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1.
一次海雾过程大气波导形成机理的数值研究 总被引：1，自引：0，他引：1
依据船舶导航雷达与沿岸气象探空观测数据得知,2005年6月1～3日黄海海域发生了1次大范围波导现象;进一步结合卫星云图与沿岸测站水平能见度观测,发现此次波导伴随1次明显的平流海雾过程。利用WRF模式对此次海雾与波导过程进行了数值模拟,发现:(1)海雾始于黄海中部,绝大部分海雾的雾顶由于弱逆温、湿度梯度较小而不存在波导;(2)雾区随其北部低压的逐渐东移而向东扩展,呈现西部薄、东部厚的结构,雾体顶部由于存在逆温与湿度锐减而形成了波导,混合均匀的雾体则成为波导基础层,薄雾顶部为非贴海表面波导,而厚雾顶部则为悬空波导;(3)雾区受低压西部冷空气的影响向南消退,波导基础层逐渐变薄乃至消失,雾体之上的逆温与湿度锐减层随之下降,非贴海表面波导被强度较弱的贴海波导所替代。分析结果表明:黄海平流海雾与波导有密切的联系,海雾形成及其发展改变了海洋大气边界层的温度与湿度垂直结构,从而导致了波导的发生与演变,大气波导可认为是海雾的"副产品"。 相似文献
2.
一次春季黄海海雾和东海层云关系的研究 总被引：2，自引：1，他引：1
结合多种观测数据和数值模拟结果对2011年3月12—13日的一次黄海海雾过程进行分析。观测数据分析表明:此次黄海海雾过程与东海层云之间存在密切的联系。地面高低压位置为水汽从层云区向北输送提供了有利的环流条件;黄海上空天气尺度下沉运动,加强了海洋大气边界层(MABL)层结的稳定性,MABL顶自南向北高度降低,有利于水汽在向北输送过程中不断向海面聚集;下沉导致的干层以及逆温层对海雾的发生发展起重要作用。模式结果进一步证明天气尺度下沉运动与MABL内的下沉在29°—30°N附近同位相叠加,使得该海区上空的下沉运动明显增强,边界层高度迅速下降。下沉可能会导致气块温度升高,云滴蒸发,来自层云区的水汽随流场向北向下输送逐渐接近冷海面凝结成雾,近海面水汽的平流输送使海雾进一步向北发展。本研究为海雾预报提供新的参考思路。 相似文献
3.
黄海雾季开始日期的确定及其年际变化 总被引：1，自引：0，他引：1
根据山东省14个气象站1979—2007年4次/d的大气能见度观测资料、NCEP/NCAR再分析资料、JRA等资料,提出了黄海雾季开始时间的以候为时间尺度的标准,并对影响雾季开始的可能因素进行了分析。结果表明:黄海气候平均雾季开始在第20候,从此候开始,盛行风向、湿度平流、温度平流、大气层结等都有利于海雾的产生;不同年份雾季开始的时间有差别,导致不同年份雾季开始早晚的主要原因是海-气温差、湿度、盛行风;黄东海海温正(负)距平,且东海北部黄海南部海温正(负)距平比黄海北部海温正(负)距平强度更大时,黄海北部雾季开始时间较早(晚)。海-气温差<0℃是海雾季节开始的先决条件,但对海雾季节开始的早晚没有明显的影响。黄海反气旋对大气层结的稳定有一定的贡献,有利于雾的形成和维持。逆温对于雾季的形成和维持有重要作用,但逆温强度与雾季开始的早晚没有直接关系;逆温层的高度可能影响海雾季节的发生,雾季开始偏早年逆温层更接近地面。 相似文献
