Estimation of stream temperature in firtina creek (Rize-Turkiye) using artificial neural network model

Water temperature is one of the most important environmental variables in aquatic ecosystem. Temperature changes may have positive or negative effects on organisms. High water temperatures have caused mortalities in salmonid fishes. Therefore, monitoring and prediction of potential adverse changes in water temperature is very important. Here, we have developed and tested an artificial neural network (ANN) model to predict stream temperature of Firtina Creekin Black Sea region; using local water temperature, dissolved oxygen, pH and other available meteorological data (air temperature, rainfall). Thus, enabling define suitable habitat for native Sea Trout (Salmo trutta labrax, Pallas 1811) under past drought or other adverse envIronmental conditions.     

Simulating wildfire patterns using a small-world network model

This paper presents the development and validation results of a weighted small-world network model designed to simulate fire patterns in real heterogeneous landscapes. Fire spread is simulated on a gridded landscape, a mosaic in which each cell represents an area of the land surface. In this model, the interaction between burning and non-burning cells (here, due to flame radiation) may extend well beyond nearest neighbors, and depends on local conditions of wind, topography, and vegetation. An approach based on the coupling of the solid flame model with the Monte Carlo method is used to predict the radiative heat flux from the flame generated by the burning of each combustible cell to its neighbors. The weighting procedure takes into account latency (a combustible cell will only ignite when it has accumulated enough energy along time) and flaming persistence of burning cells. The model is applied to very different fire scenarios: a historical Mediterranean fire that occurred in southeastern France in 2005 and experimental fires conducted in arid savanna fuels in South Africa in 1992. Model results are found to be in agreement with real fire patterns, in terms both of rate of spread, and of the area and shape of the burn. This work also shows that the fractal properties of fire patterns predicted by the model are similar to those observed from satellite images of three other Mediterranean fire scars.     

Estimation of the density of a clustered point pattern using a distance method

Distance-based methods use point-to-point distances or random-location-to-point distances in a cloud of points to estimate characteristics of the point pattern. One such characteristics is the density of points. The difficulty with distance-based density estimators is that their distribution depends on the spatial pattern of points. In particular, the distribution of distances is untractable for usual clustered patterns, that are often observed in natural systems. Here, we propose a density estimator for clustered patterns, based on the random-location-to-pth-point distance X _p . An approximate expression for the distribution function, F _p , of X _p was obtained by identifying the first two moments of the count of individuals in disks for a given point process with the first two moments of a negative binomial distribution. The approximate expression of F _p was then used to derive a maximum-likelihood estimator of the intensity of the point process. The quality of the approximation of F _p was assessed for homogeneous Poisson processes (for which the expression of F _p is exact) and for Matérn processes. The intensity estimator based on Matérn processes was then used to estimate tree density in a tree savanna in Mali, and it compared favorably with six robust estimators found in the literature.     

陕西关中城市群热岛效应指标初探

选取陕西关中地区12个大、小城市,1970—2009年逐月平均最高、最低和平均气温资料进行不同季节的城市热岛效应分析,对描述热岛效应的热岛强度指标进行研究,并提出以华县站为对比站的改进型温度差直线趋势作为关中城市群热岛强度衡量指标。该指标既消除了局地气候变化影响又剔除了个别小城市增温速率过快的影响。计算结果发现：无论城市规模大小,关中城市群一年四季都存在热岛效应。热岛强度冬春季强,夏秋季弱。大城市的热岛强度无论季节或年增加幅度均比小城市大。     

Assessment of canopy stomatal conductance models using flux measurements

Stomatal conductance (g) is a key parameter in controlling energy and water exchanges between canopy and the atmosphere. Stomatal conductance models proposed by Ball, Woodrow and Berry (BWB) and Leuning have been increasingly used in land surface schemes. In a recent study, a new diagnostic index was developed by Wang et al. to examine the response of g to humidity and new models were proposed to resolve problems identified in the BWB and Leuning models. This approach is theoretically sound, but relies on canopy latent heat and CO₂ fluxes and environmental variables at the leaf surface which are not available at most eddy correlation (EC) observation sites. In this study, we tested the diagnostic index by empirically correcting EC measurements to canopy-level fluxes and by replacing leaf surface variables by their corresponding ambient air variables, and re-examined the stomatal conductance models of BWB, Leuning, and Wang et al. We found that the impact of the above modifications on the evaluation of g–humidity relationships is very small. This study provides a practical approach to investigate the stomatal response to humidity using routine EC measurements.     

