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1.
The sigma coordinate, Princeton Ocean Model (POM) has been configured for the North Atlantic Ocean between 5°N and 50°N as part of data assimilation, model predictability and intercomparison studies. The model uses a curvilinear orthogonal grid with higher resolution in the western North Atlantic and lower resolution in the eastern North Atlantic. A series of experiments, each one of a 10-year duration, are performed to evaluate the sensitivity of the ocean mean state and variability to model parameters and model configuration; these experiments include open vs. closed boundary conditions, low vs. high resolution grids, and different choices of diffusion and viscosity. The results show that the use of closed boundaries together with near-boundary buffer zones where temperature and salinity are relaxed towards the observed values give less realistic flows, weaker recirculation gyres and less realistic Gulf Stream separation than do open boundary conditions. The experiments show that the sensitivity of the ocean variability in the model to the choice of the Smagorinsky diffusion and viscosity coefficients significantly differs from one region to another and largely depends on other attributes such as the mean position of the Gulf Stream in each simulation. A 50% change in model resolution in the Gulf Stream region has a larger effect on ocean variability than a change of diffusivity by a factor of 10. In areas where either the high or the low resolution models have sufficient resolution, as in the Gulf of Mexico, they are able to produce variability comparable to that observed from altimeter data; elsewhere, model variability is underestimated. 相似文献
2.
D. W. Pierce T. P. Barnett N. Schneider R. Saravanan D. Dommenget M. Latif 《Climate Dynamics》2001,18(1-2):51-70
Decadal time scale climate variability in the North Pacific has implications for climate both locally and over North America.
A crucial question is the degree to which this variability arises from coupled ocean/atmosphere interactions over the North
Pacific that involve ocean dynamics, as opposed to either purely thermodynamic effects of the oceanic mixed layer integrating
in situ the stochastic atmospheric forcing, or the teleconnected response to tropical variability. The part of the variability
that is coming from local coupled ocean/atmosphere interactions involving ocean dynamics is potentially predictable by an
ocean/atmosphere general circulation model (O/A GCM), and such predictions could (depending on the achievable lead time) have
distinct societal benefits. This question is examined using the results of fully coupled O/A GCMs, as well as targeted numerical
experiments with stand-alone ocean and atmosphere models individually. It is found that coupled ocean/atmosphere interactions
that involve ocean dynamics are important to determining the strength and frequency of a decadal-time scale peak in the spectra
of several oceanic variables in the Kuroshio extension region off Japan. Local stochastic atmospheric heat flux forcing, integrated
by the oceanic mixed layer into a red spectrum, provides a noise background from which the signal must be extracted. Although
teleconnected ENSO responses influence the North Pacific in the 2–7 years/cycle frequency band, it is shown that some decadal-time
scale processes in the North Pacific proceed without ENSO. Likewise, although the effects of stochastic atmospheric forcing
on ocean dynamics are discernible, a feedback path from the ocean to the atmosphere is suggested by the results.
Received: 23 January 2000 / Accepted: 10 January 2001 相似文献
3.
A numerical experiment of an asynchronous coupled ocean-atmosphere model has been described in this paper.A two-layer global atmosphere general circulation model(OSU/IAP-AGCM)and a two-layer North Pacific Ocean general circulation model(NPOGCM) developed by Liu et al.(1992)are used in numerical experiment.The sea surface temperature anomaly(SSTA) corresponding to the meander of the Kuroshio is treated as the initial perturbation in the Pacific Ocean and the abnormal phenomena caused by the disturbance and the interaction between atmosphere and ocean,have been studied.The numerical experiment showed that the SST anomaly in the North Pacific could induce a new 30-60 day osciltation through the coupling between atmosphere and ocean and the interaction between the meander of the Kuroshio and atmosphere circulation is a positive feedback process. 相似文献
4.
