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1IntroductionThe oceanic Rossby waves play an importantrole in the large-scale oceanic circulations.In the o-ceans baroclinic Rossby waves have surface manifes-tations of just a fewcentimeters,and wavelengths atmid-latitudes of hundreds to thousands of ki… 相似文献
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Patrick F. Cummins Gary S.E. Lagerloef 《Deep Sea Research Part I: Oceanographic Research Papers》2004,51(12):365
Interannual variability of the sea surface height (SSH) over the northeast Pacific Ocean is hindcast with a reduced-gravity, quasi-geostrophic model that includes linear damping. The model is forced with monthly Ekman pumping fields derived from the NCEP reanalysis wind stresses. The numerical solution is compared with SSH observations derived from satellite altimeter data and gridded at a lateral resolution of 1 degree. Provided that the reduced gravity parameter is chosen appropriately, the results demonstrate that the model has significant hindcast skill over interior regions of the basin, away from continental boundaries. A damping time scale of 2 to 3 years is close to optimal, although the hindcast skill is not strongly dependent on this parameter.A simplification of the quasi-geostrophic model is considered in which Rossby waves are eliminated, yielding a Markov model driven by local Ekman pumping. The results approximately reproduce the hindcast skill of the more complete quasi-geostrophic model and indicate that the interannual SSH variability is dominated by the local response to wind forcing. There is a close correspondence the two leading empirical orthogonal modes of the local model and those of the observed SSH anomalies. The latter account for over half of the variance of the interannual signal over the region. 相似文献
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近年来厄尔尼诺期间北赤道流输运的年际变化 总被引：1，自引：0，他引：1
为了研究近年来厄尔尼诺期间北赤道流输运的年际变化,本文利用海洋客观分析数据MOAA GPV(Grid Point Value of the Monthly Objective Analysis)以及P-vector方法计算了北太平洋绝对地转流,探讨了2001~2013年期间厄尔尼诺与北赤道流输运之间的关系。在此期间发生的4次厄尔尼诺事件中,北赤道流输运在2002~2003、2006~2007、2009~2010年的厄尔尼诺成熟期都出现了明显的增强,但是在2004~2005年的厄尔尼诺成熟期并没有明显的增强。进一步分析发现,在2002~2003年、2006~2007年、2009~2010年的厄尔尼诺成熟期,10°N以南的热带西北太平洋区域出现了负的海面高度异常和气旋式环流异常,这主要是由热带环流区域出现的西风异常和正的Ekman抽吸通过Rossby波西传到热带西太平洋区域所致;但是在2004~2005年厄尔尼诺成熟期,海面温度异常的分布明显不同,西风异常和正的Ekman抽吸异常明显北移,导致负的海面高度异常和气旋式环流异常出现在了10°N以北的西北太平洋区域,使得北赤道流输运在2004~2005年的厄尔尼诺成熟期没有明显的增强。 相似文献
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The satellite altimeter data reveal that intraseasonal long Rossby wave is amplified in the western part of subtropical ocean. Based on a two and half layer ocean model we infer that the intraseasonal long Rossby wave may be amplified by the baroclinic instability. According to the baroclinic instability criterion derived from the two and half layer model, we calculate the baroclinic instability area of the Subtropical North Pacific Ocean based on Levitus98 data. The baroclinic instability area is well in accord with the amplification area of the intraseasonal long Rossby wave, and this also proves that the baroclinic instability is the main amplification mechanism of the intraseasonal long Rossby wave in the subtropical ocean. The consistency between the baroclinic instability area and potential vorticity (PV) pool is further proved in this paper, therefore, we have confidence that the intraseasonal long Rossby wave is amplified in the PV pool. Due to the relatively large ocean basin and weak ventilation, the PV pool is much larger in the North Pacific Ocean than in the North Atlantic Ocean, and this is the reason for the difference of wave amplification areas of these two Oceans. 相似文献
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利用最近20 a的大气海洋资料,分析了厄尔尼诺事件与赤道太平洋西风异常以及赤道太平洋次表层海温之间的关系.结果表明,赤道西太平洋(5°S～5°N,120°～160°E)和赤道中东太平洋(5°S～5°N,160°E～160°W)西风异常都存在着与厄尔尼诺周期一致的年际变化,但前者还包含有显著的2～3个月季节内振荡.赤道西太平洋次表层冷暖水东移也呈现年和年际时间尺度的振荡周期.在厄尔尼诺发生前,赤道西太平洋次表层海水出现持续性增暖,赤道西太平洋西风异常频率加快,强度增强.随后赤道中太平洋(160°E～160°W)出现持续性(3个月以上)强西风异常(即西风爆发),并进一步向东扩展,同时次表层暖水沿着赤道波导东移到赤道东太平洋混合层,导致赤道东太平洋海表大面积异常增暖,形成一次厄尔尼诺现象.最后,模式模拟了1980～1984年赤道太平洋海温的变化,进一步证实了赤道纬向西风异常对暖水东移起着重要的作用. 相似文献
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Oceanic Rossby waves induced by the meridional shift of the ITCZ in association with ENSO events 总被引：1，自引：0，他引：1
Hiroto Abe Youichi Tanimoto Takuya Hasegawa Naoto Ebuchi Kimio Hanawa 《Journal of Oceanography》2014,70(2):165-174
