scholarly journals Effects of Wave–Current Interactions on Bay–Shelf Exchange

2021 ◽  
Vol 51 (5) ◽  
pp. 1637-1654
Author(s):  
Dehai Song ◽  
Wen Wu ◽  
Qiang Li
Keyword(s):  
Southern China ◽  
Vertical Mixing ◽  
Momentum Equation ◽  
Wave Radiation ◽  
Wave Dissipation ◽  
Form Drag ◽  
Northerly Wind ◽  
The Mean ◽  
Wave Induced ◽  
Wave Radiation Stress

AbstractBay–shelf exchange is critical to coastal systems because it promotes self-purification or pollution dilution of the systems. In this study, the effects of wave–current interactions on bay–shelf exchange are explored in a micromesotidal system—Daya Bay in southern China. Waves can enlarge the shear-induced seaward transport and reduce the residual-current-induced landward transport, which benefits the bay–shelf exchange; however, tides work oppositely and slow the wave-induced bay–shelf exchange through vertical mixing and reduced shear-induced exchange. Five wave–current interactions are compared, and it is found that the depth-dependent wave radiation stress (WRS) contributes most to the bay–shelf exchange, followed by the wave dissipation as a source term in the turbulence kinetic energy equation, and the mean current advection and refraction of wave energy (CARWE). The vertical transfer of wave-generated pressure to the mean momentum equation (also known as the form drag) and the combined wave–current bottom stress (CWCBS) play minor roles in the bay–shelf exchange. The bay–shelf exchange is faster under southerly wind than under northerly wind because the bay is facing southeast; synoptic events such as storms enhance the bay–shelf exchange. The CARWE terms are dominant in both seasonal and synoptic variations of the bay–shelf exchange because they can considerably change the distribution of significant wave height. The WRS changes the bay–shelf exchange mainly through altering the flow velocity, whereas the wave dissipation on turbulence alters the vertical mixing. The form drag and the CWCBS have little impact on the bay–shelf exchange or its seasonal and synoptic variations.

Numerical Study on Coastal Wave and Near-Shore Current Interaction

2014 ◽  
Author(s):  
Jun Tang ◽  
Yongming Shen ◽  
Yigang Lv
Keyword(s):  
Wave Propagation ◽  
Numerical Model ◽  
Water Wave ◽  
Wave Radiation ◽  
Radiation Stress ◽  
Propagation Angle ◽  
Mild Slope Equation ◽  
Near Shore ◽  
Wave Induced ◽  
Wave Radiation Stress

Coastal waves and near-shore currents have been investigated by many researchers. This paper developed a two-dimensional numerical model of near-shore waves and currents to study breaking wave induced current. In the model, near-shore water wave was simulated by a parabolic mild slope equation incorporating current effect and wave energy dissipation due to breaking, and current was simulated by a nonlinear shallow water equation incorporating wave exerted radiation stress. Wave radiation stress was calculated based on complex wave amplitude in the parabolic mild slope equation, and this result in an effective method for calculating wave radiation stress using an intrinsic wave propagation angle that differs from the ones of using explicit wave propagation angle. Wave and current interactions were considered by cycling the wave and current equation to a steady state. The model was used to study waves and wave-induced longshore currents at the Obaköy coastal water which is located at the Mediterranean coast of Turkey. The numerical results for water wave induced longshore current were validated by measured data to demonstrate the efficiency of the numerical model, and water waves and longshore currents were analyzed based on the numerical results.

22. EFFECTS OF WAVE RADIATION STRESS AND VERTICAL MIXING ON STORM SURGE

2009 ◽  
Author(s):  
Nobuhito Mori ◽  
Rie Takada ◽  
Tomohiro Yasuda ◽  
Hajime Mase ◽  
Soo Youl Kim
Keyword(s):  
Storm Surge ◽  
Vertical Mixing ◽  
Wave Radiation ◽  
Radiation Stress ◽  
Wave Radiation Stress

scholarly journals A Combined Derivation of the Integrated and Vertically Resolved, Coupled Wave–Current Equations

