Impact of cyclonic wind field on interaction of surge–wave computations using finite-element and finite-difference models     

A. D. Rao  Indu Jain  M. V. Ramana Murthy  T. S. Murty  S. K. Dube 《Natural Hazards》2009,49(2):225-239

Both finite-element and finite-difference numerical models are applied to simulate storm surges and associated currents generated by tropical cyclones that struck the coast of Andhra Pradesh, located on the east coast of India. During a cyclone, the total water level at any location on the coast is made up of the storm surge, surge–wind wave interaction and the tide. The advanced circulation two-dimensional depth-integrated (ADCIRC-2DDI) model based on finite-element formulation and the two-dimensional finite-difference model of storm surges developed at IIT Delhi, hereafter referred as IITD storm surge model, are used. These models are driven by astronomical tides at the open ocean boundary and cyclonic asymmetric winds over the surface of the computational domain. Comparison of model simulated sea-surface elevations with coarse and finer spatial resolutions suggests that the grid resolution near the coast is very crucial for accurate determination of the surges in addition to the local bathymetry. The model underpredicts surges, and the peak surge location shifts more to the right of the landfall as the spatial resolution of the model becomes coarser. The numerical experiments also demonstrate that the ADCIRC model is robust over the IITD storm surge model for surge computations as the coastline is better represented in the former.  相似文献   

夏季东亚和西北太平洋地区的气候变异及其机理   总被引：5，自引：0，他引：5  

陆日宇  富元海 《地球科学进展》2009,24(2):123-131

夏季东亚气候异常和西北太平洋地区有着密切的联系,表现为不同纬度间强烈的相互作用。由于这一地区的不同纬度间相互作用对东亚夏季气候异常具有重要的影响,最近20年,对这种相互作用的表现形式、三维空间分布、形成机理,及其与欧亚大陆遥相关波列和热带海温的关系等都做了大量的研究。对这些研究进行综述,侧重点放在近10年以来的研究工作,并对还需进一步研究的问题进行一些探讨。  相似文献   

Equivalent forcing depth in tropical oceans     

Takeshi Doi  Tomoki Tozuka  Toshio Yamagata 《Dynamics of Atmospheres and Oceans》2010,50(3):415-423

The forcing efficiency for the first and the second baroclinic modes by the wind stress in tropical oceans has been discussed by calculating equivalent forcing depth from annual mean, seasonal, and pentadal density profiles of the observational data. In the annual mean field, the first mode is forced preferentially in the western Pacific and the Indian Ocean, whereas the second mode is more strongly excited in the Atlantic and the eastern Pacific. This difference is mostly due to the pycnocline depth; the second mode is more dominantly forced where the pycnocline depth is shallower. We also revealed large seasonal variations of the second mode's equivalent forcing depth in the western Indian Ocean. The first mode is more dominantly forced during boreal spring and fall in the western Indian Ocean, while the second mode becomes more dominantly forced during boreal summer and winter. Those are due to seasonal variations of both the zonal wind and the pycnocline depth. Moreover, we show that the excitation of the second mode in the western Pacific increases after the late 1970s, which is associated with the decreasing trend of the zonal pycnocline gradient. Revealing the variation of the equivalent forcing depth will be useful for understanding the oceanic response to winds in tropical oceans and the improvement in the predictability of air-sea coupled climate variability in the tropics.  相似文献   

