全球大气角动量的幂分布律

探讨了不同角动量的空气在全球大气中各占了多大的比例问题。指出（1）不同的地转角动量与其占有的大气质量之间为幂函数关系;（2）相对角动量仅为地转角动量的2．54％。     

比较法在“质点角动量及其守恒定律”教学中的应用

采用比较法,对非物理专业大学物理中“质点角动量及其守恒定律“章节从角动量概念、力矩概念、角动量定理和角动量守恒定律课程内容的引入以及复习两方面着手,重新编排了知识点引入的顺序,得到了不同于教材内容顺序的教学思路,得到大多数学生认可。据此认为,用比较法组织课程内容可以降低知识点的难度,加深对知识点的理解。     

近61年夏半年西南低涡的统计特征与异常发生的流型分析

利用NCEP/NCAR再分析资料,统计了1954 2014年间夏半年(5 10月)西南低涡发生次数的年际变化,并着重分析了西南低涡异常发生年份的气候特征。结果表明,西南低涡多发年,低层流场在西南低涡关键区表现为西南风旺盛且辐合异常强,气旋性切变加大,低纬季风环流增强,导致大量正角动量输送至关键区,有利于西南低涡生成;同时印度洋输送至关键区的水汽通量增加,也有利于降水发生。而西南低涡少发年,低纬季风减弱,关键区为异常北风控制,南支绕流偏弱,水平散度场表现为辐散异常强,造成角动量输送减弱,不利于西南低涡生成;且来自于印度洋的季风水汽输送减弱,亦不利于降水发生。因此,除地形和加热作用外,西风带以及季风环流带来的水汽和角动量输送也是影响西南低涡发生的重要因子。     

全球大气角动量变化的比较分析

利用日本气象局ＧＳＭ９６０３大气数值模式和客观分析资料以及美国环境预报中心大气再分析数据研究比较全球大气角动量变化。分析表明，三者大气质量再分布角动量东经９０°Ｅ分量的符合程度要好于格林威治方向的分量；而且ＧＳＭ９６０３对大气轴向相对角动量季节变化的强度模拟与其他两者一致，并明显优于第一阶段 ＡＭＩＰ ２３个大气环流模式的平均模拟结果。另外，ＧＳＭ９６０３大气相对角动量的年际变化基本显示了厄尔尼诺变化的主要历程。     

登陆台风变性过程的诊断研究

本文对一个登陆台风(Freda)的衰减阶段和变性阶段进行了涡度及角动量收支的诊断分析,主要结果表明:相对涡度和相对角动量都是反映低压变化的重要指标。衰减阶段,次网格尺度效应及摩擦作用是台风衰减的主要因子,变性阶段,次网格尺度效应对于涡度和角动量在系统内部的重新分布起了重要作用;涡度的侧边界输送和散度制造对于整个过程都是重要的。台风低压是一个角动量汇区,系统角动量主要来源于侧边界平均输送,横向质量环流对于角动量过程起着关键性作用。     

我国近海热带气旋强度突变的气候特征分析

利用２．５×２．５格距的风场及气压资料,计算分析９０１２号热带气旋登陆后维持６５小时不消的各标准时次的角动量收支。得到的结果是：９０１２号热带气旋登陆后,进入一个相对稳定的鞍型场的中心,低层有西南风急流将大量潮湿空气卷入热带气旋,为其提供充足的潜热能,北侧弱冷空气的侵入,为其提供了斜压能量;而对流层上部气旋４°－８°半径上的地转角动量的涡旋输送及β项产生的气旋角动量的输入,则是气旋中心气压和最大风速维持的直接因素。     

能谱分析在暴雨中期预报中的应用

本文分析了我省暴雨天气发生前期５００ｈＰａ扰动动能、角动量输送谱的演变特征，指出暴雨天气发生前扰动动能在长波（４～６波）有一高能中心形成，而角动量输送在中纬度有强烈的辐合中心，并建立了暴雨天气的中期能谱预报模型。     

1998年5～6月区域大气角动量收支与东亚天气尺度系统变化

利用NCEP/NCAR再分析资料计算了1998年5～6月区域角动量收支的主要分量,对比分析了范围较大的欧亚区域角动量矩和限制在欧亚大陆范围内的喜马拉雅山角动量矩的差异,发现两者有很好的相关,限制较小范围的计算表明,喜马拉雅山山脉力矩的作用显著。角动量收支项占较大量级的山脉力矩和摩擦力矩,并与梅雨锋区域的700hPa高度...     

