforward. Another requirement is that the products have to be validated against in situ observations. Furthermore, the uncertainties in the products have to be quantified, ideally on a pixel-by-pixel basis, to facilitate applications and interpretations that are consistent with the quality of the data. This paper outlines an approach that was adopted for generating an ocean-colour time series for climate studies, using data from the MERIS (MEdium spectral Resolution Imaging Spectrometer) sensor of the European Space Agency; the SeaWiFS (Sea-viewing Wide-Field-of-view Sensor) and MODIS-Aqua (Moderate-resolution Imaging Spectroradiometer-Aqua) sensors from the National Aeronautics and Space Administration (USA); and VIIRS (Visible and Infrared Imaging Radiometer Suite) from the National Oceanic and Atmospheric Administration (USA). The time series now covers the period from late 1997 to end of 2018. To ensure that the products meet, as well as possible, the requirements of the user community, marine-ecosystem modellers, and remote-sensing scientists were consulted at the outset on their immediate and longer-term requirements as well as on their expectations of ocean-colour data for use in climate research. Taking the user requirements into account, a series of objective criteria were established, against which available algorithms for processing ocean-colour data were evaluated and ranked. The algorithms that performed best with respect to the climate user requirements were selected to process data from the satellite sensors. Remote-sensing reflectance data from MODIS-Aqua, MERIS, and VIIRS were band-shifted to match the wavebands of SeaWiFS. Overlapping data were used to correct for mean biases between sensors at every pixel. The remote-sensing reflectance data derived from the sensors were merged, and the selected in-water algorithm was applied to the merged data to generate maps of chlorophyll concentration, inherent optical properties at SeaWiFS wavelengths, and the diffuse attenuation coefficient at 490 nm. The merged products were validated against in situ observations. The uncertainties established on the basis of comparisons with in situ data were combined with an optical classification of the remote-sensing reflectance data using a fuzzy-logic approach, and were used to generate uncertainties (root mean square difference and bias) for each product at each pixel.
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Kamal, Muhammad, Faaris H. Muhammad i Shifa A. Mahardhika. "Effect of image radiometric correction levels of Landsat images to the land cover maps resulted from maximum likelihood classification". E3S Web of Conferences 153 (2020): 02004. http://dx.doi.org/10.1051/e3sconf/202015302004.
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Radiometric correction of remote sensing images is required to improve the quality of image pixel values and provide a measurable physical unit of each pixel. Selection of the appropriate image radiometric and atmospheric correction level defines the success of any remote sensing-based mapping applications. This study aims to assess the effects of radiometric correction levels applied to Landsat 8 (Operational Land Imager, OLI) image acquired in 2018 to the results of the land cover classification using the Maximum Likelihood Classifier (MLC). The image was corrected into four levels of radiometric and atmospheric correction; no correction (digital number), at-sensor radiance, at-sensor reflectance (top of atmosphere, ToA), and at-surface reflectance (bottom of atmosphere, BoA). A set of classification training sample covering five land cover classes (mangroves, inland vegetation, exposed soil, built-up area, and water body) was selected from the image. To ensure fair class comparison, the number of training sample were set to be proportional to the area of targeted classes. The results of this study show that there is no difference in the classification results of each level of correction, both in the area and distribution of the classes. This finding indicates that MLC result is invariable of image correction level.
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Chen, Dong, Varada Shevade, Allison Baer, Jiaying He, Amanda Hoffman-Hall, Qing Ying, Yao Li i Tatiana V. Loboda. "A Disease Control-Oriented Land Cover Land Use Map for Myanmar". Data 6, nr 6 (13.06.2021): 63. http://dx.doi.org/10.3390/data6060063.
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Malaria is a serious infectious disease that leads to massive casualties globally. Myanmar is a key battleground for the global fight against malaria because it is where the emergence of drug-resistant malaria parasites has been documented. Controlling the spread of malaria in Myanmar thus carries global significance, because the failure to do so would lead to devastating consequences in vast areas where malaria is prevalent in tropical/subtropical regions around the world. Thanks to its wide and consistent spatial coverage, remote sensing has become increasingly used in the public health domain. Specifically, remote sensing-based land cover/land use (LCLU) maps present a powerful tool that provides critical information on population distribution and on the potential human-vector interactions interfaces on a large spatial scale. Here, we present a 30-meter LCLU map that was created specifically for the malaria control and eradication efforts in Myanmar. This bottom-up approach can be modified and customized to other vector-borne infectious diseases in Myanmar or other Southeastern Asian countries.
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Ackleson, Steven, Wesley Moses i Marcos Montes. "Remote Sensing of Coral Reefs: Uncertainty in the Detection of Benthic Cover, Depth, and Water Constituents Imposed by Sensor Noise". Applied Sciences 8, nr 12 (19.12.2018): 2691. http://dx.doi.org/10.3390/app8122691.
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Coral reefs are biologically diverse and economically important ecosystems that are on the decline worldwide in response to direct human impacts and climate change. Ocean color remote sensing has proven to be an important tool in coral reef research and monitoring. Remote sensing data quality is driven by factors related to sensor design and environmental variability. This work explored the impact of sensor noise, defined as the signal to noise ratio (SNR), on the detection uncertainty of key coral reef ecological properties (bottom depth, benthic cover, and water quality) in the absence of environmental uncertainties. A radiative transfer model for a shallow reef environment was developed and Monte Carlo methods were employed to identify the range in environmental conditions that are spectrally indistinguishable from true conditions as a function of SNR. The spectrally averaged difference between remotely sensed radiance relative to sensor noise, ε, was used to quantify uncertainty in bottom depth, the fraction of benthic cover by coral, algae, and uncolonized sand, and the concentration of water constituents defined as chlorophyll, dissolved organic matter, and suspended calcite particles. Parameter uncertainty was found to increase with sensor noise (decreasing SNR) but the impact was non-linear. The rate of change in uncertainty per incremental change in SNR was greatest for SNR < 500 and increasing SNR further to 1000 resulted in only modest improvements. Parameter uncertainty was complicated by the bottom depth and benthic cover. Benthic cover uncertainty increased with bottom depth, but water constituent uncertainty changed inversely with bottom depth. Furthermore, water constituent uncertainty was impacted by the type of constituent material in relation to the type of benthic cover. Uncertainty associated with chlorophyll concentration and dissolved organic matter increased when the benthic cover was coral and/or benthic algae while uncertainty in the concentration of suspended calcite increased when the benthic cover was uncolonized sand. While the definition of an optimal SNR is subject to user needs, we propose that SNR of approximately 500 (relative to 5% Earth surface reflectance and a clear maritime atmosphere) is a reasonable engineering goal for a future satellite sensor to support research and management activities directed at coral reef ecology and, more generally, shallow aquatic ecosystems.
