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.     

Atmospheric oscillations over the last millennium

The variations of global atmospheric oscillations over the last millennium, including the North Atlantic Oscillation (NAO), the North Pacific Oscillation (NPO) highly associated with the Pacific Decadal Oscillation (PDO), the Southern Oscillation (SO) and the Antarctic Oscillation (AAO), are studied and compared in this paper based on observations and reconstructed data. The cross correlation analysis of AAO, NAO and NPO shows that there is no significant relationship on interannual variation among them. However, the consistency on decadal variability is prominent. During A.D.1920–1940 and A.D.1980–2000, the positive (strong) phase was dominant and the negative (weak) one noticeable during A.D.1940–1980. In addition, the reconstructed atmospheric oscillations series demonstrate that the positive phase existed in the early of the last millennium for NAO and in the late of the last millennium for AAO, respectively; while it occurred in the mid-late of the last millennium for PDO and ENSO.     

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.     

Inter-hemispheric comparison of climate change in the last millennium based on the ECHO-G simulation

The commonality and difference in the variations of temperature and precipitation between the Northern Hemisphere （NH） and Southern Hemispheres （SH） in the last millennium are investigated by analysis of the millennium simulation with the ECHO-G coupled climate model. The NH mean temperature variations are generally consistent with those of the SH counterpart on the interannual, decadal and centennial time scales. But, the transition times between the medieval warm period （MWP）, the little ice age （LIA）, and the present-day warm period （PWP） in the NH leads that in the SH; and the anomaly amplitude in the NH is significantly larger than the SH counterpart. For the precipitation variations, the NH mean precipitation varies in-phase with the SH mean precipitation on decadal and centennial scales （mainly in the mid-high latitudes） but out-of-phase on the interannual scale （mainly in the low latitudes）. During the MWP the warming has comparable amplitude in the NH and SH; however, during the PWP the NH warming is considerably stronger than the SH warming. Further, the present-day temperature rises in the NH high latitudes but decreases in the SH high latitudes, which is very different from the warming pattern during the MWP. Since during the MWP the greenhouse gases （GHG） concentration stayed at a low level, we infer that the present-day opposite temperature tendency in the high latitudes between the two hemispheres may be related to the increase of the GHG concentration.     

卫星实测臭氧总量资料在区域气候模拟中的应用研究

 将卫星观测的TOMS臭氧总量资料应用于区域气候模拟中,在不同纬度的地区采用随季节变化的臭氧总量.以中国地区为例,对比模拟了考虑臭氧随季节、纬度变化和模式原有的固定臭氧值对气候的不同影响.结果发现:对区域气候模式RegCM2而言,用于研究中国地区时,模式中的臭氧总量比实际状况偏大,利用实测臭氧资料后能产生负的晴空辐射强迫,并引起云量变化,导致地表温度变化.     

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.     

武汉近百年来气温变化的多时间尺度分析

用墨西哥帽小波变换分析了武汉１９０５～１９９８年逐月气温资料,揭示了气候变化的多时间尺度结构,分析了其中存在的主要周期振荡和突变点。结果表明：武汉气候在２０世纪主要经历了冷－暖－冷－暖４个阶段,目前处于相对暖期;气温存在准２ａ、２１ａ和６５左右的周期振荡;不同时间尺度下具有不同的冷暖结构和气候突变点。     

神农架大九湖12 500 a.B.P以来的孢粉植物群与气候变化

根据孢粉分析,将神农架大九湖12500a.B.P以来的孢粉植物群划分为15个演替阶段,从寒温带针叶林到北亚热带常绿阔叶混交林等多个植被型都有出现。植被带的垂直高度随气候变化上下移动,最冷时（12500－10700a.B.P）下移900－1100m,最暖时（5200－6450a.B.P）上移500－700m,孢粉植物群所反映的古气候变化具有明显的阶段性。12500－7400a.B.P气候相对冷干,但温度和降水回升很快,最冷时年平均温度和降水比今低6．1℃和195mm;7400－3300a.B.P气候最为暖湿,但仍有波动,最暖时年平均温度和降水比今高3．9℃和195mm;3300a.B.P以后气候小幅度波动,冷暖干湿多次交替。     

Possible solar forcing of climate variability in the past 4000 years inferred from a proxy record at the southern margin of Tarim Basin

A ca. 4000a decadal-resolution climate proxy record of the mean grain-size from a lake (or mash) sediment at the southern margin of the Tarim Basin, correlates visually with the atmospheric 14C record from tree ring (residual △^14C, solar proxy) and the GISP2 ice core δ^18O record (temperature proxy). In general, △^14C maxima (solar minima) are coincident with cold (wet) periods in the study area and cold periods in the Greenland ice core. Power spectrum analysis revealed statistically significant periodicities of 196a, 121a, 97a, 62a, 45a and 33--30a, which are similar to those principal solar-oscillation periods as inferred from the atmospheric radiocarbon and other proxy records. Possible solar forcing is addressed to be the main driving forcing of climate change in the southern margin of Tarim Basin.     

An ice-core record of vegetation and climate changes in the central Tibetan Plateau during the last 550 years

We present a 550-year ice-core pollen record with a 5-year resolution from the Puruogangri ice field in the central Tibetan Plateau.Analysis of the relationship between pollen record and instrumental observations suggests that the sum of the steppe and meadow pollen taxa is a good indicator of summer (June-August) temperature,whereas the ratios of Cyperaceae/(Gramineae+Artemisia) [Cy/(G+A)] as well as M/S (meadow to steppe percentages) are indicative of humidity changes in this region.Together with δ18O and...     

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.     

Vegetation and climate changes during the last 8660 cal. a BP in central Mongolia, based on a high-resolution pollen record from Lake Ugii Nuur

Based on modern pollen studies and reliable chronology of nine AMS 14C dates, a detailed history of vegetation and climate changes during the past 8660 cal. a BP was reconstructed by a high-resolution pollen record from Ugii Nuur in central Mongolia. Poaceae-steppe dominated the study area and the climate was mild and semi-humid before 7800 cal. a BP with a noticeable cool and humid interval at 8350―8250 cal. a BP. Xerophytic plant increased and the climate became warm and dry gradually since 7800 cal. a BP...     

宏观教育系统SD模型的构建初探

按照系统动力学建模的理论和方法,分析了宏观教育系统的测量指标,并对查有梁先生的相关理论进行了统计检验和修正,最终构建了宏观教育系统的因果关系图,对实际仿真过程中需要的流图、方程等都作出了必要的估计和说明,为宏观教育系统的研究工作提供了一个新的视角。