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1.
《海洋气象学报》2014,(3)
利用实况观测资料、中尺度自动站资料、中国气象局物理量分析资料和泰山多普勒雷达资料对2013年7月18日发生在鲁西南至鲁中的暴雨过程进行了诊断分析。结果表明:强降水由500hPa西风槽、700hPa切变线、850hPa低涡、地面辐合线、以及副热带高压西北边缘的暖湿气流共同影响造成。低层前期明显的持续升温为暴雨的产生创造了良好的热力条件,副高外围的水汽输送为此次暴雨提供了充足的水汽,同时暴雨区不稳定能量的维持和层结对流不稳定的结构,有利于暴雨的产生。地面中尺度辐合线的生成和发展,是这次暴雨产生的启动机制,暴雨的分布与地面辐合线的走向基本一致。强降水期间,沿低层切变线北侧东北气流南下的冷空气与暖空气交汇,使对流加强、降水强度加大。另外,泰安地处鲁中山区向西南开口的山谷的南部,偏南气流的迎风坡,有地形产生的偏南风的辐合和抬升,地形造成的辐合上升运动对泰安地区第一个强降水时段降水具有明显的增幅作用。两个强降水时段雷达回波为混合型降水回波,反射率因子强度一般在30~35dBz,最强达40dBz,其中第一个强降水时段回波对流发展的高度更高。特殊的地势地貌也是此次暴雨产生的重要原因。 相似文献
2.
一次副热带高压边缘切变线暖区暴雨特征分析 总被引：1，自引：0，他引：1
利用常规气象观测资料、NCEP 1°×1°再分析资料以及卫星和雷达资料,对2018年6月25—26日副热带高压(简称"副高")边缘切变线暖区暴雨的大尺度环流背景、雨带的移动与传播、中尺度特征以及温湿特征等方面进行分析。结果表明:此次暖区暴雨过程是在副高稳定维持,500 hPa西风槽东移,并有低空急流配合,低空暖切变线触发不稳定能量释放的有利背景下产生的;暴雨落区位于700 hPa暖切变线和925 hPa暖切变线之间;暴雨期间,小尺度对流单体在鲁南地区触发,云顶亮温t_(bb)≤-60℃,并沿引导气流向东北方向移动;强降水区域有多个强回波中心持续影响,有明显的"列车效应",强回波持续时间长;红外云图能很好地反映天气系统的发生、发展和消亡,而水汽图像上色调暗区不明显,冷空气活动较弱;低层暖湿气流强烈发展,是造成此次暖区暴雨过程层结不稳定的主要原因;暴雨的水汽源地是孟加拉湾和南海,且强降水期间,随着西南暖湿气流的增强,水汽通量有一个跃增现象;云顶t_(bb)≤-70℃覆盖的区域、水汽通量散度负值中心可以作为暖区暴雨落区预报的参考点。 相似文献
3.
《海洋气象学报》2019,(1)
利用常规气象观测资料、NCEP/NCAR再分析资料和多普勒天气雷达资料,对2016年8月6——8日潍坊一次强对流天气的成因和预报误差进行了分析,结果表明:1) 500 hPa冷涡底部低槽、850 hPa低涡切变线和地面倒槽是主要影响天气系统,数值预报对此次天气过程的影响系统预报偏差大,而预报员对数值预报依赖程度高是此次预报失误的主要原因; 2) 850 hPa以下强的水汽辐合是强降水发生的重要条件,低层辐合和高层辐散配置导致的强垂直上升运动是暴雨产生的动力机制,位势不稳定因中高层的冷空气入侵下沉得以加强; 3)列车效应和强回波维持少动是造成短时强降水的重要回波特征,逆风区的发展和移动对于判断强降水的落区有指示作用,多普勒雷达反演风场中的中尺度辐合线是导致局地强降水发生的直接原因; 4)风廓线雷达水平风场可以连续地反映降水过程中风场垂直结构及其变化,降水发生前探测高度明显升高,中高层冷空气侵入时间与强降水的时段相对应。 相似文献
4.