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Vrana, Kenneth J., Paul-Henry Nargeolet, William Sauder, Alexandra Klingelhofer, Rebecca King, Laura Pasch, Sarah J. AcMoody i in. "Mapping RMS Titanic With GIS: Implications for Forensic Investigations". Marine Technology Society Journal 46, nr 6 (1.11.2012): 111–28. http://dx.doi.org/10.4031/mtsj.46.6.8.
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AbstractSince its loss 100 years ago, RMS Titanic continues to captivate people worldwide as an epic story of tragedy at sea and as an iconic shipwreck with many mysteries still to be unraveled from its physical remains on the ocean bottom. RMS Titanic, Inc., has completed eight expeditions to RMS Titanic in its capacity as salvor-in-possession. These efforts include the first comprehensive remote-sensing survey of the shipwreck site in 2010. During this time, the company’s focus has evolved from marine salvage to treatment of RMS Titanic as an archaeological site. An important tool in archaeological interpretation of historic shipwrecks is a geographic information system (GIS).In 2006, RMS Titanic, Inc., formally initiated the GIS-based Titanic Mapping Project. Components of the Titanic Mapping Project include data rescue, digital transfer of film media, design of GIS methodology, verification and rectification of positioning data from original field records, preparation of detailed profiles for all recovered artifacts, development of GIS attribute tables for recovered artifacts and key in situ site features, and integration of remote-sensing data from Titanic Expedition 2010. With information on over 5,500 accessioned artifacts organized within the GIS, the company looks forward to making substantive contributions to deepwater archaeological research and forensic investigations of the shipwreck site. In combination with current architectural- and engineering-related knowledge of RMS Titanic, new light can be cast on such topics as the wrecking event during that fateful night in 1912.
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de Moustier, C. "Approaches to Acoustic Backscattering Measurements From the Deep Seafloor". Journal of Energy Resources Technology 110, nr 2 (1.06.1988): 77–84. http://dx.doi.org/10.1115/1.3231369.
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Because the average ocean depth is four kilometers, seafloor investigations are mostly remote sensing operations. The primary means to determine the morphology, the structure, and the texture of the seafloor are acoustic. This paper considers the current seafloor remote sensing approaches involving acoustic backscattering. The physical constraints imposed by the ocean as a propagation medium, by the seafloor as a backscattering boundary, and by the measuring instruments are briefly reviewed. The sonar systems currently used by the oceanographic community for deep seafloor acoustic backscattering measurements deal with these constraints differently, depending on their specific application and on whether they are towed behind a ship or mounted on her hull. Towed sidescan systems such as Gloria II (U.K.), the Sea Mapping and Remote Characterization (Sea MARC) I and II, the Deep Tow system of the Marine Physical Laboratory (MPL), and hull-mounted systems, such as Swathmap all give a qualitative measure of backscattering by converting echo amplitudes to gray levels to produce a sidescan image of the seafloor. A new approach is presented which uses a Sea Beam multibeam echo-sounder to produce similar acoustic images. Quantitative measurements of backscattering have been attempted in recent experiments using the Deep Tow system and Sea Beam. Such measurements provide some insight into the geological processes responsible for the acoustic backscatter, with useful applications for geologists as well as designers and operators of bottom-interacting sonars.
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Gnanadesikan, A., J. P. Dunne i J. John. "What ocean biogeochemical models can tell us about bottom-up control of ecosystem variability". ICES Journal of Marine Science 68, nr 6 (1.01.2011): 1030–44. http://dx.doi.org/10.1093/icesjms/fsr068.
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Abstract Gnanadesikan, A., Dunne, J. P., and John, J. 2011. What ocean biogeochemical models can tell us about bottom-up control of ecosystem variability. – ICES Journal of Marine Science, 68: 1030–1044. Processes included in earth system models amplify the impact of climate variability on phytoplankton biomass and, therefore, on upper trophic levels. Models predict much larger relative interannual variability in large phytoplankton biomass than in total phytoplankton biomass, supporting the goal of better constraining size-structured primary production and biomass from remote sensing. The largest modelled variability in annually averaged large phytoplankton biomass is associated with changes in the areal extent of relatively productive regions. Near the equator, changes in the areal extent of the high-productivity zone are driven by large-scale shifts in nutrient fields, as well as by changes in currents. Along the poleward edge of the Subtropical Gyres, changes in physical mixing dominate. Finally, models indicate that high-latitude interannual variability in large phytoplankton biomass is greatest during spring. Mechanisms for producing such variability differ across biomes with internal ocean processes, such as convection complicating efforts to link ecosystem variability to climate modes defined using sea surface temperature alone. In salinity-stratified subpolar regions, changes in bloom timing driven by salinity can produce correlations between low surface temperatures and high productivity, supporting the potential importance of using coupled atmosphere–ocean reanalyses, rather than simple forced ocean reanalyses, for attributing past ecosystem shifts.
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Vijaya kumar, L. J., J. K. Kishore, P. Kesava Rao, M. Annadurai, C. B. S. Dutt, K. Hanumantha Rao, S. K. Sasamal i in. "Oil Spill Map for Indian Sea Region based on Bhuvan- Geographic Information System using Satellite Images". ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XL-8 (28.11.2014): 1085–90. http://dx.doi.org/10.5194/isprsarchives-xl-8-1085-2014.
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Oil spills in the ocean are a serious marine disaster that needs regular monitoring for environmental risk assessment and mitigation. Recent use of Polarimetric SAR imagery in near real time oil spill detection systems is associated with attempts towards automatic and unambiguous oil spill detection based on decomposition methods. Such systems integrate remote sensing technology, geo information, communication system, hardware and software systems to provide key information for analysis and decision making. <br><br> Geographic information systems (GIS) like BHUVAN can significantly contribute to oil spill management based on Synthetic Aperture Radar (SAR) images. India has long coast line from Gujarat to Bengal and hundreds of ports. The increase in shipping also increases the risk of oil spills in our maritime zone. The availability of RISAT-1 SAR images enhances the scope to monitor oil spills and develop GIS on Bhuvan which can be accessed by all the users, such as ships, coast guard, environmentalists etc., The GIS enables realization of oil spill maps based on integration of the geographical, remote sensing, oil & gas production/infrastructure data and slick signatures detected by SAR. SAR and GIS technologies can significantly improve the realization of oil spill footprint distribution maps. Preliminary assessment shows that the Bhuvan promises to be an ideal solution to understand spatial, temporal occurrence of oil spills in the marine atlas of India. The oil spill maps on Bhuvan based GIS facility will help the ONGC and Coast Guard organization.