The North Atlantic is one of the few places on the globe where the atmosphere is linked to the deep ocean through air–sea
interaction. While the internal variability of the atmosphere by itself is only predictable over a period of one to two weeks,
climate variations are potentially predictable for much longer periods of months or even years because of coupling with the
ocean. This work presents details from the first study to quantify the predictability for simulated multidecadal climate variability
over the North Atlantic. The model used for this purpose is the GFDL coupled ocean-atmosphere climate model used extensively
for studies of global warming and natural climate variability. This model contains fluctuations of the North Atlantic and
high-latitude oceanic circulation with variability concentrated in the 40–60 year range. Oceanic predictability is quantified
through analysis of the time-dependent behavior of large-scale empirical orthogonal function (EOF) patterns for the meridional
stream function, dynamic topography, 170 m temperature, surface temperature and surface salinity. The results indicate that
predictability in the North Atlantic depends on three main physical mechanisms. The first involves the oceanic deep convection
in the subpolar region which acts to integrate atmospheric fluctuations, thus providing for a red noise oceanic response as
elaborated by Hasselmann. The second involves the large-scale dynamics of the thermohaline circulation, which can cause the
oceanic variations to have an oscillatory character on the multidecadal time scale. The third involves nonlocal effects on
the North Atlantic arising from periodic anomalous fresh water transport advecting southward from the polar regions in the
East Greenland Current. When the multidecadal oscillatory variations of the thermohaline circulation are active, the first
and second EOF patterns for the North Atlantic dynamic topography have predictability time scales on the order of 10–20 y,
whereas EOF-1 of SST has predictability time scales of 5–7 y. When the thermohaline variability has weak multidecadal power,
the Hasselmann mechanism is dominant and the predictability is reduced by at least a factor of two. When the third mechanism
is in an extreme phase, the North Atlantic dynamic topography patterns realize a 10–20 year predictability time scale. Additional
analysis of SST in the Greenland Sea, in a region associated with the southward propagating fresh water anomalies, indicates
the potential for decadal scale predictability for this high latitude region as well. The model calculations also allow insight
into regional variations of predictability, which might be useful information for the design of a monitoring system for the
North Atlantic. Predictability appears to break down most rapidly in regions of active convection in the high-latitude regions
of the North Atlantic.
Received: 28 October 1996 / Accepted: 21 March 1997 相似文献
5.
Case studies in interannual to decadal climate predictability 总被引：1，自引：0，他引：1
The predictability of ocean and climate variables is investigated, using a perfect model-based case study approach that recognises that predictability is dependent on the initial climate state. In line with previous studies, large scale ocean variables show predictability for several years or more; by contrast, the predictability of climate variables is generally limited to 2 years at most. That predictability shows high sensitivity to the initial state is demonstrated by predictable climate signals arising in different regions, variables and seasons for different initial conditions. The predictability of climate variables in the second year is of particular interest, because this is beyond the timescale that is usually considered to be the limit of seasonal predictability. For different initial conditions, second year predictability is found in: temperatures in southeastern North America (winter) and western Europe (winter and summer), and precipitation in India (summer monsoon) and in the tropical South Atlantic. Second year predictability arises either from persistence of large-scale sea surface temperature (SST) and related ocean heat content anomalies, particularly in regions such as the North Atlantic and Southern Ocean, or from mechanisms that involve El Niño Southern Oscillation (ENSO) dynamics. 相似文献
6.
A high-resolution ocean general circulation model （OGCM） is used to investigate the Kuroshio path variations south of Japan. The model reproduces many important features of the Kuroshio system including its interannual bimodal variability south of Japan. A decreasing trend of the spatial averaged relative vorticity is detected when the Kuroshio takes the non-large meander （NLM） path, and during the transition period from the NLM to the large meander （LM）, a sudden release of velocity shear corresponds well to the weakening of the Shikoku recirculation gyre （SRG）, which plays a key role in modulating the Kuroshio path variations. Analysis of eddy energetics indicates that baroclinic instability is mainly responsible for the formation of the LM. In addition, further analysis shows that the strength of the SRG could be largely influenced by the baroclinic Rossby wave adjustment process, forced by the wind stress curl anomalies in the North Pacific basin, based on the model investigation. It is suggested that the cyclonic disturbances might account for the weakening of the SRG, and act as a remote trigger for the baroclinic instability of the Kuroshio south of Japan. 相似文献
7.
Ｓｈｏｒｔ－ｔｅｒｍＣｌｉｍａｔｉｃＦｌｕｃｔｕａｔｉｏｎｓｉｎＮｏｒｔｈＡｔｌａｎｔｉｃＯｓｃｉｌｌａｔｉｏｎａｎｄＦｒｅｑｕｅｎｃｙｏｆＣｙｃｌｏｎｉｃＤｉｓｔｕｒｂａｎｃｅｓｏｖｅｒＮｏｒｔｈＩｎｄｉａｎＯｃｅａｎａｎｄＮｏｒｔｈｗｅｓｔＰａｃ... 相似文献
8.