杭州城市热岛空间分布及时域-频域多尺度变化特征

利用杭州20个自动气象站逐时数据计算2006年四季各站平均热岛强度,用薄盘样条函数法研究杭州城市热岛的空间变化,发现:夏秋季时较强,而春冬季强度较弱;总体趋势是杭州市丰体城区最大,向外辐散,逐渐减弱.利用2006年2月～2007年2月逐时气象数据,结合Morlet小波变换方法分析了杭州热岛周期变化特征,发现:其在频域上具有多尺度的周期振荡,尺度主要是24 h(日)、168 h(周)和1 490 h(2月).以日为周期的热岛强度与局地气候系统、地面长波辐射、近地层热量交换、人为热的日周期变化有关;而以周为周期的热岛强度变化成因主要与人类活动及城市大气污染物排放的"周末效应"有显著的关系;以2个月为周期的变化特征与一些较大尺度的自然变化相关.结果表明,杭州城市热岛时空变化是天气系统、地面长波辐射、下垫面、大气污染、人为热、人类活动、近地层热量交换等共同作用的结果.     

天津城市热岛效应演变特征研究

城市热岛效应对城市生态环境影响极大,城市热岛及其环境效应的研究有利于城市合理规划和可持续发展。本文利用天津市1964—2003年城郊气温,1993年6月15日和2001年5月12日不同时间陆地卫星遥感资料分析了天津市热岛演变特征,结果显示天津城市发展对热岛效应影响明显,随年代以0.11℃/10a速率加强;2002年最强为1.2℃,是60年代末的2倍。7月份的热岛强度增强趋势明显;用平均气温分析热岛强度变化趋势表明:热岛强度在秋季最强春季最小,分别为0.16℃/10a和0.06℃/10a。平均最高气温差在四季中均有微弱上升趋势,平均为0.06℃/10a;平均最低气温差在秋季和冬季上升幅度最大,分别为0.16℃/10a和0.12℃/10a。不同年代遥感亮温场也表明天津城市化对热岛空间分布的影响。热岛分布基本与建成区一致,热岛中还包括许多大小不同、形状各异、强度有别的小热岛群;而且随着城市的发展,热场范围呈扩大趋势。最后对热岛变化规律的成因进行了初步分析。     

Using a 1-D mixing model to simulate the vertical flux of heat and oxygen in a lake subject to episodic mixing

A one-dimensional, two-layer lake model is used to simulate the daily temperature and oxygen profile of an English Lake in response to changes in wind, air temperature and radiation. The thermal model component derives from the TEMIX lake model originally developed by the Institute of Limnology in St. Petersburg [Mironov, D.V., Golosov, S.D., Zilitinkevitch, S.S., Kreiman, K.D., Terzhevik, A.Y., 1991. Seasonal changes of temperature and mixing conditions in a lake. In: Zilitinkevitch, S.S. (Ed.), Modelling Air–Lake Interactions. Springer-Verlag, pp. 74–90]. This paper describes the model's adaptation and its extension to incorporate dissolved oxygen to simulate periods of anoxia of short duration during summer stratification. The new oxygen model component, which is based on mass-balance principles, divides the lake into two layers in a similar way to the thermal model. Its primary purpose is to model periods of anoxia for use in studies of fish survival. The model has been tested over a 10-year period from 1991 to 1999 using daily weather data and fortnightly observations of chlorophyll a and secchi depth. Ten years of fortnightly oxygen measurements, together with 2 years of more detailed (hourly) oxygen data, indicate that simulated and observed oxygen levels are in reasonable agreement considering the sparseness of the chlorophyll observations. The balance between the relative effects of temperature and BOD on oxygen depletion is of particular importance to model accuracy.     

