山东半岛典型冷涡暴雪个例对流云及风场特征的观测与模拟   总被引：7，自引：5，他引：2       下载免费PDF全文

周淑玲  朱先德  符长静  闫丽凤  吴增茂  朱君鉴 《高原气象》2009,28(4):935-944

利用卫星云图、 多普勒天气雷达资料、 常规观测资料和MM5模式模拟结果, 分析了2005年12月4日典型冷涡造成山东半岛暴雪的云带变化、 对流单体的生成与发展、 低空急流特征及雷达强回波带的变化特征。结果表明： 冬季冷涡携带强冷空气南下, 经过渤海暖湿下垫面后影响山东半岛时, 卫星云图上从渤海到山东半岛可以清楚地分析出造成暴雪的西南-东北向结构特征的横向云带; 雷达图上, 在渤海到山东半岛形成一强降雪回波带, PPI径向速度图上可清楚地分析出暴雪区的低空急流和中尺度对流的低空辐合, 雷达径向速度垂直剖面反映暴雪产生在零速度线附近和低空急流的存在; MM5模式模拟结果显示： 暴雪发生时山东半岛在1.5 km存在低空急流, 水平风的时间-高度垂直剖面反映暴雪发生时干冷空气经过暖湿的渤海海面在700 hPa以下出现暖平流, 垂直上升运动和散度的低层辐合、 高层辐散与雷达图像反映的强降雪回波是相对应的。  相似文献   

Latest Pleistocene and Holocene glacier fluctuations in western Canada     

Brian Menounos  Gerald Osborn  John J. Clague  Brian H. Luckman 《Quaternary Science Reviews》2009,28(21-22):2049-2074

We summarize evidence of the latest Pleistocene and Holocene glacier fluctuations in the Canadian Cordillera. Our review focuses primarily on studies completed after 1988, when the first comprehensive review of such evidence was published. The Cordilleran ice sheet reached its maximum extent about 16 ka and then rapidly decayed. Some lobes of the ice sheet, valley glaciers, and cirque glaciers advanced one or more times between 15 and 11 ka. By 11 ka, or soon thereafter, glacier cover in the Cordillera was no more extensive than at the end of the 20th century. Glaciers were least extensive between 11 and 7 ka. A general expansion of glaciers began as early as 8.4 ka when glaciers overrode forests in the southern Coast Mountains; it culminated with the climactic advances of the Little Ice Age. Holocene glacier expansion was not continuous, but rather was punctuated by advances and retreats on a variety of timescales. Radiocarbon ages of wood collected from glacier forefields reveal six major periods of glacier advance: 8.59–8.18, 7.36–6.45, 4.40–3.97, 3.54–2.77, 1.71–1.30 ka, and the past millennium. Tree-ring and lichenometric dating shows that glaciers began their Little Ice Age advances as early as the 11th century and reached their maximum Holocene positions during the early 18th or mid-19th century. Our data confirm a previously suggested pattern of episodic but successively greater Holocene glacier expansion from the early Holocene to the climactic advances of the Little Ice Age, presumably driven by decreasing summer insolation throughout the Holocene. Proxy climate records indicate that glaciers advanced during the Little Ice Age in response to cold conditions that coincided with times of sunspot minima. Priority research required to further advance our understanding of late Pleistocene and Holocene glaciation in western Canada includes constraining the age of late Pleistocene moraines in northern British Columbia and Yukon Territory, expanding the use of cosmogenic surface exposure dating techniques, using multi-proxy paleoclimate approaches, and directing more of the research effort to the northern Canadian Cordillera.  相似文献   

西太平洋海面风场数据集的建立及其应用     

王振明  于华明  李阳  王凯迪  李松霖 《中国海洋大学学报(自然科学版)》2021,(4)