2015 ◽  
Vol 45 (6) ◽  
pp. 1453-1463 ◽  
Author(s):  
George Mellor
Keyword(s):  
Fluid Dynamic ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
Momentum Equation ◽  
Ocean Dynamics ◽  
Stokes Drift ◽  
Wave Radiation ◽  
Two Dimensional ◽  
Wave Radiation Stress ◽  
Stress Term

AbstractThere exist different theories representing the effects of surface gravity waves on oceanic flow fields. In the past, the author has conjectured that the vertically integrated, two-dimensional fluid equations of motion put forward by Longuet-Higgins and Stewart are correct and that theories that differ from their theory cannot be entirely correct; this paper explores these differences. Longuet-Higgins and Stewart deduced vertically integrated, two-dimensional equations featuring a wave radiation stress term in the fluid dynamic, momentum equation. More recently, the author has proposed vertically dependent, three-dimensional equations that have required correction but when vertically integrated, agreed with the earlier, two-dimensional equations. This paper derives both vertically independent and vertically dependent equations from the same base and, importantly, using the same expression for pressure in the belief that the paper will contribute to the understanding and clarification of this seemingly difficult topic in ocean dynamics. An error in the classical papers by Longuet-Higgins and Stewart has been detected. Although the final phase-averaged result was correct, the error has had consequences in the development of vertically dependent equations. The prognostic equations in this paper are for the Eulerian current plus Stokes drift; toward the end of the paper these equations are contrasted with prognostic equations for the Eulerian current alone.

scholarly journals Five-year changes in anterior segment parameters in an older population in urban southern China: the Liwan Eye Study

2019 ◽  
Vol 104 (4) ◽  
pp. 582-587 ◽  
Author(s):  
Yu Jiang ◽  
Decai Wang ◽  
Wei Wang ◽  
Feng Chen ◽  
Lanhua Wang ◽  
...  
Keyword(s):  
Anterior Chamber ◽  
Pupil Diameter ◽  
Southern China ◽  
Anterior Segment ◽  
Population Based ◽  
Light Conditions ◽  
Anterior Chamber Angle ◽  
The Mean ◽  
Angle Width

PurposeTo investigate the 5-year changes in static and dynamic anterior segment optical coherence tomography (AS-OCT) parameters and their predictors.MethodsThis was a prospective, population-based cohort study of people aged 50 years and older residing in the Liwan District, Guangzhou, China. Standardised AS-OCT scans were performed in November 2008 and November 2013 under dark and light conditions. Customised software was used to analyse horizontal AS-OCT images. Parameters in dark and measurements of light-to-dark changes were used for analyses.ResultsA total of 186 (71.8%) subjects underwent AS-OCT twice, 5 years apart and were included for analyses. The mean age in 2008 was 64.7±7.0 years, and 60.2% were women. The anterior chamber width (ACW) decreased from 11.74±0.44 mm in 2008 to 11.60±0.37 mm in 2013 (p=0.001). There was a trend towards a decrease in dynamic capacity (light-to-dark changes) in the anterior segment, with decreased iris thickness at 750 µm (ΔIT750), ΔACW, Δ anterior chamber area (ACA) and Δ pupil diameter at 5 years (all p<0.05). After adjusting for age and sex, the following baseline parameters were associated with a greater decrease rate in trabecular iris space area at 500 µm (TISA500) at 5 years: TISA500, IT750 and ACA in dark (p<0.001 for all).ConclusionsAnterior chamber angle width decreased and the amount of light-to-dark changes declined during 5-year follow-up. Subjects with greater height, wider angle width and thicker iris at baseline have greater angle narrowing at follow-up.

scholarly journals Evaluating the Effects of Façade Greening on Human Bioclimate in a Complex Urban Environment

2015 ◽  
Vol 2015 ◽  
pp. 1-15 ◽  
Author(s):  
Britta Jänicke ◽  
Fred Meier ◽  
Marie-Therese Hoelscher ◽  
Dieter Scherer
Keyword(s):  
Heat Stress ◽  
Short Wave ◽  
Wave Radiation ◽  
Short Wave Radiation ◽  
Long Wave ◽  
Building Facades ◽  
Urban Heat ◽  
The Mean ◽  
Human Bioclimate ◽  
Radiant Temperature

