南海台风生成前48 h环流特征及热力与动力条件

利用1979—2019年4—11月中国气象局上海台风研究所热带气旋最佳路径资料和静止卫星红外云图资料,筛选出189例南海台风,结合欧洲中期天气预报中心1°×1°再分析资料,分析南海台风生成前48 h至生成时刻的天气环流和动力、热力条件。结果表明：南海台风生成于热带洋面大范围的高海表温度、高水汽含量和高不稳定层结区,其生成前的主要环境背景环流是赤道辐合带、西南季风或东风波等;台风生成前扰动中心常常处于其北侧风切变小而南侧风切变大的过渡带中,少数扰动中心倾向于风切变小值中心附近,风切变与扰动的发展之间无显著相关;扰动中心一般与垂直涡度中心重合,垂直涡度中心是表征扰动自身强弱的物理量,但垂直涡度自身的大小与未来扰动发展趋势关系不明显,而Okubo-Weiss（OW）指数则对于扰动的发展以及扰动位置确定有较好的指示意义;在扰动发展过程中,扰动中心附近存在一个贯穿整个对流层的位涡柱,低层扰动部分与位涡柱中的中低层位涡相互作用,有利于扰动发展。     

因子的持续和转折对我国盛夏降水预测效果的影响

由于影响我国盛夏（7—8月）降水异常的主要因子前期（或从冬季到夏季）不同的月际演变特征对其后降水异常的影响不同,所以针对影响因子的月际“持续异常”和“转折变化”对盛夏降水异常的预测方法也应该是不同的。本文以国家气候中心整理的78项月环流特征量指数和CPC/NOAA的30项指数为因子,设计了能够反映影响因子的月指数特征量“持续异常”和“转折变化”的两套影响因子库,用“滑动相关—逐步回归—集合分析”方法分别建立预测模型,改进预测方案,这样建立的统计预测模型重点考虑了前期影响因子不同的变化特征。用距平符号一致率（PSS）与空间距平相关系数（ACC）为指标,对比分析不同因子处理方案对我国160站盛夏（7—8月）降水预测效果的影响,结果显示：两种因子选择方案均具有一定的预测能力;相比之下,“转折变化”因子选取方案的预测效果更好;用单站交叉建模序列与实测序列的相关系数为指标,挑选其中相关系数更高的因子选取方案结果作为集合方案预测结果,集合方案的预测效果有进一步提高的潜力。     

The Weakening of the Asian Monsoon Circulation after the End of 1970＇s

The transition of the global atmospheric circulation in the end of 1970＇s can clearly be detected in the atmospheric temperature, wind velocity, and so on. Wavelet analysis reveals that the temporal scale of this change is larger than 20 years. Studies in this work indicate that the trend of the transition over the mid-latitude Asia is opposite to that of global average for some variables at the middle troposphere. Another finding of this research is that the African-Asian monsoon circulation is weaker and the trade wind over the tropical eastern Pacific is weaker as well after this transition. Such a signal may be found in the summer precipitation over China as well.     

数学模型在深圳西部港区规划中的应用

本文通过伶仃洋海区整体二维潮流盐度泥沙数学模型,从水沙角度分析了深圳西部港区的建港优势,并进一步通过局部二维潮流数学模型,对赤湾港区各种规划方案的水流变化情况进行了模拟。通过分析比较,提出了推荐方案,从而也说明数学模型这一研究手段在港口规划研究中的作用。     

一个两时间层分裂显格式海洋环流模式(MASNUM)及其检验

A two-time-level, three-dimensional numerical ocean circulation model（named MASNUM） was established with a two-level, single-step Eulerian forward-backward time-differencing scheme. A mathematical model of large-scale oceanic motions was based on the terrain-following coordinated, Boussinesq, Reynolds-averaged primitive equations of ocean dynamics. A simple but very practical Eulerian forward-backward method was adopted to replace the most preferred leapfrog scheme as the time-differencing method for both barotropic and baroclinic modes. The forward-backward method is of second-order of accuracy, computationally efficient by requiring only one function evaluation per time step, and free of the computational mode inherent in the three-level schemes. This method is superior to the leapfrog scheme in that the maximum time step of stability is twice as large as that of the leapfrog scheme in staggered meshes thus the computational efficiency could be doubled. A spatial smoothing method was introduced to control the nonlinear instability in the numerical integration. An ideal numerical experiment simulating the propagation of the equatorial Rossby soliton was performed to test the amplitude and phase error of this new model. The performance of this circulation model was further verified with a regional（northwest Pacific） and a quasi-global（global ocean simulation with the Arctic Ocean excluded） simulation experiments. These two numerical experiments show fairly good agreement with the observations. The maximum time step of stability in these two experiments were also investigated and compared between this model and that model which adopts the leapfrog scheme.     

气候平均风场作用下热带太平洋主流系和赤道行星波研究

本文使用一种水平高分辨率的热带太平洋风动环流模式耦合气候月平均风场,研究了热带太平洋主流系和温跃层厚度的分布和季节变化以及赤道行星波的传播。     

河口盐淡水混合的几个认识和概念问题

本文讨论了河口的定义,范围以及盐淡水混合的类型、程度和强度等问题,认为盐淡水混合状态 淡水混合作用是两个不同的概念,不能混为一谈。     

Adjustment time of the first baroclinic Rossby wave in the global oceans

1Introduction Planetary waves involve the main processes bywhich perturbation signal in one part of the ocean istransferred to another part.In the1970s,mostof theprevious theoretical studies focus on the local Ekmanpumping and the nondispersive long baroc…     

Argo floats revealing bimodality of large-scale mid-depth circulation in the North Atlantic

Analysis of Argo float trajectories at 1 000 m and temperature at 950 m in the North Atlantic between November 2003 and January 2005 demonstrates the existence of two different circulation modes with fast transition between them. Each mode has a pair of cyclonic - anticyclonic gyres. The difference is the location of the cyclonic gyre. The cyclonic gyre stretches from southeast to northwest in the first mode and from the southwest to the northeast in the second mode. The observed modes strongly affect the heat and salt transport in the North Atlantic. In particular, the second mode slows down the westward transport of the warm and saline water from the Mediterranean Sea.     

0917号台风“芭玛”折向东南向移动原因分析

利用NCEP全球数据同化系统(GDAS)1°×1°分析资料,对0917号台风"芭玛"折向东南向移动原因进行了分析。结果表明,中高纬度环流调整是"芭玛"折向东南向移动的根本原因;0918号台风"茉莉"通过改变外围环境场的强度、形状对"芭玛"台风产生间接影响,而两台风之间逆时针互旋以及台风"茉莉"外围强大的环流对台风"芭玛"的直接作用是台风"芭玛"折向东南向移动的关键。对台风"芭玛"经纬向UV最大风速变化诊断分析表明,"芭玛"经纬向UV最大风速中心的转移对"芭玛"折向东南向移动有重要影响,经纬向UV最大风速差的变化对"芭玛"转向具有预示作用,经纬向最大风速差的合成风方向与台风中心未来移动方向有一定的关系。