Objective Frontal Analysis Techniques Applied to Extreme/Non-Extreme Precipitation Events     

Kašpar  M. 《Studia Geophysica et Geodaetica》2003,47(3):605-631

A simple method of the objective frontal analysis (OFA) based on a thermal definition of atmospheric fronts is proposed for the area of Central Europe with the aid of gridded numerical weather prediction model (NWP model) outputs. The OFA includes both mathematical and graphical techniques that enable a computer to draw fronts entirely automatically in atmospheric cross-sections by means of one locating equation and four masking criteria. The OFA also enables to analyse the frontal wave position and the type, activity, and future development of fronts.The OFA is applied to two synoptically analogous cold-frontal situations, which occurred over the Czech Republic in summer season and were characterised by quite different precipitation amounts. The outputs (12h, 18h, and 24h forecasts) of the NWP model Europa Modell/Deutschland Modell are used in computations. The equivalent potential temperature is considered as an input thermal parameter of the OFA. The impact of applying and changing the OFA masking criteria is various and among others also depends on synoptic situation. The comparison between the objective and subjective analysed fronts subserves to evaluate the values of masking threshold constants. Some obtained results of the analysis of the extreme precipitation situation support the possibility of enhanced precipitation amounts. The analysis of the second non-extreme precipitation situation revealed a few different features that do not support the forecast of enhanced precipitation amounts. The results show the OFA could contribute to the improvement of the general short-range weather forecast.  相似文献   

永久散射体雷达干涉测量技术   总被引：18，自引：3，他引：18  

李德仁  廖明生  王艳 《武汉大学学报(信息科学版)》2004,29(8):664-668

论述了永久散射体干涉测量 (permanentscattererinterferometry ,PSI)产生的背景和基本原理 ,并介绍了其应用实例 ,讨论了PSI的技术特点和今后的发展方向  相似文献   

AMTIS大气订正算法——基于MODTRAN4．1与BRDF大气订正环   总被引：1，自引：2，他引：1  

何立明  李小文  阎广建  王华  王锦地 《遥感学报》2004,8(5):389-396

基于BRDF大气订正环的途径和核驱动模型 ,用MODTRAN创建大气参数查找表 (LookUpTable LUT) ,加入地表先验知识 ,对AMTIS(AirborneMulti angleTIR/NIRImagingSystem AMTIS)的可见光、近红外波段数据进行了大气订正 ,并根据地面数据进行了验证。结果表明 ,采用本文算法比基于地表朗伯假定的大气订正能更有效地去除大气影响  相似文献   

近6 a东北地区大气臭氧总量变化特征及其与气温的关系     

龚强  汪宏宇  王盘兴  李丽平 《南京气象学院学报》2004,27(1):113-120

利用TOMS大气臭氧总量格点资料分析了东北地区近6a(1996年8月-2002年7月)臭氧的分布特征、季节变化、变化趋势及其对气温变化的影响，并与1979—1992年的变化情况作了对比分析。结果表明：东北地区处于北半球大气臭氧高值中心的边缘，臭氧总量呈随纬度增加的分布形式，近6a区域年均值为361Du；冬春季总量较大、夏秋季较小，其中8月最小，3月最大；1979—1992年臭氧存在明显的下降趋势(冬季最为显著)，下降趋势高纬大于低纬，近6a整个区域没有系统性下降趋势；1979—1992年对流层中下部显著变暖、对流层上层和平流层低层显著变冷，且变暖率与变冷率均随纬度增高而加大，而近6a气温变幅很小，这与臭氧变化趋势基本对应，表明臭氧的辐射加热是影响平流层低层、对流层高层温度场的重要因素，同时它对对流层低层气温的影响值得进一步关注。  相似文献   

夏季黑潮区域SSTA及其与中国夏季降水的联系   总被引：5，自引：3，他引：5  

倪东鸿  孙照渤  陈海山  朱伟军 《南京气象学院学报》2004,27(3):310-316

采用海温、降水、OLR和NCEP／NCAR40a再分析资料，利用REOF方法，研究了夏季北半球海温异常(SSTA)的变化特征，结果显示：第4个REOF空间型是黑潮海温异常的典型形态。相关、合成分析表明，夏季黑潮海温正异常年时，长江流域降水偏多，洞庭湖流域显著偏多；负异常年时则反之。  相似文献   