This study investigated the eastern Pacific Intertropical Convergence Zone (ITCZ) as an atmospheric forcing to the ocean by using various observed and reanalysis data sets over 29 years. Climatologically, a zonal band of positive wind stress curl (WSC) with a 10° meridional width was exhibited along the ITCZ. A southward shift of the positive WSC band during the El Niño phase induced a negative (positive) WSC anomaly along the northern (southern) portion of the ITCZ, and vice versa during the La Niña phase. This meridional dipole accounted for more than 25 % of interannual variances of the WSC anomalies (WSCAs), based on analysis of the period 1993–2008. The negative (positive) WSCA in the northern portion of the ITCZ during the El Niño (La Niña) phase was collocated with a positive (negative) sea surface height anomaly (SSHA) that propagated westward as a Rossby wave all the way to the western North Pacific. This finding indicates that this off-equatorial Rossby wave is induced by the WSCA around the ITCZ. Our analysis of a 1.5-layer reduced gravity model revealed that the Rossby waves are mostly explained by wind stress forcing, rather than by reflection of an equatorial Kelvin wave on the eastern coastal boundary. The off-equatorial Rossby wave had the same SSHA polarity as the equatorial Kelvin wave, and generation of a phase-preserving Rossby wave without the Kelvin wave reflection was explained by meridional movement of the ITCZ. Thus, the ITCZ acts as an atmospheric bridge that connects the equatorial and off-equatorial oceanic waves. 相似文献
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On the basis of maps of sea level anomalies data set from October 1992 to January 2004, pronounced low frequency variations with periods of about 500 d are detected in the area near 20°N from 160°W to 130°E. A linear two-layer model is employed to explain the mechanism. It is found that the first-mode long baroclinic Rossby waves at 20°N in the northwest Pacific propagate westward in the form of free waves at a speed of about 10.3 cm/s. This confirms that the observed low frequency variabilities appear as baroclinic Rossby waves. It further shows that these low frequency variabilities around 20°N in the northwest Pacific can potentially be predicted with a lead up to 900 d. 相似文献
9.
T. V. Belonenko A. A. Kubrjakov S. V. Stanichny 《Izvestiya Atmospheric and Oceanic Physics》2016,52(9):920-928
Using satellite altimetry measurement data for 1993–2013, we study the spectral characteristics of Rossby waves in the Northwestern Pacific (25°–50° N, 140°–180° E). For each latitude degree, we draw integral plots of spectral power density calculated with a two-dimensional Fourier transform (2D-FFT). We compare the dispersion equations of Rossby waves calculated from the WKB-approximation and an approximation of a two-layer ocean model with the empirical velocities determined by the slope of isopleths by the Radon method; also, we compare the dispersion equations with the spectral distributions of level variations. It is shown that the main energy of Rossby waves in the Northwestern Pacific corresponds to the first baroclinic mode. At almost all latitudes, there is good agreement between the empirical phase velocities calculated by isopleths by the Radon method and the theoretical values; also, the spectral peaks correspond to graphs of the dispersion equations for the first baroclinic mode Rossby waves, except for the Kuroshio region, where some peaks correspond to the second mode. 相似文献
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Fei Chai Mingshun Jiang Richard T. Barber Richard C. Dugdale Yi Chao 《Journal of Oceanography》2003,59(4):461-475
The interdecadal climate variability affects marine ecosystems in both the subtropical and subarctic gyres, consequently the
position of the Transition Zone Chlorophyll Front (TZCF). A three-dimensional physical-biological model has been used to study
interdecadal variation of the TZCF using a retrospective analysis of a 30-year (1960–1990) model simulation. The physical-biological
model is forced with the monthly mean heat flux and surface wind stress from the COADS. The modeled winter mixed layer depth
(MLD) shows the largest increase between 30°N and 40°N in the central North Pacific, with a value of 40–60% higher during
1979–90 relative to 1964–75 values. The winter Ekman pumping velocity difference between 1979–90 and 1964–75 shows the largest
increase located between 30°N and 45°N in the central and eastern North Pacific. The modeled winter surface nitrate difference
between 1979–90 and 1964–75 shows increase in the latitudinal band between 30°N and 45°N from the west to the east (135°E–135°W),
