有限区域湿有效位能收支方程

有效位能是大气能量学中较出色的创见,它的收支方程,有助于揭示能量制造、积聚、释放条件,在理论与实际工作中都占重要地位。自六十年代史密斯(Smith,P.J.)提出有限区域有效位能及其收支方程后,很多人进行过这方面的研究。约翰逊(D.R.     

大气湿位涡影响夏季江淮降水异常的机理分析

利用欧洲中心再分析资料(ERA-40)中1958-2001年气象场资料(世界时00时),分析了降水异常年850 hPa湿位涡及其分量差异的原因.结果表明,降水异常年湿位涡和湿位涡正压部分的差异主要是由水汽的垂直分布差异引起稳定度的变化所致,而相对湿位涡和湿位涡斜压部分的差异,分别主要是由垂直涡度及纬向风的垂直切变和暖湿气流的经向切变所致.另外,还利用湿位涡的正压部分和斜压部分讨论了江淮夏季850 hPa大气性质的变化,结果表明,近50年来,大气对流不稳定减弱,而斜压不稳定增强.     

能量位涡在雷雨大风天气诊断分析中的应用

从大气基本运动方程及大气总能量概念出发,提出将大气动力学与能量天气学相结合的物理量——干能量位涡与湿能量位涡,并确定其守恒性.通过分析发现,以静力温度表达的能量位涡数学计算更方便,物理意义更明确.以2007年湖北的一次典型雷雨大风天气为例,对雷雨大风天气用能量位涡进行诊断分析.结果表明:本文提出的干能量位涡与湿能量位涡可以较好地预示雷雨大风天气,高空干能量位涡的增强与向下发展使对流层中下层不稳定能量增大,有利于雷雨大风天气发生;低层湿能量位涡的不稳定能量高值区与斜压系统耦合时预示该区域将有雷雨大风发生.     

应用新型散度方程诊断暴雨的触发和增幅机理

分析散度及其变化是进行暴雨研究的途径之,而传统的散度方程不能显示包含热力场分布影响散度演变的问题。因此,利用陈忠明等导出的新型散度方程和NCEP/NCAR(1°×1°经纬度)再分析资料,针对贵州省2007年7月25—26日持续性大暴雨天气过程,通过计算新型散度方程中的各项,定量诊断分析大气运动的正压非平衡强迫、湿斜压非地转与风垂直切变耦合强迫在暴雨发生发展过程中的作用,并与地面1、6h降水观测资料和卫星云图资料进行对比分析。探讨正压非平衡强迫、湿Q矢量与垂直风切变的湿斜压热动力耦合强迫导致辐合增加与暴雨发生、发展的动力机制。结果表明:强降水主要发生在近中性或弱不稳定层结条件下。大气运动的正压非平衡强迫导致辐合增加是强降水过程的触发机制;在暴雨维持和增幅过程中,湿斜压热动力耦合强迫在强降水的维持方面扮演了重要角色。当强降水过程发生后,才存在湿斜压热动力耦合强迫作用,湿斜压热动力耦合强迫作用是暴雨增幅的动力机制。未来6小时强降水发生的区域、降水强度、中心位置与散度演变的强负值区变化一致。新型散度方程对强降水预报有指导意义,可以作为诊断散度场演变的一种有效的数学工具。     

中尺度干、湿对流影响环境场的差异分析

用1999年6月一次梅雨锋大暴雨过程高分辨的敏感性数值模拟结果分析了对流活动对大尺度环境的反馈作用，共设计了两个敏感性方案：干绝热过程(干调整)和包含水汽及凝结潜热释放的湿过程(湿调整)，两种调整过程包含的不稳定能量不同，对环境场造成的影响也不同。通过分析，得到以下几点结论：在对流强盛期间，湿调整比干调整更能增强底层辐合和高层辐散；当对流消失后即大气从不稳定调整到稳定状态后，两种调整过程对水平风场的影响基本相同；湿调整比干调整产生的垂直速度更大；湿调整比干调整更能使大气底层温度降低、高层温度升高。干、湿调整过程都是不稳定能量释放过程，当层结不稳定能量释放、产生强对流时，强上升运动中心的中下层辐合增加、高层辐散增加，当对称不稳定能量释放时，高层指向冷区一侧的水平风分量增强，底层指向暖区一侧的水平风分量增强。水平风场受对流影响后改变的量值与原有量值相当；不稳定能量释放可影响到对流中心周围5个经纬距以上的范围。     

