Studies on wind environment around high buildings in urban areas

High buildings or architectural complex in urban areas remarkably distort the urban surface wind fields. As the air flow approaches,local strong wind may appear around the buildings. The strong wind makes the pedestrians on sidewalks, entrances and terrace very uncomfortable and causes the pedestrian level wind environment problem. In this studies, hot-wire wind measurement, wind scouring in wind tunnel and numerical computation were carried out to evaluate the wind environment of tall buildings in the prevailing flow conditions in Beijing areas. The results obtained by three techniques were compared and mutually verified. The conclusions drawn from three approaches agree with each other. Also the advantages and limitations of each method were analyzed. It is suggested that the combination of different techniques may produce better assessment of wind environment around high buildings.     

一种台风海面非对称风场的构造方法

针对台风数值预报中由于采用对称模型而导致预报误差的现实，通过引入非对称分布的台风最大风速、最大风速半径等因子，在得到台风报告中7级风和10级风的半径的基础上，利用最佳权系数方案来得到非对称的台风外围风速分布因子，从而对Chan and Williams 1987年提出的切向风廓线方案进行改造，进而得到了台风海面非对称风场的计算式。检验表明，该方法能够描述台风海面风场的非对称分布，具有较好的应用前景。     

OC4漂浮式风电平台的水弹性响应及波浪载荷研究

漂浮式风电平台在波浪中的摇晃运动会导致塔架根部产生很大的弯矩,极大地威胁平台结构安全。同时流体的附连水质量效应对平台塔架结构的动响应有着较为显著的影响,因此充分考虑这种流固耦合效应有利于更加准确地评估平台塔架的结构动响应。采用三维频域线性水弹性方法计算塔架在流体作用下的结构共振频率特征以及各阶模态振动的主坐标响应特性,然后通过弹性模态叠加法获得塔架的弯矩载荷。并结合概率学手段,预报了短期极限海况下塔架弯曲载荷响应,为新一代漂浮式风电平台结构安全性评估和方案设计提供了技术支撑。     

耗散大气中水平不均匀风场对内重力波传播的影响

采用包括耗散的射线跟踪方法,计算了在水平不均匀风场作用下,不同尺度重力波从对流层直至220km观测高度的传播,结果表明,垂直于重力波传播方向的风以及风剪切能够引起波射线的折射,从而导致重力波明显偏离初始传播方向.在强顺风场作用下,由于风场引起的捕获,大量重力波不能传播到观测高度.由于风场引起的多普勒频移,小周期的重力波在弱顺风条件下能够传播到观测高度.由于反射作用,强逆风场不支持周期低于约18min的较高频重力波的传播.而在弱逆风作用下,大部分中尺度范围重力波都能够传播到观测高度.本文统计了武汉电离层观象台的TID观测数据随热层风场的分布,统计结果与模拟结果符合较好.     

凤城市赛马镇风洞洞穴特征及发育基本条件

赛马镇风洞是我国东北规模较大的岩溶洞穴,洞长在2000m以上,已探测长度1265m.风洞具有纵坡降较小、支洞繁多、形态奇异及国内罕见的溶蚀景观“天锅”等特征.岩性、构造、水文地质特征等是控制洞穴发育的基本条件.风洞的发育约始于中更新世40万年前.     

Granule ripples in the Kumtagh Desert,China: Morphology,grain size and influencing factors

Granule ripples are found mainly in four regions of the Kumtagh Desert in China; they are characterized by an asymmetrical shape, with gentle lower slopes on both sides and abrupt crests. The ripples tend to be oriented perpendicular to the prevailing winds, except when they form near obstacles such as yardangs. The wavelengths (λ) range between 0·31 m and 26 m and heights (h) range from 0·015 m to 1 m. The relationship between wavelength and height can be described by a simple linear function, and the mean ripple index (λ/h) is about 20·4 for the study sites. The sediments are poorly sorted, with negative to very negative skewness at lee and stoss slopes and between‐ripple troughs, which confirms the ‘poured in’ and ‘shadow’ appearance described by previous researchers. The bimodal or trimodal distributions of grains (with modes of ?1·16φ, ?0·5φ and 3·16φ) and the enrichment of coarse particles at the ripple surface (with coarse granule contents ranging between 5·2% and 62·1%) indicate that the underlying layer is the original sediment source and that the granule ripples resist erosional processes. Although the impact of saltating particles and, consequently, the creep and reptation of coarse grains are responsible for granule ripple initiation at a micro‐scale, however, the characteristics of local sediments, wind regimes and topographical obstacles, as well as the feedbacks among bedform and airflow, more strongly affect the development and alignment of granule ripples at a macro‐scale.     