the modeled nitrate concentration is about 10 to 50% higher during the period of 1979–90 relative to 1964–75 values depending
upon locations. The increase in the winter surface nitrate concentration during 1979-90 is caused by a combination of the
winter MLD increase and the winter Ekman pumping enhancement. The modeled nitrate concentration increase after 1976–77 enhances
primary productivity in the central North Pacific. Enhanced primary productivity after the 1976–77 climatic shift contributes
higher phytoplankton biomass and therefore elevates chlorophyll level in the central North Pacific. Increase in the modeled
chlorophyll expand the chlorophyll transitional zone and push the TZCF equatorward.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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对海洋中起伏运动(heaving)信号的时空分布研究能够帮助我们更好地了解气候系统中的年际和年代际变率。文章通过再分析资料和模式对太平洋区域的heaving主要模态进行了研究。研究结果表明: 太平洋区域主要存在两种heaving模态: 第一模态主要表现为赤道东西两侧的温跃层异常信号反位相; 第二模态表现为赤道区域和副热带区域的温跃层异常信号呈现反位相变化的规律。本文对这两个主要heaving模态所涉及的物理过程进行详细讨论, 结果表明: 东西反位相模态主要是受赤道波动调节的结果; 而经向结构模态则主要是由赤道地区的波动和副热带区域的风应力旋度异常作用共同导致。此外, 我们还讨论了heaving模态可以通过海洋波动以及Ekman输送等过程对海盆尺度的热输送(振幅约为5×1014W)以及海洋热含量(振幅约为1.5×1020J)的再分配起到了关键的调制作用, 进一步表明heaving模态对全球气候变化有着重要的作用。 相似文献
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Rossby波对菲律宾以东太平洋海平面年际变化的影响研究 总被引：1，自引：0，他引：1
采用能够反映斜压大洋对大尺度海表面风应力旋度响应的一层半约化重力模式研究菲律宾以东太平洋海区Rossby波与海平面年际变化的关系.模式分别利用海区东侧验潮站和卫星高度计海表面数据作初始东边界,对Rossby波西传路径上的风应力旋度进行积分,得到西侧海平面信号.结果发现,模拟的海平面信号跟验潮站和卫星高度计资料相关性很高,并能模拟出海平面年际变化特征和低(高)异常信号由东侧产生并向西传播的过程,反映了一阶斜压Rossby波对菲律宾以东太平洋海区年际海平面变化的动力机制. 相似文献
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1 IntroductionIn the Equatorial Pacific, due to the difference between the atmospheric circulation and air-sea interaction, the near-surface seawater heat structure in the eastern and western Pacific presents two ℃obviously different characteristics: warm pool ( > 28 ) in the western equatorial Pacific and cold ℃tongue ( < 24 ) in the eastern equatorial Pacific. The water bodies of these two heat structures would give rise to change in spatial distribution under the action of the equato… 相似文献
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太平洋内部副热带-热带经向翻转环流(subtropical-tropical cell,STC)是连接热带和副热带的海洋通道.由于以往海洋观测资料的匮乏,前人多利用海洋模式数据进行研究,且仅限于沿单一纬度上的STC的分析,较少涉及沿不同纬度的STC的季节变异规律.利用地转海洋学实时观测阵(array for real-... 相似文献
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利用1986/1987ENSO事件前后的深水CTD资料,计算了热带西太平洋(141°~165°E,10°N~10°S)相对于不同等压面的势能空间分布和时间变化。结果表明,ENSO期间热带西太平洋单位面积上水柱的势能明显减小,而热带西太平洋势能的经向变化明显大于纬向变化。经向变化的特征是赤道外势能大于赤道上的势能。势能最大值位于4°N和4°S,而最大年际变化则发生于7°N,远大于赤道附近。最后,还分析了热带西太平洋势能分布的地域性特征,并指出了这些特征与海洋水文特征的联系。 相似文献
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Xiao-Hua Zhu Arata Kaneko Noriaki Gohda Hideo Inaba Kunio Kutsuwada Marie-Helene Radenac 《Journal of Oceanography》1998,54(2):133-141
During the IOP (Intensive Observation Period) of TOGA/COARE (Tropical Ocean and Global Atmosphere/Coupled Ocean Atmosphere
Response Experiment) from December 1992 to February 1993, four Japanese moored ADCPs (Acoustic Doppler Current Profilers)
measured vertical profiles of three-component velocities at the stations 2S (2°S, 156°E), 2N (2°N, 156°E), 154E (0°N, 154°E)
and 147E (0°N, 147°E). Power spectra of the surface current showed a pronounced peak having a period of around 14 days for
both the zonal and meridional velocities at the stations 2S and 2N near the equator, and for only the meridional velocity
at the equator. This 14-day phenomenon is considered to be a kind of equatorial wave of the first baroclinic mode, from a
comparison of the result of the vertical mode analysis and the vertical distribution of the standard deviation of band-pass
filtered velocity fluctuations. A dispersion relationship obtained from the horizontal mode analysis of this wave confirmed
that the 14-day phenomenon is a mixed Rossby-gravity wave with the westward propagating phase speed and eastward propagating
group velocity. From the cross-spectral analysis of velocity data, the average phase speed and wavelength of the wave were
estimated as 3.64 m s−1 and 3939 km, respectively, for station pair 2S∼147E. These values were in good agreement with the average phase speed and
wavelength of 3.58 m s−1 and 3836 km estimated from the dispersion curve and the observed period. A northerly wind burst blew over all the mooring
sites during the middle of the observation period. The mixed Rossby-gravity wave, which is anti-symmetric for the zonal velocity
about the equator, is likely to be forced by this northerly wind burst crossing the equator. Generation of the oceanic mixed
