Mean sea level and the marine geoid—an analysis of concepts

The current ambition to achieve a 10‐cm marine geoid focuses attention on the interdisciplinary problem of relating oceanographic to geodetic measurements, and on the apparent conflict between them along the United States’ coasts. The concepts underlying the comparisons in this conflict are analyzed, and shown to leave a possibility of diffusing the deadlock by more precise reformulations. Concepts which have been equated in practical applications under less stringent accuracy requirements need to be refined and related more precisely through interdisciplinary efforts. An example is given of a geodetic utilization of density differences in the ocean, akin to but not the same as the idea of steric leveling, in order to highlight the similarity and dissimilarity between some geodetic and oceanographic ideas.     

Diagnostic evaluation of multiple hypotheses of hydrological behaviour in a limits‐of‐acceptability framework for 24 UK catchments

Testing competing conceptual model hypotheses in hydrology is complicated by uncertainties from a wide range of sources, which result in multiple simulations that explain catchment behaviour. In this study, the limits of acceptability uncertainty analysis approach used to discriminate between 78 competing hypotheses in the Framework for Understanding Structural Errors for 24 catchments in the UK. During model evaluation, we test the model's ability to represent observed catchment dynamics and processes by defining key hydrologic signatures and time step‐based metrics from the observed discharge time series. We explicitly account for uncertainty in the evaluation data by constructing uncertainty bounds from errors in the stage‐discharge rating curve relationship. Our study revealed large differences in model performance both between catchments and depending on the type of diagnostic used to constrain the simulations. Model performance varied with catchment characteristics and was best in wet catchments with a simple rainfall‐runoff relationship. The analysis showed that the value of different diagnostics in constraining catchment response and discriminating between competing conceptual hypotheses varies according to catchment characteristics. The information content held within water balance signatures was found to better capture catchment dynamics in chalk catchments, where catchment behaviour is predominantly controlled by seasonal and annual changes in rainfall, whereas the information content in the flow‐duration curve and time‐step performance metrics was able to better capture the dynamics of rainfall‐driven catchments. We also investigate the effect of model structure on model performance and demonstrate its (in)significance in reproducing catchment dynamics for different catchments. Copyright © 2013 John Wiley & Sons, Ltd.     

THE DOWNSCALING FORECASTING OF SEASONAL PRECIPITATION IN GUANGDONG BASED ON CLIMATE FORECAST SYSTEMS PRODUCTS

The Climate Forecast Systems （CFS） datasets provided by National Centers for Environmental Prediction （NCEP）, which cover the time from 1981 to 2008, can be used to forecast atmospheric circulation nine months ahead. Compared with the NCEP datasets, CFS datasets successfully simulate many major features of the Asian monsoon circulation systems and exhibit reasonably high skill in simulating and predicting ENSO events. Based on the CFS forecasting results, a downscaling method of Optimal Subset Regression （OSR） and mean generational function model of multiple variables are used to forecast seasonal precipitation in Guangdong. After statistical analysis tests, sea level pressure, wind and geopotential height field are made predictors. Although the results are unstable in some individual seasons, both the OSR and multivariate mean generational function model can provide good forecasting as operational tests score more than sixty points. CFS datasets are available and updated in real time, as compared with the NCEP dataset. The downscaling forecast method based on the CFS datasets can predict three seasons of seasonal precipitation in Guangdong, enriching traditional statistical methods. However, its forecasting stability needs to be improved.     

海冰对南极磷虾（Euphausua superba）资源丰度的影响

利用1997-2008年南极磷虾产量及各月南极海冰面积数据,分析南极磷虾产量的时空分布,以及海冰对南极磷虾资源丰度的影响。结果表明,近年来南极磷虾年平均产量在11万t左右,主要来自48渔区,渔汛期为3—7月。但不同渔区（48．1区、48．2区和48．3区）在不同年份和季节,其产量和CPUE均有明显差异。分析认为,48区...     

