Study On the Hydraulic Characteristics of Taichung Harbour in Taiwan

For this study, field measurements of current profiles, buoy trajectories and the lag of two tidal stations were performed to explore the flow characteristics of Taichung Harbour. in order to distinguish the effects of wind drift current on circulation inside Taichung Harbour, field surveys during both summer and monsoon (winter) season were completed separately. the speed of the drift current was about 3.5% that of the, wind speed, based on the field data. the horizontal dispersion coefficients were close to Bowden's (1965) formula for the tidal current. the water temperature showed a two-layer profile, with the mixing thickness about 4 to 6 metres for the upper layer. the corresponding Richardson number was about 70. the tidal lag between the two tidal stations was 9.68 minutes. All the results agree well with the theoretical results.     

Effects of stream hydraulic conditions on foraging strategies of false dace, Pseudorasbora parva, in the lentic ecosystem

The effects of current velocity on the foraging behavior of false dace, Pseudorasbora parva, were examined in a zero velocity (stagnant) condition, and at four flow rates (5, 7, 11 and 16 cm per second). In stagnant water, the fish displayed a cruise-searching pattern, but they used a drift-feeding foraging tactic in flowing water. The shape of the transverse field of reaction field was elliptical in the stagnant condition, whereas their downward regions were restricted under the flowing conditions. The fish had a blind spot oriented directly in front of their reaction field. Although the relative swimming speed (with considering the against current velocity) increased with increasing flow velocity, the absolute search speed (ignore the against current velocity) showed about 1.2 fish body length per second at stagnant water and low flow velocity. The results of feeding rates showed stop-and wait (driff-feeding) foraging strategy is more efficient in flowing water because prey drift directly towards the fish and prey easily detected.     

Research On Zooplankton in the Gulf of Rapallo

Zooplankton samples, collected in autumn 1996 from two stations in the Gulf of Rapallo, Ligurian Sea (Rapallo Harbour and Prelo Bay, which is a more open site with lower human impacts) were analysed. at both stations, the community was dominated by copepods (mainly juveniles and adults of different species of Acartia and Oithona) and meroplankton (mainly polychaete larvae). Total zooplankton abundance in the harbour waters was significantly higher than in the nearby bay. the occurrence of Acartia grani in Rapallo Harbour and Pteriacartia josephinae in Prelo Bay is noteworthy, as they are reported for the first time in the Ligurian Sea, and A. grani has not previously been recorded to the Italian coastline. A three-day benthic chamber experiment aimed to quantify nutrient fluxes between the sediment and water column was performed in the Rapallo Harbour: the profound effects of confinement on the composition and abundance of zooplankton within the incubation chamber are discussed.     

Modeling the interaction between tides and storm surges for the Taiwan coast

An unstructured grid, two-dimensional hydrodynamic model was established and applied to the coast of Taiwan to investigate the tide-surge interaction. Tidal elevations at the open boundaries coupled with a global ocean tidal model and the meteorological conditions using a cyclone model are used to drive the model. The model was calibrated and verified with the observed tidal levels at six tidal stations for seven typhoon events to ascertain the capability and feasibility of the model. The results show reasonable agreement between the simulated and observed tidal levels. The validated model was then applied to probe the influence of tide-surge interaction on phase, water levels, and storm surge height. We found that the tide-surge interaction influenced both the magnitude and timing of the surge, which depended on the typhoon path. The storm surge heights at different tidal stations were significantly influenced by wind stresses and directions. The water level rise due to the storm surge during high tide was greater at neap tide than at spring tide. Changing tidal ranges altered the prediction of the surge enough to induce the changes in peak water levels.     

