Morphology and distribution of the three epiphytic dinoflagellate species Coolia monotis,C. tropicalis,and C. canariensis (Ostreopsidaceae,Gonyaulacales, Dinophyceae) from Vietnamese coastal waters     

The V. Ho  Lam N. Nguyen 《Ocean Science Journal》2014,49(3):211-221

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我国东北地区冬季气温变化的东亚冬季风背景          下载免费PDF全文

刘实  隋波  涂钢  冯喜媛 《应用气象学报》2014,25(1):11-21

利用中国气象局国家气象信息中心1961—2011年我国东北地区72个气象站月平均气温资料及NCEP/NCAR月平均海平面气压、500 hPa高度场及200 hPa与850 hPa风场再分析资料,对东亚冬季风强度与我国东北地区冬季气温序列经去除线性趋势处理后的变化特征进行对比分析。结果表明:去除线性趋势后,东亚冬季风强度与我国东北地区冬季气温序列的相关系数为-0.69,较原始序列更为显著;两者变化的阶段性较为同步,我国东北地区冬季气温于2004年已转入低温阶段,这与东亚冬季风同时转为偏强阶段关系密切;两者均存在20年左右的长周期,同样存在相近的阶段性短周期;我国东北地区冬季气温的增温变化趋势在1986年前后的增暖性气候突变中起重要作用。东亚冬季风强度与我国东北地区冬季气温年代际信号的相关系数达-0.86,较原始序列年代际相关更为显著;两者的年代际变化存在21.5年左右的共同准周期。东亚冬季风强度与我国东北地区冬季气温的年际变化序列存在4年左右的共同准周期。我国东北地区冬季气温的年际和年代际异常存在与东亚冬季风相关联的200 hPa东亚急流、500 hPa东亚大槽、乌拉尔高压、850 hPa风场、地面西伯利亚高压等的异常背景。  相似文献   

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赵红  张勤  瞿伟  涂锐  刘智 《大地测量与地球动力学》2014,34(3):63-67

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华东沿海ASCAT反演风速的检验和订正   总被引：2，自引：1，他引：1       下载免费PDF全文

姚日升  涂小萍  丁烨毅  王武军  邬方平  朱万云 《应用气象学报》2015,26(6):735-742

基于2010—2014年ASCAT反演风速、华东沿海14个浮标站和浙江沿海249个自动气象站资料,对华东沿海ASCAT反演风速进行检验和订正。研究表明:站点ASCAT风速误差不仅与离岸距离相关,而且与站点周围地形有关,误差较大的5个浮标站均位于舟山群岛附近海区,平均偏大4.79 m·s-1,其他海区浮标站的ASCAT反演风速平均偏差仅为0.46 m·s-1。ASCAT反演风速与浮标站风速的线性回归可有效减小反演风速误差,订正后误差大幅减小,误差越大的站点订正效果越好。相距160 km内的浮标站点间风速误差呈正相关,且站点间距越小,误差正相关越明显。考虑带影响半径的反距离权重,采用邻站方程订正法和邻站误差订正法分别对华东沿海ASCAT反演风速进行订正,均能明显减小平均偏差和均方根误差,两种方法订正效果接近,即两种方法均有较好的订正效果,可用于实际业务。  相似文献   

Observational climatology and characteristics of wintertime atmospheric blocking over Ural–Siberia     

Ho Nam Cheung  Wen Zhou  Yaping Shao  Wen Chen  Hing Yim Mok  Man Chi Wu 《Climate Dynamics》2013,41(1):63-79