《海洋气象学报》2017,(3)
利用常规观测资料、自动气象站加密观测资料、GPS/MET水汽监测资料、FY-2E卫星云图和NCEP/NCAR 1°×1°再分析资料,对副热带高压边缘山东南部连续两次强降水的形成机制进行分析。结果表明,两次强降水都是由副热带高压边缘500 h Pa弱西风槽过境影响产生的,副热带高压主体加强西移,850~700 h Pa有较强的西南急流。强降水产生在西南低空急流的前方、暖式切变线附近;西南低空急流加强北上强降水开始,急流减弱强降水结束。强降水区与CAPE的高值区、低层水汽通量高值舌、水汽辐合中心、暖平流中心有较好的对应关系。西南低空急流、GPS/MET水汽监测对强降水的短时预报有一定的指示性。对流云团TBB最低为-78~-62℃,各观测站对应最大小时雨量为40~90 mm。强降水期间,850 h Pa及以下有中尺度涡旋发展,涡旋尺度小,气压场上表现很弱,流场上表现明显,有明显的气旋性环流中心,在925 h Pa涡旋中心东南部的暖平流中心降水强度最大。第一次强降水的中尺度涡旋源地发展,稳定少动,在其东南部上升运动强且降水强度大;第二次强降水中,冷空气在低层从西北部侵入,形成气旋,向东北移动,强降水产生在冷锋前部的暖区中,对流不稳定能量高,降水强度大、范围大。 相似文献
5.
《海洋气象学报》2015,(2)
利用常规观测资料、自动站加密观测资料、NCEP1°×1°再分析资料、卫星FY-2E的TBB资料、多普勒天气雷达观测资料等,对2011年7月25日山东乳山强降水进行分析研究,结果表明:(1)这次强降水主要影响系统是高空槽、低层暖式切变线和副高边缘的低空急流。强降水产生在850h Pa和925h Pa切变线附近,低层850h Pa以下有较强的西南气流向北输送大量的水汽,强降水的水汽来源于低层近海面的水汽输送和辐合。(2)强降水产生在高温高湿区,强降水期间,低层有明显的暖平流,高层有明显的冷平流,低层暖平流增强或高层冷平流增强时,降水强度也明显增强。(3)强降水期间,乳山的特殊海岸线地形抬升作用产生的上升运动与中高层入侵的干冷空气(伴有下沉运动)相遇,从而触发对流不稳定能量释放,降水强度增大,产生强降水。(4)乳山出现短时强降水主要是由中-β尺度对流云团造成的,此次强降水的TBB在-63~-52℃,云团发展迅速,高度较高,在云团发展阶段,其反应的云顶温度比实际的云顶温度偏高。(5)风暴低层逆风区和中-γ尺度气旋性涡旋,及风暴顶的强烈辐散,利于回波发展与维持,同时使高值区维持在风暴中层及以下高度,在环境因子有利的情况下产生降水效率较高的强降水风暴。 相似文献
6.
《海洋气象学报》2018,(4)
通过对一个明显后向传播雷暴和一个无明显传播特征雷暴的环境场进行对比,分析环境场条件对雷暴传播运动的影响。结果表明:二者高空均受冷涡后部西北气流控制,有中空急流,低层受暖温度脊影响,气温较高,傍晚前后受短波槽影响,在鲁西北地区产生对流天气;后向传播雷暴的环境场水汽条件较好,大气斜压特征明显,近地面层高温高湿,θse锋区位于对流层中层,中层干空气与低层冷空气入侵,二者共同作用是雷暴的产生机制;无明显传播特征雷暴的环境场水汽条件较差,θse锋区位于850 hPa以下,对流层低层干冷空气与暖湿空气交绥是雷暴的产生机制;雷暴易发生在水汽通量散度中心北侧梯度较大的区域,主回波后部大气为不稳定层结且具有辐合中心、相对湿度较大的特征,这是产生新对流单体的关键;若雷暴区有湿平流,雷暴的下游方向有水汽辐合中心,且辐合中心具有斜压特征,有利于雷暴新生,反之,则不利于雷暴新生。 相似文献
7.