积分浊度计在沙尘暴监测网试验中应用分析   总被引：12，自引：2，他引：12  

柯宗建汤洁  王炳忠颜鹏 《气象科技》2004,32(4):258-262

中国气象局在沙尘暴监测网各站点安装了积分浊度计，这是国内首次利用积分浊度计进行大面积气溶胶光学性质的监测。文章选取北京观象台2003年9月2日至11月18日散射系数数据以及部分PMIO质量浓度数据，结合气象资料分析了观测期间散射系数的变化特征，散射系数与PMIO质量浓度以及能见度的关系，得出观测期间散射系数的平均值(标准偏差)为306．2Mm^-1(292．78Mm^-1)；风速对散射系数有重要影响；散射系数与PMIO质量浓度有较好的相关性(r=0．761)，与能见度存在负相关关系(r=-0．716)。  相似文献   

Study of the Interaction between Biological Cells of Different Shapes and Sizes and Electromagnetic Fields Produced by Natural Phenomena     

Diaz-Sandoval  Rosa  Mendoza  Blanca 《Natural Hazards》2004,31(1):143-156

We carry out a study of the interaction between electromagnetic fields produced innature and cells with no structure but with different shapes and sizes, considered asapproximations of those observed in the human body. Magnetic fields produced byvarious atmospheric and geomagnetic phenomena are compared with the fieldsgenerated by the cells themselves. Working with frequencies up to 10⁵ Hz, we found that in most cases lightning is the natural phenomena capable of producingfield intensities comparable to those generated by the cells. As a first approximationwe assume that a cell might be affected only if a field of intensity comparable to thecell's field is present. Oscillating fields of less intensity and their harmonics can involveresonant interactions with the cells, however this situation is not considered here. Under the approximation of our study we found that the size and the shape are parameters of paramount importance: lightning represents a natural hazard only for the largest cells, while the quadrangular cells are not affected by any of the natural phenomena considered here.  相似文献   

大气降尘收集方法及相关问题研究   总被引：23，自引：5，他引：23  

钱广强  董治宝 《中国沙漠》2004,24(6):779-782

降尘监测是探索大气降尘对环境的影响和生态效应评估不可缺少的手段之一。根据集尘容器内同定降尘介质的不同，目前常用的收集方法分为干法、湿法和玻璃球法3种。在实际监测中，每种方法都有不同的研究者采用，3种方法的收集效率也有一定的差别。研究表明，干法的集尘效率为湿法的73％和玻璃球法的95％；玻璃球法的集尘效率为湿法的77％。3种方法的集尘量之间具有良好的线性关系，可以依此进行数据的转换。不同的收集容器会对集尘效率产生影响，其测量精度也不相同。另外，这3种收集方法不能很好地区别干沉降和湿沉降过程，应该加以改进。因此，采用统一的标准开展大气降尘的合作研究很有必要。  相似文献   

地下水污染监测网的设计研究进展   总被引：10，自引：0，他引：10  

吴剑锋  郑春苗 《地球科学进展》2004,19(3):429-436

地下水污染监测网的设计包括取样点在空间上的采样位置和时间上的取样频率这两方面的确定，其目的是为了准确刻画污染羽在含 水层中随时间的变化状况。概要地回顾了近20年来地下水污染监测网设计的研究成果。分别介绍了统计方法、模拟方法和模拟-优化模型 等监测网设计方法的研究进展。监测网设计方法的选择取决于最终的监测目的以及可供利用的基础资料。指出参数的不确定性是影响污染监 测设计结果的最重要因素。如何将地下水污染监测网设计的理论研究真正与实际应用相结合是今后的主要研究方向。  相似文献   

Investigation of splitting gas and aqueous operators in atmospheric multiphase box models     

Rafik Djouad  Diane V. Michelangeli 《Atmospheric Research》2004,71(4):253-263

Operator splitting techniques are widely used in atmospheric modeling in order to reduce the cost of time integration and allow more flexibility by treating each operator separately. However, this is not error free and the magnitude of the error depends on whether the splitted operators commute or not and the magnitude of the splitting time step. In multiphase models, the gas and the aqueous phase chemistries are related through the gas-droplet mass transfer processes. In the present paper, we show that splitting the gas chemistry operator from the aqueous chemistry and mass transfer operator is not appropriate and leads to errors beyond the tolerated thresholds. Analytical expressions for the splitting errors are derived and numerical experiments are conducted. The LAMP chemical mechanism is employed. Time integration is performed with LSODE.  相似文献