A study of track deflection associated with the landfall of Tropical Cyclone Sidr (2007) over the Bay of Bengal and Bangladesh     

《Dynamics of Atmospheres and Oceans》2021

In this study, the dynamics of track deflection associated with Tropical Cyclone (TC) Sidr (2007) are explored using a numerical weather prediction model. It is found that (a) the simulated track of Sidr is sensitive to flow, orographic, and model vertical structure that change the environmental steering flow leading to the track deflection. In particular, the track of TC Sidr is deflected northwestward for cases with lower domain height, horizontal domain covering only part of Himalaya mountains, and varying mountain heights; (b) the simulated track of TC Sidr, when compared with GFS reanalysis data, is mainly controlled by its deep-layer environmental steering flow as a point vortex; (c) the northwestward deflection with lower domain height is caused by an artificially larger high pressure at lower levels in the vicinity of the Himalayas, due to the upward propagation of wave energy being reflected by the upper domain boundary; (d) the significant northwestward deflection associated with the varying mountain height cases is due to the cyclone vortex being advected by the northeasterly monsoonal flow, which is blocked by the mountains in the corresponding cases with mountains; (e) the northeastward track deflection after the landfall of Sidr is explained by the addition of the frictional force.In summary, the model vertical domain height and the Himalaya mountain representation play key roles in influencing the accuracy of TC Sidr track simulation, compared with other factors, such as the vertical resolution, at least for TC Sidr.  相似文献   

Effects of vertical wind shear and storm motion on tropical cyclone rainfall asymmetries over the North Indian Ocean     

《Dynamics of Atmospheres and Oceans》2021

Tropical cyclone (TC) rainfall asymmetry is often influenced by vertical wind shear and storm motion. This study examined the effects of environmental vertical wind shear (200-850 hPa) and storm motion on TC rainfall asymmetry over the North Indian Ocean (NIO): the Bay of Bengal (BoB) and the Arabian Sea (AS). Four TC groups were used in this study: Cyclonic Storm (CS), Severe Cyclonic Storm (SCS), Very Severe Cyclonic Storm (VSCS) and Extreme Severe Cyclonic Storm (ESCS). The Fourier coefficients for wave number-1 was used to analyze the structure of TC rainfall asymmetry. Results show that the maximum TC rainfall asymmetry was predominantly in the downshear left quadrant in the BoB, while it placed to downshear right quadrant in the AS, likely due to the different primary circulation strength of the TC vortex. For the most intense cyclone (ESCS), the maximum TC rainfall asymmetry was in the upshear left quadrant in the BoB, whereas it was downshear right quadrant in the AS. It is evident for both basins that the magnitude of TC rainfall asymmetry declined (increased) with TC intensity (shear strength). This study also examined the collective effects of vertical wind shear and storm motion on TC rainfall asymmetry. Here, the analysis in case of the strong shear environment (>7 m s^-1) omitted for the AS because the maximum value for this basin was about 7 m s^-1. The result showed that the downshear left quadrant was dominant in the BoB for the maximum TC rainfall asymmetry. In a weak shear environment (<5 m s^-1), on the other hand, downshear right quadrant is evident for the maximum TC rainfall asymmetry in the BoB, while it placed dominantly downshear left quadrant in the AS. In the case of motion-relative wavenumber-1, the maximum TC rainfall asymmetry was dominantly downshear for both basins.  相似文献   

A Case study of a snowstorm at the Great Wall Station,Antarctica     

杨清华  张林  薛振和  尹朝晖  邢建勇 《极地研究(英文版)》2010,21(2):137-146

A case of a snowstorm at the Great Wall Station was studied using data of NCEP (National Centers for Environmental Prediction) analysis, in situ observations and surface weather charts. The storm occurred on August 29th,2006, and brought high winds and poor horizontal visibility to the region.It was found that the storm occurred under the synoptic situation of a high in the south and a low in the north. A low-level easterly jet from the Antarctic continent significantly decreased the air temperature and humidity.Warm air advection at high level brought sufficient vapor from lower latitudes for the snowstorm to develop.The dynamic factors relating to strong snowfall and even the developmentof a snowstorm were deep cyclonic vorticity at middle and low levels,the configuration of divergence at high level and convergence at low level, and strong verticaluplift. There was an inversion layer in the low-level atmosphere during the later phase of the storm.This vertical structure of cold air at low levels and warm air at high levels may have been important to the longevity of the snowstorm.  相似文献   

