北太平洋北部的风能输入门户

风不仅驱动了上层海洋的环流,也是深层海洋运动的主要能量来源.本文主要研究了北太平洋北部的风能输入的季节性分布特征和年际变化趋势,包括风向表面波、表层地转流和表层非地转流的能量输入.基于SODA3数据的结果表明,风能输入门户随季节变化显著,其中黑潮延伸区是冬季门户,副极地流涡是春、秋季门户,大洋东边界则是夏季门户,能量输...     

Seasonal variations of the surface currents in the Tsushima Strait

Seasonal variations of the surface currents in the Tsushima Strait were investigated by analyzing the monthly mean surface currents measured with HF radar. Several new features of the surface currents have been found. One notable feature is the large, complicated seasonal variation in the current structure in the eastern channel of the strait. For example, in the southeastern and northwestern regions of the channel, southwestward countercurrents are found in summer while southeastward acrossshore currents are found in autumn and winter. The wind-driven flow (Ekman flow) as well as surface geostrophic currents are responsible for these complicated variations of the surface currents. To quantify each variation of the flow and current, the wind-driven flow was calculated from the monthly wind (more precisely, the friction velocity) using the monthly speed factor and deflection angle estimated in our previous study, and the surface geostrophic currents were then estimated by subtracting the wind-driven flow from the measured surface currents. It was found that the acrossshore currents are the wind-driven flow, and that the surface geostrophic currents flow almost in the along-shore direction, indicating the validity of the decomposition of the surface velocity into the wind-driven flow and the geostrophic currents using the speed factor and deflection angle. A real-vector empirical orthogonal function (EOF) analysis of the surface geostrophic currents shows a pair of eddies in the lee of Tsushima and Iki Islands as the first mode, which indicates that the southwestward countercurrents in the eastern channel are formed primarily by the incoming Tsushima Warm Current.     

Seasonal variability of the Antarctic Coastal Current and its driving mechanisms in the Weddell Sea

Insight into the dynamics of the Antarctic Coastal Current (ACoC) is achieved by quantifying the contributions of its driving mechanisms to the seasonal variability of its barotropic and baroclinic components. These mechanisms are sought out in the local wind, the sea-ice concentration, wind curl of the Weddell Gyre (Sverdrup transport) and the thermohaline forcing related to warming/cooling and ice melting and freezing. These driving mechanisms induce most of the seasonal variability of both the barotropic and baroclinic components of the ACoC by deepening the pycnocline towards the coast and sharpening the baroclinic profile following thermal wind balance. The resulting coastal current has mainly a barotropic transport (82%) and a major annual cycle, which explains 37% of this component's variability (tides and other high-frequency events generate 40%). The wind contributes with 58% of the seasonal variability of the barotropic component and 23% of the baroclinic; the sea-ice concentration contributes with 8% and 18%, respectively; Sverdrup transport with 4% and 30% and the thermohaline forcing with 30% and 29%. The results of this study are obtained with analysis of fifteen CTD sections (potential density and geostrophic velocities) of RV-Polarstern obtained between 1992 and 2005, as well as composite, spectral and harmonic analyses of 9 years of time series from moored instruments (current speed and temperature), wind speed, atmospheric pressure and sea-ice concentration of satellite imagery.     

基于SODA资料的南海表层风能输入的空间分布与长期趋势研究

海面风不仅是驱动上层海洋运动的主要动力, 其能量也是维持海洋表层流动的主要机械能来源。为了分析南海表层流风能输入的变化, 用SODA(Simple Ocean Data Assimilation)(1901—2010)资料估算了风向南海表层流(表层地转流+表层非地转流)的能量输入。结果表明, 风向南海表层流、表层地转流和表层非地转流输入的能量总体均呈减少趋势, 110年间分别减小了约56%、65%和49%。导致风能输入减小的最主要因素是风应力的减弱(减小了35%)。由于南海受季风系统的控制, 风向表层流及其各成分输入的能量呈现出显著的季节性变化。冬季风能输入最强, 高值区位于南海西部及北部区域, 呈一个显著的“回力镖”状结构。这些结果对深入认识南海环流具有理论意义。     