新疆地区对流层中下层及地面温湿变化特征

针对新疆地区1969-2009年近40年对流层中下层以及地面温湿变化特征,利用经过质量控制的中国新疆地区14个探空站1969-2009年比湿和温度资料,采用线性回归、滑动t检验等方法对新疆地区温度、湿度变化趋势和突变年进行分析,并用同一时期12个地面站的降水资料对比分析新疆地区降水量的变化特征。结果表明：南疆和北疆500hPa和850hPa高空比湿在1980年中后期均有增加的趋势,2005年后均又发生了由升转降的变化;地面比湿和降水总体均呈显著增加趋势,南疆地区降水在2005年后为持续负距平,与高空比湿变化特征一致;41年期间两个区域的温度变化在对流层中下层和地面都呈显著增加趋势,且地面增温最显著,增温速率随高度增加而降低。北疆和南疆地区500hPa比湿分别在1989年、1985年,南疆850hPa在1986年均发生由降转升的显著性突变,且均在2005年发生由升转降的显著性突变;北疆地区850hPa和两个区域地面比湿均在1986年发生突变,之后显著变湿;北疆和南疆500hPa温度分别在1985年、1986年发生由降转升的显著突变,两个区域850hPa和地面温度均在1996年发生相同突变,显著水平都达到0．01。     

Impacts of the local land-use system in a semi-arid region of northeastern China on soil properties, crop growth, and weed communities

We examined changes in soil properties, crop biomass, and weed communities in the Horqin Sandy Land of China to elucidate cropland degradation. We studied three local cropland types having periods of cultivation of up to 20 years: maize cropland on lowlands without irrigation (nonirrigated lowland), maize cropland on flat sandy lands with irrigation (irrigated flatland), and bean-centered cropland on sand dunes without irrigation (nonirrigated dunes). Soil properties and crop biomass were more degraded in nonirrigated lowland and nonirrigated dunes than in irrigated flatland. Weed communities in the nonirrigated croplands were the type that become established in drier conditions, whereas wetland weeds were more abundant on irrigated flatland. Trends of change in each indicator did not always occur in parallel and differed statistically among the cropland types. Monitoring these indicators within the context of local land-use systems can provide scientific evidence on which to base local management practices or recommendations for change.     

Comparison between predictions using different simplified Newmarks' block-on-plane models and field values of earthquake induced displacements

The study is concerned with the assessment of simplified Newmarks' block-on-plane models available in the literature for evaluating the permanent earthquake induced displacements of cut slopes and embankments, and the recommendation of a well-verified model/procedure. For this purpose, incidents of earthquake induced displacements of geotechnical structures, were collected from worldwide literatures and used in the study. Actual values of displacements were compared with predictions using different models.Based on the analyses, interpretations and discussions in this study, it was concluded that the Nadim and Whitman method (Nadim F, Whitman RV. Journal of the Geotechnical Engineering Division, ASCE 1983;109(GT7):915–931) is the most accurate method for obtaining the earthquake induced displacement. The correlation coefficient between predicted values using the Nadim and Whitman method and the actual recorded ones for geotechnical structures was 0.770; the highest among correlation coefficients for other methods.     

运用BP网络预测地下水位

人工神经网络是一门新兴的交叉学科，是处理非线性问题的有效方法。本文把影响地下水位的因素集作为网络的输入向量，地下水位本身作为网络的输出向量，构成了预测地下水位的ＢＰ网络模型。一个实例的应用实践表明，用ＢＰ网络预测地下水位较准确地反映了客观实际，比其它方法如回归模型具有较高的拟合精度和预测精度。     

多层递阶回归分析

在经典多层递阶预报模型中,预报因子对模型的贡献大小主要取决于各因子间的相对量值差异,而与预报因子本身的实际预报价值关系甚微。本文针对这一缺陷,提出了一种回归分析与多层递阶方法相结合的统计预报模型——多层递阶回归分析。它既摒弃了经典统计理论中的固定参数预报模型,又较好地消除了由于变量间相对量值差异所造成的贡献差异,充分体现了高相关因子在预报模型中的重要作用。实例计算结果表明,多层递阶回归分析方法的预报效果明显优于经典多层递阶方法和回归分析。     

耀斑主相动力学模型的谱诊断

本文对一个耀斑主相动力学模型进行了谱诊断，包括同时计算ＣａＸＩＸ，Ｈα和ＣａＩＩＫ谱线轮廓演化系列．与地面光学观测及最新的Ｙｏｈｋｏｈ／ＢＣＳ观测结果比较显示，计算轮廓及其特性在实测的范围以内，从而说明该耀斑主相动力学模型在一般性反映耀斑主相演化方面的合理性，同时也意味着有相当一部分耀斑，其在主相演化过程中没有额外的加热源作用．