利用气象卫星、多普勒天气雷达、区域自动气象观测站及常规气象观测资料,结合NCEP/NCAR逐日6 h再分析资料(0. 25°×0. 25°),对2018年18号台风"温比亚"及其残骸长时间影响山东引发特大暴雨的成因进行分析发现:1)此次极端降水可分为三个阶段,分别受台风外围螺旋云系、倒槽和变性后温带气旋冷锋影响,其中弱冷空气与台风倒槽相互作用对强降水的产生和维持起到了重要作用。2)"温比亚"缓慢北上过程中,强降水落区从台风东侧逆时针转至其北部倒槽附近,并逐渐远离台风中心,台风强度逐渐减弱。3)冷空气在对流层中层与台风倒槽相互作用,中层冷暖平流增强形成锋区,斜压不稳定能量增强,暖湿空气在锋区附近上升,并与低层倒槽辐合上升运动相配合,引发了倒槽附近特大暴雨的发生。4)此次过程中,低空急流稳定维持,源源不断地将水汽自东海输送至台风倒槽附近,水汽输送集中在800 hPa以下,850 hPa水汽通量辐合强度大于8×10-6g·cm~(-2)·hPa~(-1)·s~(-1)区域与暴雨落区的形态和位置对应良好。5)对流层中层的弱冷空气和低层的强暖湿气流促进了对流不稳定层结的发展和维持,低层强风速带在鲁中山区迎风坡强迫抬升不断触发中尺度对流系统,在中高层气流引导和地形作用下产生"列车效应",也是此次过程中局地特大暴雨产生的重要因素。 相似文献
8.
《海洋气象学报》2014,(2)
通过常规观测资料、NCEP1°×1°再分析资料和加密自动站资料,对2012年7月7—10日连续发生在鲁东南地区的两次大暴雨过程进行了成因分析。分析表明:副热带高压的西伸北抬和稳定维持使西南低空急流长时间维持为大暴雨连续发生提供了充足的水汽和能量。第一次过程鲁东南位于切变线南侧和西南急流左侧;第二次过程鲁东南位于低涡东南象限和地面气旋东北象限。强降水中心位于850hPa高能舌顶端和925hPa高能中心重合处。第一次过程无明显冷空气,是边界层的强辐合和上升运动造成了强降水;第二次过程近地面有冷空气侵入,辐合和上升运动中心到达700hPa把水汽输送到较高的高度,有利于高效率降水的产生。 相似文献
9.
台风麦莎影响期间山东半岛大暴雨成因的分析 总被引：3，自引：0，他引：3
2005年8月7-8日,在0509号台风麦莎登陆后北上影响山东的过程中,对流的发展在台风外围具有明显的不对称性,积云对流在台风中心的东北侧得到强烈发展,强降水集中出现在山东半岛东部.利用常规观测资料、卫星云图和NCEP1o1o再分析资料,对这次台风大暴雨天气过程作了分析,并进一步对强降水发生时的物理量场与流场进行诊断分析.结果表明:低空急流输送充足的水汽和强烈的水汽辐合为暴雨发生提供了有利的水汽条件,大暴雨落区出现在低层辐合、高层辐散及强烈的上升运动区内,与高能量锋区有很好的对应关系;较强正涡度平流与暖平流沿低空急流向山东半岛输送是造成对流不对称发展的主要原因,高空急流与低空急流在山东半岛的耦合为大暴雨的发生提供了动力条件. 相似文献
10.
“黑格比”后期异常强降水形成机理分析 总被引：1，自引：0，他引：1
0814号强台风黑格比2008年9月25日08时减弱成低压进入越南高平后,在外围云系有明显中尺度对流云团发展,引发广西西南部新一轮比热带风暴本身更具破坏力的暴雨到大暴雨降雨。对美国国家环境预报中心(NCEP)提供的再分析资料、常规观测资料及雷达回波等研究结果,认为南亚高压西退造成负涡度向对流层中低层延伸,使500 hPa的西太平洋副热带高压出现减弱东退现象,成为低压后部对流云团在广西西南部停滞发展的背景条件。造成此次暴雨的4个中尺度对流云团,都是沿着暖切变右(北)侧100—200km范围内从东南往西北方向产生、移动的,中尺度降水落区呈东南-西北的带状分布。暖切变、垂直方向上的抽吸作用、θse的高值始终呈漏斗状的湿中性特征以及湿Q矢量对次级环流的激发作用等是此次低压后部中尺度对流云团的加强机制;而湿舌、湿Q矢量辐合区与未来强降水出现区域、出现时间对应较好。 相似文献
11.
