scholarly journals In situ observations of turbulent ship wakes and their spatiotemporal extent

Ocean Science ◽  
2021 ◽  
Vol 17 (5) ◽  
pp. 1285-1302
Author(s):  
Amanda T. Nylund ◽  
Lars Arneborg ◽  
Anders Tengberg ◽  
Ulf Mallast ◽  
Ida-Maja Hassellöv
Keyword(s):  
Baltic Sea ◽  
Spatial Scales ◽  
Turbulent Wake ◽  
Ex Situ ◽  
Landsat 8 ◽  
Ship Traffic ◽  
In Situ Observations ◽  
Temporal And Spatial ◽  
Thermal Wake

Abstract. In areas of intensive ship traffic, ships pass every 10 min. Considering the amount of ship traffic and the predicted increase in global maritime trade, there is a need to consider all types of impacts shipping has on the marine environment. While the awareness about, and efforts to reduce, chemical pollution from ships is increasing, less is known about physical disturbances, and ship-induced turbulence has so far been completely neglected. To address the potential importance of ship-induced turbulence on, e.g., gas exchange, dispersion of pollutants, and biogeochemical processes, a characterisation of the temporal and spatial scales of the turbulent wake is needed. Currently, field measurements of turbulent wakes of real-size ships are lacking. This study addresses that gap by using two different methodological approaches: in situ and ex situ observations. For the in situ observations, a bottom-mounted acoustic Doppler current profiler (ADCP) was placed at 32 m depth below the shipping lane outside Gothenburg harbour. Both the acoustic backscatter from the air bubbles in the wake and the dissipation rate of turbulent kinetic energy were used to quantify the turbulent wake depth, intensity, and temporal longevity for 38 ship passages of differently sized ships. The results from the ADCP measurements show median wake depths of 13 m and several occasions of wakes reaching depths > 18 m, which is in the same depth range as the seasonal thermocline in the Baltic Sea. The temporal longevity of the observable part of the wakes had a median of around 10 min and several passages of > 20 min. In the ex situ approach, sea surface temperature was used as a proxy for the water mass affected by the turbulent wake (thermal wake), as lowered temperature in the ship wake indicates vertical mixing in a thermally stratified water column. Satellite images of the thermal infrared sensor (TIRS) onboard Landsat-8 were used to measure thermal wake width and length, in the highly frequented and thus major shipping lane north of Bornholm, Baltic Sea. Automatic information system (AIS) records from both the investigated areas were used to identify the ships inducing the wakes. The satellite analysis showed a median thermal wake length of 13.7 km (n=144), and the longest wake extended over 60 km, which would correspond to a temporal longevity of 1 h 42 min (for a ship speed of 20 kn). The median thermal wake width was 157.5 m. The measurements of the spatial and temporal scales are in line with previous studies, but the maximum turbulent wake depth (30.5 m) is deeper than previously reported. The results from this study, combined with the knowledge of regional high traffic densities, show that ship-induced turbulence occurs at temporal and spatial scales large enough to imply that this process should be considered when estimating environmental impacts from shipping in areas with intense ship traffic.

scholarly journals <i>In situ</i> observations of turbulent ship wakes and their potential implications for vertical mixing

2020 ◽  
Author(s):  
Amanda T. Nylund ◽  
Lars Arneborg ◽  
Anders Tengberg ◽  
Ulf Mallast ◽  
Ida-Maja Hassellöv
Keyword(s):  
Spatial Scales ◽  
Vertical Mixing ◽  
Turbulent Wake ◽  
Ex Situ ◽  
Landsat 8 ◽  
Spatial And Temporal Scales ◽  
Ship Traffic ◽  
Temporal And Spatial ◽  
Thermal Wake