功能区对热岛发生频率及其强度的影响

通过定点观测的方法对商业区、工业区、社区和森林公园的热岛发生频率及其强度进行了研究.结果显示,功能区对热岛发生频率及其强度具有明显的影响,但在各季节影响规律各不相同.总体来说,商业区和森林公园对热岛发生频率及其强度影响较大,商业区对热岛效应具有正效应.而森林公园对其则趋向于负效应.结果表明,城市各功能区的热岛效应可以通过生态型功能区规划和特殊管理方式进行缓解.     

我国中亚热带人工林水热通量对干旱差异响应的模拟研究

季节性干旱现象在我国中亚热带地区时有发生,为了研究该区域大气-生态系统之间的相互作用关系及其碳水收支状况,2002年起在江西省千烟洲（26.7°N,115.1°E）人工林生态系统建立了通量观测塔。2003年7月该人工林生态系统遭遇了历史上少有的高温少雨天气,本研究应用基于生理生态学过程的EALCO（Ecological Assimilation of Land and Climate Observation）模型及2003和2004年通量观测数据对该生态系统的水热通量进行了模拟,同时分析了干旱胁迫对它们产生的影响。结果显示,模型能够很好的模拟该生态系统的能量通量的日变化,净辐射、显热和潜热通量模拟值与实测值相关系数的平方（R2）及标准差分别为0.99和8.05 W.m-2;0.81和41.02 W.m-2;0.90和31.49 W.m-2,模型可以解释87%的日蒸散量的变化。从模拟结果看,2003年7月下旬（发生较严重干旱胁迫）较2004年同期（干旱程度轻）相比,冠层及土壤水势下降约2倍,植物蒸腾的日变化形式改变,根系吸水滞后冠层蒸腾的时间缩短约半小时,冠层导度下降40%～60%。模拟与观测结果均表明,2003年7月下旬每天正午的波文比大都介于1～2.2,而2004年同期正午的波文比则介于0.2～0.6。EALCO模型通过Ball模型将植物碳水过程耦合在一起,从而可以很好的模拟植物的气孔行为,进而准确的模拟植物水热过程对干旱的响应。土壤水分匮乏对冠层导度的限制是2003年干旱期间冠层潜热通量模拟值下降的根本原因。     

我国中亚热带人工林水热通量对干旱差异响应的模拟研究

季节性干旱现象在我国中亚热带地区时有发生,为了研究该区域大气-生态系统之间的相互作用关系及其碳水收支状况,2002年起在江西省千烟洲(26.7°N,115.1°E)人工林生态系统建立了通量观测塔。2003年7月该人工林生态系统遭遇了历史上少有的高温少雨天气,本研究应用基于生理生态学过程的EALCO(Ecological Assimilation of Land and Climate Observation)模型及2003和2004年通量观测数据对该生态系统的水热通量进行了模拟,同时分析了干旱胁迫对它们产生的影响。结果显示,模型能够很好的模拟该生态系统的能量通量的日变化,净辐射、显热和潜热通量模拟值与实测值相关系数的平方(R2)及标准差分别为0.99和8.05 W.m-2;0.81和41.02 W.m-2;0.90和31.49 W.m-2,模型可以解释87%的日蒸散量的变化。从模拟结果看,2003年7月下旬(发生较严重干旱胁迫)较2004年同期(干旱程度轻)相比,冠层及土壤水势下降约2倍,植物蒸腾的日变化形式改变,根系吸水滞后冠层蒸腾的时间缩短约半小时,冠层导度下降40%～60%。模拟与观测结果均表明,200...     

An analytical model of an urban heat island circulation in calm conditions

Environmental Fluid Mechanics - We obtain an analytical model solution to an idealization of an urban heat island (UHI) circulation—the steady shallow convective flow of a viscous stably...     