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《海洋气象学报》2017,(1)
选取2012年4月14日的一次存在东西2片雾区的黄海春季海雾为研究对象,借助WRF(Weather Research and Forecasting)模式,采用循环3DVAR(3-Dimensional Variational)数据同化方案,考虑了湿度控制变量的背景误差协方差CV6,进行了AIRS(Atmospheric Infrared Sounder)卫星温度与湿度廓线数据的同化试验,并基于同化试验结果探讨了此次海雾的形成机制。同化试验结果表明:同化AIRS卫星温度与湿度廓线数据后,模式能成功再现海雾的形成过程,特别是东西2片雾区之间的晴空区的存在,这归功于AIRS数据的同化能够显著改善海上大气边界层的温湿结构、影响海雾的低层高压的范围与强度;机制分析揭示:东西2片雾均为典型的平流冷却雾,但二者厚薄和气团来源不同;海上高压控制黄海西岸陆地的暖空气入海,受低海温的冷却作用降温先形成逆温层,然后逆温层底部生成了较薄的西侧雾区;来自黄海中部的空气向东北移动至朝鲜半岛西部海域,高压下沉增温形成一个顶部较高的稳定层,从而生成较厚的东侧雾区;高压中心下沉区内,近海面风速小使得机械湍流弱,空气增温与海温暖舌共同作用下使得近海面气海温差小,海雾无法生成导致了晴空区的存在。 相似文献
6.
利用2007—2018年CALIPSO卫星数据对春夏季黄海海雾的高度特征进行了统计,并借助MTSAT可见光卫星云图、"葵花8号"可见光卫星云图和KMA地面天气图对控制海雾产生的天气形势进行了分析,进一步讨论了各天气型下黄海海雾的高度特征。研究结果表明:(1)黄海海雾的平均雾顶高度是211 m,海雾高度最大值为370 m,大多数黄海海雾雾顶高度介于100～400 m;(2)7月的海雾雾顶高度高于其他月份,为260 m;(3)控制黄海海雾生成发展的主要天气型有入海变性高压型和大陆低压低槽东移型,入海变性高压控制下的弱偏南风区域的雾顶高度相对较高,大陆低压低槽控制下的槽前风速稍大区域的雾顶高度偏高。 相似文献
7.
《中国海洋大学学报(自然科学版)》2015,(6)
基于日本气象厅Multi-functional Transport Satellite(MTSAT)可见光卫星云图、韩国气象局天气图和美国国家环境预报中心Climate Forecast System Reanalysis(CFSR)数据,选取2007—2012年2~6月发生的32次黄海海雾个例进行研究。首先统计分析了黄海海雾的天气特征,接着归纳总结了有利于黄海海雾生成的天气系统类型,进而分别挑选了各类型的一次个例,解释其海上大气逆温层成因。结果表明:(1)黄海海雾天气系统可分为入海变性高压(南高北低、东高西低和独立高压)、中国大陆东移低压或低槽、北太平洋高压脊和入西太平洋高压4类,各自所占比例约为62.5%、21.9%、9.4%和6.2%。(2)天气系统控制下的冷暖平流与海面湍流冷却作用决定了海上大气逆温层的形成。海雾生成前,天气系统在演变过程中支配着形成逆温的暖气团,暖气团来源于陆上,则主要是上层强暖平流、下层弱暖(冷)平流导致逆温;暖气团来源于海上,则多由近冷海面的湍流混合、冷却降温形成逆温。 相似文献
8.