The evaluation of the effectiveness of countermeasures for a reduction of urban heat stress, such as façade greening, is challenging due to lacking transferability of results from one location to another. Furthermore, complex variables such as the mean radiant temperature(Tmrt)are necessary to assess outdoor human bioclimate. We observedTmrtin front of a building façade in Berlin, Germany, which is half-greened while the other part is bare.Tmrtwas reduced (mean 2 K) in front of the greened compared to the bare façade. To overcome observational shortcomings, we applied the microscale models ENVI-met, RayMan, and SOLWEIG. We evaluated these models based on observations. Our results show thatTmrt(MD = −1.93 K) and downward short-wave radiation (MD = 14.39 W/m2) were sufficiently simulated in contrast to upward short-wave and long-wave radiation. Finally, we compare the simulated reduction ofTmrtwith the observed one in front of the façade greening, showing that the models were not able to simulate the effects of façade greening with the applied settings. Our results reveal that façade greening contributes only slightly to a reduction of heat stress in front of building façades.

Tracking the mean annual velocity and vertical mixing of bedload tracers

2020 ◽  
pp. 371-380
Author(s):  
A. Cain ◽  
M. Iannetta ◽  
C. Muirhead ◽  
E. Papangelakis ◽  
T. Raso ◽  
...  
Keyword(s):  
Vertical Mixing ◽  
The Mean

scholarly journals The Status and Associated Factors  of Early Childhood Caries among 3- to 5-year-old Children in Guangdong, Southern  China: A Provincial Cross-sectional Survey

2020 ◽  
Author(s):  
Jianbo Li ◽  
Weihua Fan ◽  
Yueshan Zhou ◽  
Linmei Wu ◽  
Wei Liu ◽  
...  
Keyword(s):  
Preschool Children ◽  
Oral Health ◽  
Associated Factors ◽  
Early Childhood Caries ◽  
Southern China ◽  
Guangdong Province ◽  
Deciduous Teeth ◽  
Cross Sectional Survey ◽  
Cross Sectional ◽  
The Mean

Abstract Background: Dental caries of deciduous teeth (Early Childhood Caries, ECC) has become a crucial oral health problem over the decades in China. The aim of this study was to examine the prevalence and severity of ECC among preschool children from Guangdong Province, Southern China. In addition, to assess the association of ECC with reported oral health-related behaviors.Methods: A cross-sectional survey was carried out in Guangdong Province by means of an equal-sized, stratified, multistage random sampling method. According to the standard for clinical dentition examination of the WHO 2013 criteria, the presence of ECC was determined by the dmft (decayed-missing-filled tooth) index using a CPI (Community Periodontal Index) probe. A questionnaire about caries-related factors was completed by each of the participants’ parents or grandparents through a face-to-face and one-on-one interview. Then, t-test, Chi2 tests, One-Way ANOVA served for statistical analysis, and logistic regression analysis as well as covariance analysis were executed to identify potential associated factors for ECC.Results: There were 2592 3- to 5-year-old preschool children. The prevalence (% dmft >0) of ECC was 68.3 (95% CI: 66.5-70.1), the mean dmft was 4.36 (95% CI: 4.17-4.55), and the filled rate was 1.2%. In multivariable modeling, associated factors for both prevalence and mean dmft were older age, rural areas, consumption of sweets before sleep, dental visit history, low household income, and low parental education level. Initiating toothbrushing after 3 years of age and being exclusively/ predominantly breastfed indicated only the prevalence; being female and frequently consuming sweetened milk/powdered milk indicated only the mean dmft.Conclusions: The preschool children in Guangdong Province experienced a significant amount of ECC. More attention should be given to children’s dental health for deciduous teeth. Associated factors for ECC included demographics, oral health measures, dietary factors, and socioeconomic factors.

scholarly journals Responses of runoff to historical and future climate variability over China

