Storm surge forecasting: quantifying errors arising from the double-counting of radiational tides

Abstract. Tide predictions based on tide-gauge observations are not just the astronomical tides, they also contain radiational tides – periodic sea level changes due to atmospheric conditions and solar forcing. This poses a problem of double-counting for operational forecasts of total water level during storm surges. In some surge forecasting, a regional model is run as tide-only, with astronomic forcing alone; and tide-and-surge, forced additionally by surface winds and pressure. The surge residual is defined to be the difference between these configurations and is added to the local harmonic predictions from gauges. Here we use the Global Tide and Surge Model based on Delft-FM to investigate this in the UK and elsewhere, quantifying the weather-related tides that may be double-counted in operational forecasts. We show that the global S2 atmospheric tide is captured by the tide-surge model, and observe changes in other key constituents, including M2. We also quantify the extent to which the Highest Astronomical Tide, which is derived from tide predictions based on observations, may contain weather-related components.

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Radiational tides: their double-counting in storm surge forecasts and contribution to the Highest Astronomical Tide

Ocean Science ◽

10.5194/os-14-1057-2018 ◽

2018 ◽

Vol 14 (5) ◽

pp. 1057-1068 ◽

Cited By ~ 5

Author(s):

Joanne Williams ◽

Maialen Irazoqui Apecechea ◽

Andrew Saulter ◽

Kevin J. Horsburgh

Keyword(s):

Tide Gauge ◽

Storm Surges ◽

Double Counting ◽

Atmospheric Conditions ◽

Sea Level Changes ◽

Astronomical Tide ◽

Operational Forecasts ◽

The Difference ◽

The Uk ◽

Total Water Level

Abstract. Tide predictions based on tide-gauge observations are not just the astronomical tides; they also contain radiational tides – periodic sea-level changes due to atmospheric conditions and solar forcing. This poses a problem of double-counting for operational forecasts of total water level during storm surges. In some surge forecasting, a regional model is run in two modes: tide only, with astronomic forcing alone; and tide and surge, forced additionally by surface winds and pressure. The surge residual is defined to be the difference between these configurations and is added to the local harmonic predictions from gauges. Here we use the Global Tide and Surge Model (GTSM) based on Delft-FM to investigate this in the UK and elsewhere, quantifying the weather-related tides that may be double-counted in operational forecasts. We show that the global S2 atmospheric tide is captured by the tide-and-surge model and observe changes in other major constituents, including M2. The Lowest and Highest Astronomical Tide levels, used in navigation datums and design heights, are derived from tide predictions based on observations. We use our findings on radiational tides to quantify the extent to which these levels may contain weather-related components.

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Implementation of a chemical background method for atmospheric OH measurements by laser-induced fluorescence: characterisation and observations from the UK and China

Atmospheric Measurement Techniques ◽

10.5194/amt-13-3119-2020 ◽

2020 ◽

Vol 13 (6) ◽

pp. 3119-3146 ◽

Cited By ~ 2

Author(s):

Robert Woodward-Massey ◽

Eloise J. Slater ◽

Jake Alen ◽

Trevor Ingham ◽

Danny R. Cryer ◽

...

Keyword(s):