湿有效位能及其在暴雨分析和预报中的应用

有效位能是大气能量学中很重要的创见之一。早在本世纪初,马古拉斯(M.Margules)讨论气旋发展的能源时就已提出(当时称为有效动能)。可惜的是,其后半个世纪,虽有人继续研究这个问题,但进展不大。本世纪五十年代,洛伦兹(E.N.Lorenz)在上述研究的基础上,重新提出有效位能的概念及其表达式,并用于大气环流的研究。继洛伦兹之后,达顿(J.A.Dutton)与约翰逊(D.R.Johnson)以及范米根(Van Mieghen J.)进行了更全面、更系统、更严谨的讨论。 六十年代末,史密斯(Smith P.J.)提出有限区域有效位能及其收支方程后,把有效位能概念及其收支方程用于天气分析研究者日益增多。 大气中的水汽对天气变化有很大影响,在天气分     

湿有效位能的一种近似表达式及其计算方案

大气中的水份对天气变化有很大影响。所以在天气分析预报中,考虑了水汽的温湿特征量,比仅用位温的效果要好。由此推想,在有效位能的计算中,假若再计入潜热能项,将更接近大气能量的实际情况。可能正是这个缘故,E.N.洛伦茨(Lorenz)、谢义炳提出的湿有效位能(mAE)概念受到了很多人的重视。为此,讨论湿有效位能的近似表达式及其计算方案是有意义的。一、近似表达式类似于把单位气柱中的内能与位能之和称为总位能那样,本文把单位气柱中的内能、潜热能、位能之和,称为湿总位能(mTE):     

从不稳定能量角度对条件不稳定相关问题的讨论

大多数深厚的局地对流是在条件不稳定的层结中发生的,这就有必要考虑较厚气层对由底部上升气块所可能产生的总影响。从能量角度讨论了条件不稳定问题中的不稳定能量和对流有效位能,并利用观测资料、结合实例分析了单站地面湿静力能与条件不稳定中不稳定能量的关系。主要结论如下:（1）从能量观点,对对流有效位能的两种定义进行了讨论,认为对流有效位能定义为正、负不稳定能量之差时,其与动能相联系的表达式中包含了低层抬升速度,可以更全面地用于强对流天气预报,尤其是中国南方暖季的强对流预报。（2）气块从底层上升时,无论经历的是干绝热还是湿绝热过程,湿静力能守恒,所以总能量的变化就是动能的变化,等于外界合力对气块做功的大小,不存在湿静力能向动能的转换。（3）从本质上来说,单站低层湿静力能的时序变化用于对流预报的意义在于预示着正、负不稳定能量的改变,从而影响不稳定能量的值。这可以弥补由于高空探测时间分辨率较粗,不能计算逐时正、负不稳定能量的不足。      

大气环流的正斜压流型特征与季风类型

利用 NCEP/NCAR的 1 982～ 1 994年全球 1 2层等压面上的风场资料 ,计算了大气流场的正压分量 (即质量加权垂直平均 )和斜压分量 (即各层实际风与正压分量的差值 ) ,分析了全球冬夏季正斜压流场的分布特征 ,并从地面风场的正斜压流型角度对全球季风进行了分类。指出 :斜压流场和正压流场的季节变化都可以产生冬夏季盛行风向的反转 ,因而都能够产生季风。斜压流场反映了大气中不均匀加热 (主要是海陆热力差异 )所驱动的热力环流 ,而正压流场则主要代表动力作用所产生的环流 ,这对认识季风的性质很有意义。进一步分析表明 :亚洲热带地区、非洲、南美等典型季风区属斜压流型季风区 ,南、北半球太平洋中部的副热带地区也为季风区 ,但属正压流型季风区 ,而东亚副热带地区则属正斜压流型共同组成的混合流型季风区。     

