Improving the Specular Point Positioning Accuracy of Ship-Borne GNSS-R Observations in China Seas Based on Comprehensive Geophysical Correction

The accurate modeled GNSS-R reflection delay, which is indispensable for the quantification, modeling, and correction of the GNSS-R altimetry sea-state bias, can be obtained based on the accurate modeled position of the specular point. At present, the reflection surface model of the specular point positioning still has the mean dynamic topography (MDT) error and the deviation of the vertical (DOV) error relative to the instantaneous sea surface. In this study, the following studies have been carried out. Based on the ship-borne GNSS-R observations in China seas, we introduced various elevation parameters including the MDT to correct the elevation error of the reflection surface. We introduced the DOV based on the elevation correction, and the DOV correction positioning method was proposed to correct the slope error of the reflection surface. The specular point was positioned on the instantaneous sea reflection surface. We verified the instantaneous sea reflection surface model and the specular point positioning results, analyzed the relationship between the position correction distance and the reflection incident angle, and discussed the spatial distribution characteristics of the MDT correction distance. The results showed that the reflection surface modeling and the specular point positioning were accurate. The positioning error increased to varying degrees with the increase of the reflection incident angle. The MDT correction improved the positioning by 0.91 m, and the DOV correction further improved the positioning by 0.12 m. Based on the combined application of the two kinds of correction positioning, the positioning was comprehensively improved by 0.99 m. The MDT correction of China seas gradually increased from the north to south. While in the regional sea areas, it gradually decreased from the north to south and showed randomness. The relative position between the antennas and their random changes introduced uncertainty, which can be reduced by integration. The new instantaneous sea reflection surface model and the corresponding specular point positioning method can provide accurate modeled reflection delay for the sea-state bias correction of ship-borne GNSS-R observations, and they can be extended to satellite-borne global observations.

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Mean Dynamic Topography Modeling Based on Optimal Interpolation from Satellite Gravimetry and Altimetry Data

Applied Sciences ◽

10.3390/app11115286 ◽

2021 ◽

Vol 11 (11) ◽

pp. 5286

Author(s):

Yihao Wu ◽

Jia Huang ◽

Hongkai Shi ◽

Xiufeng He

Keyword(s):

Ocean Circulation ◽

Interpolation Method ◽

Optimal Interpolation ◽

Surface Model ◽

Geopotential Model ◽

Generation Model ◽

Dynamic Topography ◽

Altimetry Data ◽

Mean Dynamic Topography ◽

Gaussian Filtering

Mean dynamic topography (MDT) is crucial for research in oceanography and climatology. The optimal interpolation method (OIM) is applied to MDT modeling, where the error variance–covariance information of the observations is established. The global geopotential model (GGM) derived from GOCE (Gravity Field and Steady-State Ocean Circulation Explorer) gravity data and the mean sea surface model derived from satellite altimetry data are combined to construct MDT. Numerical experiments in the Kuroshio over Japan show that the use of recently released GOCE-derived GGM derives a better MDT compared to the previous models. The MDT solution computed based on the sixth-generation model illustrates a lower level of root mean square error (77.0 mm) compared with the ocean reanalysis data, which is 2.4 mm (5.4 mm) smaller than that derived from the fifth-generation (fourth-generation) model. This illustrates that the accumulation of GOCE data and updated data preprocessing methods can be beneficial for MDT recovery. Moreover, the results show that the OIM outperforms the Gaussian filtering approach, where the geostrophic velocity derived from the OIM method has a smaller misfit against the buoy data, by a magnitude of 10 mm/s (17 mm/s) when the zonal (meridional) component is validated. This is mainly due to the error information of input data being used in the optimal interpolation method, which may obtain more reasonable weights of observations than the Gaussian filtering method.

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Influence of Sea State on Sea Surface Height Oscillation from Doppler Altimeter Measurements in the North Sea

Remote Sensing ◽

10.3390/rs10071100 ◽

2018 ◽

Vol 10 (7) ◽

pp. 1100 ◽

Cited By ~ 4

Author(s):

Ferdinando Reale ◽

Fabio Dentale ◽

Eugenio Carratelli ◽

Luciana Fenoglio-Marc

Keyword(s):

North Sea ◽

Sea Surface Height ◽

Sea Surface ◽

Sea State ◽

The North ◽

The North Sea

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Weakly nonlinear theory and sea state bias estimations