Atmospheric Chemistry ◽

Ambient Air ◽

Laser Induced Fluorescence ◽

Excitation Wavelength ◽

Atmospheric Conditions ◽

Wide Range ◽

Model Predictions ◽

The Difference ◽

The Uk ◽

Interference Tests

Abstract. Hydroxyl (OH) and hydroperoxy (HO2) radicals are central to the understanding of atmospheric chemistry. Owing to their short lifetimes, these species are frequently used to test the accuracy of model predictions and their underlying chemical mechanisms. In forested environments, laser-induced fluorescence–fluorescence assay by gas expansion (LIF–FAGE) measurements of OH have often shown substantial disagreement with model predictions, suggesting the presence of unknown OH sources in such environments. However, it is also possible that the measurements have been affected by instrumental artefacts, due to the presence of interfering species that cannot be discriminated using the traditional method of obtaining background signals via modulation of the laser excitation wavelength (“OHwave”). The interference hypothesis can be tested by using an alternative method to determine the OH background signal, via the addition of a chemical scavenger prior to sampling of ambient air (“OHchem”). In this work, the Leeds FAGE instrument was modified to include such a system to facilitate measurements of OHchem, in which propane was used to selectively remove OH from ambient air using an inlet pre-injector (IPI). The IPI system was characterised in detail, and it was found that the system did not reduce the instrument sensitivity towards OH (< 5 % difference to conventional sampling) and was able to efficiently scavenge external OH (> 99 %) without the removal of OH formed inside the fluorescence cell (< 5 %). Tests of the photolytic interference from ozone in the presence of water vapour revealed a small but potentially significant interference, equivalent to an OH concentration of ∼4×105 molec. cm−3 under typical atmospheric conditions of [O3] =50 ppbv and [H2O] =1 %. Laboratory experiments to investigate potential interferences from products of isoprene ozonolysis did result in interference signals, but these were negligible when extrapolated down to ambient ozone and isoprene levels. The interference from NO3 radicals was also tested but was found to be insignificant in our system. The Leeds IPI module was deployed during three separate field intensives that took place in summer at a coastal site in the UK and both in summer and winter in the megacity of Beijing, China, allowing for investigations of ambient OH interferences under a wide range of chemical and meteorological conditions. Comparisons of ambient OHchem measurements to the traditional OHwave method showed excellent agreement, with OHwave vs OHchem slopes of 1.05–1.16 and identical behaviour on a diel basis, consistent with laboratory interference tests. The difference between OHwave and OHchem (“OHint”) was found to scale non-linearly with OHchem, resulting in an upper limit interference of (5.0±1.4) ×106 molec. cm−3 at the very highest OHchem concentrations measured (23×106 molec. cm−3), accounting for ∼14 %–21 % of the total OHwave signal.

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Monsoon-Induced Surge during High Tides at the Southeast Coast of Vietnam: A Numerical Modeling Study

Geosciences ◽

10.3390/geosciences9020072 ◽

2019 ◽

Vol 9 (2) ◽

pp. 72 ◽

Cited By ~ 1

Author(s):

Nguyen Thuy ◽

Tran Tien ◽

Cecilie Wettre ◽

Lars Hole

Keyword(s):

Spring Tide ◽

Ocean Model ◽

Clear Trend ◽

Astronomical Tide ◽

Southeast Coast ◽

Regional Ocean Model System ◽

Operational Forecasts ◽

Regional Ocean Model ◽

Coast Of Vietnam ◽

Total Water Level

In this study, monsoon-induced surge during high tides at the Southeast coast of Vietnam was analyzed based on the observed tide data at the Vung Tau station in the period between 1997—2016. Specifically, the surge was determined by removing the astronomical tide from the observed total water level. The two-dimensional Regional Ocean Model System (ROMS 2D) was applied to simulate the surge induced by monsoons during spring tide. The surge observations showed that the change of peak surge did not follow a clear trend, of either an increase or decrease, over time. A peak surge of over 40 cm appeared mainly in October and November, although the peak of the astronomical tide was higher in December. ROMS 2D was validated with the observational data, and the model could sufficiently reproduce the wind-induced surge during high tides. This study therefor ere commends for ROMS 2D to be used in operational forecasts in this area.

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Evolution of extreme Total Water Levels along the northern coast of the Iberian Peninsula

Natural Hazards and Earth System Science ◽

10.5194/nhess-11-613-2011 ◽

2011 ◽

Vol 11 (2) ◽

pp. 613-625 ◽

Cited By ~ 1

Author(s):

D. F. Rasilla Álvarez ◽

J. C. García Codron

Keyword(s):

Iberian Peninsula ◽

Water Level ◽

Sea Level ◽

Tide Gauge ◽

Water Levels ◽

Northern Coast ◽

Atmospheric Conditions ◽

Total Water ◽

Total Water Level

Abstract. This paper assesses the evolution of storminess along the northern coast of the Iberian Peninsula through the calculation of extreme (1%) Total Water Levels (eTWL) on both observed (tide gauge and buoy data) and hindcasted (SIMAR-44) data. Those events were first identified and then characterized in terms of oceanographic parameters and atmospheric circulation features. Additionally, an analysis of the long-term trends in both types of data was performed. Most of the events correspond to a rough wave climate and moderate storm surges, linked to extratropical disturbances following a northern track. While local atmospheric conditions seem to be evolving towards lesser storminess, their impact has been balanced by the favorable exposure of the northern coast of the Iberian Peninsula to the increasing frequency and strength of distant disturbances crossing the North Atlantic. This evolution is also correctly reproduced by the simulated long-term evolution of the forcing component (meteorological sea level residuals and wave run up) of the Total Water Level values calculated from the SIMAR 44 database, since sea level residuals have been experiencing a reduction while waves are arriving with longer periods. Finally, the addition of the rate of relative sea level trend to the temporal evolution of the atmospheric forcing component of the Total Water Level values is enough to simulate more frequent and persistent eTWL.

