Forced response of atmospheric oscillations during the last millennium simulated by a climate system model

Variations in global atmospheric oscillations during the last millennium are simulated using the climate system model FGOALS_gl. The model was driven by reconstructions of both natural forcing (solar variability and volcanic aerosol) and anthropogenic forcing (greenhouse gases and sulfate aerosol). The model results are compared against proxy reconstruction data. The reconstructed North Atlantic Oscillation (NAO) was out of phase with the Pacific Decadal Oscillation (PDO) in the last millennium. During the Medieval Warm Period (MWP), the NAO was strong while the PDO was weak. During the Little Ice Age (LIA), the NAO was weak while the PDO was strong. A La Niña-like state prevailed in the MWP, while an El Niño-like state dominated in the LIA. This phenomenon is particularly obvious in the 15th, 17th and 19th centuries. Analysis of the model output indicates that the NAO was generally positive during 1000?C1400 AD and negative during 1650?C1900 AD. There is a discrepancy between the simulation and reconstruction during 1400?C1650 AD. The simulated PDO generally varies in parallel with the reconstruction, which has a negative phase during the MWP and a positive phase during the LIA. The correlation coefficient between the reconstruction and simulation is 0.61, and the correlation is statistically significant at the 1% level. Neither the La Niña-like state of the MWP nor the El Niño-like state of the LIA is reproduced in the model. Both the reconstructed and the simulated Antarctic Oscillations had a negative phase in the early period of the last millennium and a positive phase in the late period of the last millennium. The Asian-Pacific Oscillation was generally strong during the WMP and weak during the LIA, and the correlation coefficient between the simulation and reconstruction is 0.50 for the period 1000?C1985 AD. The analysis suggests that the specified external forcings significantly affected the evolution of atmospheric oscillation during the last millennium.     

Simulated analysis of summer climate on centennial time scale in eastern China during the last millennium

Using Lanczos filtered simulation results from the ECHO-G coupled ocean-atmosphere model, this study analyzes the spatiotemporal structure of temperature and precipitation on centennial time scale to examine how climate change in eastern China responded to external forcing during the last millennium. The conclusions are (1) eastern China experienced a warm-cold-warm climate transition, and the transition from the warm period to the cold period was slower than the cold to warm transition which followed it. There was more rainfall in the warm periods, and the transitional peak and valley of precipitation lag those of temperature. The effective solar radiation and solar irradiance have significant impacts on the temporal variation of both temperature and precipitation. Volcanic activity plays an important role in the sudden drop of temperature before the Present Warm Period (PWP). There is a positive correlation between precipitation and volcanic activity before 1400 A.D., and a negative relationship between the two thereafter. The concentration of greenhouse gases increases in the PWP, and the temperature and precipitation increase accordingly. (2) The spatial pattern of the first leading empirical orthogonal function (EOF) mode of temperature on centennial time scale is consistent with that on the inter-annual/inter-decadal (IA-ID) time scales; namely, the entirety of eastern China is of the same sign. This pattern has good coherence with effective solar radiation and the concentrations of greenhouse gases. The first leading EOF mode of precipitation on centennial time scale is totally different from that on the IA-ID time scales. The first leading mode of centennial time scale changes consistently over the entirety of eastern China, while the middle and lower reaches of the Yangtze and Yellow Rivers are the opposite to the rest of eastern China is the leading spatial pattern on IA-ID time scale. The distribution of precipitation on centennial time scale is affected by solar irradiance and greenhouse gas concentrations.     

A comparison of the Medieval Warm Period, Little Ice Age and 20th century warming simulated by the FGOALS climate system model

To compare differences among the Medieval Warm Period (MWP), Little Ice Age (LIA), and 20th century global warming (20CW), six sets of transient and equilibrium simulations were generated using the climate system model FGOALS_gl. This model was developed by the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences. The results indicate that MWP warming is evident on a global scale, except for at mid-l...     

Response of the East Asian summer monsoon to large volcanic eruptions during the last millennium

The responses of the East Asian summer monsoon （EASM） to large volcanic eruptions were analyzed using a millennial simulation with the FGOALS-gl climate system model. The model was driven by both natural （solar irradiance, volcanic eruptions） and anthro- pogenic （greenhouse gases, sulfate aerosols） forcing agents. The results showed cooling anomalies after large volcanic eruptions almost on a global scale. The cooling over the continental region is stronger than that over the ocean. The precipitation generally decreases in the tropical and subtropical regions in the first summer after large volcanic eruptions. Cooling with amplitudes up to -0.3 ℃ is seen over eastern China in the first summer after large volcanic eruptions. The East Asian continent is dominated by northeasterly wind anomalies and the corresponding summer rainfall exhibits a coherent reduction over the whole of eastern China. An analysis of the surface heat flux suggested the reduction in summer precipitation over eastern China can be attributed to a decrease of moisture vapor over the tropical oceans, and the weakening of the EASM may be attributed to the reduced land-sea thermal contrast after large volcanic eruptions.     

