A review of the shelf-slope circulation along Australia’s southern shelves: Cape Leeuwin to Portland     

John F. Middleton  John A.T. Bye 《Progress in Oceanography》2007,75(1):1-41

A review is presented of the ocean circulation along Australia’s southern shelves and slope. Uniquely, the long, zonal shelf is subject to an equatorward Sverdrup transport that gives rise to the Flinders Current - a small sister to the world’s major Western Boundary Currents. The Flinders Current is strongest near the 600 m isobath where the current speeds can reach 20 cm/s and the bottom boundary layer is upwelling favourable. It is larger in the west but likely intermittent in both space and time due to possibly opposing winds, thermohaline circulation and mesoscale eddies. The Flinders Current may be important to deep upwelling within the ubiquitous canyons of the region.During winter, the Leeuwin Current and local winds act to drive eastward currents that average up to 20-30 cm/s. The currents associated with the intense coastal-trapped wave-field (6-12 day band) are of order 25-30 cm/s and can peak at 80-90 cm/s. Wintertime winds and cooling also lead to downwelling to depths of 200 m or more and the formation of dense coastal water within the Great Australian Bight and the South Australian Sea. Within the Great Australian Bight, the thermohaline circulation associated with this dense water is unknown, but may enhance the eastward shelf-edge, South Australian Current. The dense salty water formed within Spencer Gulf is known to cascade as a gravity current to depths of 200 m off Kangaroo Island. This dense water outflow and meanders in the shelf circulation also fix the locations of a sequence of quasi-permanent mesoscale eddies between the Eyre Peninsula and Portland.During summer, the average coastal winds reverse and surface heating leads to the formation of warm water in the western Great Australian Bight and the South Australian Sea. No significant exchange of shelf water and gulf water appears to occur due to the presence of a dense, nutrient-rich (sub-surface) pool that is upwelled off Kangaroo Island. The winds lead to weak average coastal currents (<10 cm/s) that flow to the north-west. In the Great Australian Bight, the wind stress curl can lead to an anticyclonic circulation gyre that can result in shelf-break downwelling in the western Great Australian Bight and the formation of the eastward, South Australian Current. In the east, upwelling favourable winds and coastal-trapped waves can lead to deep upwelling events off Kangaroo Island and the Bonney Coast that occur over 3-10 days and some 2-4 times a season. The alongshore currents here can be large (∼40 cm/s) and the vertical scales of upwelling are of order 150 m (off Kangaroo Island) and 250 m (off the Bonney Coast).Increasing evidence suggests that El Nino events (4-7 year period) can have a major impact on the winter and summer circulation. These events propagate from the Pacific Ocean and around the shelf-slope wave-guide of West Australia and into the Great Australian Bight. During winter El Nino events, the average shelf currents may be largely shut-down. During summer, the thermocline may be raised by up to 150 m. The nature and role of tides and surface waves is also discussed along with uncertainties in the general circulation and future research.  相似文献   

Wind and current patterns in an arctic coast Lagoon     

Joseph A. Dygas  David C. Burrell 《Ocean Engineering》1976,3(5):317-327

The response of wind-drift currents to the prevailing summer wind regime is reported for Simpson Lagoon on the Beaufort Sea (Arctic Ocean) coast of Alaska. Wind and current measurements were taken over the period July 17 to October 20 and August 11 to September 18, 1972, respectively, at a site eastward of the Colville River delta. Mean wind speeds and the frequency of occurrence of westerly storms tend to increase from July to October. Prevailing currents within the lagoon are towards the W to NW driven by the prevailing northeasterly winds. Relatively rapid reversals of current direction occur in response to alternating easterly and westerly winds. Cross correlations of power spectra of the filtered E-W components of the lagoon current record with the concurrent wind data gave a periodicity of 4–5 days at a 70% level of coherence. A linear correlation of −0·83 was obtained between the E-W components of the filtered current record and the wind record, and net water transport (from a progressive current vector analysis) over this period was determined to be towards the WNW with a mean vector velocity of 10·6 cm/sec.  相似文献   

Hydrographic and atmospheric analysis of an autumnal upwelling event in the Ria of Vigo (NW Iberian Peninsula)   总被引：2，自引：0，他引：2  

