Relationship between the tropical cyclone genesis over the Northwest Pacific and the sea surface temperature anomalies

Using the tropical cyclone (TC) data derived from the Joint Typhoon Warning Center (JTWC) and the sea surface temperature data derived from the Joint Environmental Data Analysis Center (JEDAC) at the Scripps Institute of Oceanography from January 1955 to December 2000, we analyzed the relationship between the TC genesis over the Northwest Pacific (NWP) and the sea surface temperature anomalies (SSTA) over the Pacific basin. A long-term trend indicated that the highest frequency of monthly TC genesis appeared earlier and the annual genesis sum increased gradually during the last half century with some oscillations. No significant synchronous correlation was found between the NWP TC events and the SSTA over the Pacific basin, while the annual sum of TC genesis was closely related with the SSTA averaged from the first three months (January, February and March) of the year in the equatorial western and eastern Pacific and over mid-high latitudes of the North Pacific. The results implied that there are an interannual El Nio SSTA mode in the equatorial western and eastern Pacific and an interdecadal SSTA mode in the northern Pacific, which affected the TC genesis. A regression analysis between the first three-month SSTA and the annual TC sum based on two time scales was conducted. The correlation coefficient between simulated and observed TC sums reached a high value of 0.77.     

Relationship between the tropical cyclone genesis over the Northwest Pacific and the sea surface temperature anomalies

Using the tropical cyclone (TC) data derived from the Joint Typhoon Warning Center (JTWC) and the sea surface temperature data derived from the Joint Environmental Data Analysis Center (JEDAC) at the Scripps Institute of Oceanography from January 1955 to December 2000, we analyzed the relationship between the TC genesis over the Northwest Pacific (NWP) and the sea surface temperature anomalies (SSTA) over the Pacific basin. A long-term trend indicated that the highest frequency of monthly TC genesis appeared earlier and the annual genesis sum increased gradually during the last half century with some oscillations. No significant synchronous correlation was found between the NWP TC events and the SSTA over the Pacific basin, while the annual sum of TC genesis was closely related with the SSTA averaged from the first three months (January, February and March) of the year in the equatorial western and eastern Pacific and over mid-high latitudes of the North Pacific. The results implied that there are an interannual El Nio SSTA mode in the equatorial western and eastern Pacific and an interdecadal SSTA mode in the northern Pacific, which affected the TC genesis. A regression analysis between the first three-month SSTA and the annual TC sum based on two time scales was conducted. The correlation coefficient between simulated and observed TC sums reached a high value of 0.77.     

环流循环除尘系统分离柱内旋风流场分析

由柱坐标系下的Navier-Stokes方程出发,建立了环流循环除尘系统分离柱内流速场新的数学模型,利用具有成熟使用经验的加权残值法对流场进行求解,并与实验结果进行了比较。结果表示,所采用的数学模型和计算方法是可行的。     

导叶式旋风管排气管内流动减阻的试验研究

通过对导叶式旋风管内流动参数的测量分析,发现排气管内气流旋转强度高,并存在“滞流”、“倒流”及逆压梯度等无益于颗粒分离的流动状态,造成排气管内压力损失约占旋风管总压降的22%。在排气管内安装框形结构后,可有效削弱和抑制上述耗能流动,在保证分离效率基本不变的前提下,使旋风管减阻幅度达到9%。     

A reduced‐order simulated annealing approach for four‐dimensional variational data assimilation in meteorology and oceanography

Four‐dimensional variational data assimilation in meteorology and oceanography suffers from the presence of local minima in the cost function. These local minima arise when the system under study is strongly nonlinear. The number of local minima further dramatically increases with the length of the assimilation period and often renders the solution to the problem intractable. Global optimization methods are therefore needed to resolve this problem. However, the huge computational burden makes the application of these sophisticated techniques unfeasible for large variational data assimilation systems. In this study, a Simulated Annealing (SA) algorithm, complemented with an order‐reduction of the control vector, is used to tackle this problem. SA is a very powerful tool of combinatorial minimization in the presence of several local minima at the cost of increasing the execution time. Order‐reduction is then used to reduce the dimension of the search space in order to speed up the convergence rate of the SA algorithm. This is achieved through a proper orthogonal decomposition. The new approach was implemented with a realistic eddy‐permitting configuration of the Massachusetts Institute of Technology general circulation model (MITgcm) of the tropical Pacific Ocean. Numerical results indicate that the reduced‐order SA approach was able to efficiently reduce the cost function with a reasonable number of function evaluations. Copyright © 2008 John Wiley & Sons, Ltd.     

220t/h立式旋风炉运行中应注意的几个问题

与其它炉型相比，旋风炉在运行方面有其特殊的要求，本文对国产立式旋风炉运行应注意的几个关键问题进行了分析．     

The persistent anomaly of summertime circulation over the Ural Mountains

The tropical heating and transient activity features during the period of the persistent anomaly of summertime circulation over the Ural Mountains are studied, and a possible mechanism responsible for formation and maintenance of persistent anomalies is proposed. The mechanism can be summarized as a kind of self-sustaining through a two-way interaction of stationary wave with transient eddies under the consistent forcing of abnormal heating in the tropics.     

西德LTG旋风除尘器除尘性能的测定与分析

目前,如何选择良好的除尘设备处理纺织生产中的纤维性粉尘,已引起各方面的极大重视。本文针对此问题,分析测定了从西德LTG公司引进的旋风除尘器的结构特点和除尘性能,以供选用LTG旋风除尘器时参考。     

轴流导叶式旋风管内气固两相流的实验研究

为研究颗粒分离机理,提高分离性能,采用五孔球探针测试仪及等动采样法对轴流导叶式旋风管内气固两相流速度与压力分布进行了测量,并分别对不同导流锥和排尘结构参数下的纯气流流场及颗粒浓度场分布进行了对比分析。实验结果表明,旋风管内气流切向速度分布呈典型的准Rankin涡结构,固相颗粒分布在离心力作用下沿径向分为近壁的密相区与中心的稀相区。减小导流锥下口内径,采用带有排尘侧缝的单锥排尘结构有利于旋风管内颗粒的分离。     

1980-2015年间北部湾海域热带气旋的变化及特征分析

由于地理特征独特,北部湾地区常年遭受热带气旋的影响。热带气旋引起的波浪灾害和风暴潮灾害对广西沿海经济、生活造成了巨大影响。本文采用中国气象局热带气旋最佳路径数据集,研究了1980—2015年间进入北部湾的热带气旋的变化及特征,对北部湾海域内热带气旋的频数、强度、持续时长、功耗指数等年际趋势变化进行分析。结果表明:1980—2015年,北部湾地区热带气旋的频数、持续时长呈波动减小趋势,其强度呈波动增加趋势,整体上功率耗散系数(Power Dissipation Index,PDI)的正效应大于负效应。本研究为北部湾地区的海洋防灾减灾提供了相关科学依据。