基于火灾模型的消防应急平台架构和功能分析

为预防并应对丽江古城发生大规模火灾,提出了消防应急平台架构。该平台包括信息获取、应急智能和决策指挥3大系统,运用地理信息系统(GIS)技术,将基础空间信息和消防安全信息整合,将火灾模拟分析、风险评估与消防应急指挥、数字应急预案制订有机结合起来。其中的火灾预测预警模型采用了基于元胞自动机的城区火灾蔓延模型。结合人员疏散和损失评估模型进行风险评估。消防应急决策指挥流程实现火灾预测与消防指挥的融合,为提高火灾安全管理和消防指挥能力提供了帮助。     

对卫星遥感大气订正6S模型中的算法的探讨

对6S模型中的算法进行了探讨,并提出了不同的看法：a．6S模型中将向上辐射强度分解为5个组分是没有必要的,事实上其中有些组分很难计算,其计算结果也不够精确,同时这5个组分之和也并不严格等于总辐射强度;b．6S模型对邻近效应的计算也存在着较大误差;c．一维地-气耦合辐射的数值计算只是一个很简单的问题,宜首选国际辐射传热界发展的离散坐标法来求解;d．宜选用逆向蒙特卡罗法来分析邻近效应．另外,对最近提出的多步法做了进一步扩展,以使其能计算更多的向上辐射强度组分．最后,提出了一种更便于大气订正的向上辐射强度划分方法．     

高斯-谢尔光束通过湍流大气任意粗糙目标的散射统计特性

基于广义惠更斯-菲涅耳原理和任意粗糙目标模型,考虑大气湍流对激光从发射机到目标和从目标到接收机的影响,研究部分相干高斯-谢尔光束经任意粗糙目标散射后的统计特性.我们假设相位结构函数占优,推导了接收场处互相关函数的表达式,平均强度以及波前相干长度大小,并对此进行数值模拟.结果表明,接收面的平均强度与粗糙面的横向相关长度与表面高度均方根有关;接收场的波前相干长度与湍流强度、表面粗糙度、传播距离和光源相干度有关.     

Building a high-resolution regional climate model for the Heihe River Basin and simulating precipitation over this region

Based on the Regional Integrated Environmental Model System （RIEMS 2.0） developed by START TEA-COM RRC and Department of Atmospheric Science of Nanjing University, a dataset of observation and remote sensing over the Heihe River Basin （HRB） was used to recalibrate the model＇s parameters, including topography elevation, land cover type, saturated soil water po- tential, saturated soil hydraulic conductivity, field moisture capacity, wilting point moisture, soil porosity, and parameter b of soil hydraulic conductivity, to build a high-resolution regional climate model for the HRB. Continuous simulation for the period from January 1 to December 31, 2000 was conducted using the regional climate model, with NCEP-FNL reanalysis data as the driving fields. The study focused on the ability of the model to simulate precipitation in the HRB. The analysis results showed the following： （1） For precipitation, the model could reproduce well the spatial pattern and seasonal cycle in different regions of the HRB, simulated precipitation was overestimated in the upper reaches of the HRB and underestimated in the lower reaches of the HRB, and seasonal precipitation biases were mostly in the range of -39.9%-9.6% of observations, which is mostly consistent with the IPCC report （2001）. （2） The model could reproduce reasonably temporal evolution of pentad precipitation in different regions. Correlation coefficients between the simulated and observed pentad precipitation were 0.8123, 0.5064, and 0.7033 in the upper, middle, and lower reaches of the HRB, respectively. They reached a significance level of 1%. （3） Dynamical downscaling of a high-resolution regional climate model was used to overcome the deficiency of long-term, high-temporal/spatial-resolution meteorological dataset in the HRB, and to drive directly the integrated model that coupled ecological-hydrological and socioeco- nomic processes in the HRB.     

Uncertainties in assessing the effect of climate change on agriculture using model simulation and uncertainty processing methods

Model simulation is an important way to study the effects of climate change on agriculture.Such assessment is subject to a range of uncertainties because of either incomplete knowledge or model technical uncertainties,impeding effective decision-making to climate change.On the basis of uncertainties in the impact assessment at different levels,this article systematically summarizes the sources and propagation of uncertainty in the assessment of the effect of climate change on agriculture in terms of the climate projection,the assessment process,and the crop models linking to climate models.Meanwhile,techniques and methods focusing on different levels and sources of uncertainty and uncertainty propagation are introduced,and shortcomings and insufficiencies in uncertainty processing are pointed out.Finally,in terms of how to accurately assess the effect of climate change on agriculture,improvements to further decrease potential uncertainty are suggested.     