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Sarangi, R. K. "Observation of Oceanic Eddy in the Northeastern Arabian Sea Using Multisensor Remote Sensing Data". International Journal of Oceanography 2012 (24.07.2012): 1–9. http://dx.doi.org/10.1155/2012/531982.
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An oceanic eddy of size about 150 kilometer diameter observed in the northeastern Arabian Sea using remote sensing satellite sensors; IRS-P4 OCM, NOAA-AVHRR and NASA Quickscat Scatterometer data. The eddy was detected in the 2nd week of February in Indian Remote Sensing satellite (IRS-P4) Ocean Color Monitor (OCM) sensor retrieved chlorophyll image on 10th February 2002, between latitude 16°90′–18°50′N and longitude 66°05′–67°60′E. The chlorophyll concentration was higher in the central part of eddy (~1.5 mg/m3) than the peripheral water (~0.8 mg/m3). The eddy lasted till 10th March 2002. NOAA-AVHRR sea surface temperature (SST) images generated during 15th February-15th March 2002. The SST in the eddy’s center (~23°C) was lesser than the surrounding water (~24.5°C). The eddy was of cold core type with the warmer water in periphery. Quickscat Scatterometer retrieved wind speed was 8–10 m/sec. The eddy movement observed southeast to southwest direction and might helped in churning. The eddy seemed evident due to convective processes in water column. The processes like detrainment and entrainment play role in bringing up the cooler water and the bottom nutrient to surface and hence the algal blooming. This type of cold core/anti-cyclonic eddy is likely to occur during late winter/spring as a result of the prevailing climatic conditions.
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Arnold, S. R., D. V. Spracklen, J. Williams, N. Yassaa, J. Sciare, B. Bonsang, V. Gros i in. "Evaluation of the global oceanic isoprene source and its impacts on marine organic carbon aerosol". Atmospheric Chemistry and Physics 9, nr 4 (18.02.2009): 1253–62. http://dx.doi.org/10.5194/acp-9-1253-2009.
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Abstract. We have combined the first satellite maps of the global distribution of phytoplankton functional type and new measurements of phytoplankton-specific isoprene productivities, with available remote marine isoprene observations and a global model, to evaluate our understanding of the marine isoprene source and its impacts on organic aerosol abundances. Using satellite products to scale up data on phytoplankton-specific isoprene productivity to the global oceans, we infer a mean "bottom-up" oceanic isoprene emission of 0.31±0.08 (1σ) Tg/yr. By minimising the mean bias between the model and isoprene observations in the marine atmosphere remote from the continents, we produce a "top-down" oceanic isoprene source estimate of 1.9 Tg/yr. We suggest our reliance on limited atmospheric isoprene data, difficulties in simulating in-situ isoprene production rates in laboratory phytoplankton cultures, and limited knowledge of isoprene production mechanisms across the broad range of phytoplankton communities in the oceans under different environmental conditions as contributors to this difference between the two estimates. Inclusion of secondary organic aerosol (SOA) production from oceanic isoprene in the model with a 2% yield produces small contributions (0.01–1.4%) to observed organic carbon (OC) aerosol mass at three remote marine sites in the Northern and Southern Hemispheres. Based on these findings we suggest an insignificant role for isoprene in modulating remote marine aerosol abundances, giving further support to a recently postulated primary OC source in the remote marine atmosphere.
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Juhls, Bennet, Pier Paul Overduin, Jens Hölemann, Martin Hieronymi, Atsushi Matsuoka, Birgit Heim i Jürgen Fischer. "Dissolved organic matter at the fluvial–marine transition in the Laptev Sea using in situ data and ocean colour remote sensing". Biogeosciences 16, nr 13 (11.07.2019): 2693–713. http://dx.doi.org/10.5194/bg-16-2693-2019.
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Abstract. River water is the main source of dissolved organic carbon (DOC) in the Arctic Ocean. DOC plays an important role in the Arctic carbon cycle, and its export from land to sea is expected to increase as ongoing climate change accelerates permafrost thaw. However, transport pathways and transformation of DOC in the land-to-ocean transition are mostly unknown. We collected DOC and aCDOM(λ) samples from 11 expeditions to river, coastal and offshore waters and present a new DOC–aCDOM(λ) model for the fluvial–marine transition zone in the Laptev Sea. The aCDOM(λ) characteristics revealed that the dissolved organic matter (DOM) in samples of this dataset are primarily of terrigenous origin. Observed changes in aCDOM(443) and its spectral slopes indicate that DOM is modified by microbial and photo-degradation. Ocean colour remote sensing (OCRS) provides the absorption coefficient of coloured dissolved organic matter (aCDOM(λ)sat) at λ=440 or 443 nm, which can be used to estimate DOC concentration at high temporal and spatial resolution over large regions. We tested the statistical performance of five OCRS algorithms and evaluated the plausibility of the spatial distribution of derived aCDOM(λ)sat. The OLCI (Sentinel-3 Ocean and Land Colour Instrument) neural network swarm (ONNS) algorithm showed the best performance compared to in situ aCDOM(440) (r2=0.72). Additionally, we found ONNS-derived aCDOM(440), in contrast to other algorithms, to be partly independent of sediment concentration, making ONNS the most suitable aCDOM(λ)sat algorithm for the Laptev Sea region. The DOC–aCDOM(λ) model was applied to ONNS-derived aCDOM(440), and retrieved DOC concentration maps showed moderate agreement to in situ data (r2=0.53). The in situ and satellite-retrieved data were offset by up to several days, which may partly explain the weak correlation for this dynamic region. Satellite-derived surface water DOC concentration maps from Medium Resolution Imaging Spectrometer (MERIS) satellite data demonstrate rapid removal of DOC within short time periods in coastal waters of the Laptev Sea, which is likely caused by physical mixing and different types of degradation processes. Using samples from all occurring water types leads to a more robust DOC–aCDOM(λ) model for the retrievals of DOC in Arctic shelf and river waters.
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Naumova, Ksenia O., i Elena V. Stanis. "Assessment of the open-mining prevalence on the territory of Moscow region". RUDN Journal of Ecology and Life Safety 28, nr 4 (15.12.2020): 349–60. http://dx.doi.org/10.22363/2313-2310-2020-28-4-349-360.