2004年冬季风期间一次强寒潮过程的能量收支研究

利用1°(纬度)×1°(经度)的NCEP再分析资料和常规站点观测资料对2004年12月28～31日的一次强寒潮、冷涌过程作了研究,研究结果表明:(1)此次强寒潮事件在我国南海引发了强烈的冷涌,该支冷涌一直向南越过赤道影响南半球.大尺度环境场有利于此次寒潮、冷涌事件的爆发,本次寒潮属于“横槽转竖型”,其中200 hPa的西风带大槽经历了一次调整,500hPa经历了一次明显的横槽转竖过程,对流层低层蒙古高压稳定维持,其东侧的偏北大风是冷空气南下的有利条件.(2)此次寒潮大风区内的动能制造以正压动能制造和斜压动能制造为主,寒潮爆发初期,以正压制造过程为主,此后,由于有效位能释放的作用增强,斜压制造过程与正压制造强度相当,大风区随着动能制造的增强而增强;当斜压、正压动能制造均减弱,大风区亦随之减弱.(3)有效位能收支表明,整层有效位能的释放与大风区相对应,有效位能的释放有利于寒潮、冷涌的维持.寒潮大风区内,对流层高层受有效位能释放的影响最大,有效位能和风能可以互相转换;对流层中层所受的影响最小,且以风能向有效位能转换为主;对流层低层则以有效位能向动能转化为主,十分有利于低层风速的增大和维持.     

Climate policy strength compared: China,the US,the EU,India, Russia,and Japan

The few systematic international comparisons of climate policy strength made so far have serious weaknesses, particularly those that assign arbitrary weightings to different policy instrument types in order to calculate an aggregate score for policy strength. This article avoids these problems by ranking the six biggest emitters by far – China, the US, the EU, India, Russia, and Japan – on a set of six key policy instruments that are individually potent and together representative of climate policy as a whole: carbon taxes, emissions trading, feed-in tariffs, renewable energy quotas, fossil fuel power plant bans, and vehicle emissions standards. The results cast strong doubt on any idea that there is a clear hierarchy on climate policy with Europe at the top: the EU does lead on a number of policies but so does Japan. China, the US, and India each lead on one area. Russia is inactive on all fronts. At the same time climate policy everywhere remains weak compared to what it could be.

Policy relevance

This study enables climate policy strength, defined as the extent to which the statutory provisions of climate policies are likely to restrict GHG emissions if implemented as intended, to be assessed and compared more realistically across space and time. As such its availability for the six biggest emitters, which together account for over 70% of global CO₂ emissions, should facilitate international negotiations (1) by giving participants a better idea of where major emitters stand relative to each other as far as climate policy stringency is concerned, and (2) by identifying areas of weakness that need action.     

1,800 Years of abrupt climate change, severe fire, and accelerated erosion, Sierra Nevada, California, USA

This paper provides both a detailed history of environmental change in the Sierra Nevada over the past 1,800 years and evidence for climate teleconnections between the Sierra Nevada and Greenland during the late Holocene. A review of Greenland ice core data suggests that the magnitudes of abrupt changes in temperature and precipitation increased beginning c. 3,700 and 3,000 years ago, respectively. Precipitation increased abruptly 1,300 years ago. Comparing paleotemperature data from Cirque Peak, CA with paleoprecipitation data from Pyramid Lake, NV suggests that hot temperatures occurred at the beginnings of most severe droughts in the Sierra Nevada over the past 1,800 years. Severe fires and erosion also occurred at Coburn Lake, CA at the beginning of all severe droughts in the Sierra Nevada over the past 1,800 years. This suggests that abrupt climate change during the late Holocene caused vegetation and mountain slopes in some areas to be out of equilibrium with abruptly changed climates. Finally, the ending of drought conditions in Greenland coincided with the beginning of drought conditions in the Sierra Nevada over the past 1,800 years, perhaps as a result of the rapidly changed locations of the Earth??s major precipitation belts during abrupt climate change events.     