Journal of Geophysical Research Atmospheres ◽

10.1029/1998jc900128 ◽

1999 ◽

Vol 104 (C4) ◽

pp. 7641-7647 ◽

Cited By ~ 29

Author(s):

Tanos Elfouhaily ◽

Donald Thompson ◽

Douglas Vandemark ◽

Bertrand Chapron

Keyword(s):

Nonlinear Theory ◽

Sea State ◽

Weakly Nonlinear ◽

Weakly Nonlinear Theory ◽

Sea State Bias

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Operability Guidelines For Product Tanker In Heavy Weather In The Adriatic Sea

Annual of Navigation ◽

10.1515/aon-2015-0008 ◽

2014 ◽

Vol 21 (1) ◽

pp. 95-106

Author(s):

Luka Mudronja ◽

Marko Katalinić ◽

Rino Bošnjak ◽

Pero Vidan ◽

Joško Parunov

Keyword(s):

Wave Height ◽

Adriatic Sea ◽

Wave Spectrum ◽

Extreme Weather ◽

The South ◽

Sea State ◽

M Wave ◽

The North ◽

Limiting Values ◽

Deck Wetness

AbstractThis paper presents operability guidelines for seafarers on a product tanker which navigates in the Adriatic Sea during heavy weather. Tanker route starts from the Otranto strait in the south to the island Krk in the north of Adriatic Sea. Heavy weather is caused by south wind called jugo (blowing from E-SE to SS-E, sirocco family). Operability guidelines are given based on an operability criteria platform for presenting ship seakeeping characteristics. Operability criteria considered in this paper are propeller emergence, deck wetness and bow acceleration of a product tanker. Limiting values of mentioned criteria determine sustainable speed. Heavy weather is described by extreme sea state of 7.5 m wave height. Wave spectrum used in this paper is Tabain spectrum which is developed specifically for Adriatic Sea. Seafarer's approach of decisions making in extreme weather is also shown and servers as a guideline for further research of the authors.

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Extreme Wave Condition at Doggerbank

Journal of Offshore Mechanics and Arctic Engineering ◽

10.1115/1.4033564 ◽

2016 ◽

Vol 138 (4) ◽

Author(s):

Espen Engebretsen ◽

Sverre K. Haver ◽

Dag Myrhaug

Keyword(s):

Wind Turbines ◽

Wind Farm ◽

Offshore Wind ◽

Extreme Condition ◽

Exceedance Probability ◽

Extreme Wave ◽

Sea State ◽

Wave Condition ◽

The North ◽

Wave Conditions

In design of offshore wind turbines, extreme wave conditions are of interest. Usually, the design wave condition is taken as the sea state corresponding to an annual exceedance probability of 2 × 10−2, i.e., a return period of 50 years. A possible location for a future wind farm, consisting of bottom fixed wind turbines, is the Doggerbank area. The water depth in this area varies from about 60 m in the north to about 20 m in the south. The hindcast database NORA10 provides sea state characteristics from 1957 to present over a domain covering Doggerbank. Regarding the deeper areas just north of Doggerbank, this hindcast model is found to be of good quality. Larger uncertainties are associated with the hindcast results as we approach shallower water further south. The purpose of the present study is to compare sea state evolution over Doggerbank as reflected by NORA10 with the results of the commonly used shallow water hindcast model SWAN. The adequacy of the default parameters of SWAN for reflecting changes in wave conditions over a sloping bottom is investigated by comparison with model test results. Extreme wave conditions for two locations 102.5 km apart in a north–south direction are established using NORA10. This is done using both, an all sea states approach and a peak over threshold (POT) approach. Assuming the extremes for the northern position to represent good estimates, the wave evolution southward is analyzed using SWAN. The extreme condition obtained from NORA10 in the northern position is used as input to SWAN and the results from the two hindcast models are compared in the southern position. SWAN seems to suggest a somewhat faster decay over Doggerbank compared to NORA10.

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Modeling dust emission response to MIS 3 millennial climate variations from the perspective of East European loess deposits

Climate of the Past Discussions ◽

10.5194/cpd-9-143-2013 ◽

2013 ◽

Vol 9 (1) ◽

pp. 143-185 ◽

Cited By ~ 2

Author(s):

A. Sima ◽

M. Kageyama ◽

D.-D. Rousseau ◽

G. Ramstein ◽

Y. Balkanski ◽

...