冬季降雪过程对城市大气气态汞污染的影响

2009年降雪和非降雪期间对北京西北城区的气态总汞浓度进行了连续采样,比较了降雪期间、非降雪期间的气态总汞浓度日变化过程;降雪期间气态总汞浓度的降低和恢复过程。结果表明,降雪和非降雪期间大气气态总汞浓度的日均值有显著差异,降雪期间气态总汞的平均浓度为5．64ng·m^-3,非降雪期间的平均浓度为7．43ng·m^-3,前者约为后者的70％。降雪后约7h气态总汞浓度恢复到降雪前水平。研究中分析了气象因素（气压、风速、阵风速度、气温和相对湿度）对于气态总汞浓度的影响,结果表明：降雪期间主要受到风速（r=-0．527）和阵风速度（r=-0．574）的影响;非降雪期间主要受到风速（r=-0．691）,阵风速度（r=-0．726）和相对湿度（r=0．692）的影响,并且相对湿度的影响与风速的影响相近。降雪和非降雪期间气态总汞的日变化有所差异：非降雪期间气态总汞浓度在午夜和清晨较高,日变化趋势与相对湿度一致;降雪期间气态总汞的日变化没有明显规律。     

The Coastal Environmental Characteristics of Taiwan

There are three major factors affecting the coastal environment in Taiwan: tidal current, long-shore current and land subsidence. in Taiwan, most industrial areas are located on the southwestern coast. Most of the pollutants from the factories are discharged directly to the ocean, harbours or rivers. the pollutants in harbours or rivers will eventually be delivered to coastal waters. There, the tidal current is the major force dispersing the pollutants nearshore. the polluted water extends to an area about 5 km on both sides from the discharge source, and within about 3-4 km off-shore. in this study, Hsien-Da Harbour in southwestern Taiwan is cited to explain the effects of tidal current on the coastal environment. the long-shore current induced by breaking waves is the major force shaping the coastal morphology. Along the western coast of Taiwan, the long-shore current mainly flows northward along the southern section, and southward along the northern section. in the last one hundred years, in general, the coast has been eroded along the northern and southern sections of western coast, and some reclaimed lands were formed in the middle section. Recently, erosion in some coastal zones is quite serious because of excess groundwater extraction, especially along the southwestern coast. Groundwater extraction might also induce land subsidence. There are some areas near the coast which suffer serious land subsidence problems.     

The Coastal Environmental Characteristics of Taiwan

Abstract

There are three major factors affecting the coastal environment in Taiwan: tidal current, long-shore current and land subsidence. in Taiwan, most industrial areas are located on the southwestern coast. Most of the pollutants from the factories are discharged directly to the ocean, harbours or rivers. the pollutants in harbours or rivers will eventually be delivered to coastal waters. There, the tidal current is the major force dispersing the pollutants nearshore. the polluted water extends to an area about 5 km on both sides from the discharge source, and within about 3–4 km off-shore. in this study, Hsien-Da Harbour in southwestern Taiwan is cited to explain the effects of tidal current on the coastal environment. the long-shore current induced by breaking waves is the major force shaping the coastal morphology. Along the western coast of Taiwan, the long-shore current mainly flows northward along the southern section, and southward along the northern section. in the last one hundred years, in general, the coast has been eroded along the northern and southern sections of western coast, and some reclaimed lands were formed in the middle section. Recently, erosion in some coastal zones is quite serious because of excess groundwater extraction, especially along the southwestern coast. Groundwater extraction might also induce land subsidence. There are some areas near the coast which suffer serious land subsidence problems.     

Spatio-temporal variation of near-surface wind speed over Qinghai-Tibet Plateau from 1970 to 2020北大核心CSCD

基于1970-2020年青藏高原区域及其附近154个气象站点的风速风向观测数据,采用线性拟合等方法,分析该地区年平均和季节平均近地面风速的时空分布特征和日变化特征.结果表明:(1)青藏高原区域1970-2020年年均风速在0.6-4.2m/s之间,青藏高原主体年均风速较高,高原周边地区风速较低;(2)青藏高原区域1970-2020年间近地面风速呈极显著下降趋势,2000年以后呈极显著增加趋势;(3)青藏高原区域1970-2020年间近地面风速春季最大,冬、夏次之,秋季最小,不同季节平均风速均是高原主体大于高原周边,4个季节的平均风速均呈极显著降低趋势,春季平均风速降低的速率最大;(4)大气环流驱动力的减弱可能是青藏高原区域地面风速呈减弱趋势的主导性因素.青藏高原近地面风速显著的变化特征可为青藏高原风能资源开发利用、农林生态系统开发与保护等提供科学依据.(图5参46)     

