对流层大气的负熵流和熵产生

将原始熵平衡方程应用于大气系统，详细计算了对流层大气平均状态下的负熵流和熵产生及其各项分量，得出了它们之间的一些数量关系，并应用熵理论初步解释了大气运动的某些规律，对于天气预报和气候变化的研究具有一定参考意义。     

一次远距离台风暴雨过程的熵流指数演变

应用耗散结构理论,结合河南省一次远距离台风暴雨过程,分析了大气排熵指数、边界层上部广义相当位温及广义相当位温平流等三个熵流指数与暴雨的发生和落区的关系,得到:大气排熵指数由高值向低值的演变有利于对流的发展,从而导致对流暴雨形成;暴雨落在大气排熵指数负值中心或负值轴线附近区域;远距离台风暴雨产生前,有高熵空气在边界层上部聚集,边界层高熵中心往往与暴雨落区对应;边界层上部高熵平流的移向往往预示了强降水的未来移向。     

Chanchu台风(0601)精细结构中的熵流特征分析

在耗散结构理论的基础上,根据热力学第二定律推导出了熵平衡方程。利用高分辨率模式输出资料通过对比Chanchu台风(0601)螺旋雨带上游、中游和下游及眼壁附近不同区域对流单体和熵流分布情况,揭示出负熵流值与台风的强对流单体有密切联系。基于负熵流与台风精细结构的配置分析,研究中尺度范围内熵流随Chanchu台风发生、发展、消亡各阶段的演变特征。分析表明,对流单体在从雨带上游至下游的演变过程中,熵流分布特征也会发生相应的变化,强对流单体与负熵流大值区相对应;当对流单体减弱,负熵流也随之减弱;当单体最后合并并汇入眼墙时,负熵流彼此合并旋入眼墙,有助于眼墙中深厚对流的维持和发展;此外,负熵流对于Chanchu台风在各发展阶段的强度变化也有一定的指示意义,揭示了负熵流对大气系统的组织化作用。      

河南一次西南涡暴雨的大气排熵指数特征分析

应用耗散结构理论,基于广义相当位温构建大气排熵指数,利用常规观测资料、地面加密自动站雨量资料、NCEP/NCAR 1°×1°再分析资料等,对2008年7月21—23日一次西南低涡东移造成的河南省大范围暴雨过程的大气排熵指数进行诊断分析,结果表明:大气排熵指数的演变与此次西南涡暴雨落区和雨强关系密切,暴雨落在负排熵指数中心偏南一侧,大雨以上降水分布在排熵指数负值中心轴线附近及其偏南侧;强降水开始前,排熵指数明显减小,强降水持续时间与排熵指数低值维持时间联系紧密;雨强不仅与排熵指数低值有关,且与低值维持时间、6h变化量也有密切关系。排熵指数低值中心位置和中心值的强弱变化与该个例中西南低涡中心位置和其强弱变化具有较好一致性。     

熵的演化与暴雨形成和落区的探讨

应用耗散结构理论，提出了大气中“湿滴”的具体计算公式和“相对湿滴”的概念，推导了便于在大气中实际应用的总熵流表达式。结合湖北省两次暴雨及特大暴雨天气过程，初步分析归纳了熵的演化与强对流暴雨和落区的关系；熵的演化与台风低压引发的暴雨和落区的关系，指出了两种暴雨过程的共同点和不同点；对台风低压的移动规律得到了某些有益的认识。     

“达维”台风大暴雨过程熵流特征分析

应用耗散结构理论,对2012年8月3—4日发生在河北省海岸带的一次台风暴雨过程进行诊断分析,着重分析了大气排熵指数、边界层上部平均广义相当位温与暴雨的发生和落区的关系。结果表明:副热带高压稳定少动和台风外围强盛的东南风急流造成了本次历史罕见的大暴雨局地特大暴雨天气;大气排熵指数由高值向低值的演变有利于对流的发展,从而导致对流暴雨形成;负熵流区涵盖了强对流或对流性大暴雨发生的主要区域,暴雨产生前5~6 h,有高熵空气在边界层上部聚集,暴雨区位于高熵中心附近、低空切变线和地面辐合线附近,与高熵舌伸展的区域相一致。     

大气中的耗散结构与对流运动

本文论证熵平衡方程可用来判断大气中对流和降水的发生,非线性热力学理论中的超熵产生可用来判断天气系统的产生.     