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Lands disturbed by open cuts and associated dumps often become unsuitable for further use as construction sites. Disturbed lands are technogenically altered soils with new changed physicomechanical and physicochemical properties. The paper examines the results of researching the disturbed lands of common mineral resources open cuts in Moscow region, provides a description of the causes and types of land disturbance, as well as examples of images of disturbed lands on satellite images. For this purposes, thematic and topographic maps and remote sensing materials - satellite images of the territory of the Moscow region were used. The problems of impact of common mineral resources extraction on the natural complexes in the region, the scale of technogenic transformation of the earth surface as a result of open cuts mining as well as the geoecological problems arising in this case are considered. Numerical geoecological assessment of sand quarries in Moscow region is also given.
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Camiolo, Martina D., Ezequiel Cozzolino, Ana I. Dogliotti, Claudia G. Simionato i Carlos A. Lasta. "An empirical remote sensing algorithm for retrieving total suspended matter in a large estuarine region". Scientia Marina 83, nr 1 (26.03.2019): 53. http://dx.doi.org/10.3989/scimar.04847.22a.
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The Río de la Plata is a large, shallow estuary located at approximately 35°S and flowing into the southwestern Atlantic Ocean. It carries a high amount of nutrients and suspended particulate matter, both organic and inorganic, to the adjacent shelf waters and is considered among the most turbid estuarine systems in the world. Knowledge of the concentration and spatial and temporal variability of these materials is critical for any biological study in the Río de la Plata. In this work, the relationship between suspended particulate matter and turbidity is empirically established in order to derive suspended particulate matter maps from satellite data (MODIS-Aqua) for the Río de la Plata region. A strong correlation between suspended particulate matter and turbidity was found (Pearson correlation coefficient =0.91) and the linear regression (slope =0.76 and intercepts =12.78, R2=0.83) explained 83% of the variance. The validation of the empirical algorithm, using co-located and coincident satellite and in situ measurements, showed good results with a low mean absolute error (14.60%) and a small and positive bias (3.04%), indicating that the estimated suspended particulate matter values tend to slightly overestimate the field values.
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Immordino, Francesco, Mattia Barsanti, Elena Candigliota, Silvia Cocito, Ivana Delbono i Andrea Peirano. "Application of Sentinel-2 Multispectral Data for Habitat Mapping of Pacific Islands: Palau Republic (Micronesia, Pacific Ocean)". Journal of Marine Science and Engineering 7, nr 9 (12.09.2019): 316. http://dx.doi.org/10.3390/jmse7090316.
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Sustainable and ecosystem-based marine spatial planning is a priority of Pacific Island countries basing their economy on marine resources. The urgency of management coral reef systems and associated coastal environments, threatened by the effects of climate change, require a detailed habitat mapping of the present status and a future monitoring of changes over time. Here, we present a remote sensing study using free available Sentinel-2 imagery for mapping at large scale the most sensible and high value habitats (corals, seagrasses, mangroves) of Palau Republic (Micronesia, Pacific Ocean), carried out without any sea truth validation. Remote sensing ‘supervised’ and ‘unsupervised’ classification methods applied to 2017 Sentinel-2 imagery with 10 m resolution together with comparisons with free ancillary data on web platform and available scientific literature were used to map mangrove, coral, and seagrass communities in the Palau Archipelago. This paper addresses the challenge of multispectral benthic mapping estimation using commercial software for preprocessing steps (ERDAS ATCOR) and for benthic classification (ENVI) on the base of satellite image analysis. The accuracy of the methods was tested comparing results with reference NOAA (National Oceanic and Atmospheric Administration, Silver Spring, MD, USA) habitat maps achieved through Ikonos and Quickbird imagery interpretation and sea-truth validations. Results showed how the proposed approach allowed an overall good classification of marine habitats, namely a good concordance of mangroves cover around Palau Archipelago with previous literature and a good identification of coastal habitats in two sites (barrier reef and coastal reef) with an accuracy of 39.8–56.8%, suitable for survey and monitoring of most sensible habitats in tropical remote islands.
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Bagomaev, A. A., i N. O. Guseynova. "Identification of temperature anomalies in the western Caspian Sea in 2017 based on remote sensing data". South of Russia: ecology, development 15, nr 4 (17.01.2021): 63–74. http://dx.doi.org/10.18470/1992-1098-2020-4-63-74.
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Aim. The study of temperature anomalies in the western Caspian Sea based on space imagery materials in order to detect upwelling phenomena.Materials and Methods. We used temperature indicators of seawater for the summer season of 2017 when a sharp decrease by more than 2 °C in average daily temperature occurred. Space images were obtained from the specialized centres of Ocean Color NASA, Earth Science Data Systems NASA and SATIN. Remote sensing data were processed using SeaDAS and ArcGIS programs. Ground data were obtained from the resources of the Unified State System of Information about the Situation in the World Ocean (ESIMO). An ArcGIS database was created and maps compiled.Results. The first upwelling occurred on 9-17 June 2020. The minimum water temperature in the Makhachkala area was 14°C with an increase in salinity to 12%o over an area of 1,500 sq.km. An increase in the content of dissolved oxygen of up to 9.70 mg/l and pH 8.64 was recorded. A second upwelling of medium intensity occurred from 19 June-July 1 with a minimum temperature of 17.9C. The decrease in temperature was 2.8°C with an increase in salinity by 1%o. The surface area was 454 sq.km. A third case of upwelling was recorded from 26 August-September 1 and was characterised by a decrease in water temperature of 7.4C (near the coast, 17.1°C). The average salinity increase was 0.32%o while the 02 concentration was 8 mg/l over an area of 500 sq.km.Conclusion. Due to its large size, the Caspian Sea is characterised by spatial inhomogeneity of oceanological parameters, which can be recorded based on the results of processing satellite images and their verification using ground data. In the western part of the sea the upwelling is periodic and of different scales.
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Parard, G., A. A. Charantonis i A. Rutgerson. "Remote sensing algorithm for sea surface CO<sub>2</sub> in the Baltic Sea". Biogeosciences Discussions 11, nr 8 (12.08.2014): 12255–94. http://dx.doi.org/10.5194/bgd-11-12255-2014.