Seasonal deformation of the North Equatorial Countercurrent in the Atlantic Ocean

The geostrophic circulation of active and intermediate layers in the north Tropical Atlantic is analysed on the basis of data collected in the transatlantic study area in 1986–1987. Its seasonal features are also found. Quasi-steady eddy formations and their relation to the bottom topography are considered for the intermediate region. The influence of these formations on the kinematics of large-scale currents in this layer is substantiated. Structures of large-scale tropical cyclonic and anticyclonic eddy formations are specified. A strategy for further studies in the Tropical Atlantic is suggested.Translated by Mikhail M. Trufanov.     

Variations of the seasonal behavior of geostrophic circulation in the Black Sea

On the basis of the results of processing of the archival hydrological data, we analyze the seasonal behavior of geostrophic circulation in the Black Sea and its long-term variations. It is shown that the variations of currents on the decadal time scales with different manifestations in different seasons lead to changes in the characteristics of the seasonal course of geostrophic circulation in the second half of the last century. The intensification of winter circulation and weakening of summer circulation observed since the mid-1970s result in the increase in the amplitude of the annual course of current velocity on the sea surface. We also discuss possible causes of variations in the intensities of geostrophic currents in the Black Sea.     

Geostrophic Circulation of Waters in the South Atlantic Ocean and Its Seasonal Variability

Based on an analysis of the monthly average diagrams of dynamic topography, we reveal some specific features of the geostrophic circulation of waters in the South Atlantic Ocean. We present an improved picture of the structure and annual variability of the climatic large-scale circulations. They are compared with similar climatic cells of the large-scale circulation of waters in the north part of the ocean. Quantitative estimates of the characteristics of seasonal oscillations of the field of dynamic heights are obtained.     

赤道印度洋上层环流辐合辐散的年际变异成因分析

印度洋上层海气相互作用对印度洋和太平洋气候系统有重要影响。目前针对印度洋气候态环流特征已有较为全面的研究,但针对印度洋环流的年际变化及其季节性差异的特征分析和具体作用机制,仍缺乏深入的研究。本文利用1979—2007年Simple Ocean Data Assimilation(SODA)再分析资料研究了赤道印度洋表层辐合辐散的年际变异及其季节依赖性。结果表明,以赤道为中心,印度洋上层异常海流,在经向上形成显著的辐合(辐散)现象,究其原因主要是赤道纬向风异常形成的Ekman流所导致。进一步分析表明,热带印度洋异常纬向风的成因与太平洋-印度洋的热力强迫过程作用有关,并且不同的热力强迫过程呈现出显著的季节差异性。此热力强迫过程,具体可分为3种类型:第一类是太平洋纬向海表热力差异的遥强迫作用,主要发生在冬末春初,热带太平洋的纬向热力差异通过调节Walker环流,在印度洋激发出一个异常的次级环流,对应的大气低层形成纬向风异常;第二类是东-西印度洋海表热力差异的局地强迫作用导致的局地环流,使赤道印度洋上空形成纬向风异常,此过程在春末夏初较为显著;第三类是太平洋-印度洋热力差协同作用的结果,使赤道印度洋盛行异常的纬向风,此过程在秋季起主导作用。     

基于Argo浮标的西北太平洋环流特征分析

基于2004 年1 月～2009 年12 月月平均Argo(Array for Real-time Geostrophic Oceanography)温盐格点资料, 结合P-vector 方法重构了西北太平洋绝对地转流, 重点分析了西北太平洋环流时空变化特征。结果表明, 基于Argo 资料西北太平洋三维结构特征与以前的研究结果是一致的。与WOA09(World Ocean Atlas 2009)计算的纬向流相比, Argo 资料计算的纬向流要偏大。北赤道逆流(NECC)、北赤道流(NEC)、黑潮再生流(KCC)和黑潮延伸体(KE)都有明显的季节和年际变化。NECC 和NEC 基本上呈现春强秋弱的季节变化特征, KCC 和KE 的季节特征与NECC 和NEC 存在反相关系。NECC 和NEC 表现出周期为1～2 a 的年际信号, KCC 和KE 为非周期性的年际信号。表层NEC 流核所在位置以及NEC南边界位置都有南移的趋势。另外, NEC、KCC 和KE 的流量也呈逐渐增大的趋势。     