Keyword(s):

North Atlantic ◽

General Circulation ◽

Reference Site ◽

Dust Emission ◽

Dust Storms ◽

Surface Model ◽

Climate Signal ◽

The North ◽

Loess Deposits ◽

The North Atlantic

Abstract. European loess sequences of the last glacial period (~ 100–15 kyr BP) show periods of strong dust accumulation alternating with episodes of reduced sedimentation, favoring soil development. In the western part of the loess belt centered around 50° N, these variations appear to have been caused by the North Atlantic rapid climate changes: the Dansgaard-Oeschger (DO) and Heinrich (H) events. It has been recently suggested that the North-Atlantic climate signal can be detected further east, in loess deposits from Stayky (50° 05.65' N, 30° 53.92' E), Ukraine. Here we use climate and dust emission modeling to investigate this data interpretation. We focus on the areas north and northeast of the Carpathians, where loess deposits can be found, and the corresponding main dust sources must have been located as well. The simulations, performed with the LMDZ atmospheric general circulation model and the ORCHIDEE land-surface model, represent a Greenland stadial, a DO interstadial and an H event respectively. Placed in Marine Isotope Stage 3 (~ 60–25 kyr BP) conditions, they only differ by the surface conditions imposed in the North Atlantic between 30° and 63° N. The main source for the loess deposits in the studied area is identified as a dust deflation band, with two very active spots located west–northwest from our reference site. Emissions only occur between February and June. Differences from one deflation spot to another, and from one climate state to another, are explained by analyzing the relevant meteorological and surface variables. Over most of the source region, the annual emission fluxes in the "interstadial" experiment are 30 to 50% lower than the "stadial" values; they would only be about 20% lower if the inhibition of dust uplift by the vegetation were not taken into account. Assuming that lower emissions result in reduced dust deposition leads us to the conclusion that the loess-paleosol stratigraphic succession in the Stayky area reflects indeed North-Atlantic millennial variations. In the main deflation areas of Western Europe, the vegetation effect alone determined most of the ~ 50% stadial-interstadial flux differences. Even if its impact in Eastern Europe is less pronounced, this effect remains a key factor in modulating aeolian emissions at millennial timescale. Conditions favorable to initiating particularly strong dust storms within a few hundred kilometers upwind from our reference site, simulated in the month of April of the "H event" experiment, support the identification of H events as layers of particularly coarse sedimentation in some very detailed profiles.

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On the physical constraints for the exceeding probability of deep water rogue waves

10.5194/egusphere-egu21-3961 ◽

2021 ◽

Author(s):

Saulo Mendes ◽

Alberto Scotti ◽

Paul Stansell

Keyword(s):

Sample Size ◽

Rogue Wave ◽

Probability Distributions ◽

Rogue Waves ◽

Uneven Distribution ◽

Large Set ◽

Sea State ◽

Sampling Variability ◽

The North ◽

Wave Heights

(manuscript accepted into Applied Ocean Research https://www.researchgate.net/publication/344786014)AbstractNearly four decades have elapsed since the first efforts to obtain a realistic narrow-banded model for extreme wave crests and heights were made, resulting in a couple of dozen different exceeding probability distributions. These models reflect results of numerical simulations and storm records measured from oil platforms, buoys, and more recently, satellite data. Nevertheless, no consensus has been achieved in either deterministic or operational approaches. Typically, distributions found in the literature analyze a very large set of waves with large variations in sea-state parameters while neglecting homogeneous smaller samples, such that we lack a suitable definition for the sample size and homogeneity of sea variables, also known as sampling variability (Bitner-Gregersen et al., 2020). Naturally, a possible consequence of such sample size inconsistency is the apparent disagreement between several studies regarding the prediction of rogue wave occurrence, as some studies can report less rogue wave heights while others report more rogue waves or the same statistics predicted by Longuet-Higgins (1952), sometimes a combination of the three in the very same study (Stansell, 2004; Cherneva et al., 2005). In this direction, we have obtained a dimensionless parameter capable of measuring how large the deviations in sea state variables can be so that accuracy in wave statistics is preserved. &#160;In particular, we have defined which samples are too heterogeneous to create an accurate description of the uneven distribution of rogue wave likelihood among different storms (Stansell, 2004). Though the literature is rich in physical bounds for single waves, here we describe empirical physical limits for the ensemble of waves (such as the significant steepness) devised to bound these variables within established and prospective wave distributions. Furthermore, this work supplies a combination of sea state parameters that provide guidance on the influence of sea states influence on rogue wave occurrence. Based on these empirical limits, we conjecture a mathematical model for the dependence of the expected maximum of normalized wave heights and crests on the sea state parameters, thus explaining the uneven distribution of rogue wave likelihood among different storms collected by infrared laser altimeters of the North Alwyn oil platform discussed in Stansell (2004). Finally, we demonstrate that for heights and crests beyond 90% of their thresholds (H>2H1/3&#160;for heights), the exceeding probability becomes stratified, i.e. they resemble layers of probability curves according to each sea state, suggesting the existence of a dynamical definition for rogue waves rather than purely statistical.&#160;ReferencesBitner-Gregersen, E. M., Gramstad, O., Magnusson, A., Malila, M., 2020. Challenges in description of nonlinear waves due to sampling variability. J. Mar. Sci. Eng. 8, 279.Longuet-Higgins, M., 1952. On the statistical distribution of the heights of sea waves. Journal of Marine Research 11, 245&#8211;265.Stansell, P., 2004. Distribution of freak wave heights measured in the north sea. Appl. Ocean Res. 26, 35&#8211;48.Cherneva, Z., Petrova, P., Andreeva, N., Guedes Soares, C., 2005. Probability distributions of peaks, troughs and heights of wind waves measured in the black sea coastal zone. Coastal Engineering 52, 599&#8211;615.