正压大气中尺度半平衡和准平衡动力学模式

应用描写正压大气运动的基本方程组，分析了中尺度大气运动的物理特征，指出非平衡强迫运动是引起中尺度重要天气演变的根本原因。中尺度动力学方程组是中尺度动力学理论研究的基础，因此，结合中尺度大气运动的基本特征，依据严格的尺度分析理论和摄动理论，简化基于流体力学和热力学的大气动力学方程组使之能够恰当地描述出中尺度运动的基本特征，对于中尺度动力学的发展是极为必要的。基于非线性平衡方程所得到的半平衡和准平衡动力学模式分别与半地转和准地转模式极为相似，它们可以较精确地描述中尺度大气运动的基本特征，因而，可作为中尺度动力学研究的理论基础。将准平衡动力学模式应用于中尺度涡旋系统的研究，结论表明中尺度平衡涡旋系统主要是受梯度风控制，其流场和气压场的发展演变则由一个演化方程来描写，获得了较为理想的结果。     

全球大气位温的两个不等价约束及其服从Gamma分布的证明

本文对全球大气位温积分守恒和热力学总熵守恒的物理含义及其不等价性进行了讨论。认为，作为对大气热力学状态较完整的描述，应将大气热力学总熵守恒这一约束条件补入数值预报模式中去。利用最大熵原理和上述两个约束条件，在理论上对大气位温服从Gamma分布这一从实际资料中揭示出来的事实进行了证明，得到了理论与实际完全吻合的结果。     

开放多相系熵密度平衡方程在暴雨预报中的应用

利用耗散结构理论的相关知识,从非平衡态理论的熵密度平衡方程出发,计算了2004年6月23日发生在湖南西部和北部地区暴雨发生前24h至暴雨结束前12h每隔6h对流层中低层的熵变场。通过对各个不同时刻的熵变场的分析与比较,讨论了熵场变化与暴雨区域、强度及其演变之间的关系,为暴雨强度和落区预报提供了参考指标。     

对台风麦莎(2005)的熵流特征初步分析

根据热力学第二定律推导出熵平衡方程,并在数值模拟输出结果的基础上利用熵平衡方程中的熵流项来分析2005年台风"麦莎"发生、发展和消亡各阶段的熵流特征.(1) 从对流层的低层到对流层的高层,台风中心附近的熵流分布会逐渐由负熵流占优势互补趋向于以正熵流为主;(2) 对流层中层500 hPa的负熵流分布显示出,随着台风的强度加强(减弱),台风中心附近的负熵流强度也会随之加强(减弱);(3) 台风中心附近的负熵流分布和强度特征对于台风强度和未来移动路径有一定的指示意义.     

Predictability of a large-scale flow conducive to extreme precipitation over the western Alps

Summary The quality of numerical weather prediction has improved considerably since its beginning. Over the last decade, in the North Hemisphere and more specifically over Europe, the accuracy of global numerical weather predictions of 500 hPa height has increased by one day. However this remarkable achievement has to be considered true for average conditions since it is computed over many days/seasons with very different flow patterns and atmospheric states. It is known that atmospheric predictability and model errors are highly flow-dependent therefore an increase in skill for average conditions may not imply the same improvements in specific conditions. Moreover the potential value of numerical weather prediction is perceived to be higher in some specific conditions, like high-impact weather events. There is therefore a growing need to know the forecasting accuracy of significant weather events, something that cannot be easily inferred through average scores, not least because of the rarity of these events. For these reasons, a study has been carried out to examine the skill of the European Centre for Medium-Range Weather Forecast (ECMWF) global forecasting system in predicting a specific flow configuration that is believed to be associated with extreme precipitation events over the Alpine region. Despite quantitative predictions of extreme precipitations is still challenging, it was found that the large-scale flow conducive to major rain events has better predictive skill than average conditions. This is perhaps surprising since it is a common perception to associate severe weather with low predictability.     

ENTROPY FLOW CHARACTERISTICS ANALYSIS OF TYPHOON MATSA (0509)

The evolution of Typhoon Matsa (0509) is examined in terms of entropy flow through an entropy balance equation derived from the Gibbs relation, according to the second law of thermodynamics. The entropy flows in the various significant stages of (genesis, development and decaying) during its evolution are diagnosed based on the outputs of the PSU/NCAR mesoscale model (known as MM5). The results show that: (1) the vertical spatial distribution of entropy flow for Matsa is characterized by a predominantly negative entropy flow in a large portion of the troposphere and a positive flow in the upper levels; (2) the fields of entropy flows at the middle troposphere (500 hPa) show that the growth of the typhoon is greatly dependent on the negative entropy flows from its surroundings; and (3) the simulated centres of heavy rainfall associated with the typhoon match well with the zones of large negative entropy flows, suggesting that they may be a significant indicator for severe weather events.     

AOGS第六届学术年会气象学研究报告综述

简要综述了第六届亚洲大洋洲地球科学学会（AOGS）学术年会有关天气和气候的可预报性、协同亚洲季风试验、季风变化及其模拟与预测、气候变化与热带气候灾害、中层大气研究、中尺度气象学与台风研究以及卫星资料应用等方面的报告内容。在全球气候变化的大背景下,季风的年代际变化特征,可能成因及其对天气气候的影响是目前研究的热点问题之一。对亚洲季风系统形成机制的探讨及其与气候系统关系的研究有助于提高数值模式对季风系统的模拟能力,从而能够更好地预测季风系统及其演变。集合预报,特别是多模式超级集合预报方法引起了人们广泛的兴趣。研究报告指出,多个积云对流参数化方案的集成、集合卡曼滤波、条件非线性最优扰动法以及滑动训练期超级集合预报技术对数值天气预报的准确率都有明显改善。＂可预报性障碍＂在数值模式对大气环流的预报中同样存在。＂可预报性障碍＂本质上反映了系统的季节变化对预报结果的影响。研究还表明,热带气旋频率和强度的变化取决于在其形成的海域是动力因子还是热力因子起主导作用,如热力因子起主导作用则气候变暖会使该区域的热带气旋活动频率和强度增加。一些研究指出,中高纬度阻塞形势持续异常及南海的热源异常可能是造成2008年初中国南方低温、雨雪和冰冻灾害的主要原因。Formosat-2和Formosat-3等卫星观测资料的广泛应用将极大地提高数值天气预报、气候监测和空间天气预报水平。     

