scholarly journals Model Based Assessment of the Reflection Behavior of Tidal Waves at Bathymetric Changes in Estuaries

Water ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 489
Author(s):  
Vanessa Sohrt ◽  
Sebastian S.V. Hein ◽  
Edgar Nehlsen ◽  
Thomas Strotmann ◽  
Peter Fröhle
Keyword(s):  
Cross Sectional ◽  
High Agreement ◽  
Tidal Waves ◽  
Level Data ◽  
Water Level Data ◽  
Abrupt Changes ◽  
Water Effects ◽  
Potential Impact ◽  
Tidal Constituents ◽  
Harmonic Components

Estuaries are often modified by human activities. Adjustments in the morphology of an estuary have a potential impact on the hydrodynamics and on the reflection behavior of the tide. The influence of such system changes on the complex tidal regime with a large number of superimposed tidal constituents is not fully understood yet. The reflection properties of estuaries that are characterized by abrupt changes in geometry are systematically investigated on the basis of simplified estuary model approaches to improve the understanding of the oscillation and reflection behavior of tidal waves in estuaries. The reflection coefficients at abrupt cross-sectional changes are determined by two different methods, i.e., an analytical energy-based approach and a hydrodynamic numerical (HN) model. Comparisons indicate a high agreement of the results of the different methods when evaluating the reflection coefficient. The tidal constituents are reflected at partial and total reflectors and amplified by shoaling depending on the water depths, the height of the bottom step and the horizontal constriction. A harmonic analysis of simulated water level data partly shows the formation and amplification of higher harmonic components as a result of shallow water effects. The interaction with reflectors results in an increasing amplification of the tidal constituents and the tide.

Comparison of predictions of a numerical model and observations of tides in Bass Strait

1985 ◽  
Vol 36 (6) ◽  
pp. 737 ◽  
Author(s):  
CB Fandry ◽  
GD Hubbert ◽  
PC McIntosh
Keyword(s):  
Numerical Model ◽  
Sea Level ◽  
Travelling Waves ◽  
Phase Lag ◽  
Tidal Amplitude ◽  
Tidal Constituent ◽  
Tidal Waves ◽  
Level Data ◽  
Grid Points ◽  
Tidal Constituents

A depth-averaged numerical model is used to describe the tidal regime in Bass Strait. Tidal constants corresponding to the four major tidal constituents (M2, S2, O1 and K1) are calculated at the grid points of the model, and co-amplitude and co-phase contours drawn for each of the constituents. At 17 locations in Bass Strait, the computed tidal constants are in excellent agreement with those obtained from flow and sea-level data. The dominant tidal constituent is found to be the semi-diurnal, M2, tide, which is predicted by the model with an accuracy of 10% in sea-level amplitude and 10� in phase. The M2 tide in Bass Strait is generated by two oppositely travelling waves, one entering the eastern end and another entering the western end with a phase lag of about 3 h. Some amplification of these waves occurs as they move from the deep water into the much shallower continental shelf waters of the Strait, and their superposition causes a large tidal amplitude (up to 1.2 m) to occur in central Bass Strait. The other three constituents are much weaker than the M2 constituent, and are driven by tidal waves entering from the western end. They propagate eastwards, emerging at the eastern end with little change in amplitude throughout the Strait.

scholarly journals Impact of temperature and relative humidity on the transmission of COVID-19: a modelling study in China and the United States

BMJ Open ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. e043863
Author(s):  
Jingyuan Wang ◽  
Ke Tang ◽  
Kai Feng ◽  
Xin Lin ◽  
Weifeng Lv ◽  
...  
Keyword(s):  
Regression Analysis ◽  
Relative Humidity ◽  
Human Mobility ◽  
The United States ◽  
Reproductive Number ◽  
Cross Sectional ◽  
The Usa ◽  
Higher Temperature ◽  
Potential Impact ◽  
The Impact

ObjectivesWe aim to assess the impact of temperature and relative humidity on the transmission of COVID-19 across communities after accounting for community-level factors such as demographics, socioeconomic status and human mobility status.DesignA retrospective cross-sectional regression analysis via the Fama-MacBeth procedure is adopted.SettingWe use the data for COVID-19 daily symptom-onset cases for 100 Chinese cities and COVID-19 daily confirmed cases for 1005 US counties.ParticipantsA total of 69 498 cases in China and 740 843 cases in the USA are used for calculating the effective reproductive numbers.Primary outcome measuresRegression analysis of the impact of temperature and relative humidity on the effective reproductive number (R value).ResultsStatistically significant negative correlations are found between temperature/relative humidity and the effective reproductive number (R value) in both China and the USA.ConclusionsHigher temperature and higher relative humidity potentially suppress the transmission of COVID-19. Specifically, an increase in temperature by 1°C is associated with a reduction in the R value of COVID-19 by 0.026 (95% CI (−0.0395 to −0.0125)) in China and by 0.020 (95% CI (−0.0311 to −0.0096)) in the USA; an increase in relative humidity by 1% is associated with a reduction in the R value by 0.0076 (95% CI (−0.0108 to −0.0045)) in China and by 0.0080 (95% CI (−0.0150 to −0.0010)) in the USA. Therefore, the potential impact of temperature/relative humidity on the effective reproductive number alone is not strong enough to stop the pandemic.

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