Regional difference of aridity/ humidity conditions change over China during the last thirty years

Scientists have found that the global average surface temperature has increased by 0.6±0.2℃ since the late 19th century based on various evidence[1]. From the 1980s, temperature has experienced the most rapid warming to an extent of abrupt change statistically[2,3]. Global warming has attracted extensive attention from multiple depart-ments and has been an important issue related to global politics. Many scientific communities have made great efforts on climate change research and global env…     

变风量HVAC系统模型定性分析

利用能量与质量守恒定律,通过建立包括通风,室内围护结构、户外环境条件等诸因素的非线性时延控制数学模型,给出了保证系统有唯一正平衡态及系统全局渐近稳定的充分条件,分析表明,系统的平均点与各环境参数有关,在平衡状态下,室内气温约为28℃,最后借助一个实例,说明本文的结果可以帮助人们根据环境特点,去选择适当的HVAC控制系统。本文提供的方法同样适用于PI,PID控制系统的分析。     

A comparison of the Medieval Warm Period, Little Ice Age and 20th century warming simulated by the FGOALS climate system model

To compare differences among the Medieval Warm Period (MWP), Little Ice Age (LIA), and 20th century global warming (20CW), six sets of transient and equilibrium simulations were generated using the climate system model FGOALS_gl. This model was developed by the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences. The results indicate that MWP warming is evident on a global scale, except for at mid-latitudes of the North Pacific. However, the magnitude of the warming is weaker than that in the 20th century. The warming in the high latitudes of the Northern Hemisphere is stronger than that in the Southern Hemisphere. The LIA cooling is also evident on a global scale, with a strong cooling over the high Eurasian continent, while the cooling center is over the Arctic domain. Both the MWP and the 20CW experiments exhibit the strongest warming anomalies in the middle troposphere around 200?C300 hPa, but the cooling center of the LIA experiment is seen in the polar surface of the Northern Hemisphere. A comparison of model simulation against the reconstruction indicates that model??s performance in simulating the surface air temperature changes during the warm periods is better than that during the cold periods. The consistencies between model and reconstruction in lower latitudes are better than those in high latitudes. Comparison of the inter-annual variability mode of East Asian summer monsoon (EASM) rainfall during the MWP, LIA and 20CW reveals a similar rainfall anomalies pattern. However, the time spectra of the principal component during the three typical periods of the last millennium are different, and the quasi-biannual oscillation is more evident during the two warm periods. At a centennial time scale, the external mode of the EASM variability driven by the changes of effective solar radiation is determined by the changes of large scale land-sea thermal contrast. The rainfall anomalies over the east of 110°E exhibit a meridional homogeneous change pattern, which is different from the meridional out-of-phase change of rainfall anomalies associated with the internal mode.     

基于火灾模型的消防应急平台架构和功能分析

为预防和应对丽江古城发生大规模火灾,提出了消防应急平台架构。该平台包括信息获取、应急智能和决策指挥三大系统,运用地理信息系统(GIS)技术,将基础空间信息和消防安全信息整合,将火灾模拟分析、风险评估与消防应急指挥、数字应急预案制订有机结合起来。其中的火灾预测预警模型采用了基于元胞自动机的城区火灾蔓延模型。结合人员疏散和损失评估模型进行风险评估。消防应急决策指挥流程实现火灾预测与消防指挥的融合,为提高火灾安全管理和消防指挥能力提供了帮助。     

利用系统动能学建立可行性分析模型

系统动能学是提供建立动态性复杂性系统的工具.在许多领域都已经有应用的实例.通过系统动能学的流线图来模拟系统结构,并获得系统量化的数据,且可以提供决策参考.研究所提出的方法不必通过方程式,直接以流线图通过Powers-im软件建构的技巧来达到研究目的.对韩国荣山江水运建设的可行性分析建立因果关系模型并进行分析.     

接入系统导线选择技术比较模型与方法研究

导线在电力系统中起着传输电能的作用,是连接发电部分和负荷部分之间的桥梁。导线在电力系统稳定性,线路损耗和投资经济性方面也占据着重要的地位。合理的选择导线,是电力系统设计中的重要环节。以潮流计算为基础,建立基于线损的比较模型和验证方法,通过实例验证得出此模型选择接入系统导线大大减少线路损耗。     

服装CAD系统数学模型的研究

从服装CAD系统功能的需要出发，运用计算机图形学中的相关方法，建立服装CAD系统中主要功能模块的数学模型．为服装CAD系统开发提供了基本的方法和思路．     

丰田公司轮胎气压报警系统分析

通过对丰田公司研制的轮胎气压报警系统进行分析,阐述了其几项关键技术及组成部件、工作原理、使用方法等,并对轮胎气压报警系统的发展趋势作了展望.     

橡胶垫隔震支座的一种弹塑性计算模型

为有效地防止地震作用对建筑结构和部件引起的破坏运动,文章采用Ansys8.1程序中已有的单元,建立了橡胶隔震支座的弹塑性计算模型。通过典型结构实例分析,初步证明了文章建议的方法简便有效,较合理地模拟了模型,能够满足工程验算要求,为隔震结构工程计算提供了合理方法和理论根据。