利用瞬变扰动分析的原理,提供了一个可以客观判定海雾发生时天气类型的方法。在分类结果的基础上,对环流形势、散度和垂直速度以及温度湿度的垂直廓线等进行合成分析,得到低空(1 000 h Pa)为低压扰动下发生海雾(L型海雾)的环流和物理量场基本特征,并与高压控制下海雾(H型海雾)进行对比,结果表明:1)L型海雾位势高度负异常扰动主要表现在低层,其平均值为-65.66 gpm,向上逐渐减弱;2)L型海雾在发生时其逆温强度小于H型海雾,雾层较厚,雾层上空湿度仍然比较大,而H型海雾雾层上空有比较明显的干层;3)L型海雾在垂直方向上的分布具有三层结构,第一层1 000~950 h Pa为辐合伴有弱上升和下沉运动,第二层950~850 h Pa为辐散伴有弱下沉运动,第三层850~500 h Pa为逐渐加强的上升运动;H型海雾为两层结构,1 000 h Pa为辐散伴有弱的上升和下沉运动,950~500 h Pa为一致的下沉运动;4)概率密度统计分析进一步定量表明了L型和H型海雾发生时垂直运动以及相对湿度在各层中的分布情况。这些结论对黄海西北部夏季低压环流形势下海雾的预报提供了重要参考。 相似文献
9.
《中国海洋大学学报(自然科学版)》2016,(8)
基于WRF(Weather Researchand Forecasting)模式及其3DVar(3-DimensionalVariational)模块,发展了一套多普勒雷达径向风数据的同化方案。针对2次黄海海雾个例展开了一系列同化效果对比数值试验,详细分析了同化雷达径向风数据对雾区产生改进的原因。研究结果表明:(1)仅同化常规观测数据不足以纠正初始场中海上大气边界层湿度偏干的状态,导致海雾模拟失败或雾区严重偏小,因此在同化多普勒雷达径向风数据之前,必须先同化从海雾卫星观测中提取的湿度信息;(2)同化多普勒雷达数据不仅显著地直接改进了近海面大气流场,而且会间接改善温度场,从而进一步提高海雾的模拟效果——2次海雾个例模拟雾区的ETS(Equitable Threat Score)评分改进率分别达到66.7%与62.1%;(3)黄海海雾数值模拟中首先要改进海上大气边界层的湿度与温度层结,在此基础上进一步改进近海面大气流场十分必要。 相似文献
10.
夏季黄海表面冷水对大气边界层及海雾的影响 总被引：3，自引：0，他引：3
海表面温度(SST)是海气界面上的1个物理量,受到海洋潮汐、海底地形等因素影响,并对海洋大气边界层有着重要的影响.夏季的黄海,由于黄海冷水团的存在和陆架锋的影响,或是潮汐混合的作用导致海水的垂直混合,使海表面温度的分布产生复杂的结构.通过对卫星观测的海表面温度数据分析,发现在夏季黄海有几个SST冷中心的存在:辽东半岛以及山东半岛的顶端、朝鲜半岛的西侧、山东半岛南侧、江苏外海和黄海南部等.本文利用一系列船舶观测资料、卫星遥感数据、再分析数据分析等,并运用数值模拟研究黄海的冷中心对其上大气的影响.在冷区之上,大气稳定度增加,抑制了近海面大气的垂直混合,使海表面风速减弱.通过对船测数据的分析,在冷区位置有海雾多发区的存在,黄海南部冷区上的海雾发生频率达到15％以上.Weather Research and Forecasting(WRF)模式的数值模拟表明,冷中心降低上空的温度,使海表面风速减弱,形成厚度达500m的逆温层,为海雾的形成创造了有利的条件.与船测数据结果所不同的是黄海南部冷中心之上的海雾发生频率可以达到30％,去掉冷区影响的试验表明冷区较冷的海表面温度最多可以使海雾的发生频率增加15％以上. 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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《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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Coastal inundation associated with extreme sea levels is the main factor which leads to the loss of life and property whenever a severe tropical cyclonic storm hits the Indian coasts. The Andhra and Orissa coasts are most vulnerable for coastal inundation due to extreme rise in sea levels associated with tropical cyclones. Loss of life may be minimized if extreme sea levels and associated coastal flooding is predicted well in advance. Keeping this in view, location specific coastal inundation models are developed and applied for the Andhra and Orissa coasts of India. Several numerical experiments are carried out using the data of past severe cyclones that struck these regions. The simulated inland inundation distances are found to be in general agreement with the reported flooding. 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
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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