Modelling dependence structures of extreme wind speed using bivariate distribution: a Bayesian approach

When investigating extremes of weather variables, it is seldom that a single weather station determines the damage, and extremes may be caused from the combined behaviour of several weather stations. To investigate joint dependence of extreme wind speed, a bivariate generalised extreme value distribution (BGEVD) was considered from frequentist and Bayesian approaches to analyse the extremes of component-wise monthly maximum wind speed at selected weather stations in South Africa. In the frequentist approach, the parameters of extreme value distributions (EVDs) were estimated with maximum likelihood, whereas in the Bayesian approach the Markov Chain Monte Carlo (MCMC) technique was used with the Metropolis–Hastings algorithm. The results showed that when fitted to component-wise maxima of extreme weather variables, the BGEVD provided apparent benefits over the univariate method, which allowed information to be pooled across stations and resulted in improved precision of the estimates for the parameters and return levels of the distributions. The paper also discusses a method to construct informative priors empirically using historical data of the underlying process from weather characteristics of four pairs of surrounding weather stations at various distances. The results from the Bayesian analysis showed that posterior inference might be affected by the choice of priors that were used to formulate the informative priors. From the results, it could be inferred that the Bayesian approach provides a satisfactory estimation strategy in terms of precision, compared with the frequentist approach, because it accounts for uncertainty in parameters and return level estimations.     

Facilitation by Pinus flexilis during succession: a hierarchy of mechanisms benefits other plant species

Studies of facilitation have primarily been limited to single mechanisms, species, or environments. We examined interacting mechanisms governing the facilitative effects of Pinus flexilis on two later successional understory species, Pseudotsuga menziesii and Ribes cereum, in different microhabitats and seasons at the ecotone between the Rocky Mountain forests and Great Plains grasslands in Montana, USA. In field surveys, 69% of Pseudotsuga and 91% of Ribes were located beneath P. flexilis even though P. flexilis subcrowns accounted for a small proportion of available habitat. For three years, we monitored the survival of Pseudotsuga and Ribes seedlings experimentally planted beneath P. flexilis and in the open at a windward and a leeward site. Survival of both species was highest beneath P. flexilis at a site topographically protected from strong unidirectional winds (38% for Pseudotsuga and 63% for Ribes), and lowest at a windward site and in the open where tree crowns did not provide shelter from winds (2% and 6%, respectively). These results suggest that wind amelioration contributed to the facilitative effect of P. flexilis. However, even at the leeward site, where wind speed was low, survival of Pseudotsuga and Ribes was higher beneath P. flexilis, suggesting the importance of shade. To explore the relative importance of different mechanisms, we designed an experiment with six treatments: "shade," "shade + wind," "shade + drift," "wind," "drift," and a "control." After two years, we found shade to be of overwhelming importance for the survival of Pseudotsuga and Ribes. Without shade, no other treatments were significant, but once shade was provided, wind amelioration and snow pack accumulation increased survival of Pseudotsuga, suggesting that these different facilitative mechanisms functioned in a nested hierarchical manner: some mechanisms were important only when others were already functioning. Many studies have demonstrated multiple interacting mechanisms in the way that plants interact, but to our knowledge hierarchical interactive processes have not been previously documented. If the effects of positive or competitive mechanisms are often hierarchical, then studies of isolated mechanisms may not accurately assess their importance in nature.     