再分析风场数据至今已发展了约30年,目前人们使用区域乃至全球网格化再分析数据集愈加频繁,但风场再分析数据在强天气过程中的强度明显不足,将风场再分析数据同台风观测数据相融合是解决问题的重要途径,本文通过“构建经验台风圆形风场-叠加台风移行风场-流入角修正-叠加背景再分析风场”的基本思路,融合了西太平洋联合警报中心的所有台风观测数据,形成了一套1981—2016年再分析和台风观测相结合的风场数据集。本文选取近十年在中国南海登陆的6例台风,通过与气象观测站数据对比,发现这六例台风相较于再分析数据都有10%以上的误差减小,本工作对于东中国海及南海等台风多发区域风能资源评估的整体提升可达4%,单点风能平均提高55 W/m^2。最后,通过海洋动力数值试验验证高风速下的水位模拟误差可以减少至工程标准的10%以内。综上,本文认为合成风场有助于海洋灾害和风能资源的评估和研究。  相似文献   

Evaluation of the anthropogenic influx of metallic pollutants into Puck Bay,southern Baltic     

《Applied Geochemistry》1998,13(3):293-304

Distributions of 15 elements with depth in two sediment cores from Puck Bay in the Gulf of Gdansk show that Ag, Cd, Pb, Zn and possibly Cu and Ni are anthropogenically enriched in the sediments there. The concentrations of these elements decrease sharply with depth in the sediment column and the elements are preferentially enriched in the <2 μm size fraction of the sediment. The sequence of element enrichment depends on whether the enrichment factor (EF) and the anthropogenic factor (AF) are used to calculate the element enrichment. By contrast, the anthropogenic elements show no systematic decrease in concentration with depth in a sediment core taken from near the mouth of the Vistula River. This reflects the higher sedimentation rate there such that the entire upper 20 cm of the core was deposited during the major, post-war period of industrialization in Poland. In addition, these elements are enriched in the 2–63 μm fraction compared to the <2 μm fraction in these sediments. This suggests that the heavy metals are mainly adsorbed on Fe oxyhydroxide particles with diameters greater than 2 μm at the hydrological front where Vistula river water mixes with brackish Baltic water. It appears that heavy-metal pollution of sediments in parts of Puck Bay may be greater than that near the mouth of the Vistula River which may reflect, in part, the higher sedimentation rate near the mouth of the Vistula River. The mode of incorporation of heavy-metals into the sediments in the two areas may also be different.  相似文献   

Relationship between hydrology and seasonal distribution of suspended sediments on the continental shelf of the Bay of Biscay     

《Deep Sea Research Part II: Topical Studies in Oceanography》1999,46(10):1979-2001

Numerous oceanographic cruises (with hydrology, water sampling, drift current measurements) carried out since 1980 on the continental shelf of the Bay of Biscay, together with available NOAA/AVHRR infra-red images, form the basis of a proposed explanation for the processes responsible for the distribution of suspended sediments on the shelf. The seasonal hydrographic structure of continental shelf waters is of paramount importance in sediment distribution. In summer, there is an horizontal stratification of water masses, and suspended sediment distribution is closely related to the thermo-haline structure. A fresher water mass with less suspended material lies on a thicker and more turbid homogeneous layer. During winter, when sediment discharge from the rivers often reaches its annual maximum, an oceanic thermo-haline wedge occurs on the shelf at around −100 m. As a result, winter turbidity values on the outer continental shelf are low (comparable to summer values), and a permanent nepheloı̈d layer is never observed. The wedge, which lasts for several months, may act as a filter, preventing transport to the slope. High turbidities on the external shelf and the continental slope are only measured in spring, when the thermo-haline wedge disappears. It seems possible that during winter time, suspended materials brought by rivers are deposited in the “Grande Vasière” (the “large mud patch”). It is postulated that the position of this mud patch is linked to the long-term stable location of the thermo-haline front that separates oceanic waters from the colder and less salty coastal waters.  相似文献   