This study investigates the climatological aspects and temporal characteristics of wintertime Ural-Siberian blocking (USB, centered over 30°–100°E), for the period 1980/1981–2009/2010. Sixty-eight events are identified and their physical structure is diagnosed using thermodynamic and geostrophic vorticity tendency equations. In climatology, horizontal advections play a fundamental role in constructing a USB event, in which the anticyclonic center is a warm core in the troposphere and a cold core in the lower stratosphere. The decay of the thermal structure is related to diabatic cooling along the vertical structure and warm advection in the lower stratosphere. Meanwhile, the collapse of the height structure is caused primarily by cyclonic vorticity advection. A strong interrelationship exists between the intensity and extension of USB events. The temporal characteristics of USB events are analyzed by examining strong and weak events, which are of high and low intensity. The strong events are probably preceded by an open ridge over Europe and a cyclogenesis over the Mediterranean Sea, and their formation is followed by the stronger amplification of a Rossby wave packet across Eurasia. On the other hand, the weak events are likely to be triggered by surface cold anomalies over Siberia. Overall, the evolution of a USB event forms a dynamic linkage with the Siberian high, in which the decay stage of the USB event is accompanied by a southeastward migration of the Siberian high and a subsequent cold air outbreak in East Asia. These results advance our understanding of USB and its relationship with East Asian winter monsoon activities.  相似文献   

气象装备寿命概念及其在气象装备保障中的应用     

房岩松  涂爱琴  黄磊 《气象科技》2013,41(5):861-863

将现已广泛应用于电子产品、机械设备尤其是军工产品制造和应用领域的寿命周期概念和理论引进到气象装备技术保障领域中,对气象装备的设计寿命、实际寿命、经济寿命、技术寿命和剩余使用寿命等几种不同的寿命概念进行了定义,并就每种寿命概念的应用进行了初步探讨.充分认识装备寿命的不同概念,将有助于提高气象装备维护、维修、更新、报废等各个业务环节的科学性,尤其是剩余使用寿命的概念,它的预测和应用将会促进现代维护维修理念的建立.  相似文献   

The influence of vegetation variation on Northeast Asian dust activity   总被引：2，自引：0，他引：2  

Rui Mao  Chang-Hoi Ho  Song Feng  Dao-Yi Gong  Yaping Shao 《Asia-Pacific Journal of Atmospheric Sciences》2013,49(1):87-94

In this study, we investigate the influence of vegetation variations on dust activity (dust load, dust transport in the troposphere, and dust weather frequency) over Northeast Asia during springtime. By using the Integrated Wind Erosion Modeling System, two model experiments are run over four-month periods, from February 1 to May 31, for each year from 1982 to 2006; one experiment uses the observed atmospheric conditions and vegetation (OBS), and the other uses the specified atmospheric conditions in 2006 and the observed vegetation (CTRL). Comparison of the two model experiments reveals that there are sensitive regions in southeastern Mongolia and central northern China, in which vegetation has a large potential to influence dust activity due to both the high dust emission rate and large variations in vegetation coverage. Over these sensitive regions, vegetation effectively lessens dust loads on interannual and interdecadal timescales; dust load is decreased by 2864 μg m^?2 for an increment of 0.1 in the normalized difference vegetation index (NDVI). Vegetation increase in the sensitive areas also reduces two major branches of dust transports in the low troposphere; one stretches from eastern Mongolia to regions northeastward, and the other flows across the south of northeastern China to Korea. In addition to dust loads and transports, vegetation increase in the sensitive areas evidently decreases dust storm frequency and blowing dust frequency, but it exerts a weak influence on the floating dust frequency. In the sensitive regions, as NDVI increases by 0.1, dust storms, blowing dust, and floating dust decrease by 4.0 days/spring, 1.5 days/spring, and 0.2 days/spring, respectively. In summary, vegetation variations in southeastern Mongolia and central northern China have considerable impact on northeast Asian dust during springtime.  相似文献   

Dynamic response of flexible rockfall barriers under different loading geometries   总被引：1，自引：1，他引：0  

Raymond C. H. Koo  Julian S. H. Kwan  Carlos Lam  Charles W. W. Ng  Jack Yiu  Clarence E. Choi  Axel K. L. Ng  Ken K. S. Ho  W. K. Pun 《Landslides》2017,14(3):905-916