Diving of the sea snake Pelamis platurus in the Gulf of Panamá

The horizontal movement patterns of eleven yellow-bellied sea snakes [Pelamis platurus (Linnaeus)] were determined incidentally to acoustic tracking studies of their diving behavior in the Gulf of Panamá during 1983–1985. The average speed of the snakes was 1.9 km h^-1 (range 0.3 to 7.1 km). Movement direction is influenced by phasic northsouth tidal currents and secondarily affected by combinations of factors that affect local current velocity. The velocity of diving snakes did not always agree with that observed for the surface current. Drift rate was not correlated with average or maximum dive depth, however, snakes that surfaced to breathe one or more times during a period had greater average drift rates than those that did not surface. The role of such factors as feeding, predator avoidance, thermoregulation, orientation, and the avoidance of surface turbulence are considered in a discussion of the adaptive significance of diving for P. platurus. Diving in this species may enable it to avoid surface disturbance, facilitate relative position changes within the surface drift, and contribute to various aspects of its feeding behavior.     

Looking for the clock mechanism responsible for circatidal behavior in the oyster Crassostrea gigas

Valve activity rhythm of the oyster Crassostrea gigas is mainly driven by tides in the field, but in the laboratory, only a circadian clock mechanism has been demonstrated. In an attempt to reconcile these results, the mechanisms underlying the circatidal rhythm were studied in the laboratory under different entrainment or free-running regimes and in the field at Arcachon (44°39′N/1°09′W) in February–April 2011). Results confirm the existence of a circadian clock in C. gigas. Under entrainment regimes (12-h dark/12-h light photoperiod and tidal cycles simulated by a reversing current flow), oysters exhibited both circadian and circatidal cycles. Under free-running conditions (e.g., continuous darkness), the endogenous rhythm appeared to be circadian. There was no experimental evidence for an endogenous circatidal rhythm, even in oysters just transferred from the field, where a clear tidal cycle was expressed. There are two possible mechanisms to explain tidal behavior in C. gigas: an exogenous tidal cue that drives tidal activity and masks the circadian rhythm and an endogenous circatidal clock that is sensitive to tidal zeitgebers and runs at tidal frequency.     

The Water Quality of Kingston Harbour: Evaluating the Use of the Planktonic Community and Traditional Water Quality Indices

Abstract

Kingston Harbour has been experiencing increased levels of organic pollution since initial ecological assessments in 1971. to develop a new baseline of eutrophication in the Harbour 20 years later, and determine the most appropriate indices to be used in the continued monitoring the area, the water quality of Kingston Harbour was reassessed between December 1992 and 1993, by contemporaneous sampling of traditional water column parameters and planktonic communities at 28 stations within the Harbour. Indices used for water quality assessment were temperature, salinity, light penetration, dissolved oxygen, BOD and nutrients (nitrates-N, phosphate-P and ammonia-N). Results indicated that the planktonic community provided the most reliable index of increased eutrophication and changes in water quality. While physical variables indicated little change in Harbour waters and chemical variables indicated significant but erratic changes, the planktonic community displayed the classic characteristics of eutrophication. Phytoplankton biomass (a maximum of 148 mg m^?3 chlorophyll a) was 5 to 10 times greater than in 1971 while zooplankton abundances (maximum of 80,000 animals m^?3) were 4 times greater. in both cases the community composition had altered and there were fewer taxa than previously found.     

Sediment resuspension by wind in a shallow lake of Esteros del Iberá (Argentina): a model based on turbidimetry

A model based on empirical relationships is used to study frequency and magnitude of the sediment resuspension by wind-induced waves. The model has been developed for Laguna Galarza, a mesotrophic round-shaped shallow lake located in Esteros del Iberá wetland. Given the logistic and accessibility difficulties of this macrosystem, the installation of automated field stations facilitated continuous data acquisition. Using the wave theory, a daily spatial model of resuspension was built from simultaneous time series of hourly measurements of infrared nephelometric turbidity, wind speed and wind direction. The model was used to predict total suspended solids in another lake of the wetland (Laguna Iberá) showing a good agreement with observed field values, even although Laguna Iberá has a more irregular contour and a eutrophic state. Finally, we apply the model to discuss the ecological impacts of resuspension on the distribution of the littoral communities and to characterize the composition of the particulate suspended matter of the limnetic ecosystem. The model was useful to simulate the possible implications of the recent alterations of the wetland water level on the resuspension regime of the open water bodies.     

