青藏高原加热作用对夏季东亚大气环流影响的初步模拟实验

青藏高原夏季的加热作用对东亚大气环流有很大影响,过去从天气学角度对这问题有过不少研究,本文主要用流体力学模拟试验的方法进行了初步研究。 从模拟三种不同基本流场的试验中初步看出:青藏高压的形成主要在于耸立在对流层中部的高原加热作用,这种加热作用使中、下层产生巨大的辐合,高空产生巨大的辐散,高原上空西风带的北撤、高原南面东风带的建立、高原上空高压和高原上热低压的建立以及季风经圈环流的形成等现象,都有内在的联系,其关键在于高原的加热作用。西南季风的形成和活动也与高原加热有密切联系,随着高原加热量的增强,在实验中还可以看到高原东侧的切变线北移,因此青藏高原的加热作用对我国夏季雨带北移也有一定的影响。高原表面上的热量主要通过中、小尺度的对流性系统输送给大气,并维持高原大型环流的运转。     

动力系统实测数据的非线性混沌特性的判定

本文利用相位随机化的替代数据方法，给出了一个对动力系统实测时间序列数据的特性进行判定的方法·计算结果表明：相位的充分随机化可提高判别的准确程度·把此判据用于随机时序与非线性混沌时序所得的判据值有明显的差异·     

经验正交函数与遗传算法结合的副热带高压位势场非线性模型反演

针对副热带高压的动力预报模型难以准确构建的困难,基于T106数值预报产品500 hPa位势高度场序列,用经验正交函数（EOF）分解方法对位势场序列进行了时、空分解,引入了动力系统重构思想,以EOF分解的空间模态的时间系数序列作为动力模型变量,用遗传算法全局搜索和并行计算优势,进行了动力模型参数的优化反演,建立了客观合理的非线性动力模型．通过对动力模型积分和EOF的时、空重构,实现了副热带高压的中、长期预报．试验结果表明,本文反演的动力模型的副热带高压预报效果优于常规的数值预报产品,该研究工作为副热带高压等复杂天气系统和要素场预报提供了新的方法思路和技术途径．     

基于气温指数的我国天气衍生品定价研究

本文以时间序列分析中的ARMA模型和均值回复模型为基础,依据不同的纬度自北向南依次选取了北京、南京、杭州和广州作为合约城市,基于四城市1951-2011年的历史气温数据对各模型参数进行估计,并运用蒙特卡洛模拟定量检验各模型对我国天气衍生品定价的适应性。研究表明:基于日波动率的均值回复模型在预测准确性以及对不同基线温度的适应性方面要优于基于月波动率的均值回复模型和ARMA模型,更适合我国天气衍生品的定价;不同的基线温度对于各模型的预测准确率有较大的影响,因此我国在推出天气衍生品时如果考虑冬夏季月份设置不同的基线温度,那么冬季基线温度不宜过低,夏季基线温度不宜过高。     

一种非经典晶体塑性本构模型及其应用

根据不可逆变形过程中材料微结构的储能特性，采用由弹簧和塑性阻尼器构成的简单机械模型建立了不采用屈服判据的单晶本构关系·在此基础上形成了与ＫＢＷ自洽理论相应的多晶计算格式·计算格式中无需对滑移系的开动和滑移方向进行搜索，使计算过程大为简化·在多晶体分析中，提出了一种基于正２０面体各面内取向随机分布单晶响应的高斯平均和在空间完全均匀分布的２０个方向上算术平均的混合平均方案，与通常的纯高斯积分平均方案相比，在计算精度和效率上都有较大提高·用所发展的模型和算法分析了３１６不锈钢在具有代表性的路径下的循环塑性，得到了与实验相一致的结果·     

涡度方程的时空客观分解与副热带高压的突变与分岔

为了分析研究副热带高压异常活动的动力学机理,基于热力强迫和涡动耗散效应的大气偏微涡度方程,采用Galerkin方法进行方程的时-空变量分离,针对常规方法在空间基函数选择中存在的主观人为性,提出从实际资料场序列中用经验正交函数(EOF)分解与遗传算法结合客观反演空间基函数的思想.选择一组三角函数族作为广义空间基函数,以该基函数与EOF典型场的误差最小二乘和基函数间的完备正交性构造双约束泛函,再引入遗传算法进行空间基函数曲面拟合和系数优化,反演得到客观合理的副热带高压常微动力模型.最后,基于所得非线性动力学模型,对热力强迫作用下的副热带高压的动力学行为和机理进行了分析和讨论,发现太阳辐射加热和纬向海陆热力差异是影响副热带地区位势和流场变化从而导致副高强弱变化和中期进退活动的重要因素,前者以渐变为主;后者则更多表现出突变的特性.通过分析,得到了一些有意义的结果.     