Abstract. In areas of intensive ship traffic, ships pass every ten minutes. Considering the amount of ship traffic and the fact that global maritime trade is predicted to increase, there is a need to consider all effects shipping has on the marine environment; both pollution and physical disturbances. This paper studies a previously disregarded physical disturbance, namely ship-induced vertical mixing in the turbulent wake. A characterization of the temporal and spatial scales of the turbulent wake is needed to estimate its effect on gas exchange, dispersion of pollutants, and to identify in which areas ship-induced vertical mixing could have an impact on local biogeochemical cycles. There is a lack of field measurements of turbulent wakes of real-size ships, and this study addresses that gap by in situ and ex situ measurements of the depth, width, length, intensity and longevity of the turbulent wake for ~240 ship passages of differently sized ships. A bottom-mounted Acoustic Doppler Current Profiler (ADCP) was placed at 32 m depth below the ship lane outside Gothenburg harbour, and used to measure wake depth and temporal longevity. Thermal satellite images of the Thermal Infrared Sensor (TIRS) onboard Landsat 8 were used to measure thermal wake width and spatial longevity, using satellite scenes from the major ship lane North of Bornholm, Baltic Sea. Automatic Information System (AIS) records from both the investigated areas were used to identify the ships inducing the wakes. The results from the ADCP measurements show median wake depths of ~ 10 m, and several occasions of wakes reaching depths > 18 m. The temporal longevity of the wakes had a median of around 8 min and several passages of > 20 min. The satellite analysis showed a median thermal wake length of 13.7 km, and the longest wake extended over 60 km, which would correspond to a temporal longevity of 1 h 42 min (for a ship speed of 20 knots). The median thermal wake width was 157.5 m. The measurements of the spatial and temporal scales are in line with previous studies, but the deep mixing and extensive longevity presented in this study, has not previously been documented. The results from this study have shown that ship-induced vertical mixing occurs at temporal and spatial scales large enough to imply that this process should be considered when estimating environmental impact from shipping in areas with intense ship traffic. Moreover, the possibility that deep vertical mixing could occur in a highly frequent manner highlights the need of further studies to better characterize the spatial and temporal development of the turbulent wake.

The importance of the turbulent ship wake regime for pollutant fate and transport

2021 ◽  
Author(s):  
Amanda T. Nylund ◽  
Rickard Bensow ◽  
Mattias Liefvendahl ◽  
Arash Eslamdoost ◽  
Anders Tengberg ◽  
...  
Keyword(s):  
Fate And Transport ◽  
In Situ Measurements ◽  
Ex Situ ◽  
Landsat 8 ◽  
Turbulent Regime ◽  
Near Wake ◽  
Ship Wake ◽  
Spatiotemporal Scales ◽  
The Impact

&lt;p&gt;This interdisciplinary study with implications for fate and transport of pollutants from shipping, investigates the previously overlooked phenomenon of ship induced mixing. When a ship moves through water, the hull and propeller induce a long-lasting turbulent wake. Natural waters are usually stratified, and the stratification influences both the vertical and horizontal extent of the wake. The altered turbulent regime in shipping lanes governs the distribution of discharged pollutants, e.g. PAHs, metals, nutrients and non-indigenous species. The ship related pollutant load follows the trend in volumes of maritime trade, which has almost tripled since the 1980s. In heavily trafficked areas there may be one ship passage every ten minutes; today shipping constitutes a significant source of pollution.&lt;/p&gt;&lt;p&gt;To understand the environmental impact of shipping related pollutants, it is essential to know their fate following regional scale transport. However, previous modelling efforts assuming discharge at the surface will not adequately reflect the input values in the regional models. Therefore, it is urgent to bridge the gaps between the spatiotemporal scales from high-resolution numerical modeling of the flow hydrodynamics around the ship, mixing processes and interaction of the ship and wake with stratification, and parameterization in regional oceanographic modeling. Here this knowledge gap is addressed by combining an array of methods; in situ measurements, remote sensing and numerical flow modeling.&lt;/p&gt;&lt;p&gt;A bottom-mounted Acoustic Doppler Current Profiler was placed under a ship lane, for &lt;em&gt;in-situ&lt;/em&gt; measurements of the vertical and temporal expansion of turbulent wakes. In addition, &lt;em&gt;ex-situ&lt;/em&gt; measurements with Landsat 8 Thermal Infrared Sensor were used to estimate the longevity and spatial extent of the thermal signal from ship wakes. The computational modelling was conducted using well resolved 3D RANS modelling for the hull and the near wake (up to five ship lengths aft), a method typically used for the near wake behaviour in analysing the propulsion system. As this is not feasible to use for a far wake analysis, the predicted wake is then used as input for a 2D+time modelling for the sustained wake up to 30min after the ship passage. These results, both from measurements and numerical models, are then combined to analyse how ship-induced turbulence influence at what depth discharged pollutants will be found.&lt;/p&gt;&lt;p&gt;This first step to cover the mesoscales of the turbulent ship wake is necessary to assess the impact of ship related pollution. In-situ measurements show median wake depth 13.5m (max 31.5m) and median longevity 10min (max 29min). Satellite data show median thermal wake signal 13.7km (max 62.5km). A detailed simulation model will only be possible to use for the first few 100m of the ship wake, but the coupling to a simplified 2D+time modelling shows a promising potential to bridge our understanding of the impact of the ship wake on the larger scales. Our model results indicate that the natural stratification affects the distribution and retention of pollutants in the wake region. The depth of discharge and the wake turbulence characteristics will in turn affect the fate and transport of pollutants on larger spatiotemporal scales.&lt;/p&gt;