Change in North American Atmospheric Conditions Associated with Deep Convection and Severe Weather using CRCM4 Climate Projections

Severe weather has important social and economic impacts. Some studies have indicated that its intensity may increase over this century as a consequence of climate change induced by greenhouse gases. This study aims to investigate the possibility of a future increase in deep convective events over North America resulting from the evolution of favourable atmospheric conditions. Our analysis is based on an ensemble of projections performed using the Canadian Regional Climate Model (CRCM) at 45?km resolution, driven by different Global Climate Models (GCMs) and reanalyses. We concentrate our study on Convective Available Potential Energy (CAPE), vertical wind shear, and convective precipitation. Based on two different approaches to linking atmospheric conditions and severe weather, we find that the number of extreme weather events is expected to increase during the twenty-first century. In agreement with other studies on this subject, we find that CAPE is expected to increase, whereas wind shear is expected to decrease slightly. Through the analysis of the CRCM's convective precipitation outputs, we show that severe convective liquid precipitation events may become both more frequent and slightly more intense. Sensitivity experiments show that results depend on the driving GCM although they confirm the general conclusions. Additional experiments conducted with reduced humidity input at the lateral boundaries show the significant role that the humidity level of the driving GCMs has on simulated extreme regional events. At the regional level results are, in general, consistent with those found at the continental scale, but large inter-regional variations exist.     

Nonlinearity and Finite-Time Instability in a T21L3 Quasigeostrophic Model

In this paper,a nonlinear optimization method is used to explore the finite-time instability of the atmospheric circulation with a three-level quasigeostrophic model under the framework of the conditional nonlinear optimal perturbation (CNOP).As a natural generalization of linear singular vector (SV),CNOP is defined as an initial perturbation that makes the cost function the maximum at a prescribed forecast time under certain physical constraint conditions.Special attentions are paid to the different structures and energy evolutions of the optimal perturbations.The results show that the most instable region of the global atmospheric circulation lies in the midlatitude Eurasian continent.More specially,SV and CNOP in the total energy norm with an optimization time of 2 days both present localness:they are mainly located in the midlatitude Asian continent and its east coast.With extension of the optimization time,SVs are more upstream and less localized in the zonal direction,and CNOPs differ essentially from SVs with broader zonal and meridional coverages; as a result,CNOPs acquire larger kinetic and available potential energy amplifications than SVs in the nonlinear model at the corresponding optimization time.For the climatological wintertime flow,it is seen that the baroclinic terms remain small over the entire time evolution,and the energy production comes essentially from the eddy kinetic energy,which is induced by the horizontal shear of the basic flow.In addition,the effects of SVs and CNOPs on the Eurasian atmospheric circulation are explored.The results show that the weather systems over the Eurasian continent in the perturbed fields by CNOPs are stronger than those by SVs at the optimization time.This reveals that the CNOP method is better in evaluating the instability of the atmospheric circulation while the SV method underestimates the possibility of extreme weather events.     

台风暴雨大气熵变场的诊断和对比分析

本文借助于熵平衡方程，对两个深入内陆的台风暴雨过程在负熵流作用下的减熵运动进行了诊断和对比分析，得到了以下结果:（1）台风大范围暴雨和强的负熵变相对应，因此可比常规方法较好地分辨出暴雨落区；（2）负熵变的汇合能够清楚地反映出中、低纬度天气系统的相互作用，为特大暴雨和台风远距离影响的特大暴雨的出现提供先兆；（3）本文导出的熵密度变化方程可以阐明，雨区内系统的发生、发展是和降水导致熵减小的物理过程相联系的；（4）大气熵辐散，特别是中、高层的熵辐散，对暴雨发生和持续的作用，不仅和潜热加热同样重要，甚至更有决定性意义。     

A Limb Correction Method for the Microwave Temperature Sounder 2 and Its Applications

The Microwave Temperature Sounder 2 (MWTS-2) is a cross-track radiometer that has 13 channels of sampling radiances emitted from different vertical levels of the atmosphere. Because of the varying scan angles of each field of view within a scan line, observations from the MWTS-2 are subject to strong scan-position-dependent features, i.e., the limb effect. When examining brightness temperatures (TBs), weather signals observed at every temperature-sounding channel are often concealed by scan-dependent patterns. This study, therefore, proposes a limb correction method to remove scan-dependent features so that the underlying weather signals can be uncovered. Limb-corrected TBs can be used to monitor large-scale patterns over the globe as well as extreme weather events such as typhoons. Limb-corrected TBs are also more correlated with atmospheric physical variables such as temperature and liquid water path.