scholarly journals STORM STATISTICS IN THE NORTH SEA

1988 ◽  
Vol 1 (21) ◽  
pp. 71
Author(s):  
B.A. Salih ◽  
R. Burrows ◽  
R.G. Tickell
Keyword(s):  
North Sea ◽  
Climate Model ◽  
Weather Conditions ◽  
Threshold Level ◽  
Storm Events ◽  
Directional Information ◽  
The North ◽  
Empirical Procedure ◽  
The North Sea ◽  
Lag Times

Effective planning of offshore activities requires statistical information detailing storm occurrences and durations (defined as exceedences of an Hs threshold). This information is often referred to as persistence. The frequency of storm events and the probability associated with a number of successive sea states being above (or below) a given threshold level is often required by engineers to estimate the potential work period and down-time as well as to incorporate the lead and lag times needed to stop and restart interrupted operations due to severe weather conditions. However, until recently, a lack of sufficiently long data bases has precluded any meaningful investigation of this nature. Unrepresentative or misleading results can follow from data records that were measured over only a limited number of years. Furthermore, significant distortions may be introduced if the data record is not continuous as data gaps interrupt the persistence pattern. As more recorded data have become available, concerted efforts have been ' made on this topic; most notably by Houmb and Vik who developed a probabilistic model describing the statistics of storm (and calm) durations and frequencies at varying levels of sea state intensity. The present study investigates the adequacy of the semi-empirical procedure proposed by Houmb and Vik and also discusses the development of two new modelling techniques. The performance of these models are examined against wave data measured at the BP Forties field in the North Sea. A number of new statistical descriptors relating to the profile and intensity of storms have also been developed. It is recognised that wave period (Tz) and directional information must ultimately be incorporated in a storm climate model. However, this is beyond the scope of the present discussion.

scholarly journals An ensemble study of extreme storm surge related water levels in the North Sea in a changing climate

Ocean Science ◽  
2009 ◽  
Vol 5 (3) ◽  
pp. 369-378 ◽  
Author(s):  
A. Sterl ◽  
H. van den Brink ◽  
H. de Vries ◽  
R. Haarsma ◽  
E. van Meijgaard
Keyword(s):  
North Sea ◽  
Climate Model ◽  
Sea Water ◽  
Global Climate ◽  
Global Climate Model ◽  
Storm Surges ◽  
Water Levels ◽  
The North ◽  
Extreme Storm ◽  
The North Sea

Abstract. The height of storm surges is extremely important for a low-lying country like The Netherlands. By law, part of the coastal defence system has to withstand a water level that on average occurs only once every 10 000 years. The question then arises whether and how climate change affects the heights of extreme storm surges. Published research points to only small changes. However, due to the limited amount of data available results are usually limited to relatively frequent extremes like the annual 99%-ile. We here report on results from a 17-member ensemble of North Sea water levels spaning the period 1950–2100. It was created by forcing a surge model of the North Sea with meteorological output from a state-of-the-art global climate model which has been driven by greenhouse gas emissions following the SRES A1b scenario. The large ensemble size enables us to calculate 10 000 year return water levels with a low statistical uncertainty. In the one model used in this study, we find no statistically significant change in the 10 000 year return values of surge heights along the Dutch during the 21st century. Also a higher sea level resulting from global warming does not impact the height of the storm surges. As a side effect of our simulations we also obtain results on the interplay between surge and tide.

scholarly journals Interannual and Multidecadal Changes of Wind Speed and Directions over the North Sea from Climate Model Results

2016 ◽  
Vol 25 (4) ◽  
pp. 463-478 ◽  
Author(s):  
Anette Ganske ◽  
Birger Tinz ◽  
Gudrun Rosenhagen ◽  
Hartmut Heinrich
Keyword(s):  
Wind Speed ◽  
North Sea ◽  
Climate Model ◽  
The North ◽  
The North Sea

Occurrence of Freak Waves in near-coast regions of the North Sea and their potential relationship with objective weather types

