Methodological Development of the Conditional Sampling Method. Part II: Quality Control Criteria of Relaxed Eddy Accumulation Flux Measurements   总被引：1，自引：1，他引：0  

A.?K.?Fotiadi  F.?Lohou  A.?Druilhet  D.?Ser?aEmail author  F.?Said  P.?Laville  A.?Brut 《Boundary-Layer Meteorology》2005,117(3):577-603

Determination of biosphere–atmosphere exchanges requires accurate quantification of the turbulent fluxes of energy and of a wide variety of trace gases. Relaxed Eddy Accumulation (REA) is a method that has received increasing attention in recent years, because it does not require any rapid sensor for the scalar measurements as the Eddy Correlation method (EC) does. As in all micrometeorological studies, REA measurements in the atmospheric surface layer are valid under some restrictive conditions so as to be representative of a specific ecosystem. These conditions are the homogeneity of the underlying surface, stationary and horizontally homogeneous turbulence. For most experiments these conditions are not fully satisfied. Data uncertainties can also be related to not fulfilling the method principles or to the technical characteristics of the REA system itself. In order to assess REA measurement quality, a methodological approach of data analysis is developed in this study. This methodological analysis is based on the establishment of criteria for data quality control. A set of them, deduced from the mean and turbulent flow, are called ‘Dynamic criteria’ and are designated to control the stationarity and homogeneity of the w function and the validation of Taylor’s hypothesis. A second set (‘REA operational criteria’) is designed to check the sampling process and, more precisely, the homogeneity of the negative and positive selection process throughout the sampling period. A third set of criteria (‘Chemical scalar criteria’) concerns the scalar measurements. Results of the criteria application to data measured at two different experimental sites are also presented. Cut-off limits of criteria are defined based on their statistical distribution and shown to be specific for each site. Strictness of each criterion, defined by the percentage of flagged samples, is analysed in conjunction with the meteorological conditions and atmospheric stability. It is found that flagged samples mainly correspond to neutral and stable nocturnal conditions. During daytime, nearly free convection conditions can also yield poor quality data.  相似文献   

Micrometeorology and Atmospheric Boundary Layer     

S.?Pal?AryaEmail author 《Pure and Applied Geophysics》2005,162(10):1721-1745

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副热带高压边缘连续两次强降水形成机制分析          下载免费PDF全文

杨晓霞 《山东气象》2017,37(3):62-72

利用常规观测资料、自动气象站加密观测资料、GPS/MET水汽监测资料、FY-2E卫星云图和NCEP/NCAR 1°×1°再分析资料,对副热带高压边缘山东南部连续两次强降水的形成机制进行分析。结果表明,两次强降水都是由副热带高压边缘500 hPa弱西风槽过境影响产生的,副热带高压主体加强西移,850～700 hPa有较强的西南急流。强降水产生在西南低空急流的前方、暖式切变线附近;西南低空急流加强北上强降水开始,急流减弱强降水结束。强降水区与CAPE的高值区、低层水汽通量高值舌、水汽辐合中心、暖平流中心有较好的对应关系。西南低空急流、GPS/MET水汽监测对强降水的短时预报有一定的指示性。对流云团TBB最低为-78～-62 ℃,各观测站对应最大小时雨量为40～90 mm。强降水期间,850 hPa及以下有中尺度涡旋发展,涡旋尺度小,气压场上表现很弱,流场上表现明显,有明显的气旋性环流中心,在925 hPa涡旋中心东南部的暖平流中心降水强度最大。第一次强降水的中尺度涡旋源地发展,稳定少动,在其东南部上升运动强且降水强度大;第二次强降水中,冷空气在低层从西北部侵入,形成气旋,向东北移动,强降水产生在冷锋前部的暖区中,对流不稳定能量高,降水强度大、范围大。  相似文献   

线纹计量器具检定系统表修订建议     

包欢  王玉峰  付子傲  朱江  薛英 《测绘科学技术学报》2012,(1):57-60

JJG 2001-1987《线纹计量器具检定系统》是我国线纹计量器具进行量值传递的检定系统表,但其存在着许多不足,已无法满足当今计量检定的需要。此处对该检定系统表进行详细分析后给出修订建议,并介绍了目前国际上有关动向,提出了一些有益建议。  相似文献   

嵌入式马尔科夫链的地质属性建模与应用     

郭飞  葛成  韩宇 《地理与地理信息科学》2012,28(1):47-50

传统的地质统计学所形成的算法理论和方法(如克里格算法)过分依赖样品的数据,变异函数参数众多,给地质模拟造成很大困难。基于马尔科夫链的地质属性建模采用转移概率描述样品区域的各种参数变量,通过转移概率矩阵直接推导地质属性分布比例、平均长度,其简化了地质空间各向异性处理过程,克服了传统地质统计学中参数众多且复杂难以计算和地质体分布过程中存在不对称性等缺陷,使得整个地质属性建模的过程更简洁、清晰,容易理解,且建模的结果可以很好地反映地质体空间分布的复杂性。该文利用马尔科夫链对南京市河西地区的新近地质层进行了地质属性建模,实例应用表明,使用该模型进行地质属性建模可为进一步的数值模拟提供支持。  相似文献   