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Iceland, the Farallon slab, and dynamic topography of the North Atlantic

Geology ◽

10.1130/g20137.1 ◽

2004 ◽

Vol 32 (3) ◽

pp. 177 ◽

Cited By ~ 54

Author(s):

Clinton P. Conrad ◽

Carolina Lithgow-Bertelloni ◽

Keith E. Louden

Keyword(s):

North Atlantic ◽

Dynamic Topography ◽

The North ◽

The North Atlantic

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Improved Sea State Bias Estimation for Altimeter Reference Missions With Altimeter-Only Three-Parameter Models

IEEE Transactions on Geoscience and Remote Sensing ◽

10.1109/tgrs.2018.2866773 ◽

2019 ◽

Vol 57 (3) ◽

pp. 1448-1462 ◽

Cited By ~ 4

Author(s):

Nelson Pires ◽

M. Joana Fernandes ◽

Christine Gommenginger ◽

Remko Scharroo

Keyword(s):

Bias Estimation ◽

Sea State ◽

Sea State Bias

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Tectonic influence of Large Igneous Provinces on source-to-sink systems, the case study of Shetland during the Palaeocene - Preliminary results

10.5194/egusphere-egu21-13122 ◽

2021 ◽

Author(s):

Lucas Albanese Valore ◽

Christian Haug Eide ◽

Tor Oftedal Sømme

Keyword(s):

North Sea ◽

Sediment Supply ◽

Dynamic Topography ◽

Sedimentary Record ◽

Mantle Dynamics ◽

Exceptional Preservation ◽

The North ◽

Source To Sink ◽

The North Sea ◽

Forcing Mechanisms

The source-to-sink approach to sedimentology has become an increasingly valuable approach for addressing how external and internal forcing mechanisms are tied together in time and space. Processes that are initiated deep within the lower mantle can eventually propagate and affect shallow crustal sedimentary systems. This is important to predict the presence of reservoirs in areas of little data, and to interpret the sedimentary record in terms of climate and tectonic settings during deposition. To address this issue, we will study the Early Palaeogene succession of the East Shetland Platform in the North Sea, which was deposited during the emplacement of the Icelandic Plume. The plume&#8217;s activity is hypothesized to be the cause of a major uplift cycle in the continental source areas, which is coeval to a sharp increase in sedimentation rates recorded in the East Shetland Platform during the Palaeocene. However, this relationship is still in need of accurate constraints derived from data with better spatial and temporal resolution, particularly due to overlapping climatic and tectonic controls, regional-to-local variations in sediment supply systems and overall gaps in the sedimentary record. This correlation can benefit from high-quality 3D seismic data on the platform, especially due to an exceptional preservation of shelf-edge geometries that are absent elsewhere. Using different 3D and 2D seismic surveys, well data and biostratigraphic data from the Shetland Platform and the North Sea, we will quantify sediment volumes supplied through time. The observed sediment volumes will be investigated using models of dynamic topography, plume activity and paleoclimatic data to closely relate supplied volumes to changes in relief, catchment geometries, precipitation and other key forcing parameters. Ultimately, we aim to investigate the relative influence of both tectonics and climate, as both long term (mantle dynamics) and short term (Palaeocene-Eocene Thermal Maximum) have been interpreted to play an important role in this system.&#160;

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