副热带高压对登陆台风影响的数值模拟研究   总被引：1，自引：0，他引：1  

季亮  费建芳  黄小刚 《气象学报》2010,68(1):39-47

中国登陆台风多发于夏季,尤其对于登陆后继续北上深入内陆的热带气旋,逐渐与其所处的中纬度环境场发生相互作用,强度衰减缓慢甚至再次发展,且伴随有台风动力、热力结构的转变(ET过程).同时,夏季多伴有副热带高压的活跃与西伸趋势,然而该系统与台风之间相互作用的物理机制仍不十分清楚,这已成为提高台风预报能力的主要障碍之一.文中选取1997年第11号台风"温妮"为研究个例,通过中尺度模式MM5模拟再现了该台风登陆后经历初期减弱、变性及变性后再次发展的演变过程.采用Davis等提出的片段位涡反演方法,改变模式积分初始时刻台风东部副热带高压强度,通过数值模拟与诊断分析的方法,深入研究不同强度副热带高压系统对台风陆上维持、变性和发展的影响.研究表明,副热带高压强度的加强加快了台风中心的北移速度,冷空气提前下沉入侵台风中心,加快台风的变性,配合暖气团的强迫抬升激发强烈的对流层中高层锋生,台风变性后冉次加强幅度增大.副热带高压强度的改变直接影响台风中心上空高空形势,而后者与台风强度的变化有较好的相关性.  相似文献   

THE ROLE OF COLD AIR AND CHARACTERISTICS OF WATER VAPOR IN BOTH TCS NANMADOL (0428) AND IRMA (7427) MAKING LANDFALL ON CHINA IN WINTERTIME   总被引：2，自引：1，他引：1  

何洁琳  管兆勇  万齐林  王黎娟 《热带气象学报(英文版)》2010,16(2):160-170

The NCEP/NCAR reanalysis data are used to investigate the role of cold air and moisture characteristics during the evolution of two cases of tropical cyclones (Nanmadol and Irma) which made landfall on China in wintertime. The results are shown as follows. (1) The East Asia trough steered the cold air into the tropical ocean in early winter. The tropical cyclones moved in opposite directions with a high moving out to sea and the enhancement of the pressure gradient at the periphery played a role in maintaining and strengthening the intensity of the storms. The intrusion of weak cold air into the low levels of the tropical cyclones strengthened them by improving the cyclonic disturbance when they were still over the warm sea surface. When the cold air was strong enough and intruded into the eyes, the warm cores were damaged and stuffed before dissipation. (2) The tropical cyclones were formed in a convergence zone of moisture flux and their development could enhance the disturbance of water vapor convergence, thus strengthening the moisture convergence zone. However, when they were outside the moisture zone, the storms could not gain sufficient water vapor and became weak. There were no belts of strong moisture transportation during the wintertime tropical cyclone processes.  相似文献   

福建一次秋季大范围暴雨成因分析   总被引：5，自引：2，他引：3  

吴启树  郑颖青  沈新勇  陈珠峰  林金凎 《气象科学》2010,30(1):126-131

应用常规观测资料及NCEP再分析等资料,对2008年10月5—6日福建大范围暴雨成因进行诊断分析。结果表明:热带低压倒槽与冷空气共同作用使暴雨区低层气旋性辐合加强,上升运动加剧;差动温度平流增强斜压大气对称不稳定度;次级环流圈的形成和维持加大了降水强度并延长了降水持续时间;南海低层偏南气流为暴雨区输送了源源不断的水汽,同时也提供了动力和热力条件,对不稳定能量的积累、输送和释放起了关键作用;暴雨区层结不稳定维持较长时间,垂直风切变为对流系统的发展提供动能,造成对流系统斜压发展,激发位势不稳定能量释放;螺旋度在诊断低压中心位置、发展和移动的能力比垂直速度或涡度单一因子更好,但与降水中心位置存在滞后现象。  相似文献   

热带气旋风雨影响范围人机交互识别业务系统   总被引：1，自引：1，他引：0  

万日金  赵兵科  张维  鲁晓琴 《气象科学》2010,30(5):741-745

主要介绍新近开发并投入业务使用的热带气旋(Tropical Cyclone,简称TC)风雨影响范围人机交互识别业务系统。该系统收集各省逐时逐分观测风雨资料建立TC影响地面风雨数据库,并充分利用M ICAPS(气象信息综合分析处理系统)综合显示多气象要素功能和交互划定区域功能确定TC影响范围,然后使用计算机图形学中区域内外射线判别法由程序挑选出影响范围内站点,再检索风雨资料数据库相应丰富数据,生成TC影响时大风和降水报表文件,以供TC过程影响分析和台风年鉴编撰。该系统克服了以往主观专家分离法耗时耗力的缺点,又避免了客观分离法的较大误差,大大提高了台风年鉴编撰工作效率和业务自动化水平,还可为台风大风降雨气候研究提供更为准确的资料。  相似文献   