西风角动量输送的气候特征及其与急流关系研究

利用1958～1997年NCEP/NCAR一日四次的风场再分析资料,系统地分析了季节平均西风角动量（即u角动量）经向、垂直输送通量及其三个分量（平均经圈环流、定常波、瞬变涡输送通量）的气候特征,特别是讨论了12～2月、6～8月它们与东、西风带、副热带西风急流、极夜急流之间的联系。结果表明:（1）包含纬度因子的角动量通量与动量通量在高纬地区存在显著差别,高纬对流层上部的强动量输送中心在角动量通量中不明显。而u角动量强经向输送主要在中低纬对流层顶附近和冬半球高纬平流层顶附近,副热带西风急流和极夜西风急流均位于u角动量强向极输送中心及其高纬一侧的辐合区中。（2）发现三个输送分量对急流维持的作用随纬度、季节不同。北半球冬季（夏季）的副热带西风急流主要由平均经圈环流（强度相当的定常波和瞬变涡）强经向输送及辐合维持;南半球西风急流全年均由平均经圈环流和瞬变涡旋输送及辐合维持;冬半球中平流层极夜急流主要由定常波、瞬变涡旋输送及其辐合共同维持。（3）热带东风区是牵连角动量（即Ω角动量）的高值区,它主要由平均经圈环流向对流层上部输送;冬半球副热带及中纬西风区存在u角动量垂直输送的切变区,它主要由平均经圈环流和瞬变涡旋完成;热带对流层顶附近有u角动量的定常波弱向下输送。     

全球500kPa角动量与EP通量的季节变化

利用ＥＣＭＷＦ提供的９ａ（１９８Ｏ－１９８８）资料，从定性和定量角度分析５００ｈＰａ全球东西风带的角动量和ＥＰ通量的季节过渡。结果发现：不仅角动量存在明显的季节性急变，而且反映波活动的ＥＰ通量也存在相应的季节性急变。另外，季节性急变的发生时间在东西风带亦有所不同。     

1980-2010年冬季北极涛动季节内振荡的成因分析

采用NCEP/NCAR日平均再分析资料,对冬季热带外低频振荡(大气角动量收支及地形力矩)与AO(Arctic Oscillation)指数进行计算,通过功率谱和统计分析发现,它们都存在30~60 d的周期,大气角动量收支与山脉力矩的变化为正相关,且显著响应AO变化。通过动力学诊断分析初步认为,北半球两大地形的山脉力矩作用于纬向大气角动量,副热带纬向西风发生变化,改变南北西风偶极子结构,使得AO产生变化,而且在两大地形中以喜马拉雅山脉地形作用为主。通过对喜马拉雅山脉地区的动力学诊断发现,在高(低)AO指数阶段,喜马拉雅山脉地区激发准定常行星波并作用于副热带西风,导致副热带西风偏弱(偏强),高纬西风偏强(偏弱),因而AO偏强(偏弱),平流层极涡偏强(偏弱),极涡强(弱)中心偏向东北亚。     

Atmospheric Angular Momentum Transport and Balance in the AGCM-SAMIL

NCEP/NCAR reanalysis data and the spectral atmospheric general circulation Model (AGCM) of IAP/LASG (SAMIL) are employed to investigate the transport and balance of atmospheric angular momentum (AAM). It is demonstrated that SAMIL depicts the general features of the AAM transport and balance reasonably well. The AAM sources are in the tropics and sinks are in the mid-latitudes. The strongest meridional transport occurs in the upper troposphere. The atmosphere gains westerly momentum and transports it upward in the areas of surface easterlies, and downward into the areas of surface westerlies. Consequently, AAM balance is maintained. Systematic biases of the model compared to the reanalysis and observations are revealed. Possible mechanisms for these biases are investigated. In SAMIL, the friction torque in the tropics is stronger compared to the observations, which is probably due to the excessive precipitation along the Inter-tropical convergence zone (ITCZ) in the model, since the simulated Hadley circulation is much stronger than observed. In the winter half of the year, the transport center is in the lower troposphere in the SAMIL model, but it is in the upper troposphere in the reanalysis and observations. These discrepancies also suggest that simulations of convection and tropical precipitation need to be improved and that higher resolution is necessary for a quantitative simulation of AAM transport and balance. Results also demonstrate that the analysis of the transport and balance of atmospheric angular momentum is a powerful tool in diagnosing climate models for potential improvement.     

Spatial and Temporal Variations of Atmospheric Angular Momentum and Its Relation to the Earth Length of Day

The characteristics of atmospheric-angular-momentum （AAM） and length-of-day （LOD） on different timescales are investigated in this paper, on the basis of the NECP/NCAR reanalysis data and an LOD dataset for 1962-2010. The variation and overall trend of the AAM anomaly （AAMA） at different latitudes are presented, and the relationship between AAMA and LOD is discussed. The AAMAs in different latitude regions exhibit different patterns of variation, and the AAMA in the tropics makes a dominant contribution to the global AAMA. In the tropics, the AAMA propagates poleward to the extratropical regions. It is confirmed that a downward propagation of the AAMA occurs in the lower stratosphere. Correlation analysis shows that the relationship between AAMA and LOD varies significantly on different timescales. Specifically, the tropical AAMA is positively correlated with LOD on short timescales, but they are not obviously correlated on long timescales. This indicates that the interaction between AAM and the earth＇s angular momentum follows the conservative restriction on short timescales, but the influence of the earth angular momentum on that of the atmosphere depends on the interaction process on long timescales.     