热传导强化气相抽提处理苯系物污染土壤实验

以苯系物(BTEX)污染土壤为研究对象,研究加热源功率和加热时间对土壤苯系物去除率的影响;实验通过分析尾气和冷凝水的污染物浓度来判断实验的终止时间点.结果显示,在3个功率100、200 W和400 W作用下,各污染物的残留浓度较低,所需要的处理时间分别为168.5、122.5 h以及104 h,消耗的总电能分别为:0.49、0.56 KW.h.Kg-1TS以及0.81 kW.h.Kg-1TS.功率越高,土壤中BTEX去除效率越高,同时能耗也越大.实验通过分析处理前后土壤中有机质含量,发现在加热的条件下有机质会逐渐减少,功率越高,有机质去除的速率越快,越有利于污染物的去除.本文的结果可证实通过加热可有效提高土壤中苯系物的气相抽提去除效率,对现场中试的开展提供参数依据.     

深圳市蛇口半岛人工填海及其城市热岛效应分析

为满足日益增长的土地需求,人工填海已成为目前世界范围内沿海地区城市空间扩张的主要方式。深圳作为中国首批经济特区和改革开放先锋,在经历30多年经济高速发展和城市快速变迁后,已由过去的小渔村发展为现代化国际大都市,与此同时,也开展了大量人工填海工程。城市热岛效应,作为城市热环境评价的重要指标,随着人工填海的快速推进会愈发明显,从而会导致城市热环境和微气候改变,加剧大气污染,严重影响着城市人居生态环境。然而,针对人工填海对城市热岛效应影响的具体研究并不多见。基于TM及ETM+遥感数据,对深圳市蛇口半岛人工填海区域的城市扩张及其热岛效应进行了分析,并对该区域地表温度的变化与归一化植被指数(NDVI)的关系进行了探讨,以期为沿海地区城市热环境的研究和空间地理的合理规划提供参考。结果表明,①该区域1999年至2009年间人工填海面积增加近16 km2,相当于1999年整个蛇口半岛面积的1/3。②利用城市热岛效应表达模型对1999年、2009年蛇口半岛的热岛分布等级进行了分析。研究表明,2009年热岛区域较1999年显著扩张,绿岛面积显著减少,弱热岛、中等热岛、强热岛面积均有不同程度地增长。强热岛正向变化最显著,2009年的强热岛面积相较于1999年增加了5.5倍,中等热岛的扩张面积也超过了1999年的4倍。③热岛扩张区域与人工填海增加区域高度吻合,可见人工填海工程显著增强了城市的热岛效应。④蛇口半岛区域地表温度与植被指数NDVI呈现显著负相关(P<0.01)。地表温度在蛇口半岛两侧的人工填海区形成高值区,在南山和赤湾山植被覆盖指数较高的区域形成低值区,而城市建筑群居中。     

Modelling the dynamics of coral reef macroalgae using a Bayesian belief network approach

Macroalgae are a major benthic component of coral reefs and their dynamics influence the resilience of coral reefs to disturbance. However, the relative importance of physical and ecological processes in driving macroalgal dynamics is poorly understood. Here we develop a Bayesian belief network (BBN) model to integrate many of these processes and predict the growth of coral reef macroalgae. Bayesian belief networks use probabilistic relationships rather than deterministic rules to quantify the cause and effect assumptions. The model was developed using both new empirical data and quantified relationships elicited from previous studies. We demonstrate the efficacy of the BBN to predict the dynamics of a common Caribbean macroalgal genus Dictyota. Predictions of the model have an average accuracy of 55% (implying that 55% of the predicted categories of Dictyota cover were assigned to the correct class). Sensitivity analysis suggested that macroalgal dynamics were primarily driven by top–down processes of grazing rather than bottom–up nutrification. BBNs provide a useful framework for modelling complex systems, identifying gaps in our scientific understanding and communicating the complexities of the associated uncertainties in an explicit manner to stakeholders. We anticipate that accuracies will improve as new data are added to the model.     