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Towards using state-of-the-art climate models to help constrain estimates of unprecedented UK storm surges

Natural Hazards and Earth System Science ◽

10.5194/nhess-21-3693-2021 ◽

2021 ◽

Vol 21 (12) ◽

pp. 3693-3712

Author(s):

Tom Howard ◽

Simon David Paul Williams

Keyword(s):

Climate Model ◽

State Of The Art ◽

Tide Gauge ◽

Storm Surges ◽

Shape Parameters ◽

Model Simulations ◽

Shelf Seas ◽

Coastal Flood Risk ◽

Current Guidance ◽

The Uk

Abstract. Our ability to quantify the likelihood of present-day extreme sea level (ESL) events is limited by the length of tide gauge records around the UK, and this results in substantial uncertainties in return level curves at many sites. In this work, we explore the potential for a state-of-the-art climate model, HadGEM3-GC3, to help refine our understanding of present-day coastal flood risk associated with extreme storm surges, which are the dominant driver of ESL events for the UK and wider European shelf seas. We use a 483-year present-day control simulation from HadGEM3-GC3-MM (1/4∘ ocean, approx. 60 km atmosphere in mid-latitudes) to drive a north-west European shelf seas model and generate a new dataset of simulated UK storm surges. The variable analysed is the skew surge (the difference between the high water level and the predicted astronomical high tide), which is widely used in analysis of storm surge events. The modelling system can simulate skew surge events comparable to the catastrophic 1953 North Sea storm surge, which resulted in widespread flooding, evacuation of 32 000 people, and hundreds of fatalities across the UK alone, along with many hundreds more in mainland Europe. Our model simulations show good agreement with an independent re-analysis of the 1953 surge event at the mouth of the river Thames. For that site, we also revisit the assumption of skew surge and tide independence. Our model results suggest that at that site for the most extreme surges, tide–surge interaction significantly attenuates extreme skew surges on a spring tide compared to a neap tide. Around the UK coastline, the extreme tail shape parameters diagnosed from our simulation correlate very well (Pearson's r greater than 0.85), in terms of spatial variability, with those used in the UK government's current guidance (which are diagnosed from tide gauge observations), but ours have smaller uncertainties. Despite the strong correlation, our diagnosed shape parameters are biased low relative to the current guidance. This bias is also seen when we replace HadGEM3-GC3-MM with a reanalysis, so we conclude that the bias is likely associated with limitations in the shelf sea model used here. Overall, the work suggests that climate model simulations may prove useful as an additional line of evidence to inform assessments of present-day coastal flood risk.

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Towards using state-of-the-art climate models to help constrain estimates of unprecedented UK storm surges

10.5194/nhess-2021-184 ◽

2021 ◽

Author(s):

Tom Howard ◽

Simon David Paul Williams

Keyword(s):