AN ATMOSPHERIC MOTION EQUATION BUILT ON THE CONSERVATIVE RELATIONSHIP OF THE ANGULAR MOMENTUM EXCHANGE BETWEEN THE SOLID EARTH AND THE ATMOSPHERE ON SEASONAL-ANNUAL TIMESCALE*

Within the seasonal-annual timeseale,there exists an angular momentum conservative exchange relationship between the solid earth and the atmosphere,and their angular momentum exchange not only can cause variations in length-of-day(LOD) but also can express anomalies in atmospheric general circulation.Therefore,their angular momentum exchange mechanism should be introduced into the general circulation model.Considering the angular momentum anomalous exchange caused by the air-earth interface friction effect,a whole-layer atmospheric motion equation is derived in this paper including the earth spin anomalous friction force parameterized by using the change in the earth rotation rate.Through analysing the equation,it shows that the magnitude of the earth spin anomalous friction force is the same as that of Coriolis force on seasonal-annual timescale.     

AN ATMOSPHERIC MOTION EQUATION BUILT ON THE CONSERVATIVE RELATIONSHIP OF THE ANGULAR MOMENTUM EXCHANGE BETWEEN THE SOLID EARTH AND THE ATMOSPHERE ON SEASONAL-ANNUAL TIMESCALE

Within the seasonal-annual timeseale,there exists an angular momentum conservative exchange relationship be-tween the solid earth and the atmosphere,and their angular momentum exchange not only can cause variations inlength-of-day(LOD)but also can express anomalies in atmospheric general circulation.Therefore,their angular mo-mentum exchange mechanism should be introduced into the general circulation model.Considering the angular momentum anomalous exchange caused by the air-earth interface friction effect,awhole-layer atmospheric motion equation is derived in this paper including the earth spin anomalous friction forceparameterized by using the change in the earth rotation rate.Through analysing the equation,it shows that the magni-tude of the earth spin anomalous friction force is the same as that of Coriolis force on seasonal-annual timescale.     

季风低压角动量收支的研究

本文给出移动坐标系中角动量收支方程,并采用FGGE IIIb资料,对发生在印度地区1979年8月6—11日的季风低压作了角动量收支的诊断分析,得到:(i)在低压发展期间,角动量的时间变率为正;低压减弱期为负。(ii)水平侧边界角动量输送是系统角动量的主要来源,而高层东风和低层西风的增强、减弱,则是影响这种输送的重要因素。(iii)在气压场不对称的情况下,侧边界附近的气压力矩是另一个重要的角动量源。(iV)摩擦力矩是主要的角动量汇。据此,可以推论,对于印度季风扰动的发展、维持,水平侧边界输送和边界附近气压力矩的作用最为重要。     

The Role of diabatic heating, torques and stabilities in forcing the radial- vertical circulation within cyclones part iii: case study of lee-side cyclones

１．ＩｎｔｒｏｄｕｃｔｉｏｎＡｎａｇｒｅｅｍｅｎｔｂｅｔｗｅｅｎｔｈｅｓｉｍｕｌａｔｅｄａｎｄ“ｏｂｓｅｒｖｅｄ”ａｚｉｍｕｔｈａｌｙ－ａｖｅｒａｇｅｄｍａｓ－ｗｅｉｇｈｔｅｄｒａｄｉａｌｍｏｔｉｏｎｓｈａｓｂｅｎｅｓｔａｂｌｉｓｈｅｄｆｏｒｔｈｅＯ...     

Reexamination of the Relationship between Tropical Cyclone Size and Intensity over the Western North Pacific

This study reexamines the correlation between the size and intensity of tropical cyclones (TCs) over the western North Pacific from the perspective of individual TCs, rather than the previous large-sample framework mixing up all TC records. Statistics show that the positive size-intensity correlation based on individual TCs is relatively high. However, this correlation is obscured by mixing large samples. The weakened correlation based on all TC records is primarily due to the diversity in the size change relative to the same intensity change among TCs, which can be quantitatively measured by the linear regression coefficient (RC) of size against intensity. To further explore the factors that cause the variability in RCs that weakens the size-intensity correlation when considering all TC records, the TCs from 2001 to 2020 are classified into two groups according to their RC magnitudes, within which the high-RC TCs have a larger size expansion than the low-RC TCs given the same intensity change. Two key mechanisms responsible for the RC differences are proposed. First, the high-RC TCs are generally located at higher latitudes than the low-RC TCs, resulting in higher planetary vorticity and thus higher planetary angular momentum import at low levels. Second, the high-RC TCs are susceptible to stronger environmental vertical wind shear, leading to more prolific outer convection than the low-RC TCs. The positive feedback between outer diabatic heating and boundary layer inflow favors the inward import of absolute angular momentum in the outer region, thereby contributing to a larger size expansion in the high-RC TCs.