Exaggerated orientation scatter of nocturnal passerine migrants close to breeding grounds: comparisons between seasons and latitudes

Using tracking radars, we investigated the variability of flight directions of long-distance nocturnal passerine migrants across seasons (spring versus autumn migration) and sites at the southern (56° N) and northern (68° N) ends of the Scandinavian Peninsula (Lund versus Abisko). Whilst most migrants at Lund are on passage to and from breeding sites in Fennoscandia, the majority of the migrants at Abisko are close to their breeding sites, and migration at Abisko thus to a large degree reflects initial departure from breeding sites (autumn) or final approach to breeding destinations (spring). The radar data were used to test predictions about differences in orientation and wind drift effects between adult and juvenile birds (a large proportion of autumn migrants consists of juvenile birds on their first journey), between situations far away from or near the goals and between different phases of migration (initial departure, en route passage, final approach to goal). The concentrations (both total and within-night concentrations) of flight directions differed significantly between seasons as well as sites, with the highest concentration at Lund in spring (mean vector length of track directions, r = 0.79) and lowest at Abisko during spring (r = 0.35). Partial wind drift and partial compensation were recorded at Lund, with a similar effect size in spring and autumn, whilst possible wind drift effects at Abisko were obscured by the large directional scatter at this site. The results from Lund support the prediction that the high proportion of juveniles in autumn contributes to increase the directional scatter during this season, whilst there was no support for predictions of differential wind drift effects between seasons and situations with different goal distances. The most striking and surprising result was the exceedingly large scatter of flight directions at Abisko, particularly in spring. We suggest that such an exaggerated scatter may be associated with final approach orientation, where migrants reach their specific goals from all various directions by final navigation within a more wide-ranging goal region. The larger scatter of autumn flight directions at Abisko compared to Lund may be due to exploratory flights in variable directions being more common at initial departure from breeding sites than later during migratory passage. These surprising results highlight the importance of studying and analysing orientation during final approach to (and initial departure from) migratory goals for understanding the orientation systems of migratory birds.     

河西地区近50年参考作物蒸散量的演变趋势及其影响因素

根据河西地区17站点近50年的逐日气象资料,利用Penman-Monteith方程计算了逐日ET0,以Mann-Kendall法对各站不同季节、年ET0平均总量进行趋势检验。结果表明：武威、古浪、天祝3站年ET0呈增加趋势,其余14站均呈下降趋势,其中有9站通过显著性水平检验。春、夏、秋、冬四季酒泉地区和张掖地区各站ET0值均呈下降趋势,武威地区各站变化趋势不一致,且前者ET0值下降趋势总体较后者明显。典型站点ET0与气候要素多元线形回归分析表明：风速是不同季节、不同站点影响ET0变化的首要因子。其次,最高温度、相对湿度、日照时数也是影响年ET0及各站点不同季节ET0变化的主要因子。     

Bayesian modelling of extreme wind speed at Cape Town,South Africa

In the framework of generalized extreme value (GEV) distribution, the frequentist and Bayesian methods have been used to analyse the extremes of annual maxima wind speed recorded by automatic weather stations in Cape Town, Western Cape, South Africa. In the frequentist approach, the GEV distribution parameters were estimated using maximum likelihood, whereas in the Bayesian method the Markov Chain Monte Carlo technique with the Metropolis–Hastings algorithm was used. The results show that the GEV model with trend in the location parameter appears to be a better model for annual maxima data. The paper also discusses a method to construct informative priors empirically using historical data of the underlying process from other weather stations. The results from the Bayesian analysis show that posterior inference might be affected by the choice of priors and hence by the distance between a weather station used to formulate the priors and the point of interest.     