Structure of a dense release produced by varying initial conditions

Buoyancy driven flows such as gravity currents, present in nature and human made applications, are conveyors of particles or dissolved substances for long distances with clear implications for the environment. This transport depends on the triggering conditions of the current. Gravity currents are experimentally simulated under varying initial conditions by combining three different initial buoyancies and five volumes of dense fluid released. The horizontal and vertical structures of the gravity currents are analysed and it is shown that the variation on the initial configuration is conditioning for these. Vertical transport through the gravity current is influenced at the bottom by the solid wall over which the current flows, and at the upper interface by the contact with the ambient water. The relative contribution of shear stress at the bottom and at the upper interfaces are estimated and analysed in terms of the initial triggering conditions of the current; these two compete with the buoyancy, the driver of the current, determining mixing and entrainment. By using a proper parametrization, which accounts for both initial volume of release and location of the observation position relative to the lock, a relation between the resistance at the bottom and at the upper interfaces with the initial conditions of release (i.e. the lock-length) has been found; this is found to be independent of the initial density in the lock. The present study shows that the variation of the initial conditions have consequences on (1) the configuration of the currents and on (2) the hydrodynamics of the currents, including mass and momentum exchanges, which are in addition mutually dependent.     

Design of a water quality monitoring network in a large river system using the genetic algorithm

Despite several decades of operations and the increasing importance of water quality monitoring networks, the authorities still rely on experiential insights and subjective judgments in siting water quality monitoring stations. This study proposes an integrated technique which uses a genetic algorithm (GA) and a geographic information system (GIS) for the design of an effective water quality monitoring network in a large river system. In order to develop a design scheme, planning objectives were identified for water quality monitoring networks and corresponding fitness functions were defined using linear combinations of five selection criteria that are critical for developing a monitoring system. The criteria include the representativeness of a river system, compliance with water quality standards, supervision of water use, surveillance of pollution sources and examination of water quality changes. The fitness levels were obtained through a series of calculations of the fitness functions using GIS data. A sensitivity analysis was performed for major parameters such as the numbers of generations, population sizes and probability of crossover and mutation, in order to determine a good fitness level and convergence for optimum solutions. The proposed methodology was applied to the design of water quality monitoring networks in the Nakdong River system, in Korea. The results showed that only 35 out of 110 stations currently in operation coincide with those in the new network design, therefore indicating that the effectiveness of the current monitoring network should be carefully re-examined. From this study, it was concluded that the proposed methodology could be a useful decision support tool for the optimized design of water quality monitoring networks.     

Estimation of distribution algorithm enhanced particle swarm optimization for water distribution network optimization

The optimization of a water distribution network (WDN) is a highly nonlinear, multi-modal, and constrained combinatorial problem. Particle swarm optimization (PSO) has been shown to be a fast converging algorithm for WDN optimization. An improved estimation of distribution algorithm (EDA) using historic best positions to construct a sample space is hybridized with PSO both in sequential and in parallel to improve population diversity control and avoid premature convergence. Two water distribution network benchmark examples from the literature are adopted to evaluate the performance of the proposed hybrid algorithms. The experimental results indicate that the proposed algorithms achieved the literature record minimum (6.081 M$) for the small size Hanoi network. For the large size Balerma network, the parallel hybrid achieved a slightly lower minimum (1.921M€) than the current literature reported best minimum (1.923M€). The average number of evaluations needed to achieve the minimum is one order smaller than most existing algorithms. With a fixed, small number of evaluations, the sequential hybrid outperforms the parallel hybrid showing its capability for fast convergence. The fitness and diversity of the populations were tracked for the proposed algorithms. The track record suggests that constructing an EDA sample space with historic best positions can improve diversity control significantly. Parallel hybridization also helps to improve diversity control yet its effect is relatively less significant.     

Further studies on the pressure tolerance of deep-sea crustacea,with observations using a new high-pressure trap

A deep-sea benthic trap is described with which amphipods (Tmetonyx cicada) were both collected and observed at their ambient pressure of 134 atm. T. cicada collected with decompression from the same depth and locality were more sensitive to subsequent recompression than those amphipods brought to the surface at their ambient pressure. T. cicada from 2700 m experience irreversible injury during decompression to atmospheric pressure. The pressure tolerance of the deep-sea mysid Gnathophausia zoea was measured and compared with the tolerance of mid-water decapods and the shallow-water Crangon crangon. G. zoea became more sensitive to high pressure with prolonged exposure to atmospheric pressure. Deep sea animals exhibit a tolerance to high pressure related to their normal ambient pressure; sensitivity to decompression is also related to normal ambient pressure.