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Abstract. Studies of coastal seas in Europe have brought forth the high variability in the CO2 system. This high variability, generated by the complex mechanisms driving the CO2 fluxes makes their accurate estimation an arduous task. This is more pronounced in the Baltic Sea, where the mechanisms driving the fluxes have not been as highly detailed as in the open oceans. In adition, the joint availability of in-situ measurements of CO2 and of sea-surface satellite data is limited in the area. In this paper, a combination of two existing methods (Self-Organizing-Maps and Multiple Linear regression) is used to estimate ocean surface pCO2 in the Baltic Sea from remotely sensed surface temperature, chlorophyll, coloured dissolved organic matter, net primary production and mixed layer depth. The outputs of this research have an horizontal resolution of 4 km, and cover the period from 1998 to 2011. The reconstructed pCO2 values over the validation data set have a correlation of 0.93 with the in-situ measurements, and a root mean square error is of 38 μatm. The removal of any of the satellite parameters degraded this reconstruction of the CO2 flux, and we chose therefore to complete any missing data through statistical imputation. The CO2 maps produced by this method also provide a confidence level of the reconstruction at each grid point. The results obtained are encouraging given the sparsity of available data and we expect to be able to produce even more accurate reconstructions in the coming years, in view of the predicted acquisitions of new data.
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Xie, Futai, Zui Tao, Xiang Zhou, Tingting Lv i Jin Wang. "Spatial and Temporal Variations of Particulate Organic Carbon Sinking Flux in Global Ocean from 2003 to 2018". Remote Sensing 11, nr 24 (9.12.2019): 2941. http://dx.doi.org/10.3390/rs11242941.
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The monitoring of particulate organic carbon (POC) flux at the bottom of the euphotic layer in global ocean using remote sensing satellite data plays an important role in clarifying and evaluating the ocean carbon cycle. Based on the in situ POC flux data, this paper evaluated various estimation models. The global ocean POC flux from 2003 to 2018 was calculated using the optimal model, and its temporal and spatial variation characteristics were analyzed. In general, the annual average of global ocean POC flux is about 8.5–14.3 Gt C yr − 1 for period of 2003–2018. In the spatial dimension, the POC flux in the mid-latitude ocean (30–60°) is higher than that in the low-latitude (0–30°). The POC flux in Continental Margins with water depth less than 2000 m accounted for 30% of global ocean, which should receive more attention in global carbon cycle research. In the time dimension, the global POC flux decreases year by year generally, but the POC flux abnormally decreases during El Niño and increases during La Niña. In addition, due to global warming, sea ice melting, and bipolar sea area expansion, POC flux in high-latitude oceans (60–90°) is increasing year by year.
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Casella, Daniele, Marco Meloni, Anne A. Petrenko, Andrea M. Doglioli i Jerome Bouffard. "Coastal Current Intrusions from Satellite Altimetry". Remote Sensing 12, nr 22 (10.11.2020): 3686. http://dx.doi.org/10.3390/rs12223686.
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The use of satellite-based data in coastal regions for the monitoring of fine-scale ocean dynamics, impacting marine ecosystems, is a difficult challenge. A random forest algorithm to detect slope current intrusions into the Gulf of Lion, Mediterranean Sea, has been developed using both improved coastal altimetry data and 10 year-long numerical simulations. The results have been compared to an independent dataset of in situ measurements from a bottom-moored Acoustic Doppler Current Profiler. The algorithm results are very promising: 93% of slope current intrusions have been correctly identified, and the number of false alarms is moderate. The dependence of the algorithm on several environmental factors is discussed in the paper. From the oceanographic point of view, our results confirm the strong impacts of horizontal winds in the dynamic of the intrusion events in the study area. Our methodology combining numerical modeling, in situ data and new machine-learning tools proves effective in improving the capabilities of ocean remote sensing in coastal areas.
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Cruz Gómez, R. C., i S. N. Bulgakov. "Remote sensing observations of the coherent and non-coherent ring structures in the vicinity of Lesser Antilles". Annales Geophysicae 25, nr 2 (8.03.2007): 331–40. http://dx.doi.org/10.5194/angeo-25-331-2007.
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Abstract. The North Brazil Current Rings (NBCR) penetration into the Caribbean Sea is being investigated by employing a merged altimeter-derived sea height anomaly (TOPEX/Poseidon, Jason-1 and ERS-1, 2), the ocean surface color data (SeaWiFS) and Global Drifter Program information. Four strategies are being applied to process the data: (1) calculations of the Okubo-Weiss parameter for NBCR identification, (2) longitude-time plots (also known as Hovmöller diagrams), (3) two-dimensional Radon transforms and (4) two-dimensional Fourier transforms. A twofold NBCR structure has been detected in the region under investigation. The results have shown that NBC rings mainly propagate into the Caribbean Sea along two principal pathways (near 12° N and 17° N) in the ring translation corridor. Thus, rings following the southern pathway in the fall-winter period can enter through very shallow southern straits as non-coherent structures. A different behavior is observed near the northern pathway (~17° N), where NBC rings are thought to have a coherent structure during their squeezing into the eastern Caribbean, i.e. conserving the principal characteristics of the incident rings. We attribute this difference in the rings' behavior to the vertical scales of the rings and to the bottom topography features in the vicinity of the Lesser Antilles.
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Jolliff, Jason K., Sherwin Ladner, Travis A. Smith, Stephanie Anderson, Mark David Lewis, Sean C. McCarthy, Richard L. Crout, Ewa Jarosz i Adam Lawson. "On the Potential Optical Signature of Convective Turbulence over the West Florida Shelf". Remote Sensing 13, nr 4 (9.02.2021): 619. http://dx.doi.org/10.3390/rs13040619.
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Atmospheric cold front propagation across the northern Gulf of Mexico is characterized by elevated surface wind velocities and a ~10–15 °C drop in surface air temperatures. These meteorological conditions result in significant heat energy losses from the surface ocean to the overlying atmosphere. These seasonally recurring cold-air outbreak events may penetrate the southern portion of the West Florida continental shelf and initiate turbulent and convective overturn of the water column. Examination of true color images derived from ocean-viewing, satellite-based radiometer data reveals coincident and substantial surface water discolorations that are optically similar to smaller-scale “whiting events,” despite the regional-scale extent of the observed phenomenon (>25,000 km2). Coupled air–sea numerical simulations suggest the surface water discoloration occurs and is sustained where the entire water column is dynamically unstable. The simulation results indicate significant density (σt) inversions between the surface and bottom waters. Thus, the combined numerical model and remote sensing analysis suggest that convective turbulence may be contributing to the sustained ventilation of bottom waters containing a high concentration of suspended particulates. High-temporal resolution true color images rendered from the GOES-R Advanced Baseline Imager (ABI) data appear to support the surface water discoloration’s turbulent-driven nature.