Climate Model ◽

State Of The Art ◽

Tide Gauge ◽

Storm Surges ◽

Shape Parameters ◽

Model Simulations ◽

Shelf Seas ◽

Coastal Flood Risk ◽

Current Guidance ◽

The Uk

Abstract. Our ability to quantify the likelihood of present-day extreme sea level (ESL) events is limited by the length of tide gauge records around the UK, and this results in substantial uncertainties in return level curves at many sites. In this work, we explore the potential for a state-of-the-art climate model, HadGEM3-GC3, to help refine our understanding of present-day coastal flood risk associated with extreme storm surges, which are the dominant driver of ESL events for the UK and wider European shelf seas. We use a 483-year present-day control simulation from HadGEM3-GC3-MM (1/4 degree ocean, approx 60 km atmosphere in mid-latitudes) to drive a northwest European shelf seas model and generate a new dataset of simulated UK storm surges. The variable analysed is the skew surge (the difference between the high water level and the predicted astronomical high tide), which is widely used in analysis of storm surge events. The modelling system can simulate skew surge events comparable to the catastrophic 1953 North Sea storm surge, which resulted in widespread flooding, evacuation of 32 thousand people and hundreds of fatalities across the UK alone, along with many hundreds more in mainland Europe. Our model simulations show good agreement with an independent re-analysis of the 1953 surge event and suggest that a skew surge event of this magnitude has an expected frequency of about 1 in 500 years at the mouth of the river Thames. For that site, we also revisit the assumption of skew surge/tide independence. Our model results suggest that at that site for the most extreme surges, tide/surge interaction significantly attenuates extreme skew surges on a spring tide compared to a neap tide. Around the UK coastline, the extreme tail shape parameters diagnosed from our simulation correlate very well (Pearson's r greater than 0.85), in terms of spatial variability, with those used in the UK government's current guidance (which are diagnosed from tide-gauge observations), but ours can be diagnosed without the use of a subjective prior. Despite the strong correlation, our diagnosed shape parameters are biased low relative to the current guidance. This bias is also seen when we replace HadGEM3-GC3-MM with a reanalysis, so we conclude that the bias is likely associated with limitations in the shelf sea model used here. Overall, the work suggests that climate model simulations may prove useful as an additional line of evidence to inform assessments of present-day coastal flood risk.

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ATTITUDE TO OPEN ACCESS IN RUSSIAN SCHOLARLY COMMUNITY: 2018. SURVEY RESULTS AND ANALYSIS

Scholarly Research and Information ◽

10.24108/2658-3143-2018-1-1-6-21 ◽

2018 ◽

Vol 1 (1) ◽

pp. 6-21 ◽

Cited By ~ 2

Author(s):

I. K. Razumova ◽

N. N. Litvinova ◽

M. E. Shvartsman ◽

A. Yu. Kuznetsov

Keyword(s):

Open Access ◽

Open Access Publishing ◽

Scholarly Community ◽

Research Areas ◽

Survey Results ◽

The Difference ◽

Policies And Programs ◽

The Uk ◽

High Level ◽

Access Policies

Introduction. The paper presents survey results on the awareness towards and practice of Open Access scholarly publishing among Russian academics.Materials and Methods. We employed methods of statistical analysis of survey results. Materials comprise results of data processing of Russian survey conducted in 2018 and published results of the latest international surveys. The survey comprised 1383 respondents from 182 organizations. We performed comparative studies of the responses from academics and research institutions as well as different research areas. The study compares results obtained in Russia with the recently published results of surveys conducted in the United Kingdom and Europe.Results. Our findings show that 95% of Russian respondents support open access, 94% agree to post their publications in open repositories and 75% have experience in open access publishing. We did not find any difference in the awareness and attitude towards open access among seven reference groups. Our analysis revealed the difference in the structure of open access publications of the authors from universities and research institutes. Discussion andConclusions. Results reveal a high level of awareness and support to open access and succeful practice in the open access publications in the Russian scholarly community. The results for Russia demonstrate close similarity with the results of the UK academics. The governmental open access policies and programs would foster the practical realization of the open access in Russia.

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THE VALUE OF ROBUST STATISTICAL FORECASTS IN THE COVID-19 PANDEMIC

National Institute Economic Review ◽

10.1017/nie.2021.9 ◽

2021 ◽

Vol 256 ◽

pp. 19-43

Author(s):

Jennifer L. Castle ◽

Jurgen A. Doornik ◽

David F. Hendry

Keyword(s):

Structural Change ◽

Measurement Errors ◽

Epidemiological Models ◽

Short Term ◽

Data Measurement ◽

Policy Interventions ◽

Changing Trends ◽

Technological Advances ◽

The Difference ◽

The Uk

The Covid-19 pandemic has put forecasting under the spotlight, pitting epidemiological models against extrapolative time-series devices. We have been producing real-time short-term forecasts of confirmed cases and deaths using robust statistical models since 20 March 2020. The forecasts are adaptive to abrupt structural change, a major feature of the pandemic data due to data measurement errors, definitional and testing changes, policy interventions, technological advances and rapidly changing trends. The pandemic has also led to abrupt structural change in macroeconomic outcomes. Using the same methods, we forecast aggregate UK unemployment over the pandemic. The forecasts rapidly adapt to the employment policies implemented when the UK entered the first lockdown. The difference between our statistical and theory based forecasts provides a measure of the effect of furlough policies on stabilising unemployment, establishing useful scenarios had furlough policies not been implemented.

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