Energy distributions of the large-scale horizontal currents caused by wind in the baroclinic ocean

Wind is the main energy source for the generation of the internal waves and the ocean mixing. Wunsch[1] estimated that about 1 TW (1 TW = 1012 W) energy was transported into the ocean from the winds by us-ing the altimeter data. Watanabe et al.[2] numerically calculated that the mixing processes obtained 0.7 TW energy from the global wind, which afforded most of the energy needed by the maintenance of the Merid-ional Overturning Circulation (MOC). During the past 50 years, in the Norther…     

黄海暖流的路径及机制研究

利用NASA/AVHRR 反演的每日海表面温度资料, 法国航天局AVISO 发布的海表面高度资料,中国气象科学数据共享服务网成山头台站的日均风场资料, 首先对黄海海表面温度分布进行了分析,揭示了表征黄海暖流的暖水舌存在两个分支。然后对1981 年10 月～2010 年5 月这两个分支发生情况进行了统计, 得出两个分支并...     

2010年西北太平洋与南海热带气旋活动异常的成因分析

利用中国气象局热带气旋（TC）资料、NCEP/NCAR 再分析资料和美国 NOAA 向外长波辐射（OLR）等资料,分析了2010年西北太平洋（WNP）及南海（SCS）热带气旋活动异常的可能成因,讨论了同期大气环流配置和海温外强迫对TC生成和登陆的动力和热力条件的影响。结果表明,2010年生成TC频数明显偏少,生成源地显著偏西,而登陆TC频数与常年持平。导致7～10月TC频数明显偏少的大尺度环境场特征为：副热带高压较常年异常偏强、西伸脊点偏西,季风槽位置异常偏西,弱垂直风切变带位置也较常年偏西且范围偏小,南亚高压异常偏强,贝加尔湖附近对流层低高层均为反气旋距平环流,这些关键环流因子的特征和配置都不利于 TC 在WNP的东部生成。影响TC活动的外强迫场特征为：2010年热带太平洋经历了El Ni?o事件于春末夏初消亡、La Ni?a事件于7月形成的转换;7～10月,WNP海表温度维持正距平,140°E以东为负距平且对流活动受到抑制;暖池次表层海温异常偏暖,对应上空850 hPa为东风距平,有利于季风槽偏西和TC在WNP的西北侧海域生成。WNP海表温度和暖池次表层海温的特征是2010年TC生成频数偏少、生成源地异常偏西的重要外强迫信号。有利于7～10月热带气旋西行和登陆的500 hPa风场特征为：北太平洋为反气旋环流距平,其南侧为东风异常,该东风异常南缘可到25°N,并向西扩展至中国大陆地区;南海和西北太平洋地区15°N以南的低纬也为东风异常;在这样的风场分布型下,TC容易受偏东气流引导西行并登陆我国沿海地区。这是2010年生成TC偏少但登陆TC并不少的重要环流条件。     

青海互助一次局地强降水天气多普勒雷达回波分析

利用西宁CINRAD/CD多普勒天气雷达资料及自动站观测数据等从影响降水的主要因子方面探讨了2011年7月2日晚青海互助县一次局地强降水的成因,结果表明:多单体强回波带的活动是造成互助短时强降水的主要原因;速度图上强的辐合和逆风区是预报强降水的关键因子;垂直风廓线图上强烈的垂直风切变是不稳定能量积聚的表现,与强降水联系紧密;垂直累计液态含水量(VIL)和回波顶高也能为强降水预报提供有效信息。