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Kerfoot, W. Charles, Martin M. Hobmeier, Gary Swain, Robert Regis, Varsha K. Raman, Colin N. Brooks, Amanda Grimm, Chris Cook, Robert Shuchman i Molly Reif. "Coastal Remote Sensing: Merging Physical, Chemical, and Biological Data as Tailings Drift onto Buffalo Reef, Lake Superior". Remote Sensing 13, nr 13 (22.06.2021): 2434. http://dx.doi.org/10.3390/rs13132434.
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On the Keweenaw Peninsula of Lake Superior, two stamp mills (Mohawk and Wolverine) discharged 22.7 million metric tonnes (MMT) of tailings (1901–1932) into the coastal zone off the town of Gay. Migrating along the shoreline, ca. 10 MMT of the tailings dammed stream and river outlets, encroached upon wetlands, and contaminated recreational beaches. A nearly equal amount of tailings moved across bay benthic environments into critical commercial fish spawning and rearing grounds. In the middle of the bay, Buffalo Reef is important for commercial and recreational lake trout and lake whitefish production (ca. 32% of the commercial catch in Keweenaw Bay, 22% along southern Lake Superior). Aerial photographs (1938–2016) and five LiDAR and multispectral over-flights (2008–2016) emphasize: (1) the enormous amounts of tailings moving along the beach; and (2) the bathymetric complexities of an equal amount migrating underwater across the shelf. However, remote sensing studies encounter numerous specific challenges in coastal environments. Here, we utilize a combination of elevation data (LiDAR digital elevation/bathymetry models) and in situ studies to generate a series of physical, chemical, and biological geospatial maps. The maps are designed to help assess the impacts of historical mining on Buffalo Reef. Underwater, sand mixtures have complicated multispectral bottom reflectance substrate classifications. An alternative approach, in situ simple particle classification, keying off distinct sand end members: (1) allows calculation of tailings (stamp sand) percentages; (2) aids indirect and direct assays of copper concentrations; and (3) permits determinations of density effects on benthic macro-invertebrates. The geospatial mapping shows how tailings are moving onto Buffalo Reef, the copper concentrations associated with the tailings, and how both strongly influence the density of benthic communities, providing an excellent example for the International Maritime Organization on how mining may influence coastal reefs. We demonstrate that when large amounts of mine tailings are discharged into coastal environments, temporal and spatial impacts are progressive, and strongly influence resident organisms. Next steps are to utilize a combination of hi-resolution LiDAR and sonar surveys, a fish-monitoring array, and neural network analysis to characterize the geometry of cobble fields where fish are successful or unsuccessful at producing young.
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Hernández, Ruth Artemisa Aguilera, Manuel Darío Salas Araiza, Adriana Saldaña Robles, Alberto Saldaña Robles, Mónica Trejo Durán i Noé Saldaña Robles. "Remote hyperspectral sensing for the early detection of Melanaphis sacchari Zehntner, 1897 (Hemiptera: Aphididae) infestations in sorghum leaves". Australian Journal of Crop Science, nr 15(02):2021 (3.02.2021): 224–32. http://dx.doi.org/10.21475/ajcs.21.15.02.p2735.
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This paper aims to study the reflectance signature information of infested and non-infested sorghum leaves (Sorghum vulgare L.) by sugarcane aphid (Melanaphis sacchari) to discriminate infested sorghum. The study treatments were 0 (0 aphids/leaf), 1 (1-20 aphids/leaf), 2 (21-50 aphids/leaf), 3 (> = 51 aphids/leaf), 4 (> = 51 aphids/leaf + visible damage), 5 (abiotic stress) and 6 (> = 51 aphids/leaf + abiotic stress). An Ocean OpticsTM HR4000 spectrometer was used. The multifactor ANOVA and Kruskal-Wallis tests at 95% confidence indicated that the reflectance at 402.95, 528.43, 658.36, 788.13, and 965.14 nm wavelengths have significant differences between treatments and with the control. Also Kernel Discriminant analysis was carried out and the combination of the wavelengths centered at 788.17 and 965.14 nm allows 70 % of correct classification of treatments. The results indicate that it is possible to detect M. sacchari infested sorghum by using the spectral information of some specific wavelengths. This study may enable the research of an aerial sensor to make recommendation maps of application pesticides.
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Lior, Itzhak, Anthony Sladen, Diego Mercerat, Jean-Paul Ampuero, Diane Rivet i Serge Sambolian. "Strain to ground motion conversion of distributed acoustic sensing data for earthquake magnitude and stress drop determination". Solid Earth 12, nr 6 (17.06.2021): 1421–42. http://dx.doi.org/10.5194/se-12-1421-2021.
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Abstract. The use of distributed acoustic sensing (DAS) presents unique advantages for earthquake monitoring compared with standard seismic networks: spatially dense measurements adapted for harsh environments and designed for remote operation. However, the ability to determine earthquake source parameters using DAS is yet to be fully established. In particular, resolving the magnitude and stress drop is a fundamental objective for seismic monitoring and earthquake early warning. To apply existing methods for source parameter estimation to DAS signals, they must first be converted from strain to ground motions. This conversion can be achieved using the waves' apparent phase velocity, which varies for different seismic phases ranging from fast body waves to slow surface and scattered waves. To facilitate this conversion and improve its reliability, an algorithm for slowness determination is presented, based on the local slant-stack transform. This approach yields a unique slowness value at each time instance of a DAS time series. The ability to convert strain-rate signals to ground accelerations is validated using simulated data and applied to several earthquakes recorded by dark fibers of three ocean-bottom telecommunication cables in the Mediterranean Sea. The conversion emphasizes fast body waves compared to slow scattered waves and ambient noise and is robust even in the presence of correlated noise and varying wave propagation directions. Good agreement is found between source parameters determined using converted DAS waveforms and on-land seismometers for both P and S wave records. The demonstrated ability to resolve source parameters using P waves on horizontal ocean-bottom fibers is key for the implementation of DAS-based earthquake early warning, which will significantly improve hazard mitigation capabilities for offshore earthquakes, including those capable of generating tsunami.
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Pastusiak, Tadeusz. "Nautical electronic maps of S-411 standard and their suitability in navigation for assessment of ice cover condition of the Arctic Ocean". Polish Cartographical Review 48, nr 1 (1.03.2016): 17–28. http://dx.doi.org/10.1515/pcr-2016-0002.
