基于ExcelVBA实现箱图剔除法确定化探异常下限

尽管目前地球化学异常下限的计算方法较多,但不同程度上存在计算过程复杂、应用范围较窄、相关专业软件普及程度低等问题。针对这些问题,笔者提出将EDA技术与经典统计概率法相结合的方法,并应用Excel下的程序开发工具进行VBA编程,在Excel中实现异常下限的快速计算。该方法具有计算简便、异常下限稳健以及应用范围广等优点。依据方法原理,该方法仅适用于来自单一母体的数据样本,来源母体可通过分形图给出初步判定方法。     

基于“水文频率-水质”拟合曲线的河流水质变异与等级特征值分析方法

时空特征分析对全面掌握水质变异规律具有重要意义,但现有的水质时空特征分析方法仍存在水质变异次序不分、水质变幅极值不清、水质评价特征值不明等不足。为更加清晰地探析水质时空特征信息,以秦淮河为研究对象,参考工程水文学经验频率法,建立“水文频率-水质”拟合曲线用于探索流域内高/低活动区不同时间段和丰/枯水期不同河段水质变异特征,并与传统的箱线图法进行对比。结果表明:与箱线图相比,“水文频率-水质”拟合曲线可量化关键水质评判点与特征值信息,使水质时空变异过程更为清晰。在时间上“水文频率-水质”拟合曲线的最佳形式为线性曲线,水质浓度一般不会发生突变;在空间上“水文频率-水质”拟合曲线的最佳形式为指数曲线,水质浓度有较大可能发生突增。各时间段高活动区氮磷浓度大于低活动区,各水体断面丰水期氮磷浓度低于枯水期。该方法分析过程简单方便,结果直观有序,能将水质信息以统计规律自动反映出来,在水质采样点、采样时间和采样频率典型时可作为优选方法用于河流水质时空特征研究。     

高分辨地形对华南区域GRAPES模式地面要素预报影响的研究

华南区域GRAPES模式动力框架的更新使得高分辨地形数据能够进入模式。引入SRTM数据实现静态数据更新,结合模式内置数据,进行了批量模拟试验;通过站点检验方式,对批量试验结果进行对比,得出以下结论:对比业务使用的Topo10 m地形、Topo30 s地形、SRTM地形和基于SRTM多种插值方案得到的地形,海拔偏差的空间分布和分位数统计都有明显的改善,复杂地形区域的改善效果更显著。通过地面要素平均绝对误差(MAE)箱须图统计和模式西部站点绝对误差(AE)时间序列图对比分析,发现高分辨地形试验的2 m气温和10 m风速MAE和AE有大幅度的改善。高分辨地形对模式静态数据的改善是2 m气温和10 m风速MAE下降的主要原因,地形复杂区域对MAE改善的贡献高于模式其他区域。高分辨地形进入模式后会引起动力过程计算的虚假扰动,适当的滤波平滑能够抑制扰动,从而进一步提高预报精度。      

AN OPERATIONAL STATISTICAL SCHEME FOR TROPICAL CYCLONE INDUCED RAINFALL FORECAST

A non-parametric method is used in this study to analyze and predict short-term rainfall due to tropical cyclones(TCs) in a coastal meteorological station. All 427 TCs during 1953-2011 which made landfall along the Southeast China coast with a distance less than 700 km to a certain meteorological station- Shenzhen are analyzed and grouped according to their landfalling direction, distance and intensity. The corresponding daily rainfall records at Shenzhen Meteorological Station(SMS) during TCs landfalling period(a couple of days before and after TC landfall) are collected. The maximum daily rainfall(R-24) and maximum 3-day accumulative rainfall(R-72) records at SMS for each TC category are analyzed by a non-parametric statistical method, percentile estimation. The results are plotted by statistical boxplots, expressing in probability of precipitation. The performance of the statistical boxplots is evaluated to forecast the short-term rainfall at SMS during the TC seasons in 2012 and 2013. Results show that the boxplot scheme can be used as a valuable reference to predict the short-term rainfall at SMS due to TCs landfalling along the Southeast China coast.     

OPERATIONAL FORECAST OF RAINFALL INDUCED BY LANDFALLING TROPICAL CYCLONES ALONG GUANGDONG COAST

Following previous studies of the rainfall forecast in Shenzhen owing to landfalling tropical cyclones(TCs), a nonparametric statistical scheme based on the classification of the landfalling TCs is applied to analyze and forecast the rainfall induced by landfalling TCs in the coastal area of Guangdong province, China. All the TCs landfalling with the distance less than 700 kilometers to the 8 coastal stations in Guangdong province during 1950—2013 are categorized according to their landfalling position and intensity. The daily rainfall records of all the 8 meteorological stations are obtained and analyzed. The maximum daily rainfall and the maximum 3 days' accumulated rainfall at the 8 coastal stations induced by each category of TCs during the TC landfall period(a couple of days before and after TC landfalling time) from 1950 to 2013 are computed by the percentile estimation and illustrated by boxplots. These boxplots can be used to estimate the rainfall induced by landfalling TC of the same category in the future. The statistical boxplot scheme is further coupled with the model outputs from the European Centre for Medium-Range Weather Forecasts(ECMWF) to predict the rainfall induced by landfalling TCs along the coastal area. The TCs landfalling in south China from 2014 to 2017 and the corresponding rainfall at the 8 stations area are used to evaluate the performance of these boxplots and coupled boxplots schemes. Results show that the statistical boxplots scheme and coupled boxplots scheme can perform better than ECMWF model in the operational rainfall forecast along the coastal area in south China.     

干贮粉煤灰降水渗透深度的统计分析

根据某热电厂贮灰场模拟降水30 mm、50 mm、100 mm和150 mm的试验数据,采用统计方法分析不同降水强度下粉煤灰随着降水渗透至地下的深度,以确定各种降水条件下贮灰场渗滤液是否能够达到含水层,造成地下水污染。运用箱线图直观了解不同降水量下含水量发生显著性变化的土层深度,进一步使用秩和检验方法,利用本底值与降水影响情况下样本土壤含水量数值进行比较分析。结果表明,在0.1显著性水平下,污染液不能达到含水层。