Particulate amino acids in Wadden Sea waters — seasonal and tidal variations     

《Journal of Sea Research》1999,41(1-2):141-148

Particulate amino acids (THAA) were measured in the East Frisian Wadden Sea at monthly intervals from February to December 1995. Each time two tidal cycles were sampled at hourly intervals. THAA made up between 3 and 50% (mean 15±7%) of the particulate organic carbon and between 9.3 and 104% (mean 49±20%) of the total nitrogen pools. Seasonal variations of THAA followed the development of phytoplankton in the water column while tidal variability was controlled largely by physical forcing such as tidal current velocities and wave action. The overall molar composition of the THAA pool appears to be dominated by a detrital signal originating from erosion of surface sediments.  相似文献   

波浪破碎下湍流混合的实验研究     

牟海迪  刘云龙  袁媛  鞠莲  刘娟  孟静  陈旭 《海洋与湖沼》2021,52(3):551-561

波浪破碎过程产生的湍流动量和能量垂向输运对于加快海洋上混合层中垂向混合具有显著效果。采用二维实验室水槽中对波浪破碎过程进行模拟。对采集的波浪振幅时间序列采用希尔伯特变换定位破碎波位置,波浪的破碎率随有效波高的增加而增大,波浪谱分析得到的波浪基本周期与有效周期结果相似。实验中采用粒子图像测速技术(particle image velocimetry, PIV)计算波浪破碎过程中湍动能耗散率的空间分布。湍流强度与波浪的相位密切相关,波峰位置处湍流活动最为剧烈,而且波峰位置处湍流混合区内湍动能耗散率量值的垂向分布基本保持不变,即出现"湍流饱和"现象,湍流影响深度可以达到波高的70%—90%。计算湍流扩散系数的垂向分布发现,湍流扩散在混合区上部随深度的增大以指数函数的形式增加,在混合区下部趋于稳定。作为对比,在相同位置处对声学多普勒流速测量仪(acoustic Doppler velocimeter, ADV)测量的单点流速做频谱分析,发现与该位置处PIV湍动能耗散率结果量级处于同一水平,进一步验证了实验结果的准确性。  相似文献   

Modeling the westward transversal current in the southern Yellow Sea entrance: a case study in winter 2007     

Ding  Yang  Bao  Xianwen  Zhou  Lingling  Bi  Congcong  Yao  Zhigang  Ma  Chao  Chu  Qinqin 《Ocean Dynamics》2020,70(6):803-825

Ocean Dynamics - The westward transversal current (TC) in the southern Yellow Sea entrance was investigated during winter 2007 using a numerical ocean model. The three-dimensional structures and...  相似文献   

A maximum-entropy compound distribution model for extreme wave heights of typhoon-affected sea areas     

王莉萍  孙效光  吕可波  徐德伦 《中国海洋工程》2012,26(1):49-58

A new compound distribution model for extreme wave heights of typhoon-affected sea areas is proposed on the basis of the maximum-entropy principle.The new model is formed by nesting a discrete distribution in a continuous one,having eight parameters which can be determined in terms of observed data of typhoon occurrence-frequency and extreme wave heights by numerically solving two sets of equations derived in this paper.The model is examined by using it to predict the N-year return-period wave height at two hydrology stations in the Yellow Sea,and the predicted results are compared with those predicted by use of some other compound distribution models.Examinations and comparisons show that the model has some advantages for predicting the N-year return-period wave height in typhoon-affected sea areas.  相似文献   

渤黄东海潮能通量与潮能耗散   总被引：7，自引：0，他引：7  

李培良  李磊  左军成  陈美香  赵玮 《中国海洋大学学报(自然科学版)》2005,35(5):713-718,724

利用同化高度计资料和沿岸验潮站资料对潮汐数值模式进行同化,根据同化后的数值模式结果,对渤黄东海中的潮能通量和潮能耗散进行了研究.M2分潮从太平洋进入渤黄东海的潮能为122.499GW,占4个主要分潮进入总量的79%.黄海是半日分潮潮能耗散的主要海区.全日分潮则主要耗散在东海.全日分潮在遇到陆坡的阻挡以后有一部分潮能沿着冲绳海槽向西南传播,并有一部分潮能反射回太平洋,其中O1分潮通过C3断面反射回太平洋的潮能,约占其传入东海潮能的44%.  相似文献