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Abstract The research on the ice cover of waterways, rivers, lakes, seas and oceans by satellite remote sensing methods began at the end of the twentieth century. There was a lot of data sources in diverse file formats. It has not yet carried out a comparative assessment of their usefulness. A synthetic indicator of the quality of data sources binding maps resolution, file publication, time delay and the functionality for the user was developed in the research process. It reflects well a usefulness of maps and allows to compare them. Qualitative differences of map content have relatively little impact on the overall assessment of the data sources. Resolution of map is generally acceptable. Actuality has the greatest impact on the map content quality for the current vessel’s voyage planning in ice. The highest quality of all studied sources have the regional maps in GIF format issued by the NWS / NOAA, general maps of the Arctic Ocean in NetCDF format issued by the OSI SAF and the general maps of the Arctic Ocean in GRIB-2 format issued by the NCEP / NOAA. Among them are maps containing information on the quality of presented parameter. The leader among the map containing all three of the basic characteristics of ice cover (ice concentration, ice thickness and ice floe size) are vector maps in GML format. They are the new standard of electronic vector maps for the navigation of ships in ice. Publishing of ice cover maps in the standard electronic map format S-411 for navigation of vessels in ice adopted by the International Hydrographic Organization is advisable in case is planned to launch commercial navigation on the lagoons, rivers and canals. The wide availability of and exchange of information on the state of ice cover on rivers, lakes, estuaries and bays, which are used exclusively for water sports, ice sports and ice fishing is possible using handheld mobile phones, smartphones and tablets.
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Trembanis, Arthur, Alimjan Abla, Ken Haulsee i Carter DuVal. "Benthic Habitat Morphodynamics-Using Remote Sensing to Quantify Storm-Induced Changes in Nearshore Bathymetry and Surface Sediment Texture at Assateague National Seashore". Journal of Marine Science and Engineering 7, nr 10 (18.10.2019): 371. http://dx.doi.org/10.3390/jmse7100371.
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This study utilizes repeated geoacoustic mapping to quantify the morphodynamic response of the nearshore to storm-induced changes. The aim of this study was to quantitatively map the nearshore zone of Assateague Island National Seashore (ASIS) to determine what changes in bottom geomorphology and benthic habitats are attributable to storm events including hurricane Sandy and the passage of hurricane Joaquin. Specifically, (1) the entire domain of the National Parks Service offshore area was mapped with side-scan sonar and multibeam bathymetry at a resolution comparable to that of the existing pre-storm survey, (2) a subset of the benthic stations were resampled that represented all sediment strata previously identified, and (3) newly obtained data were compared to that from the pre-storm survey to determined changes that could be attributed to specific storms such as Sandy and Joaquin. Capturing event specific dynamics requires rapid response surveys in close temporal association of the before and after period. The time-lapse between the pre-storm surveys for Sandy and our study meant that only a time and storm integrated signature for that storm could be obtained whereas with hurricane Joaquin we could identify impacts to the habitat type and geomorphology more directly related to that particular storm. This storm impacts study provides for the National Park Service direct documentation of storm-related changes in sediments and marine habitats on multiple scales: From large scale, side-scan sonar maps and interpretation of acoustic bottom types, to characterize as fully as possible habitats from 1 to 10 m up to many kilometer scales, as well as from point benthic samples within each sediment stratum and these results can help guide management of the island resources.
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Bissonnette, Luc R., Gilles Roy i Grégoire Tremblay. "Lidar-Based Characterization of the Geometry and Structure of Water Clouds". Journal of Atmospheric and Oceanic Technology 24, nr 8 (1.08.2007): 1364–76. http://dx.doi.org/10.1175/jtech2045.1.
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Abstract Lidar remote sensing measurements of low-level water clouds in the form of vertical soundings and instantaneous (∼1 min) azimuth-over-elevation scans are reported. Retrievals are made of the liquid water content and effective droplet diameter at the same range, time, and angular resolutions as those of the measurements. The results are presented as time–height plots and two-dimensional horizontal maps of the retrieved parameters. The cloud structure is resolved by calculating histograms, spatial autocorrelation functions, and power spectra. The distribution of the horizontal inhomogeneities is characterized over the size range from 10 to ∼1000 m. The Kolmogorov −5/3 power-law dependence is verified in all cases, but the −5/3 regime is broken into two subregimes that are separated by a sudden increase in the energy density level. The results illustrate how lidars can contribute meaningful information on cloud structure at high spatial and temporal resolutions, in near–real time, and over extended periods of time.
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Rajabi, Mahmoud, Hossein Nahavandchi i Mostafa Hoseini. "Evaluation of CYGNSS Observations for Flood Detection and Mapping during Sistan and Baluchestan Torrential Rain in 2020". Water 12, nr 7 (18.07.2020): 2047. http://dx.doi.org/10.3390/w12072047.
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Flood detection and produced maps play essential roles in policymaking, planning, and implementing flood management options. Remote sensing is commonly accepted as a maximum cost-effective technology to obtain detailed information over large areas of lands and oceans. We used remote sensing observations from Global Navigation Satellite System-Reflectometry (GNSS-R) to study the potential of this technique for the retrieval of flood maps over the regions affected by the recent flood in the southeastern part of Iran. The evaluation was made using spaceborne GNSS-R measurements over the Sistan and Baluchestan provinces during torrential rain in January 2020. This area has been at a high risk of flood in recent years and needs to be continuously monitored by means of timely observations. The main dataset was acquired from the level-1 data product of the Cyclone Global Navigation Satellite System (CYGNSS) spaceborne mission. The mission consisted of a constellation of eight microsatellites with GNSS-R sensors onboard to receive forward-scattered GNSS signals from the ocean and land. We first focused on data preparation and eliminating the outliers. Afterward, the reflectivity of the surface was calculated using the bistatic radar equations formula. The flooded areas were then detected based on the analysis of the derived reflectivity. Images from Moderate-Resolution Imaging Spectroradiometer (MODIS) were used for evaluation of the results. The analysis estimated the inundated area of approximately 19,644 km2 (including Jaz-Murian depression) to be affected by the flood in the south and middle parts of the Sistan and Baluchestan province. Although the main mission of CYGNSS was to measure the ocean wind speed in hurricanes and tropical cyclones, we showed the capability of detecting floods in the study area. The sensitivity of the spaceborne GNSS-R observations, together with the relatively short revisit time, highlight the potential of this technique to be used in flood detection. Future GNSS-R missions capable of collecting the reflected signals from all available multi-GNSS constellations would offer even more detailed information from the flood-affected areas.
