海拔高度对土壤温度的影响(节译)

对土壤温度的季节性变化,曾进行了广泛的研究。其中如何区分气象因子和土壤物理特性对地温的影响感到因难。本文通过实例证明,至少在英国,后者的影响和前者相比是次要的;其次的难题是所能得到的多数土壤温度资料是09时(世界时)的定时记录。本文指出,仔细考虑所能得到的有限的连续观测资料,可以在一定程度上解决这难题。最后文章指出,在夏天,土壤温度随海拔的升高而大辐度的下降(比气温降得快),在冬天,地温随海拔的升高降温减慢,有时甚至增温,多数情况下,比气温降温小,这些重要的现象,认为可以得到解释。     

空洞卷积U-Net的遥感影像道路提取方法

针对从遥感影像上提取道路出现的细节特征丢失、提取结果模糊的问题,该文提出了一种基于空洞卷积U-Net的遥感影像道路提取算法:①以U-Net为基础网络,将低层细节特征与高层语义特征进行多特征融合,更好地还原道路目标细节;②为了进一步提高网络对道路细节特征的识别能力,在U-Net中引入空洞卷积模块,学习更多的语义信息来改善提取结果出现的模糊问题.在Massachusetts roads和高分辨率城市道路影像Cheng roads dataset数据集下的实验结果表明,在召回率、精度和F1-score指标分别达到了82.5％、86.7％、84.5％;93.2％、92.1％、92.6％.与基础的U-Net相比,该算法在解决细节特征丢失和提取结果模糊问题方面更具有应用价值.     

基于随机森林和Landsat8 OLI影像的脐橙果园种植信息提取

针对从中分辨率遥感影像中提取果园种植信息所面临的特征维数高、提取精度低等问题,采用随机森林算法进行特征优选,进而提取脐橙果园种植信息.以重庆奉节为研究区,首先选取春、秋、冬3季Landsat 8 OLI遥感数据生成光谱特征、植被指数特征和纹理特征,并结合地形因子构建初始特征集;再通过随机森林算法确定优选特征集;最后基于随机森林分类器,利用初始特征集和优选特征集进行脐橙果园的提取实验,并对各实验结果进行了精度评估和对比分析.研究结果表明,基于随机森林算法构建的优选特征集能在降低特征维度的情况下获得较高的精度,总体精度和Kappa系数分别为90.71％和0.89.     

Chemical contamination of a coral reef by the grounding of a cruise ship in Bermuda

Bulk metal analyses of surficial sediments collected around the Norwegian Crown cruise ship grounding site in Bermuda indicated significant but localized contamination of reef sediments by copper and zinc, caused by the stripping of the tri-butyltin (TBT)-free antifouling (AF) paint (Intersmooth 460) from the underside of the hull. Highest copper and zinc values were found in heavily compacted and red-pigmented sediments inside the impact scar and were comparable to levels found close to slip ways of local boat yards where AF paints from hull stripping and cleaning processes are washed into the sea. The re-distribution of AF contaminated sediments by storms and deposition on nearby reefs constitutes a significant ecological risk that could delay recovery processes and reduce the effectiveness of remediation efforts. Whilst the ecotoxicological effects of AF paint particles interspersed with sediment is unknown, and in need of further study, it is argued that the significance of AF paint contamination of grounding sites has been overlooked.     

揭阳新旧站气象观测资料对比分析

利用揭阳新、旧观测站2010年观测资料,选取其中气温、气压、相对湿度、风向风速等气象要素资料,采用差值分析方法进行对比分析.结果表明:新站月平均气温、月平均最高最低气温、月平均本站气压均比旧站偏低,气温偏低的幅度不大,气压偏低的幅度较大.两站最多风向及频率不完全一致,新站月平均风速比旧站略偏大;新站相对湿度比旧站偏大.气象要素产生差异的原因主要是由新旧站址的观测环境、海拔高度、下垫面差异以及城市热岛效应造成的.     

Estimating recharge rates with analytic element models and parameter estimation

Quantifying the spatial and temporal distribution of recharge is usually a prerequisite for effective ground water flow modeling. In this study, an analytic element (AE) code (GFLOW) was used with a nonlinear parameter estimation code (UCODE) to quantify the spatial and temporal distribution of recharge using measured base flows as calibration targets. The ease and flexibility of AE model construction and evaluation make this approach well suited for recharge estimation. An AE flow model of an undeveloped watershed in northern Wisconsin was optimized to match median annual base flows at four stream gages for 1996 to 2000 to demonstrate the approach. Initial optimizations that assumed a constant distributed recharge rate provided good matches (within 5%) to most of the annual base flow estimates, but discrepancies of >12% at certain gages suggested that a single value of recharge for the entire watershed is inappropriate. Subsequent optimizations that allowed for spatially distributed recharge zones based on the distribution of vegetation types improved the fit and confirmed that vegetation can influence spatial recharge variability in this watershed. Temporally, the annual recharge values varied >2.5-fold between 1996 and 2000 during which there was an observed 1.7-fold difference in annual precipitation, underscoring the influence of nonclimatic factors on interannual recharge variability for regional flow modeling. The final recharge values compared favorably with more labor-intensive field measurements of recharge and results from studies, supporting the utility of using linked AE-parameter estimation codes for recharge estimation.     

Ground water modeling applications using the analytic element method

Though powerful and easy to use, applications of the analytic element method are not as widespread as finite-difference or finite-element models due in part to their relative youth. Although reviews that focus primarily on the mathematical development of the method have appeared in the literature, a systematic review of applications of the method is not available. An overview of the general types of applications of analytic elements in ground water modeling is provided in this paper. While not fully encompassing, the applications described here cover areas where the method has been historically applied (regional, two-dimensional steady-state models, analyses of ground water-surface water interaction, quick analyses and screening models, wellhead protection studies) as well as more recent applications (grid sensitivity analyses, estimating effective conductivity and dispersion in highly heterogeneous systems). The review of applications also illustrates areas where more method development is needed (three-dimensional and transient simulations).