scholarly journals Modelling and quantifying the spatial distribution of post-wildfire ash loads

2016 ◽  
Vol 25 (2) ◽  
pp. 249 ◽  
Author(s):  
Chris J. Chafer ◽  
Cristina Santín ◽  
Stefan H. Doerr
Keyword(s):  
Spatial Distribution ◽  
Polynomial Regression ◽  
Spatial Scales ◽  
Fire Severity ◽  
Spectral Ratio ◽  
Landsat 8 ◽  
Applied Model ◽  
Sampling Locations ◽  
Before And After

Ash is generated in every wildfire, but its eco-hydro-geomorphic effects remain poorly understood and quantified, especially at large spatial scales. Here we present a new method that allows modelling the spatial distribution of ash loads in the post-fire landscape, based on a severe wildfire that burnt ~13 600 ha of a forested water supply catchment in October 2013 (2013 Hall Road Fire, 100 km south-west of Sydney, Australia). Employing an existing spectral ratio-based index, we developed a new spectral index using Landsat 8 satellite imagery: the normalised wildfire ash index (NWAI). Before- and after-fire images were normalised and a differenced wildfire ash image (dNWAI) computed. The relationship between dNWAI and ash loads (t ha−1) quantified in situ at nine sampling locations burnt under a range of fire severities was determined using a polynomial regression (R2 = 0.98). A spatially applied model was computed within a geographic information system (GIS) to illustrate the spatial distribution of ash across the area burnt and to estimate ash loads in the five subcatchments affected by the wildfire. Approximately 181 000 tonnes of ash was produced by the wildfire, with specific loads increasing with fire severity. This new tool to model wildfire ash distribution can inform decisions about post-fire land management in future wildfires in the region. It can also be adapted for its application in other fire-prone environments.

Characteristics of Landsat 8 OLI-derived NDVI by comparison with multiple satellite sensors and in-situ observations

2015 ◽  
Vol 164 ◽  
pp. 298-313 ◽  
Author(s):  
Yinghai Ke ◽  
Jungho Im ◽  
Junghee Lee ◽  
Huili Gong ◽  
Youngryel Ryu
Keyword(s):  
Landsat 8 ◽  
Landsat 8 Oli ◽  
Satellite Sensors ◽  
In Situ Observations

scholarly journals Application of HYSPLIT and WRF/Chem Models to Investigate the Dust Storm Episodes