Modelling of the response of the tropical Atlantic Ocean to synoptic fluctuations of wind in the intra-tropical convergence zone

The paper discusses the results of numerical modelling of the tropical Atlantic response to synoptic fluctuations of the wind speed zonal component within the intra-tropical convergence zone. The experiment was carried out in the framework of a multi-level non-linear baroclinic model. The impact of zonal ocean currents on the generation and propagaton of forced temperature and kinetic energy oscillations is studied.Translated by V. Puchkin.     

Upper ocean high resolution regional modeling of the Arabian Sea and Bay of Bengal

In this paper, effort is made to demonstrate the quality of high-resolution regional ocean circulation model in realistically simulating the circulation and variability properties of the northern Indian Ocean(10°S–25°N,45°–100°E) covering the Arabian Sea(AS) and Bay of Bengal(BoB). The model run using the open boundary conditions is carried out at 10 km horizontal resolution and highest vertical resolution of 2 m in the upper ocean.The surface and sub-surface structure of hydrographic variables(temperature and salinity) and currents is compared against the observations during 1998–2014(17 years). In particular, the seasonal variability of the sea surface temperature, sea surface salinity, and surface currents over the model domain is studied. The highresolution model's ability in correct estimation of the spatio-temporal mixed layer depth(MLD) variability of the AS and BoB is also shown. The lowest MLD values are observed during spring(March-April-May) and highest during winter(December-January-February) seasons. The maximum MLD in the AS(BoB) during December to February reaches 150 m (67 m). On the other hand, the minimum MLD in these regions during March-April-May becomes as low as 11–12 m. The influence of wind stress, net heat flux and freshwater flux on the seasonal variability of the MLD is discussed. The physical processes controlling the seasonal cycle of sea surface temperature are investigated by carrying out mixed layer heat budget analysis. It is found that air-sea fluxes play a dominant role in the seasonal evolution of sea surface temperature of the northern Indian Ocean and the contribution of horizontal advection, vertical entrainment and diffusion processes is small. The upper ocean zonal and meridional volume transport across different sections in the AS and BoB is also computed. The seasonal variability of the transports is studied in the context of monsoonal currents.     

基于Argo资料的北太平洋绝对地转流计算

针对海洋实测流速资料极其匮乏的事实, 利用2004 年1 月~2009 年12 月月平均的Argo 温盐格点资料, 结合改进的P-vector 方法重构北太平洋绝对地转流流场。与卫星高度计和实测流速的比较以及相关性分析表明, 重构的绝对地转流是可信的, 可以用来研究不同大尺度环流特征及其动力结构。可以为研究海洋动力过程和气候变化提供一套有用的流场数据。     

Long-term variability of oceanic frontal zones associated with large-scale atmospheric forcing

Global satellite sea surface temperature (SST) measurements and NCEP/NCAR reanalysis wind data for the period of 1982–2009 have been used to study the relationship between long-term variability of oceanic frontal zones (OFZ) and large-scale atmospheric forcing. Statistically significant positive correlations between the maximum magnitude of the meridional gradient of zonally averaged SST and meridional shear of zonal wind (which is an estimate of the Ekman convergence intensity) were found for all subpolar and subtropical OFZ of the World Ocean. Variability of the latitudinal position of OFZ cores may be associated with Ekman advection variability due to zonal wind variations. Strengthening of zonal wind results in a shift of subpolar OFZ cores to the south/north in the Northern/Southern hemispheres.     