Accuracy of forecasting in a Nordic paper mill's supply chain: A case study     

《Norsk geografisk tidsskrift. Norwegian journal of geography》2012,66(2):104-113

The article compares the accuracy of forecasted and actual supply chain cost and price factors in a Nordic paper mill's sales to customers in two large European countries. Empirical longitudinal research data covering the years between 2002 and 2008 were obtained from a large integrated Finnish paper mill, and consisted of sales volumes, paper prices, variable costs, and transport costs. It was expected that the mill would be able to forecast demand, prices and costs accurately, but the empirical findings showed that the forecasts for paper price, demand, and cost varied from one market to another and were not highly accurate. In addition, the forecasting of gross margins seemed to be very inexact. It is concluded that there is a need for more reliable forecasting methods in the paper industry to anticipate economic development as paper demand and costs change.  相似文献   

国内价值链构建下地方产业集群升级机理研究     

陈维忠 《地域研究与开发》2012,31(3):13-17

承接产业转移是广大中西部地区的重大发展机遇。在分析全球价值链(GVC)的基础上,立足于我国经济梯度,提出了构建国内价值链(NVC)的基本思路。根据劳动力、资源、市场和区位等不同要素,明确了国内价值链主要划分为生产者驱动价值链、购买者驱动价值链、原材料驱动价值链和混合驱动价值链4种形式,重点分析了在不同价值链下地方产业集群升级的重点和方向,提出了不同的地方产业集群升级模式和内在机理。  相似文献   

The effect of transient eddy on interannual meridional displacement of summer East Asian subtropical jet   总被引：3，自引：0，他引：3  

向洋  杨修群 《大气科学进展》2012,29(3):484-492

Using ERA-40 reanalysis daily data for the period 1958-2002,this study investigated the effect of transient eddy(TE) on the interannual meridional displacement of summer East Asian subtropical jet(EASJ) by conducting a detailed dynamical diagnosis.The summer EASJ axis features a significant interannual coherent meridional displacement.Associated with such a meridional displacement,the TE vorticity forcing anomalies are characterized by a meridional dipole pattern asymmetric about the climatological EASJ axis.The TE vorticity forcing anomalies yield barotropic zonal wind tendencies with a phase meridionally leading the zonal wind anomalies,suggesting that they act to reinforce further meridional displacement of the EASJ and favor a positive feedback in the TE and time-mean flow interaction.However,The TE thermal forcing anomalies induce baroclinic zonal wind tendencies that reduce the vertical shear of zonal wind and atmospheric baroclinicity and eventually suppress the TE activity,favoring a negative feedback in the TE and time-mean flow interaction.Although the two types of TE forcing tend to have opposite feedback roles,the TE vorticity forcing appears to be dominant in the TE effect on the time-mean flow.  相似文献   

近30a来北半球对流层大气月均环流的涡动减弱现象   总被引：1，自引：1，他引：0  

杨哲  管兆勇  蔡佳熙 《南京气象学院学报》2012,(6):702-711

利用1980-2009年NCEP／NCAR月平均再分析资料,研究了在全球变暖背景下北半球对流层大气涡动减弱现象。结果表明：北半球涡度拟能30a来整体呈减弱趋势,在北太平洋地区和极地减弱尤为显著,12．5～50°N为影响北半球大气涡动变化的关键区域。由于对流层200hPa以下大气的增暖,特别是中高纬地区显著增暖,减弱了经向温度梯度,使得副热带西风急流的强度亦呈减弱趋势。这与涡度拟能的变化有显著的正相关关系。分析了北半球正压Rossby波动诊断量E和热量经向涡动通量的变化,表明中纬度波能传播在不同地区有不同趋势,而热量的经向涡动输送与涡度拟能的变化也呈现显著的正相关关系,减弱明显。研究结果对深刻认识大气环流变化规律和理解全球变暖的可能影响具有重要意义。  相似文献   

高空形势与山东半岛冷流暴雪的关系     

褚昭利  李建华 《气象与环境科学》2012,35(2):44-48

采用常规观测资料和NCEP1°×1°资料,对山东半岛2005年、2008年、2010年的几次典型冷流暴雪过程进行了分析。分析结果表明：冷流暴雪的高空形势主要分为高空冷涡型和高空横槽型。高空冷涡型较高空横槽型降雪量偏大,暴雪站点多。高空冷涡型500hPa层以上的位涡值较高空横槽型偏大,高层位涡有利于低层正涡度的加强,促使低层产生低压环流及辐合上升运动,上升运动加强了海面水汽的垂直输送,故高空冷涡型上升速度较高空横槽型强,湿层较厚,高空冷涡型较高空横槽型更容易产生暴雪过程。  相似文献