The temperature dependent,infrared absorption cross-sections for the chlorofluorocarbons: CFC-11, CFC-12, CFC-13, CFC-14, CFC-22, CFC-113, CFC-114, and CFC-115

The infrared absorption cross-sections for eight commonly used halogenated methanes and ethanes have been measured as a function of temperature from 203 to 293 K. High resolution spectra (0.03 cm^-1) have been used to derive integrated band strengths and peak cross-sections associated with the spectral features in the infrared region from 600 to 1500 cm^-2. The values obtained in this study are compared to those from previous reports, and recommendations are made for uses in atmospheric sensing and radiative energy transfer models. The observed temperature dependence in the spectral features is also discussed.     

基于L波段探空的云区边界识别改进算法

利用气象业务中使用的L波段探空数据和毫米波云雷达观测资料,分析探空相对湿度在入云和出云时的变化规律,提出一种基于探空相对湿度阈值与梯度相结合的云区边界识别改进算法,并利用云雷达观测数据对算法识别结果进行验证.利用北京市南郊观象台2019年1—6月层状云样本验证分析,结果表明:改进算法相比相对湿度阈值法,对云区边界识别更...     

Wind-Driven, Double-Gyre, Ocean Circulation in a Reduced-Gravity, 2.5-Layer, Lattice Boltzmann Model

A coupled lattice Boltzmann （LB） model with second-order accuracy is applied to the reduced-gravity, shallow water, 2.5-layer model for wind-driven double-gyre ocean circulation. By introducing the secondorder integral approximation for the collision operator, the model becomes fully explicit. The Coriolis force and other external forces are included in the model with second-order accuracy, which is consistent with the discretization accuracy of the LB equation. The feature of the multiple equilibria solutions is found in the numerical experiments under different Reynolds numbers based on this LB scheme. With the Reynolds number increasing from 3000 to 4000, the solution of this model is destabilized from the anti-symmetric double-gyre solution to the subtropic gyre solution and then to the subpolar gyre solution. The transitions between these equilibria states are also found in some parameter ranges. The time-dependent variability of the circulation based on this LB simulation is also discussed for varying viscosity regimes. The flow of this model exhibits oscillations with different timescales varying from subannual to interannual. The corresponding statistical oscillation modes are obtained by spectral analysis. By analyzing the spatiotemporal structures of these modes, it is found that the subannual oscillation with a 9-month period originates from the barotropic Rossby basin mode, and the interarmual oscillations with periods ranging from 1.5 years to 4.6 years originate from the recirculation gyre modes, which include the barotropic and the baroclinic recirculation gyre modes.     

The microstructure of selected, small, isolated, cumulus clouds near Red Deer, Alberta

Physical experiments designed to explore the potential of rain augmentation through airborne glaciogenic seeding on small, isolated non-precipitating cumuliform clouds near Red Deer, Alberta were carried out during the period 1982–1985. The microstructure of 90 cumulus congestus clouds have been documented through repeated in-situ sampling using a cloud physics instrumented aircraft platform. Observations from the inspection passes of 57 clouds seeded with either dry ice pellets or silver iodide pyrotechnics, and all the passes of 33 natural clouds are presented.Measurements of the cloud droplet concentration indicate that Alberta cumulus clouds are typically continental in nature, with an average droplet concentration of 535 cm⁻³ and an average droplet diameter of 10.6 μm. Alberta clouds have average liquid water contents of 0.57 g m⁻³, with a peak 1-sec value of 3.17 g m⁻³. The 1-km average liquid water contents are 0.83 g m⁻³, with a peak value of 2.81 g m⁻³. Cloud lifetimes vary between 11 and 20 minutes. Concentrations of naturally occurring ice crystals are found to be low. The average maximum 1-km ice concentration was 31⁻¹, and the peak 1-km concentration was 73.11⁻¹ in the natural cloud dataset. Evidence of precipitation-sized particles was detected in 21% (7 of 33) of the clouds, and precipitation below cloud base was detected in 6% (2 of 33) of the clouds.A comparison of the Alberta cloud characteristics to the cumulus clouds from different locations showed that there are some distinct differences between Alberta clouds and the clouds from the other regions.     