Climatic variability of transport in the upper layer of the Antarctic Circumpolar Current from hydrological and satellite data

Based on the satellite altimetry dataset of sea level anomalies, the climatic hydrological database World Ocean Atlas-2009, ocean reanalysis ECMWF ORA-S3, and wind velocity components from NCEP/NCAR reanalysis, the interannual variability of Antarctic Circumpolar Current (ACC) transport in the ocean upper layer is investigated for the period 1959–2008, and estimations of correlative connections between ACC transport and wind velocity components are performed. It has been revealed that the maximum (by absolute value) linear trends of ACC transport over the last 50 years are observed in the date-line region, in the Western and Eastern Atlantic and the western part of the Indian Ocean. The greatest increase in wind velocity for this period for the zonal component is observed in Drake Passage, at Greenwich meridian, in the Indian Ocean near 90° E, and in the date-line region; for the meridional component, it is in the Western and Eastern Pacific, in Drake Passage, and to the south of Africa. It has been shown that the basic energy-carrying frequencies of interannual variability of ACC transport and wind velocity components, as well as their correlative connections, correspond to the periods of basic large-scale modes of atmospheric circulation: multidecadal and interdecadal oscillations, Antarctic Circumpolar Wave, Southern Annual Mode, and Southern Oscillation. A significant influence of the wind field on the interannual variability of ACC transport is observed in the Western Pacific (140° E–160° W) and Eastern Pacific; Drake Passage and Western Atlantic (90°–30° W); in the Eastern Atlantic and Western Indian Ocean (10°–70° E). It has been shown in the Pacific Ocean that the ACC transport responds to changes of the meridional wind more promptly than to changes of the zonal wind.     

Reconstruction of the three-dimensional salinity and temperature fields of the Black Sea on the basis of satellite altimetry measurements

The methodology of joint processing of the satellite altimetry and occasional hydrological observations in the Black Sea for 1993–2012 is developed. The original technique for reconstruction of the 3D temperature and salinity fields in the deep-sea part is proposed and implemented. This technique makes it possible to identify the depths at which a contribution of adiabatic processes to the deformation of the temperature and salinity profiles of the sea is predominant. Daily-averaged 3D fields of the seawater temperature and salinity in a baroclinic layer on a regular grid are reconstructed. The evaluation of accuracy of the reconstructed temperature and salinity arrays is performed by comparing them with the data of hydrological exploration. Structures of the temperature and salinity fields are correlated naturally with topography of the altimetric level and clearly indicate the synoptic variability. Seasonal and interannual variabilities of the kinetic energy (averaged over horizons of the 63–400 m layer) of the geostrophic currents calculated using the dynamic method makes it possible to reveal a sharp increase in the kinetic energy of the currents in the winter season of 2002. A high correlation is found between the interannual variability of the ERA-Interim wind stress curl averaged over the surface of the deep sea part and the kinetic energy of the geostrophic currents in the 63–400 m layer.     

赤道中印度洋上层环流结构与季节变化特征分析

本文通过分析RAMA印度洋观测浮标系统锚系ADCP实测资料,对赤道中印度洋上层海流季节变化进行了研究。研究结果表明,0°,80.5°E纬向流垂向剖面呈现上150m层一致的东向流,而经向流在100m以浅呈现表层向北次表层向南的翻转流结构。赤道中印度洋上层纬向流季节信号被半年周期的东向射流Wyrtki Jets(WJs)所控制。WJs发生于季风方向转换的季节,4—5月份较弱,10—11月份较强。赤道中印度洋上层经向流年周期信号显著。北半球夏季与冬季分别出现风应力旋度驱动的Sverdrup南向流与北向流。本文结论为赤道中印度洋上层环流季节变化特征的研究提供了观测角度的支持。     

Estimating ocean transports with dynamic height moorings: An application in the Atlantic Deep Western Boundary Current at 26°N