Arne Schnack-Friedrichsen Angela M. Davis Jim D. Bennell Dei G. Huws 《Marine Georesources & Geotechnology》2001,19(4):221-243
The interdependence between the seismo-acoustic properties of a marine sediment and its geotechnical/physical parameters has been known for many years, and it has been postulated that this should allow the extraction of geotechnical information from seismic data. Though in the literature many correlations have been published for the surficial layer, there is a lack of information for greater sediment depths. In this article, a desktop study on a synthetic seafloor model illustrates how the application of published near-surface prediction equations to subsurface sediments (up to several tens of meters burial depth) can lead to spurious predictions. To test this further, acoustic and geotechnical properties were measured on a number of sediment core samples, some of which were subjected to loading in acoustically-equipped consolidation cells (oedometers) to simulate greater burial depth conditions. For low effective pressures (representing small burial depths extending to around 10 meters subsurface), the general applicability of established relationships was confirmed: the prediction of porosity, bulk density, and mean grain size from acoustic velocity and impedance appears generally possible for the investigated sedimentary environments. As effective pressure increases through, the observed relationships deviate more and more from the established ones for the near-surface area. For the samples tested in this study, in some instances increasing pressure even resulted in decreasing velocities. There are several possible explanations for this abnormal behavior, including the presence of gas, overconsolidation, or bimodal grain size distribution. The results indicate that an appropriate depth correction must be introduced into the published prediction equations in order to obtain reliable estimates of physical sediment properties for greater subsurface depths. 相似文献
12.
Shigehisa Nakamura 《Marine Geodesy》2000,23(1):55-61
Specific properties of the interannual sea level variations and annual tides in the Northwestern Pacific were studied. Several tide stations were monitored. The monthly mean sea level for the year of 1995 was analyzed at each tide station. A seismic event in 1995, some tectonic activity around the subject area, and the Kuroshio (the oceanic western boundary current) may possibly contaminate results which would have occurred from the astronomical annual tide alone. 相似文献
13.
The effect of different fixation and storage protocols on the flow cytometric (FCM) simultaneous analysis of bacterioplankton and phytoplankton in coastal seawater samples (Mediterranean coastal lagoons) was investigated. FCM measurements (cell number, fluorescence and scatter characteristics) were obtained through DAPI staining. Three fixatives [glutaraldehyde (GA), formaldehyde (FA) and paraformaldehyde (PFA)] and two storage (3 months duration) methods (5 °C and −196 °C) were tested. Two dominant populations were detected in studied samples: bacteria and eukaryotic picophytoplankton. Adding fixatives (2% final concentration) appears necessary to obtain FCM exhaustive counts of all the bacteria and phytoplanktonic cells. This was related to the permeation effect of fixatives which allowed a better DAPI staining of the cells. Maximum fluorescence, i.e. optimal staining of the cells was obtained with FA or PFA, and significant lower fluorescences with GA. Fixed samples stored at 5 °C induced rapid cell loss. Only storage in liquid nitrogen of samples fixed with FA or PFA, allows mid-term (≥4 months) preservation of bacteria or picophytoplankton cell numbers, and limited evolution of DAPI-induced fluorescence and scatter characteristics. 相似文献
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15.
《海洋学报(英文版)》2014,(9):F0003-F0003
<正>Acta Oceanologica Sinica(AOS)is a comprehensive academic journal edited by the Editorial Committee of Acta Oceanologica Sinica and is designed to provide a forum for important research papers of the marine scientific community which reflect the information on a worldwide basis.The journal publishes scholarly papers on marine science and technology,including physics,chemistry,biology, 相似文献
16.