M. deCastro  A.W. Dale  M. Gmez-Gesteira  R. Prego  I. Alvarez 《Estuarine, Coastal and Shelf Science》2006,68(3-4):529

An autumnal upwelling event was observed in the Ria of Vigo (NW Iberian Peninsula) on 15th November 2001. This event was analyzed by means of thermohaline variables measured at CTD stations located in the study area, satellite sea surface temperature and wind data provided by QuikSCAT. Salinity and temperature distributions revealed that the upwelled water mass was Eastern North Atlantic Central Water (ENACW), typically observed during summer upwelling events. However, previous to the upwelling event, the characteristic autumnal body of water was recorded on 31st October 2001. Subsequent sea surface temperature and upwelling index corroborated the presence of an autumnal upwelling event of approximately 15 days duration. The probability of upwelling-favorable winds (from 1999 to 2004) was lower during autumn–winter than during spring–summer, although they may occur at any time of the year. Probabilities of 45% were calculated for February and November, with the highest probability (65%) corresponding to July.  相似文献   

COARE算法估算海气界面热通量的个例对比分析   总被引：2，自引：1，他引：1  

杨清华  张蕴斐  孙兰涛  吴辉碇 《海洋预报》2005,22(4):1-13

本文先对NCEP分析风、QSCAT/NCEP混合风、MM5中尺度模式分析风场进行了比对分析,发现具有高分辨率的QSCAT/NCEP混合风资料给出的高风速数值较好,但给出的高风速开始时间相对较早;NCEP分析风资料给出的高风速数值明显偏小;MM5分析风场较为可信,只不过模拟的高风速数值还是相对偏小.使用COARE算法（版本3.0）计算了四种资料情况下的渤、黄海海域一次冷空气大风过程的海表面湍流热通量,并与MM5诊断分析结果进行了对比分析.结果发现相同资料情况下,MM5结果跟COARE算法所算海气热通量（包括感热和潜热）在区域分布和时间变化规律上均较为一致,中、低风速情况下,结果比较接近;但是高风速情况下两者差异显著.  相似文献   

青岛近海地区SO2和SO42-干沉降速率的季节变化     

王泽杰  祁建华  于丽敏  高会旺 《海洋湖沼通报》2006,(4):86-93

用小麦岛和团岛观测站提供的青岛近海气象和水温资料,以适于SO2气体和硫酸盐(SO42-)气溶胶的干沉降模型研究了模型中的输送阻尼对两种污染物质干沉降速率的贡献,并计算了2003年青岛近海地区两种污染物质干沉降速率的季节变化。结果表明:对SO2而言,粘性副层传输系数对沉降速率的贡献大于空气动力学传输系数;对于SO42-,空气动力学传输系数对沉降速率的贡献要大于表面传输系数。SO2和SO42-的干沉降速率变化范围分别为0.187~0.868cm/s和0.188~0.532cm/s。两种污染物质干沉降速率的四季变化有相似的规律,即冬季>秋季>春季>夏季。  相似文献   

山东大风天气的低频特征及机理分析          下载免费PDF全文

郑丽娜  刘冬冬  何鹏程 《海洋气象学报》2021,41(2):70-77

利用山东省122个国家级地面气象观测站的风速数据与欧洲中期天气预报中心(ECMWF)提供的ERA-interim再分析数据,采用小波分析、带通滤波等方法对2015年9月—2020年9月山东的大风天气及相应的低频大气环流形势进行分析。结果表明,近几年山东的大风天气有增加的趋势,春季大风发生频次最多,秋季最少;山东半岛东部大风频次最多,鲁南地区最少;全年只有7月偏南大风站次较偏北大风多,其余月份多以偏北大风为主。山东大风具有显著的11～13 d与20～23 d的低频振荡周期。其中,春季大风以11～13 d的振荡周期为主,秋、冬季以20～23 d的振荡周期为主,夏季大风的振荡周期不明显。振荡周期的演变与大范围的大风过程有对应关系,大范围的大风过程大致发生在振荡的波峰处。春季偏北大风盛行时,多伴有经向风自北向南的传播。秋季大约以35°N为界,对流层中高层在35°N以北,经向风自南向北传播,35°N以南,则是自北向南传播,对流层中低层反之。山东春季大风产生之前,乌拉尔山东侧低频气旋与黄海上空低频反气旋同时出现并东移,之后衍生出华北低频反气旋与渤海低频气旋,这两个系统的加强促使华北上空偏北风加大,为山东大风的产生提供了可能。同时,华北地区经向风正距平逐渐被负距平所代替,是山东大风天气产生的又一先兆。  相似文献   