2016 ◽  
Author(s):  
Parya Broomandi ◽  
Bahram Dabir ◽  
Babak Bonakdarpour ◽  
Yousef Rashidi
Keyword(s):  
Spatial Distribution ◽  
Dust Storm ◽  
Middle Eastern ◽  
Dust Storms ◽  
Dust Particles ◽  
Temporal And Spatial Distribution ◽  
Range Transport ◽  
In Situ Observations ◽  
Temporal And Spatial

Background: Long-range transport of dust aerosol has intense impacts on theatmospheric environment over wide areas. Methods: The annual and seasonal changes inmeteorological parameters associated with the occurrence of dust storms were studied. Thefeatures of an intense dust storm and its transport characteristics were studied during June 7thto June 9th 2010 in Ahvaz city. Temporal and spatial distribution of Middle Eastern dust stormevent was analyzed by models of HYSPLIT and WRF/Chem, and in- situ observations. Results:A disagreement between the occurrences of dust storms, temperature, relative humidity andrainfall, show the major source of dust storms over Ahvaz city are neighboring countries. UsingHYSPLIT results, the dust particles are mainly transported from north western region of Iraqand eastern Syria to downward areas including Ahvaz city. The arrived Dust aerosols mixedwith local anthropogenic emissions, led to the highest PM10 concentration of 4200 ppm. Themodel results were found to well reproduce temporal and spatial distribution of mineral dustconcentrations according to in-situ measurements. Conclusion: The performance of WRF/Chemwas acceptable for simulation of temporal and spatial distributions of dust storm events.Therefore, it can be taken as a reference in daily air quality forecasting.

Global In-Situ Observations of Essential Climate and Ocean Variables by the Global Drifter Program. Applications and Impacts

2020 ◽  
Author(s):  
Luca Centurioni ◽  
Verena Hormann
Keyword(s):  
North Atlantic Ocean ◽  
Spatial Scales ◽  
Data Access ◽  
Ocean Climate ◽  
The North ◽  
Free Data ◽  
Forecast Models ◽  
In Situ Observations ◽  
The Impact

&lt;p&gt;Accurate estimates and forecasts of physical and biogeochemical processes at the air-sea interface must rely on integrated in-situ and satellite surface observations of essential Ocean/Climate Variables (EOVs /ECVs). Such observations, when sustained over appropriate temporal and spatial scales, are particularly powerful in constraining and improving the skills, impact and value of weather, ocean and climate forecast models. The calibration and validation of satellite ocean products also rely on in-situ observations, thus creating further positive high-impact applications of observing systems designed for global sustained observations of EOV and ECVs.&lt;/p&gt;&lt;p&gt;The Global Drifter Program has operated uninterrupted for several decades and constitutes a particular successful example of a network of multiparametric platforms providing observations of climate, weather and oceanographic relevance (e.g. air-pressure, sea surface temperature, ocean currents). This presentation will review the requirements of sustainability of an observing system such as the GDP (i.e. cost effectiveness, peer-review of the observing methodology and of the technology, free data access and international cooperation), will present some key metrics recently used to quantify the impact of drifter observations, and will discuss two prominent examples of GDP regional observations and the transition to operations of novel platforms, such us wind and directional wave spectra drifters, in sparsely sampled regions of the Arabian Sea and of the North Atlantic Ocean.&lt;/p&gt;

scholarly journals Sputtering of Au Induced by Single Xe Ion Impacts

1999 ◽  
Vol 585 ◽  
Author(s):  
R. C. Birtcher ◽  
S. E. Donnelly
Keyword(s):  
Average Diameter ◽  
Ex Situ ◽  
Reflection And Transmission ◽  
Transmission Electron ◽  
Transmission Geometry ◽  
In Situ Observations ◽  
Carbon Foils ◽  
Au Thin Films ◽  
Sputtering Yields

AbstractSputtering of Au thin films has been determined for Xe ions with energies between 50 and 600 keV. In-situ transmission electron microscopy was used to observe sputtered Au during deposition on a carbon foil near the specimen. Total reflection and transmission sputtering yields for a 62 nm thick Au thin film were determined by ex-situ measurement of the total amount of Au on the carbon foils. In situ observations show that individual Xe ions eject Au nanopanicles as large as 7 nm in diameter with an average diameter of approximately 3 nm. Particle emission correlates with crater formation due to single ion impacts. Nanoparticle emission contributes significantly to the total sputtering yield for Xe ions in this energy range in either reflection or transmission geometry.