多尺度天气分析理论和应用Ⅱ:锋面和气旋的形成机制     

叶更新 《高原气象》2013,32(4)

利用多尺度天气分析理论,研究了锋面和气旋的形成机制.结果表明,冷、暖气团是由不同性质的亚微团在环境力的作用下向不同方向运动而形成的,而它们的交界面就是锋面.急流附近强动能梯度力能促进微团的分离,因此锋面与急流有很好的对应关系.另外,低空急流附近存在上干冷下暖湿的稳定气流,原因在于急流之上的能量梯度力与重力的方向相反,导致该区域微团所受到的作用力为零,形成稳定的结构.但当微团运动到急流出口处时,这种平衡不再存在,暖湿微团向上运动而干冷微团向下运动,形成剧烈的天气变化.地球自转所形成的离心力使得轻微团产生向北、向上的运动分量,导致极锋向北倾斜.气旋的形成同样是由亚微刚的分离而产生的.当轻微团离开微团,在绝对环境涡度场的作用下将发生旋转,旋转的方向与初始涡度的方向一致,在北半球地转涡度的垂直分量向上,为逆时针旋转,南半球为顺时针旋转.在气旋的形成过程中,轻亚微团在气压梯度力场和绝对涡度力的作用下呈现螺旋运动,是气旋系统普遍存在螺旋云带和雨带的原因.水汽是气旋在形成和加强过程中的基本能源,由于发生地的不同,温带气旋和台风在水汽输送方式上亦有差别:温带气旋主要依靠低空暖输送带进行水汽输送;台风因为发生在热带海洋,水汽充沛,各个层次都有水汽供应.气旋运动主要受三个力的制约:环境气压梯度场力、绝对涡度场力和环境涡度力,这三个力的作用导致台风在沿副热带高压边缘运动的同时,还存在蛇形路径和打转运动.  相似文献   

卫星臭氧资料的发展与应用     

刘寅  邹晓蕾 《气象学报》2016,74(1):1-17

随着卫星探测技术的进步、天气学和气候学理论的不断完善,以及高性能计算机广泛应用,卫星臭氧资料的种类得到极大丰富并被应用到多个研究领域中,取得了一系列重要成果。文中介绍了主要星载臭氧探测仪的发展概况,回顾了卫星臭氧资料在气象领域的应用研究成果,主要包括卫星臭氧资料在气旋或低压过程中、全球或区域臭氧的气候分布及变化特征、高原臭氧分布及变化特点、数值应用等方面的应用研究,并展望了卫星臭氧资料研究的未来发展趋势。   相似文献   

Why relatively fewer people died? The case of Bangladesh’s Cyclone Sidr   总被引：1，自引：1，他引：0  

Bimal Kanti Paul 《Natural Hazards》2009,50(2):289-304

Cyclone Sidr, a Category IV storm, struck the southwestern coast of Bangladesh on November 15, 2007 killing 3,406 people. Despite a similar magnitude, Sidr claimed far fewer lives than Cyclone Gorky, also a Category IV storm, which struck Bangladesh in 1991 causing an estimated 140,000 fatalities. The relatively low number of deaths experienced with Sidr is widely considered the result of Bangladesh government’s efforts to provide timely cyclone forecasting and early warnings, and successful evacuation of coastal residents from the projected path of Cyclone Sidr. Using information collected from both primary and secondary sources, this study identified several other reasons for the unexpectedly lower mortality associated with Cyclone Sidr relative to Cyclone Gorky. Fewer casualties may be attributed to a number of physical characteristics of Cyclone Sidr, such as duration of the storm and storm surge, landfall time and site, varied coastal ecology, and coastal embankment. This article recommends improvements to the cyclone warning systems, establishment of more public cyclone shelters, and implementation of an education campaign in coastal areas to increase the utilization of public shelters for future cyclone events.  相似文献   