2020 ◽  
Author(s):  
Jens Möller ◽  
Ina Teutsch ◽  
Ralf Weisse
Keyword(s):  
North Sea ◽  
German Bight ◽  
Climate Model ◽  
Rogue Waves ◽  
Freak Waves ◽  
Weather Types ◽  
The North ◽  
Ocean Atmosphere ◽  
The Future ◽  
The North Sea

<p>Rogue waves are a potential threat for both shipping and offshore structures like wind power stations or oil platforms. While individual Rogue waves are short-lived and almost unpredictable, there is a chance to predict the probability of the occurrence of freak waves in conjunction with different weather types. The German Ministry of Transport and digital Infrastructure has tasked its Network of Experts to investigate the possible evolutions of extreme threats for shipping and offshore wind energy plants in the German Bight, the south-eastern part of the North Sea near the German coast.</p><p>In this study, we present an analysis from the co-occurrence of freak waves with different weather types in the German Bight in the past (from observations). In addition, we investigate potential changes of the occurrence of freak waves in the future due to a changing climate and changing appearance of the relevant weather types (by use of a coupled Regional Ocean-Atmosphere Climate Model, MPI-OM).</p><p>The investigation indicates a connection between the probability of the occurrence of freak waves at different stations and certain weather types. Potentially, this relationship could be used for warning crews of ships or offshore constructions. In a coupled Regional Ocean-Atmosphere Climate Model (MPI-OM) under scenario RCP8.5 we detect an increase of just such weather types, which are correlated with high waves, for the future.</p>

scholarly journals The simultaneous occurrence of surge and discharge extremes for the Rhine delta

2013 ◽  
Vol 13 (8) ◽  
pp. 2017-2029 ◽  
Author(s):  
S. F. Kew ◽  
F. M. Selten ◽  
G. Lenderink ◽  
W. Hazeleger
Keyword(s):  
North Sea ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Storm Surges ◽  
Future Climate ◽  
Simultaneous Occurrence ◽  
Rhine River ◽  
The North ◽  
The North Sea

Abstract. The low-lying Netherlands is at risk from multiple threats of sea level rise, storm surges and extreme river discharges. Should these occur simultaneously, a catastrophe will be at hand. Knowledge about the likelihood of simultaneous occurrence or the so-called "compound effect" of such threats is essential to provide guidance on legislation for dike heights, flood barrier design and water management in general. In this study, we explore the simultaneous threats of North Sea storm surges and extreme Rhine river discharge for the current and future climate in a large 17-member global climate model ensemble. We use a simple approach, taking proxies of north-northwesterly winds over the North Sea and multiple~day precipitation averaged over the Rhine basin for storm surge and discharge respectively, so that a sensitivity analysis is straightforward to apply. By investigating soft extremes, we circumvent the need to extrapolate the data and thereby permit the model's synoptic development of the extreme events to be inspected. Our principle finding based on the climate model data is that, for the current climate, the probability of extreme surge conditions following extreme 20-day precipitation sums is around 3 times higher than that estimated from treating extreme surge and discharge probabilities as independent, as previously assumed. For the future climate (2070–2100), the assumption of independence cannot be rejected, at least not for precipitation sums exceeding 7 days.

scholarly journals WAVE GROUP FORMATION AMONG STORM WAVES

1974 ◽  
Vol 1 (14) ◽  
pp. 7 ◽  
Author(s):  
H. Rye
Keyword(s):  
North Sea ◽  
Group Formation ◽  
Weather Conditions ◽  
Wave Group ◽  
Average Correlation ◽  
The North ◽  
Storm Waves ◽  
Stormy Weather ◽  
Wave Heights ◽  
The North Sea

Wave data obtained m the North Sea for stormy weather conditions are analyzed to determine the extent of wave group formation among large waves; i.e. the number of large waves succeeding each other in one single run. Three periods associated with the passage of high sea states are examined. The average correlation between succeeding wave heights is found to be +0.2H, which indicates that wave heights do have a "memory". Wave group formations are found to be more pronounced when the sea is growing than decaying. The average lengths of wave runs are calculated.