江苏三次不同量级降雪过程的对比分析

利用常规观测资料和NCEP 1°×1°再分析资料,通过对发生在江苏的三次不同量级的区域性暴雪、大雪和中雪过程典型个例进行对比分析,发现降雪时,700hPa低空急流的位置和强度是影响降雪量级的主要因素之一;降雪区上空涡度的垂直分布遵循低层负涡度、中层正涡度和高层负涡度的配置,暴雪时正涡度强且正涡度区最为深厚,动力抬升作用强,中雪发生时正涡度区相对最为浅薄,不利于形成强辐合抬升,动力抬升作用弱。且暴雪和大雪发生时基本上整层都为垂直螺旋度正值区,中雪时没有出现明显的正值区;暴雪和大雪过程时中低层都具有明显的逆温层,中高层西南急流造成的对流层中层的爆发性增温是逆温层形成的关键,中雪发生时不一定有逆温层结;降雪强度与湿位涡分量绝对值存在一定的正相关关系。     

承德市一次由快速发展气旋诱发的大风天气分析

利用常规观测资料和NCEP/NCAR(1°×1°)逐6 h再分析资料,对承德市2017年5月5—6日大风天气的环流形势和物理量进行分析,结果表明气旋的快速发展(气旋加深率0.84 B)导致锋生加强,引发气压和变压梯度加大是导致大风的直接原因。500 hPa高压脊东移迫使冷空气向南堆积,高空槽不断发展成为冷涡,温度平流为地面气旋的发展提供热力条件,高低层涡度平流的差异,也是地面气旋快速发展的重要原因;当1.5 PVU位涡面伸展至对流层低层时,局地位涡异常在气旋的发展过程中不可忽视;高空急流出口区发生质量调整,出口区左侧的辐散强度达10×10~(-5) s~(-1),使低层大气减压,有利于气旋发展。     

Weeds, Insects, and Diseases

The geographic distribution, vigor, virulence, and agricultural impact of weeds, insects, and plant pathogens will be affected by climatic changes accompanying the global "greenhouse effect." Weed/crop competitive interactions, particularly among species differing in photosynthetic pathway (C₃ v C₄), may be altered, with the C₃ species favored by increasing CO₂. Physiological and biochemical changes induced in host crop plants by rising CO₂ may affect feeding patterns of pest insects. Compilation of climatic thresholds for phenological development of pest insects reveals the potential for shifts in pest behavior induced by global warming and other climatic change. Generation times may be reduced, enabling more rapid population increases to occur. Poleward migration may be accelerated during the crop season. The epidemiology of plant diseases also will be altered. Prediction of disease outbreaks will be more difficult in periods of rapidly changing climate and unstable weather. Environmental instability and increased incidence of extreme weather may reduce the effectiveness of pesticides on targeted pests or result in more injury to non-target organisms. Biological control may be affected either negatively or positively. Overall, the challenge to agriculture from pests probably will increase.     

Governance,complexity, and resilience

This special issue brings together prominent scholars to explore novel multilevel governance challenges posed by the behavior of dynamic and complex social-ecological systems. Here we expand and investigate the emerging notion of “resilience” as a perspective for understanding how societies can cope with, and develop from, disturbances and change. As the contributions to the special issue illustrate, resilience thinking in its current form contains substantial normative and conceptual difficulties for the analysis of social systems. However, a resilience approach to governance issues also shows a great deal of promise as it enables a more refined understanding of the dynamics of rapid, interlinked and multiscale change. This potential should not be underestimated as institutions and decision-makers try to deal with converging trends of global interconnectedness and increasing pressure on social-ecological systems.