近年来强沙尘暴天气气候特征的分析研究   总被引：21，自引：3，他引：18  

张高英  赵思雄  孙建华 《气候与环境研究》2004,9(1):101-115

2000～2002年春季(3～5月)中国北方有12次强沙尘暴天气过程发生,其中11次与蒙古气旋有关.作者从干旱气候背景、环流状况、沙尘源、沙尘路径及天气系统等方面进行了分析,并集中对引发强沙尘暴的蒙古气旋进行了诊断分析.结果表明:在这3年中,春季我国北方强沙尘暴天气主要与蒙古气旋的发展移动有关,气旋冷锋后的大风是强沙尘暴天气发生的主要动力因子;蒙古国南部、巴丹吉林沙漠、腾格里沙漠、乌兰布和沙漠和毛乌素沙地是强沙尘暴过程的主要沙尘源地;影响我国的强沙尘暴的沙尘路径至少可分为3种类型,即偏西路径、西北路径和南疆盆地型,以西北路径居多;我国北方春季的连续干旱、气温偏高及冷空气活跃是强沙尘暴天气形成的重要气候背景.  相似文献   

Fire and cyclone damage to woody vegetation on the north coast of the Northern Territory,Australia     

D.M.J.S. Bowman  W.J. Panton 《The Australian geographer》1994,25(1):32-35

Tree stem (>2 m tall) mortality was assessed following a late dry‐season wildfire across a seasonally flooded elevation gradient at Workshop Jungle, near Darwin, in the Northern Territory of Australia. For all species combined, dead stems had significantly smaller diameter at breast height (dbh) than living stems. Assessment of tree‐stem damage following a tropical cyclone at Cobourg Peninsula, NT, revealed that damaged stems had significantly greater dbh than undamaged stems for all tree species sampled across a boundary between monsoon rainforest and savanna. A greater proportion of stems were damaged by the cyclone than by the fire (28 per cent as against 18 per cent), although there were considerable between‐community differences in the proportion of damaged stems at the two sites. The fire caused little impact (<10 per cent) on total basal area of three different forest communities on the elevation gradient at Workshop Jungle. The cyclone was found to cause >50 per cent damage to total basal area of three different communities on Cobourg Peninsula. It is suggested that the combination of a cyclone followed by an intense fire in storm debris could potentially destroy a monsoon rainforest through its impact on all tree‐size classes. This may explain why some monsoon rainforests rapidly contracted following Cyclone Tracy that destroyed the city of Darwin on Christmas Day, 1974.  相似文献   

黄海、东海海域出海气旋发展过程中尺度数值模拟   总被引：1，自引：0，他引：1       下载免费PDF全文

周明煜  Hsiaoming Hsu  袁耀初 《地球物理学报》2003,46(2):175-178

利用MM5中尺度模式对1999年6月两个出海气旋发展过程进行 数值模拟. 数值模拟的气旋出海后移动路径与实际情况基本一致. 在数值模拟基础上重点讨 论了出海气旋发展过程潜热通量和感热通量的分布及其演变情况. 气旋出海后在气旋中心区 南方和东方存在负潜热通量和感热通量区. 出海气旋的东移和发展，其前方强大正热通量区 的存在可能是重要原因之一.  相似文献   

中小尺度的多普勒径向速度场特征分析   总被引：6，自引：2，他引：6  

李军霞  汤达章  李培仁  徐芬  晋立军 《气象科学》2007,27(5):557-563

本文选取2003—2005年太原多普勒雷达资料,对中小尺度的多普勒速度场特征进行了深入研究。从逆风区厚度、尺度、强度(速度切变)等方面作了详细地分析,并与相应的回波反射率因子Z及VIL(垂直累积液态水含量)值对照。结果表明:逆风区强度与反射率因子,逆风区厚度与VIL值,逆风区底层流场结构与强回波发展趋势密切相关。而且,绝大部分逆风区出现时间较降水开始时间有1—2 h的提前。  相似文献