2017 ◽  
Author(s):  
Chuanhao Wu ◽  
Bill X. Hu ◽  
Guoru Huang ◽  
Peng Wang ◽  
Kai Xu
Keyword(s):  
Climate Variability ◽  
Arid Regions ◽  
Southern China ◽  
Aridity Index ◽  
Global Climate Models ◽  
Future Climate ◽  
Western China ◽  
Climate Projections ◽  
Positive Contribution ◽  
The Mean

Abstract. China has suffered some of the effects of global warming, and one of the potential implications of climate warming is the alteration of the temporal-spatial patterns of water resources. Based on the long-term (1960–2012) water budget data and climate projections from 28 Global Climate Models (GCMs) of the Coupled Model Intercomparison Project Phase 5 (CMIP5), this study investigated the responses of runoff (R) to historical and future climate variability in China at both grid and catchment scales using the Budyko-based elasticity method. Results show that there is a large spatial variation in precipitation (P) elasticity (from 1.2 to 3.3) and potential evaporation (PET) elasticity (from −2.3 to −0.2) across China. The P elasticity is larger in northeast and western China than in southern China, while the opposite occurs for PET elasticity. The catchment properties elasticity of R appears to have a strong non-linear relationship with the mean annual aridity index and tends to be more significant in more arid regions. For the period 1960–2012, the climate contribution to R ranges from −2.4 % a−1 to 3.3 % a−1 across China, with the negative contribution in the North China plain and the positive contribution in western China and some parts of the southwest. The results of climate projections indicate that although there is large uncertainty involved in the 28 GCMs, most project a consistent change in P (or PET) in China at the annual scale. For the period 2071–2100, the mean annual P will likely increase in most parts of China, especially the western regions, while the mean annual PET will likely increase in all of China, particularly the southern regions. Furthermore, greater increases are projected for higher emission scenarios. Overall, due to climate change, the arid regions and humid regions of China will likely become wetter and drier in the period 2071–2100, respectively (relative to the baseline 1971–2000).

scholarly journals Determinants of serum 25-hydroxyvitamin D in Hong Kong

2015 ◽  
Vol 114 (1) ◽  
pp. 144-151 ◽  
Author(s):  
Cuiling Xu ◽  
Ranawaka A. P. M. Perera ◽  
Yap-Hang Chan ◽  
Vicky J. Fang ◽  
Sophia Ng ◽  
...  
Keyword(s):  
Vitamin D ◽  
Hong Kong ◽  
Southern China ◽  
Age Groups ◽  
Dietary Vitamin ◽  
Skeletal Health ◽  
Mean Values ◽  
Hydroxyvitamin D ◽  
25 Hydroxyvitamin D ◽  
The Mean

Vitamin D plays an important role in skeletal health throughout life. Some studies have hypothesised that vitamin D may reduce the risk of other diseases. Our study aimed to estimate age-specific and sex-specific serum 25-hydroxyvitamin D (25(OH)D) status and to identify the determinants of serum 25(OH)D status in Hong Kong, a subtropical city in southern China. In 2009–2010, households in Hong Kong were followed up to identify acute respiratory illnesses, and sera from 2694 subjects were collected in three to four different study phases to permit measurement of 25(OH)D levels at different times of the year. A questionnaire survey on diet and lifestyle was conducted among children, with simultaneous serum collection in April and May 2010. The mean of serum 25(OH)D levels in age groups ranged from 39 to 63 nmol/l throughout the year with the mean values in all age groups in spring below 50 nmol/l. Children aged 6–17 years, and girls and women had significantly lower serum 25(OH)D levels than adults, and boys and men, respectively (allP< 0·001). We estimated that serum 25(OH)D levels in Hong Kong followed a lagged pattern relative to climatic season by 5 weeks with lowest observed levels in early spring (March). For children aged 6–17 years, reporting a suntan, having at least 1 servings of fish/week and having at least 1 serving of eggs/week were independently associated with higher serum 25(OH)D levels. Adequate sunlight exposure and increased intake of dietary vitamin D could improve vitamin D status, especially for children and females in the winter and spring.

Sign in / Sign up

Export Citation Format

Share Document