Seasonal variability of the sea surface height in the East China Sea along the China coast: A model study     

Yoshinobu Wakata 《Journal of Oceanography》2009,65(2):281-286

The phase of the sea surface height annual variation in the East China Sea along China’s continental coast is delayed from that in the open ocean area, most probably because of seasonal strong monsoon winds. To elucidate this mechanism, we conducted an idealized model experiment using a rectangular shallow ocean with a sloped seafloor forced by southward blowing winds. We obtain a locally confined high SSH near the western boundary found in the East China Sea. The delay of the phase of the sea surface height (SSH) along the China coast can be interpreted as follows. The SSH of the East China Sea is high over large areas in September and low in March due to the expansion/contraction of seawater, which is attributable to the sea surface heat flux. However, near the continental boundary SSH becomes high in January and low in July under the influence of a monsoon winds. The phase delay along the continental boundary should appear by superposing these two time series with a phase difference near the boundary.  相似文献   

Chlorophyll a increase induced by surface winds in the northern South China Sea   总被引：1，自引：1，他引：0  

GAO Shan  WANG Hui  LIU Guimei  HUANG Liangmin  SONG Xingyu 《海洋学报(英文版)》2012,31(4):76-88

The response of chlorophyll a (Chl a) concentration to wind stress is analyzed in the South China Sea (SCS), using in-situ data of Chl a and remote sensing data (QuikScat-sea surface wind (SSW), AVHRR-sea surface temperature (SST), AVISO merged-sea level anomalies (SLA), SeaWiFSderived Chl a and MODIS Terra-derived Chl a) in August/September/October 2004, 2006 and 2009. The variability of SSW, SST and SLA 7 d before in-situ Chl a sampling (including the work day of in-situ Chl a sampling) with the same latitude and longitude of the study area are investigated, and the correlation coefficients are calculated between these hydrographic factors and in-situ Chl a concentration. The results show that the Chl a-SSW correlation coefficients at upper layers (such as 0 m and 25 m) are more significant than those at deeper layers (such as 50, 75 and 100 m) 1-3 d before, which indicates that there is a time lag of strong surface winds stimulating phytoplankton bloom. By analyzing the relationship among the daily remote sensing derived (RSderived) SSW, SST, SLA and 3 d averaged SeaWiFS/MODIS-derived Chl a concentration in the northern SCS in September 2004 and 2009 respectively, it shows that the intensity and speed of surface winds could have great influence on extend of Chl a increase. If surface winds reach 4-5 m/s over, Chl a concentration would increase 1-3 d after the process of strong surface winds in open sea area of the northern SCS mainly during September.  相似文献   

渤海及黄海北部的风海流数值计算及余流计算   总被引：1，自引：1，他引：1  

黄磊  娄安刚  王学昌  奚盘根  黄祖珂 《中国海洋大学学报(自然科学版)》2002,32(5):695-700

依据黄渤海实测风的资料对渤海及北黄海进行了月平均风海流数值计算。计算表明 ,1月份在西北风的作用下 ,在渤海出现 1个逆时针旋转的环流 ,在辽东湾北部及黄海北部出现 1个顺时针旋转的环流 ,渤海海峡的海流北进南出。 7月份在南风和东南风的作用下 ,风海流的变化形式与 1月份大致相反 ,海峡处呈南进北出的形式。对渤海中部某点 1年的潮流资料通过低通滤波的方法计算逐时的余流值 ,得到该点 1年内表层最大的实测余流为 31.9cm/ s,全年 90 %多的时间内表层余流小于 10 cm/ s。对辽东湾北部某点和渤海湾西南部某点数月潮流资料也进行了低通滤波 ,并将得到的逐时余流与同步风作了比较。依据该 2点风和余流的关系以及黄海北部 6个点风和余流的关系验证了风海流数值计算的结果 ,表明在这些点上实测与计算结果拟合良好  相似文献