热带海表风速与海表温度日变化关系分析     

洪星园  傅云飞  冼桃  王雨  杨元建  衡志炜 《气候与环境研究》2014,19(4):437-451

利用热带测雨卫星(TRMM)搭载的微波成像仪(TMI)探测结果,在像元分辨率上同步反演的10年海表温度(SST)和海表风速(SSW)资料,研究了热带地区非降水条件下SSW变化对SST日变化的影响。结果表明热带地区SST日变化显著,SST日最小值多出现在早晨03:00(当地时间,下同)至06:00,日最大值多出现在午后17:00至19:00,SST日绝对振幅为1.9~3.4℃,日相对振幅为5%~7%。SSW变化对SST日最小值和日最大值的出现时间及SST日振幅均有明显的影响,且均呈现出区域性差异。热带地区SST日绝对振幅随SSW增大而减小,当SSW增加至9 m/s之后,SST日绝对振幅变化不再明显;二者符合特定的正弦函数关系。在风速小的情况下,暖池区域平均SST日绝对振幅异常减小了0.16℃;在风速大的情况下,秘鲁沿岸区域平均SST日绝对振幅异常增大了0.17℃,且SST随时间变化波动较大。上述研究结果为下一步研究海表感热和潜热日变化打下了基础。  相似文献   

基于集合Kalman滤波数据同化与偏差修正的热带气旋强度集合预报研究     

黄小刚  费建芳  陆汉城  韩锐 《气象学报》2010,68(1):79-87

采用基于集合Kalman滤波数据同化和偏差修正方法的集合预报技术来研究热带气旋的强度预报问题.集合预报系统考虑初值误差和模式误差,利用MM5中尺度模式,采用Anthes-kuo、Grell和Betts-Miller等积云参数化方案和High-res-olution Blaekadar、Burlk-Thompson、MRF等边界层过程的9组不同的组合,分别进行45、60和75 min的短时预报.对9个预报结果采用"镜像法",得到18个集合成员.将蓝金涡旋作为同化的观测场,18个集合成员作为集合Kalman滤波的初始背景集合,采用ENSRF算法和逐点局地分析算法进行同化.同化后的结果作为集合预报的初值,预报过程对模式参数采用前述9种组合,进行72小时预报.通过求取偏差系数对预报结果进行修正,减小模式系统误差.选2003-2004年16个台风过程作为预报个例,讨论偏差修正前后对预报结果的影响.实验结果表明,基于集合Kalman滤波数据同化的热带气旋集合预报相对于非同化的集合预报对路径预报的改进效果优于强度预报.平均而言通过偏差修正,强度集合预报的潜力得到挖掘,绝对误差明显减小,通过偏差修正减小了强度集合预报均值的误差,进而使得预报概率密度函数均值向理论值靠近,从而提高了概率预报的精度和合理性,因此基于集合预报的偏差修正分析方法,是改善热带气旋强度预报水平的有效途径.  相似文献   

基于PR和VIRS融合资料的东亚台风和非台风降水结构分析   总被引：1，自引：0，他引：1  

陈凤娇  傅云飞 《气候与环境研究》2015,20(2):188-200

借助JAXA/EORC热带台风数据集资料,实现了台风区和非台风区的分离,在此基础上,利用热带测雨卫星搭载的测雨雷达和可见光/红外扫描仪的融合观测资料,对1998~2007年东亚雨季台风及非台风降水的气候特征和降水云红外信号特征进行了分析。结果表明:1)东亚台风降水强度谱较非台风降水谱更宽,特别是对流降水主要分布在5~20 mm/h之间;强降水更多,主要分布在东亚洋面。2)雨季东亚降水的主要形式是非台风层云降水,但台风降水对局地降水量的贡献也不容忽视,例如台湾以东附近洋面可达20%。3)台风降水云亮温海陆分布差异显著;其雨顶高度在4~9 km(层云)和4.5~12.5 km(对流)之间均有分布,较非台风降水雨顶高度谱更宽。4)不同等级的台风在降水强度、覆盖区域和云顶10.8μm亮温分布上差异大。  相似文献