基于分层贝叶斯时空模型的雾霾天气过程计数分析

本文以北京市8个行政区(东城区、西城区、石景山区、海淀区、朝阳区、昌平区、顺义区、怀柔区)的PM2.5指数计算各区逐月雾霞天气过程计数频数为研究对象,选择考虑包括地表温度、相对湿度、平均风速、SO_2质量浓度和NO_2质量浓度在内的5个影响因素。本文定义雾霾天气过程,构建分层贝叶斯时空模型,在一个统计模型中对诸多影响因素进行分析,并从计数分析的角度对北京市雾霾天气现象的时空分布、影响因素进行深入讨论。通过分析得出,温度、湿度、污染物浓度对于雾霾天气过程发生具有促进作用,平均风速对于雾霾天气过程发生具有抑制作用。从时空角度分析,从时间维度上看雾霾天气过程的发生具有明显的季节性特征,冬季(1月、2月)以及3月雾霾天气过程发生次数最高,春季(4月、5月)发生次数最低,秋季发生次数略高于夏季。从空间维度上来看,中心城区(东城区、西城区、石景山、海淀区、朝阳区)雾霾天气过程发生次数明显高于郊区(顺义、昌平、怀柔),以东城区、西城区和朝阳区最为严重。     

四次函数实零点的完全判据和正定条件

本文给出了四次函数实零点的完全判据和正定条件,这一结果在研究多项式系统的奇点分析和分支问题时给出了可以实用的判据．     

一类混合比率依赖食物链扩散模型的Hopf分支

研究了一类基于混合比率依赖的三种群食物链扩散模型.利用Hurwitz判据讨论了非负常数平衡解的稳定性,并通过理论分析研究了该系统空间齐次和空间非齐次的Hopf分支,同时利用规范型理论和中心流形定理给出Hopf分支方向和分支周期解稳定性的判据.最后借助Matlab软件进行数值模拟,验证补充理论分析结果.     

时滞神经网络全局渐近稳定性条件

利用Liapunov泛函方法,结合矩阵不等式技巧,分析了时滞细胞神经网络(DCNNs)的平衡点存在的唯一性和全局渐近稳定性,保证DCNNs的全局稳定性的一个新的充分判据被得到．所得判据提供了一些参数来适当地弥补了反馈矩阵与时滞反馈矩阵之间所需要的平衡关系．这些判据可以容易被使用来设计和检验全局稳定的网络．此外,所得判据是与时滞参数无关,且比已有文献具有更少的限制．     

Rossby惯性重力孤立波与东、西太平洋副高活动的遥相关

根据季内西太平洋副高活动异常的观测事实，考虑夏季北太平洋地区500hPa层以下的有限纬带区域，应用非线性浅水模式得到了一种孤立波。该波的产生、维持及传播与中、东太平洋副高主体的活动关系密切。 通过对这类孤立波传播特征的讨论和模式大气计算分析，发现它与夏季北太平洋副热带地区存在的位势中心的传播路径和范围比较一致，太平洋中、东部副高主体位置和强度的变化通过这种孤立波的传播可能导致西太平洋副高出现相应的变化。     

An Application of Forecasting in the Alcoholic Drinks Industry

The sales of cider in the U.K. experienced an upsurge in demand during the good summer of 1975 and the record drought of 1976. Conventional linear growth seasonal forecasting systems are unable to isolate out the effects of this exceptional weather and would produce a high forecast for the (average/poor) year of 1977. Furthermore at the end of 1976 the Government imposed an Excise Duty which depressed demand still further. A model capable of isolating and measuring these (and other) effects was required and this was achieved within the framework of the Dynamic Linear Model proposed by Harrison and Stevens¹ usually referred to as the Bayesian methods.The model finally included growth and seasonality plus the effect of exceptional weather together with price, inflation and the transfer effects of price changes. The forecasts have been very satisfactory and enable future alternative pricing strategies to be investigated.     

The south-west monsoon

A review has been made of the ideas about the south-west monsoon upto 1963 and the modifications necessary in the same in the light of the results of the International Indian Ocean Expedition (IIOE) during 1963–64. Important papers on the IIOE results published in India and elsewhere have been discussed in brief from the point of their usefulness in forecasting, indicating in what respects the interpretations are against weather, climatic and topographical features of the Indo-Pakistan subcontinent. Taking into account the presence of the Western Ghats, changes which occur within about 500 km. of the west coast of the Peninsula regarding clouds and weather and depth of the moist current brought to light by the IIOE results, become intelligible. There are no cyclonic circulations in the north-east Arabian Sea and Bombay area and in the South Bay of Bengal of the type of ‘subtropical cyclone’ in the eastern Pacific; existence of the same has been postulated due to inadequate appreciation of the Indian conditions by the workers concerned.     