Flexible steel barriers are commonly constructed on steep hillsides to mitigate rockfall. The evaluation of the dynamic response of proprietary flexible barriers is conventionally performed using full-scale field tests by dropping a weight onto the barriers in accordance with the European test standard ETAG 27. The weight typically has a spherical or polyhedral shape and cannot reproduce more complex rockfall scenarios encountered in the field. A rigid slab may load a barrier over a larger area and its effect has not been investigated. In this study, a calibrated three-dimensional finite-element model was developed to study the performance of vertically and horizontally orientated rockfall barriers under concentrated areal impact loads. A new bilinear force-displacement model was incorporated into the model to simulate the behavior of the energy-dissipating devices on the barriers. The effect of different weight geometries was studied by considering impacts by a rigid single spherical boulder and a rigid slab. Results reveal that areal loading induced by a rigid slab increases the loading on the barrier foundation by up to 40 % in both horizontally and vertically positioned barriers when compared to a concentrated load scenario with a single boulder. This indicates that barriers tested under the current test standard does not give the worst-case scenario in terms of foundation loads, and barrier designers should take into account the possible effect of increased foundation loads by reinforcing the barrier posts and/or increasing their spacing.  相似文献   

A new SPH-based approach to simulation of granular flows using viscous damping and stress regularisation   总被引：2，自引：1，他引：1  

Cuong T. Nguyen  Chi T. Nguyen  Ha H. Bui  Giang D. Nguyen  Ryoichi Fukagawa 《Landslides》2017,14(1):69-81

The smoothed particle hydrodynamics (SPH) method was recently extended to simulate granular materials by the authors and demonstrated to be a powerful continuum numerical method to deal with the post-flow behaviour of granular materials. However, most existing SPH simulations of granular flows suffer from significant stress oscillation during the post-failure process, despite the use of an artificial viscosity to damp out stress fluctuation. In this paper, a new SPH approach combining viscous damping with stress/strain regularisation is proposed for simulations of granular flows. It is shown that the proposed SPH algorithm can improve the overall accuracy of the SPH performance by accurately predicting the smooth stress distribution during the post-failure process. It can also effectively remove the stress oscillation issue in the standard SPH model without having to use the standard SPH artificial viscosity that requires unphysical parameters. The predictions by the proposed SPH approach show very good agreement with experimental and numerical results reported in the literature. This suggests that the proposed method could be considered as a promising continuum alternative for simulations of granular flows.  相似文献   

Investigation of the channelling effect on pollutants dispersion between adjacent roadway tunnels     

Y. Tao  J. Dong  X. Pan  Y. Xiao  J. Tu 《International Journal of Environmental Science and Technology》2017,14(12):2733-2744

The health risks presented by noxious vehicle emissions inside tunnels has been amplified due to the increasing use of roadway tunnels. Particularly, for adjacent roadway tunnels, vehicular emissions from the upstream tunnel can further deteriorate the air quality within the following tunnels. A scale vehicle tunnel model was designed to experimentally modelled the airflow and pollutants dispersion in contiguous roadway tunnels. The channelling effect on pollutants dispersion between adjacent roadway tunnels was studied, and factors such as ventilation speed, open road section length, traffic condition (e.g. car free, car running and traffic congestion) were considered. Pollutants mass flow rate ratio between downstream and upstream tunnels was calculated to evaluate the variation of the entrained pollutants amount. For the car free condition, pollutant can be easily entrained into the downwind tunnel when the gap distance between roadway tunnels decreased. For the car running condition with fixed tunnel gap distance, the traffic speed variation barely changed the pollutants mass flow rate ratio. Furthermore, evident influences on pollutants concentration were observed from continuous congestion and partial congestion. Lastly, numerical simulation using computational fluid dynamics approach was conducted for the car free scenario, and reasonably good agreements were found for pollutants concentration ratio compared with the experimental data. The results yielded from this study further quantified the relationships among different influential factors on the pollutants dispersion between roadway tunnels, and can contribute to an improved tunnel ventilation system design, especially for the downstream tunnel.  相似文献