Maximum feasible distance of windborne cross-pollination in Brassica napus: A ‘mass budget’ model

A theory of gene dispersal by wind pollination can make an important contribution to understanding the viability and evolution of important plant groups in the Earth's changing landscape and it can be applied to evaluate concerns about the spread of engineered genes from genetically modified (GM) crops into conventional varieties via windborne pollen. Here, we present a model of cross-pollination between plant populations due to the wind. We perform a ‘mass budget’ of pollen by accounting for the number of pollen grains from release in the source population, dispersal from the source to the sink population by the wind, and deposition on receptive surfaces in the sink population. Our model can be parameterised for any wind-pollinated species, but we apply it to Brassica napus (oilseed rape or canola) to investigate the threat posed by wind pollination to GM confinement in agriculture. Specifically, we calculate the maximum feasible distance at which a particular level of windborne gene dispersal could be attained. This is equivalent to the separation distance between populations or fields required to achieve a given threshold of gene dispersal or adventitious GM presence. As required, model predictions of the upper bounds on levels of wind-mediated gene dispersal exceed observations from a wide range of published studies. For a level of gene dispersal below 0.9%, which is the EU threshold for GM adventitious presence, we predict that the maximum feasible distance for agricultural fields of B. napus is 1000 m, regardless of field shape and direction of prevailing winds. For fields closer than 1000 m, our model results do not necessarily imply that the 0.9% threshold is likely to be breached, because in this instance we have conservatively set the values of parameters where current knowledge is limited. We also predict that gene dispersal is reduced by 50% when the lag in peak flowering between the source and sink populations is 13 days, and reduced by 90% when the lag is 24 days. We identify further measurements necessary to improve the accuracy of the model predictions.     

An approach to simulate wind fields around an urban environment for wind energy application

This work proposes an approach to simulate wind flow fields around an urban environment with the aim of evaluating the potential impact of buildings on the general wind patterns and power production using the current generation of commercial wind turbines. The simulation process was performed with the aid of accessible computational tools that can potentially render the proposed procedure applicable in other cases of interest. The roughness of the urban environment was defined as the association of roughness map, topography, and an alternative process for obtaining the volumetry of buildings. A case study was conducted in a region located at the district of Boa Viagem (Recife-PE) for assessing the applicability of the approach. Scenarios were designed in order to simulate wind flow patterns and pre-identify sites that have suitable wind energy potential for electric power production by investigating the combination of wind speed magnitude and turbulence intensity. From the results obtained, it was possible to identify zones of potential wind sources that are not detected in classical wind atlas probably due to the influence of the built environment on local wind flow patterns.     

Is wind drift in migrating barnacle and brent geese, Branta leucopsis and Branta bernicla, adaptive or non-adaptive?

Whether migrating birds compensate for wind drift or not has been discussed frequently during the last decades. Observed behaviours seem to differ between species and situations. Even though complete compensation allows a bird to fly the shortest distance during its migration, this is not necessarily the optimal solution in all cases. There are certain situations when drifting with the wind, and thus getting higher groundspeed, will be more beneficial, i.e. adaptive drift. In this article, I analyse flight directions of spring migrating barnacle and brent geese, tracked by radar and optical range finder, and compare these with prevailing winds to see if these birds compensate or drift with the wind. I also use wind data from the days when the trackings were made to construct expected flight paths to see whether wind drift or compensation would be the most beneficial behaviour. The geese were found to drift partially with the wind. The drift effect was concluded to be true partial drift, i.e. not pseudodrift or drift forced by strong winds. The drift was not found to be of any obvious adaptive value, as the geese drifted irrespective of the strategy that would have been most beneficial to them. None of the situations in which drift is predicted to be adaptive was applicable to the birds and migration days in this study. A possible explanation for the observed pattern is that since these birds usually have access to favourable winds during their spring migration, selection pressures for adaptive drift or compensation behaviours might be weak.