scholarly journals Tropical Refuges with Exceptionally High Phylogenetic Diversity Reveal Contrasting Phylogenetic Structures

2015 ◽  
Vol 2015 ◽  
pp. 1-17 ◽  
Author(s):  
Lara Pugliesi ◽  
Alessandro Rapini
Keyword(s):  
Phylogenetic Diversity ◽  
Spatial Scales ◽  
Northeastern Brazil ◽  
Ex Situ ◽  
Habitat Filtering ◽  
Phylogenetic Structure ◽  
Chapada Diamantina ◽  
Limited Dispersal

Loss of phylogenetic diversity (PD) has gained increasing attention in conservation biology. However, PD is not equally distributed in a phylogeny and can be better assessed when species relatedness (phylogenetic structure: PS) is also considered. Here, we investigate PD and PS in two refuges of biodiversity in northeastern Brazil: the Bahia Costal Forest (BCF) in the Atlantic Forest domain and Chapada Diamantina (CD) in the Caatinga domain. We used geographic data of 205 species at two spatial scales and a chronogram of Apocynaceae based on matK sequences to estimate PD and PS. Our results show an exceptionally high PD in both refuges, overdispersed in BCF and clustered in CD, although this difference is less evident or absent for recent relationships, especially at a smaller spatial scale. Overall, PS suggests long-term competitive exclusion under climatic stability, currently balanced by habitat filtering, in BCF, and biome conservatism and limited dispersal leading to in situ diversification and high density of microendemics in CD. The phylogenetically clustered flora in CD, also threatened by climate changes, are naturally more vulnerable than BCF. Therefore, while in situ conservation may ensure protection of biodiversity in BCF, emergency ex situ conservation is strongly recommended in CD.

scholarly journals Regionalization with Hierarchical Hydrologic Similarity and Ex-situ Data for the Estimation of Mean Annual Groundwater Recharge at Ungauged Watersheds

2019 ◽  
Author(s):  
Ching-Fu Chang ◽  
Yoram Rubin
Keyword(s):  
Groundwater Recharge ◽  
Information Transfer ◽  
Decisive Role ◽  
Ex Situ ◽  
Watershed Characteristics ◽  
Modeling Approach ◽  
In Situ Observations ◽  
Hydrologic Responses ◽  
Ungauged Watersheds

Abstract. There are various methods available for annual groundwater recharge estimation using in-situ observations. However, a great number of watersheds around the world still remain ungauged, i.e., without in-situ observations of hydrologic responses. One approach for making estimates at ungauged watersheds is through regionalization, namely, transferring information obtained at gauged watersheds to ungauged ones. The reliability of regionalization depends on (1) the underlying system of hydrologic similarity, i.e., the similarity in how watersheds respond to precipitation input, as well as (2) the approach by which information is transferred. In this paper we present a set of ready-to-use tools for obtaining informative estimates of hydrologic responses at ungauged watersheds, using a nested tree-based modeling approach to condition the estimates on ex-situ data. It invokes a two-leveled hierarchical hydrologic similarity, where the higher level determines the relative importance of various watershed characteristics under different conditions, and the lower level performs the regionalization and estimation of hydrologic responses based on the watershed characteristics of the ungauged watershed of interest. We apply the nested tree-based modeling approach to investigate the complicated relationship between mean annual groundwater recharge and watershed characteristics, and to test the applicability and usefulness of the hierarchical hydrologic similarity. Our findings reveal the decisive role of soil available water content in hydrologic similarity at regional and annual scales, as well as certain conditions under which it is risky to resort to climate variables for determining hydrologic similarity. These findings contribute to the understanding of the physical principles governing robust information transfer.

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