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Dierssen, H. M., R. C. Zimmerman i D. J. Burdige. "Optics and remote sensing of Bahamian carbonate sediment whitings and potential relationship to wind-driven Langmuir circulation". Biogeosciences 6, nr 3 (31.03.2009): 487–500. http://dx.doi.org/10.5194/bg-6-487-2009.
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Abstract. Regions of milky white seas or "whitings" periodically occur to the west of Andros Island along the Great Bahama Bank where the bottom sediment consists of fine-grained aragonite mud. We present measurements of inherent optical properties within a sediment whiting patch and discuss the potential for monitoring the frequency, extent, and quantity of suspended matter from ocean colour satellite imagery. Sea spectral reflectance measured in situ and remotely from space revealed highly reflective waters elevated across the visible spectrum (i.e., "whitened") with a peak at 490 nm. Particulate backscattering was an order of magnitude higher than that measured at other stations throughout the region. The whiting also had one of the highest backscattering ratios measured in natural waters (0.05–0.06) consistent with water dominated by aragonite particles with a high index of refraction. Regular periodicity of 40 and 212 s evident in the light attenuation coefficient over the sampling period indicated patches of fluctuating turbidity on spatial scales that could be produced from regular rows of Langmuir cells penetrating the 5-m water column. We suggest that previously described mechanisms for sediment resuspension in whitings, such as tidal bursting and fish activity, are not fully consistent with these data and propose that wind-driven Langmuir cells reaching the full-depth of the water column may represent a plausible mechanism for sediment resuspension and subsequent whiting formation. Optics and remote sensing provide important tools for quantifying the linkages between physical and biogeochemical processes in these dynamic shallow water ecosystems.
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Dierssen, H. M., R. C. Zimmerman i D. J. Burdige. "Optics and remote sensing of Bahamian carbonate sediment whitings and potential relationship to wind-driven Langmuir circulation". Biogeosciences Discussions 5, nr 6 (8.12.2008): 4777–811. http://dx.doi.org/10.5194/bgd-5-4777-2008.
Pełny tekst źródłaStreszczenie:
Abstract. Regions of milky white seas or "whitings" periodically occur to the west of Andros Island along the Great Bahama Bank where the bottom sediment consists of fine-grained aragonite mud. We present comprehensive measurements of inherent optical properties within a whiting patch and discuss the potential for monitoring the frequency, extent, and quantity of suspended matter from ocean colour satellite imagery. Sea spectral reflectance measured in situ and remotely from space revealed highly reflective waters elevated across the visible spectrum (i.e., "whitened") with a peak at 490 nm. Particulate backscattering was an order of magnitude higher than that measured at other stations throughout the region. The whiting also had one of the highest backscattering ratios measured in natural waters (0.05–0.06) consistent with water dominated by aragonite particles with a high index of refraction. Regular periodicity of 40 and 212 s evident in the light attenuation coefficient over the sampling period indicated patches of fluctuating turbidity on spatial scales that could be produced from regular rows of Langmuir cells penetrating the 5-m water column. We suggest that previously described mechanisms for sediment resuspension in whitings, such as tidal bursting and fish activity, are not fully consistent with these data and propose that wind-driven Langmuir cells reaching the full-depth of the water column may represent a plausible mechanism for sediment resuspension and subsequent whiting formation. Optics and remote sensing provide important tools for quantifying the linkages between physical and biogeochemical processes in these dynamic shallow water ecosystems.
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Parard, G., A. A. Charantonis i A. Rutgerson. "Remote sensing the sea surface CO<sub>2</sub> of the Baltic Sea using the SOMLO methodology". Biogeosciences 12, nr 11 (4.06.2015): 3369–84. http://dx.doi.org/10.5194/bg-12-3369-2015.
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Abstract. Studies of coastal seas in Europe have noted the high variability of the CO2 system. This high variability, generated by the complex mechanisms driving the CO2 fluxes, complicates the accurate estimation of these mechanisms. This is particularly pronounced in the Baltic Sea, where the mechanisms driving the fluxes have not been characterized in as much detail as in the open oceans. In addition, the joint availability of in situ measurements of CO2 and of sea-surface satellite data is limited in the area. In this paper, we used the SOMLO (self-organizing multiple linear output; Sasse et al., 2013) methodology, which combines two existing methods (i.e. self-organizing maps and multiple linear regression) to estimate the ocean surface partial pressure of CO2 (pCO2) in the Baltic Sea from the remotely sensed sea surface temperature, chlorophyll, coloured dissolved organic matter, net primary production, and mixed-layer depth. The outputs of this research have a horizontal resolution of 4 km and cover the 1998–2011 period. These outputs give a monthly map of the Baltic Sea at a very fine spatial resolution. The reconstructed pCO2 values over the validation data set have a correlation of 0.93 with the in situ measurements and a root mean square error of 36 μatm. Removing any of the satellite parameters degraded this reconstructed CO2 flux, so we chose to supply any missing data using statistical imputation. The pCO2 maps produced using this method also provide a confidence level of the reconstruction at each grid point. The results obtained are encouraging given the sparsity of available data, and we expect to be able to produce even more accurate reconstructions in coming years, given the predicted acquisition of new data.
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Magalhaes, J. M., J. C. B. da Silva, M. C. Buijsman i C. A. E. Garcia. "Effect of the North Equatorial Counter Current on the generation and propagation of internal solitary waves off the Amazon shelf (SAR observations)". Ocean Science 12, nr 1 (12.02.2016): 243–55. http://dx.doi.org/10.5194/os-12-243-2016.
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Abstract. Synthetic aperture radar (SAR) imagery from the Amazon shelf break region in the tropical west Atlantic reveals for the first time the two-dimensional horizontal structure of an intense Internal Solitary Wave (ISW) field, whose first surface manifestations are detected several hundred kilometres away from the nearest forcing bathymetry. Composite maps and an energy budget analysis (provided from the Hybrid Coordinate Ocean Model – HYCOM) help to identify two major ISW pathways emanating from the steep slopes of a small promontory (or headland) near 44° W and 0° N, which are seen to extend for over 500 km into the open ocean. Further analysis in the SAR reveals propagation speeds above 3 m s−1, which are amongst the fastest ever recorded. The main characteristics of the ISWs are further discussed based on a statistical analysis, and seasonal variability is found for one of the ISW sources. This seasonal variability is discussed in light of the North Equatorial Counter Current. The remote appearance of the ISW sea surface manifestations is explained by a late disintegration of the internal tide (IT), which is further investigated based on the SAR data and climatological monthly means (for stratification and currents). Acknowledging the possibility of a late disintegration of the IT may help explain the remote-sensing views of other ISWs in the world's oceans.