scholarly journals Associations of Synoptic Weather Conditions With Nocturnal Bird Migration Over the North Sea

2020 ◽  
Vol 8 ◽  
Author(s):  
Iris Manola ◽  
Maja Bradarić ◽  
Rob Groenland ◽  
Ruben Fijn ◽  
Willem Bouten ◽  
...  
Keyword(s):  
North Sea ◽  
Bird Migration ◽  
Weather Conditions ◽  
The North ◽  
Synoptic Weather ◽  
The North Sea ◽  
Nocturnal Bird Migration

Northeast Atlantic and North Sea Storminess as Simulated by a Regional Climate Model during 1958–2001 and Comparison with Observations

2005 ◽  
Vol 18 (3) ◽  
pp. 465-479 ◽  
Author(s):  
Ralf Weisse ◽  
Hans von Storch ◽  
Frauke Feser
Keyword(s):  
Regional Climate Model ◽  
North Sea ◽  
North Atlantic ◽  
Climate Model ◽  
Regional Climate ◽  
Near Surface ◽  
Severe Storms ◽  
Northeast Atlantic ◽  
The North ◽  
The North Sea

Abstract An analysis of the storm climate of the northeast Atlantic and the North Sea as simulated by a regional climate model for the past 44 yr is presented. The model simulates the period 1958–2001 driven by the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalysis. Comparison with observations shows that the model is capable of reproducing impact-related storm indices such as the number of severe and moderate storms per year or the total number of storms and upper intra-annual percentiles of near-surface wind speed. The indices describe both the year-to-year variability of the frequency, as well as changes in the average intensity of storm events. Analysis of these indices reveals that the average number of storms per year has increased near the exit of the North Atlantic storm track and over the southern North Sea since the beginning of the simulation period (1958), but the increase has attenuated later over the North Sea and the average number of storms per year has been decreasing over the northeast Atlantic since about 1990–95. The frequency of the most severe storms follows a similar pattern over the northeast North Atlantic while too few severe storms occurred in other areas of the model domain, preventing a statistical analysis for these areas.

scholarly journals Advanced Intelligent Control Strategy in Dynamic Positioning (DP) System Applied to a Semi-Submersible Drilling Platform in the North Sea

2021 ◽  
Author(s):  
Mohamad Alremeihi ◽  
Rosemary Norman ◽  
Kayvan Pazouki ◽  
Arun Dev ◽  
Musa Bashir
Keyword(s):  
North Sea ◽  
Oil And Gas ◽  
Weather Conditions ◽  
Dynamic Positioning ◽  
Gas Drilling ◽  
The North ◽  
Drilling Operations ◽  
The North Sea ◽  
And Performance ◽  
Wind Currents

Abstract Dynamic Positioning (DP) systems play a crucial role in oil and gas drilling and production floaters used globally for deep-water operations. Drilling operations need to maintain automatic positioning of the platform in the horizontal-plane within the safe zone. Operating DP systems typically require highly responsive control systems when encountering prevailing weather conditions. However, DP incident analysis demonstrates that control and thruster failures have been the leading causes of accidents for the past two decades, according to the International Marine Contractors Association (IMCA). In this paper, a Predictive Neural Network (PNN) strategy is proposed for thruster allocation on a platform; it has been developed by predicting the platform response and training the network to transform the required force commands from a nonlinear Proportional Integral Derivative (PID) motion controller for each thruster. The strategy is developed for increasing safety and zone keeping of DP-assisted-drilling operations in harsh weather. This is done by allowing the platform to recover the position more rapidly whilst decreasing the risk of losing the platform position and heading, which can lead to catastrophic damage. The operational performance of the DP system on a drilling platform subjected to the North Sea real environmental conditions of wind, currents and waves, is simulated with the model incorporating the PNN control algorithm, which deals with dynamic uncertainties, into the unstable conventional PID control system for a current drilling semi-submersible model. The simulation results demonstrate the improvement in DP accuracy and robustness for the semi-submersible drilling platform positioning and performance using the PNN strategy.

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