Efficient monitoring of large-scale current systems for climate research requires the development of new techniques to estimate ocean transports. Here, a methodology for continuous estimation of dynamic height profiles and geostrophic currents from moored temperature sensors is presented. The technique is applied to moorings deployed in the Atlantic Deep Western Boundary Current at 26.5°N, off Abaco, the Bahamas (WOCE ACM-1 array). Relative geostrophic currents are referenced using bottom pressure sensors and available shipboard direct velocity (lowered-ADCP) sections over the period of the deployment, to obtain a time series of absolute volume transport. Comparison with direct velocity measurements from a complete array of current meters shows good agreement for the mean transport and its variablity on time scales longer than 10 days, but larger variability in the current meter derived transport at time scales shorter than 10 days. A rigorous error analysis assesses the contributions of various error sources in the geostrophic as well as direct transport estimates. Low-frequency drift of the bottom pressure sensors is found to be the largest error source in the geostrophic transport estimates and recommendations for improvement of the technique and related measurement technologies are made.     

Fronts and surface zonal geostrophic current along 115°E in the southern Indian Ocean

Altimeter and in situ data are used to estimate the mean surface zonal geostrophic current in the section along 115°E in the southern Indian Ocean,and the variation of strong currents in relation to the major fronts is studied.The results show that,in average,the flow in the core of Antarctic Circumpolar Current(ACC) along the section is composed of two parts,one corresponds to the jet of Subantarctic Front(SAF) and the other is the flow in the Polar Front Zone(PFZ),with a westward flow between them.The mean surface zonal geostrophic current corresponding to the SAF is up to 49 cm · s-1 at 46°S,which is the maximal velocity in the section.The eastward flow in the PFZ has a width of about 4.3 degrees in latitudes.The mean surface zonal geostrophic current corresponding to the Southern Antarctic Circumpolar Current Front(SACCF) is located at 59.7 °S with velocity less than 20 cm · s-1.The location of zonal geostrophic jet corresponding to the SAF is quite stable during the study period.In contrast,the eastward jets in the PFZ exhibit various patterns,i.e.,the primary Polar Front(PF1) shows its strong meridional shift and the secondary Polar Front(PF2) does not always coincide with jet.The surface zonal geostrophic current corresponding to SAF has the significant periods of annual,semi-annual and four-month.The geostrophic current of the PFZ also shows significant periods of semi-annual and four-month,but is out of phase with the periods of the SAF,which results in no notable semi-annual and fourmonth periods in the surface zonal geostrophic current in the core of the ACC.In terms of annual cycle,the mean surface zonal geostrophic current in the core of the ACC shows its maximal velocity in June.     

Horizontal and Vertical Structure of Geostrophic Currents in the Black Sea According to the Data of the Summer Survey Performed as a Part of the ComSBlack-92 Program

We describe the methodology and software developed for the numerical analysis of the characteristics of the horizontal and vertical structure of geostrophic currents. We present the results of computation of these characteristics according to the data of the summer survey of the Black Sea carried out as a part of the ComSBlack-92 program. The distinctive features of the space structure of geostrophic currents discovered as a result and the established parameters of their variability may supplement the existing data on the current field in the Black Sea.     

Effect of the along-strait wind on the volume transport through the Tsushima/Korea Strait in September

Recent investigation suggests that volume transport through the Tsushima/Korea Strait often has double peaks during the summer to autumn period with decreasing transport in September. The satellite-observed wind changes from weak northwestward (across-strait) in summer to strong southwestward (along-strait) in early autumn (September) in the strait. Such a strong along-strait wind is related to tropical cyclones, which frequently pass through the East China Sea in September. The effect of the along-strait wind component on the transport variation is examined using a three-dimensional numerical model. The simulated volume transport through the Tsushima/Korea Strait shows realistic seasonal and intra-seasonal variations. According to sensitivity experiments on local winds, the transport variations in September are mainly generated by strong along-strait (southwestward) wind rather than weak across-strait wind. The strait transport responds to the along-strait wind (southeastward), which produces a sea level increase along the Korean coast, resulting in the geostrophic balance across the strait. The transport minimum through the Tsushima/Korea Strait in September can be determined by the combination of the across-strait geostrophic and along-strait ageostrophic balances. The Editor-in-Chief does not recommend the usage of the term “Japan/East Sea” in place of “Sea of Japan”.