Atmospheric electricity measurements in the upper air over Poona

Atmospheric electricity measurements made during the last decade at Poona using balloon-borne sondes are briefly reviewed. The vertical distribution of potential gradient in the free atmosphere follows theoretical values only during the monsoon months, when the air is comparatively free from dust. During the summer months, the potential gradient is constant above the exchange layer and this is associated with the presence of the deep, dense dust layer that lies over the region and extends to over 10 km. into the atmosphere. The increase with height of the potential gradient above the 10 km. level during winter is shown to be closely related to the presence of the subtropical jet stream, which presumably transports electric charges to the upper levels over Poona.     

Properties of large-scale TIDs observed in Central China

This paper investigates the large scale travelling ionospheric disturbances (LSTIDs) using the observation data of an HF Doppler array located in Central China. The data observed in a high solar activity year (year 1989) are analyzed to obtain the main propagation parameters of LSTIDs such as period, horizontal phase velocity and propagating direction. Results are outlined as follows: Most of the LSTIDs propagate southward; others tend to propagate northward, mostly in summer; dispersion of most LSTIDs is matched with that of Lamb pseudomode, while others have the dispersion of long period gravity wave mode. The horizontal phase velocities of these two modes are about 220 and 450 m/s respectively. The analysis shows that LSTIDs are strongly pertinent to solar activity and space magnetic storms; thus the results presented here are significant for the research of ionospheric weather in mid-low latitude region.     

Properties of large-scale TIDs observed in central China

This paper investigates the large scale travelling ionospheric disturbances (LSTIDs) using the observation data of an HF Doppler array located in Central China. The data observed in a high solar activity year (year 1989) are analyzed to obtain the main propagation parameters of LSTIDs such as period, horizontal phase velocity and propagating direction. Results are outlined as follows: Most of the LSTIDs propagate southward; others tend to propagate northward, mostly in summer; dispersion of most LSTIDs is matched with that of Lamb pseudomode, while others have the dispersion of long period gravity wave mode. The horizontal phase velocities of these two modes are about 220 and 450 m/s respectively. The analysis shows that LSTIDs are strongly pertinent to solar activity and space magnetic storms; thus the results presented here are significant for the research of ionospheric weather in mid-low latitude region.

     

国际天然气价格驱动因素的结构性变化

页岩气开采技术的大规模应用增加了非常规天然气供应潜力,对国际天然气市场供需格局产生了较大冲击。本文利用带结构断点的协整检验、时变系数模型和条件误差修正模型等方法系统地研究了天然气价格与原油价格的动态关系,以及库存、天气和投机等短期因素对气价变化的影响。结果显示,国际天然气价格与原油价格间的协整关系在2005年飓风季与2008年金融危机期间发生了结构性变化,而且原油价格对天然气价格的影响强度呈现倒U型结构。此外,极端天气、突发性事件及投机等短期因素对气价存在显著的短期影响。不过,随着天然气供应出现过剩局面,天然气价格对这些短期因素的敏感性已大幅降低。     

Weather Risk in Offshore Projects

Risk analysis tools have been used to help manage various projects. This paper describes a case study in which an extension to the stochastic project network model was developed for a risk analysis of an oil platform installation, quantifying the possible impact of the weather on the project's schedule. Examination of the weather data suggested the use of a Markov weather model combined with a separate residence time distribution for key states. The weather model was incorporated into the stochastic project network allowing the interactions of the various project uncertainties to be examined. While the weather introduced a significant additional risk to the project, analysis of management's options indicated that much of the risk might be avoided. In particular, the analysis quantified the benefits of scheduling the project start to take advantage of the seasonal variations and hiring heavy duty equipment to operate in more arduous conditions.     

Analysing production and environmental risks in arable farming systems: A mathematical approach

In response to a growing environmental concern in Dutch society, sustainable production systems in arable farming have been developed. Amongst other things, a reduction of the dependency on chemical inputs is attempted. This paper addresses the role of risk in the adoption by farmers of new systems by means of a model that determines differences in production risks between conventional and sustainable farming systems (CAFS and IAFS).Timing of activities – setting out a management track – is particularly important in sustainable arable farming systems. Resource requirements of crop husbandry activities mainly depend on weather conditions. To assess risks caused by weather conditions, the major aspects of crop husbandry in various crops have been modelled. Using tactics in crop husbandry (decision rules) and weather uncertainty as input, crop husbandry models (HMs) calculate management tracks that require resources. The value distributions of resource requirements of crop husbandry according to different farming systems is calculated in different HMs represented by stochastic dynamic directed networks. Hence, production risks of CAFS and IAFS can be compared.On a farm, all the aspects of crop husbandry in the various crops are to be taken into account. Given the weather conditions, tactics for all the aspects are combined in an LP model of the whole farm where they compete for limited resources. In the LP model, tactics are re-assessed by means of the HMS, using information of the LP solution. This iterative procedure enables production risks of CAFS and IAFS to be compared, considering fixed, allocatable resources for the whole farm firm.