The relationship between the flux of exotic benthic foraminiferal tests (i.e. tests which are supplied from open-sea sources alone) in a tidal inlet and that of bulk sediment was analysed, which can be expressed as two first-order linear equations. According to this relationship, in order to determine net sediment transport directions in the entrance, the test concentration in surficial sediments of the tidal basin can be compared against a ‘ critical level ’. The critical level is determined for the conditions that no net transport of bulk sediment is present within the entrance. If the observed concentration (averaged over the tidal basin) is higher than the simulated critical level, then the net sediment transport is directed to landward. This method is applied to the analysis of net sand transport at Christchurch Harbour, a tidal inlet system located in southern England. In this investigation, concentrations of exotic foraminiferal tests in the surficial sediments of the tidal basin and ebb tidal delta area were obtained from the analysis of sea-bed sediment samples. A series of probable critical levels were calculated based upon the data sets with regard to: (1) sediment discharge from the rivers; (2) magnitude of sediment discharge within the entrance during the ebb; (3) the test concentration outside the harbour; (4) the thickness of the moving layer; and (5) two parameters associated with dispersive processes. The results show that the concentration in the tidal basin sediment is higher than a number of simulated critical concentrations for representative cases. Consequently, the high level of the concentration of exotic benthic foraminiferal tests within the harbour should be explained as a result of landward net transport of sands within the entrance. 相似文献
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18.
The behaviour of an axially pre-loaded cylindrical member of an offshore structure, hit by a supply ship, has been investigated. The effects of axial pre-loading on the dynamic properties of members, the extent of damage and propagation of dynamic instability in the tubular members have also been investigated. Numerical models have been validated using available experimental data from the literature although these are mostly static with no pre-loading. Axial pre-loading was found to change the dynamic characteristics of some cylindrical members quite dramatically while it had no significant effect on others. The study examined whether there was any change in the behaviour between local and global modes when the loading was dynamic rather than static. The effect of damping on the dynamic instability of axially pre-loaded tubes under lateral dynamic loads was also studied. It was observed that for some geometries the quasi-static response can be used to define the boundary between bounded and unbounded dynamic responses. The main contribution of this study, compared with previous investigations reported in the literature, is that both pre-loading and dynamic effects have been included. 相似文献
19.
Rahul Sharma 《Marine Georesources & Geotechnology》2000,18(3):237-250
Observations on seafloor features from subbottom profiling and seabed photography data show that the undisturbed and natural conditions before the benthic disturbance undergo a substantial change after operation of the disturber. The effects can be seen in the form of deep trenches and grooves, formed by the action of the sleds and the pumping of the sediment along its path, as well as sediment piles on either side of the track. Biological traces such as fecal coils, casts, tubes, burrows, and trails get obliterated in the areas of disturbance and resedimentation. The smooth, uniform nature of the seafloor observed in predisturbance phase shows microtopographic changes in and around the disturbed area as a result of sediment excavation and resettlement. Vertical mixing as well as lateral transport of sediment alter the geological, biological, physical, and chemical conditions on the seafloor, which need to be monitored over time to assess the process and the time taken for restoration of environmental conditions. 相似文献
20.
Vance P. Vicente 《Marine Ecology》1989,10(2):179-191
Abstract. Long-term changes in the distributional patterns of commercial sponges ( Spongia spp. and Hippospongia spp.) within the West Indian Region indicates that: 1) commercial sponges had a widespread distribution throughout the whole West Indian Region and were ubiquitous in very shallow water until about the first half of the present century; 2) they were fished commercially not only in the traditional northern Caribbean sites (Florida, Gulf of Mexico, Bahamas) but also in the Greater ( e. g. , Hispaniola, Jamaica) and Lesser Antilles; and 3) they became extinct throughout most of the Lesser Antilles ( e. g. , Puerto Rico, Vieques, St. Thomas) sometime during the first half of this century. Mortalities of spongiids within the Antilles were found to differ from other marine mortalities in that: 1) species disappeared from a large region; 2) species vanished from different habitats and depths; and 3) natural populations never recovered. Species richness patterns suggest that commercial sponge genera ( Spongia and Hippospongia ) evolved under slightly cooler elimatic conditions than those found at present, and that these extinctions occurred as a direct or indirect effect of positive thermal anomalies in sea surface and atmospheric temperatures between 1900–1950. The concept that species diversity is stable on a regional scale is questioned. 相似文献