Rossby-gravity wave of the first baroclinic mode is discussed in association with the atmospheric Rossby wave having the same
period. 相似文献
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A regional ocean model was used to simulate the annual cycle of the upper-ocean dynamics and its influence on ocean properties in the tropical western Indian Ocean. Surface winds and heat fluxes from the National Centers for Environmental Prediction (NCEP) reanalysis forced the model (Model_NCEP) with initial and lateral boundary conditions derived from the Simple Ocean Data Assimilation (SODA). The model findings were in good agreement with previous research, satellite and observational data as well as another model configuration forced by Comprehensive Ocean and Atmosphere Data Sets (COADS). The initial and lateral boundary conditions for Model_COADS were extracted from World Ocean Atlas 2001. Anticyclonic wind stress curl occurred to the north of Madagascar, and extended towards the Tanzanian coast throughout the year, leading to Ekman convergence and downwelling in that region. The lowest sea-surface height values during the year occurred between 5° and 12° S with an elongated and contracted shape. The East African Coastal Current (EACC) was in phase with the westward North-East Madagascar Current (NEMC) throughout the year with volume transports peaking in June through July in the model forced by NCEP reanalysis. The variability of the volume transport, ocean currents, temperature and salinity to the north of Madagascar on the path of the NEMC mirrored those in the middle Tanzanian shelf on the path of the EACC throughout the year. The NEMC seemed to influence the water masses on the Tanzanian shelf, with cooler and lower-salinity water in the South-West Monsoon, and warmer and saltier water during the North-East Monsoon. 相似文献
19.
Atsushi Kubokawa 《Journal of Oceanography》1995,51(2):207-224
Gyre-scale frontal structures, e.g., the Subtropical Front, have been well documented in the oceans. Although the generation mechanism of such a front remains unclear, it may be ascribed to the steepening of nonlinear planetary waves as discussed by Dewar (1992). To discuss the stationary wave characteristics and their shock formation in a two-layer wind-driven gyre, the present paper introduces a new coordinate, referred to as theSverdrup coordinate here, in which the Sverdrup function is used instead of the longitudinal coordinate, and especially, investigates the possibility of the frontgenesis caused by the Rossby waves emanating from the western boundary region. On theSverdrup coordinate, since the advection by the Sverdrup flow is in the direction normal to that of the Rossby wave propagation, the system becomes much simpler than that on the (x,y)-coordinate, and the solution to this coordinate does not explicitly depend on the distribution of the Ekman pumping, i.e., we can treat cases, in which the Ekman pumping is a function of bothx andy, in a similar way to the case with zonally uniform Ekman pumping. 相似文献
20.
北太平洋副热带东部模态水现在和未来的模拟分析 总被引：2，自引：1，他引：1
The present climate simulation and future projection of the Eastern Subtropical Mode Water(ESTMW) in the North Pacific are investigated based on the Geophysical Fluid Dynamics Laboratory Earth System Model(GFDL-ESM2M). Spatial patterns of the mixed layer depth(MLD) in the eastern subtropical North Pacific and the ESTMW are well simulated using this model. Compared with historical simulation, the ESTMW is produced at lighter isopycnal surfaces and its total volume is decreased in the RCP8.5 runs, because the subduction rate of the ESTMW decreases by 0.82×10-6 m/s during February–March. In addition, it is found that the lateral induction decreasing is approximately four times more than the Ekman pumping, and thus it plays a dominant role in the decreased subduction rate associated with global warming. Moreover, the MLD during February–March is banded shoaling in response to global warming, extending northeastward from the east of the Hawaii Islands(20°N, 155°W) to the west coast of North America(30°N, 125°W), with a maximum shoaling of 50 m, and then leads to the lateral induction reduction. Meanwhile, the increased northeastward surface warm current to the east of Hawaii helps strengthen of the local upper ocean stratification and induces the banded shoaling MLD under warmer climate. This new finding indicates that the ocean surface currents play an important role in the response of the MLD and the ESTMW to global warming. 相似文献