文章介绍了海洋气象导航发展的必然性及其气象航线选择的原理和影响因素。结合中央气象台海洋气象导航中心近10年来的实船导航业务，分析了北印度洋气候对冬、夏季航线选择的影响因素，指出应结合北印度洋的冬、夏季气候变化及地形特点选择不同的气象航线。该文为在实际工作中根据不同的季节及船型情况选择不同的航线、规避大风和巨浪出现频率高的区域，以及保持良好的航行条件提供了依据。 相似文献
9.
参照Griffies et al.(2009)提出的海洋—海冰耦合模式参考试验(Coordinated Ocean-ice Reference Experiments,COREs),设计了一个800年积分的数值试验,对一个质量严格守恒的压力坐标海洋环流模式(Pressure Coordinate Ocean Model,PCOM1.0)的基本模拟性能进行了评估,并与观测资料和再分析资料进行了对比。结果表明,PCOM1.0模拟的温盐场和基本流场与COREs模式的模拟水平基本接近。其中,模拟的大西洋经向翻转流在45°N附近达到18 Sv(1 Sv=106 m3 s-1),与观测估计值接近;对海表面温度的模拟误差主要集中在北太平洋黑潮区和北大西洋湾流区等中高纬度急流区;模拟的热带太平洋温跃层过于深厚;模拟的经德雷克海峡的体积输送达130 Sv,比大部分COREs模式及再分析资料都更接近于观测估计值。 相似文献
10.
Yusuke Uchiyama Ryosuke Kanki Akiko Takano Hidekatsu Yamazaki Yasumasa Miyazawa 《大气与海洋》2018,56(4):212-229
ABSTRACTFor dynamically consistent, high-resolution, yet cost-effective regional oceanic downscaling modelling, an empirical three-dimensional (3D) density estimate based on publicly available datasets is utilized for the Regional Oceanic Modeling System (ROMS) with simple data assimilation (i.e., TS nudging, where TS stands for temperature and salinity). We rely on a method built upon the two-layer model to reconstruct a mesoscale 3D temperature and salinity field, referred to as Tokyo University of Marine Science and Technology (TUMSAT)-TS, using near real-time altimeter-derived dynamic height along with Argo float profiling data. The TUMSAT-TS is first validated using in situ hydrographic data, then is implemented in the Japan Coastal Ocean Predictability Experiment (JCOPE2)-ROMS downscaling system for the Kuroshio region off Japan. We explore the usability of TUMSAT-TS by carrying out three comparative simulations with temperature and salinity nudging towards the (i) TUMSAT-TS and (ii) JCOPE2-TS fields, and (iii) without the nudging. Whereas the unassimilated case fails to properly account for the Kuroshio, both datasets individually are found to help reproduce the mesoscale variability of the Kuroshio, as well as its transient paths, volume transport, associated kinetic energy (KE) and eddy KE, and seasonally varying stratification. 相似文献
11.
An overview of decadal climate predictability in a multi-model ensemble by climate model MIROC 总被引：1，自引：1，他引：0
Yoshimitsu Chikamoto Masahide Kimoto Masayoshi Ishii Takashi Mochizuki Takashi T. Sakamoto Hiroaki Tatebe Yoshiki Komuro Masahiro Watanabe Toru Nozawa Hideo Shiogama Masato Mori Sayaka Yasunaka Yukiko Imada 《Climate Dynamics》2013,40(5-6):1201-1222
Decadal climate predictability is examined in hindcast experiments by a multi-model ensemble using three versions of the coupled atmosphere-ocean model MIROC. In these hindcast experiments, initial conditions are obtained from an anomaly assimilation procedure using the observed oceanic temperature and salinity with prescribed natural and anthropogenic forcings on the basis of the historical data and future emission scenarios in the Intergovernmental Panel of Climate Change. Results of the multi-model ensemble in our hindcast experiments show that predictability of surface air temperature (SAT) anomalies on decadal timescales mostly originates from externally forced variability. Although the predictable component of internally generated variability has considerably smaller SAT variance than that of externally forced variability, ocean subsurface temperature variability has predictive skills over almost a decade, particularly in the North Pacific and the North Atlantic where dominant signals associated with Pacific decadal oscillation (PDO) and the Atlantic multidecadal oscillation (AMO) are observed. Initialization enhances the predictive skills of AMO and PDO indices and slightly improves those of global mean temperature anomalies. Improvement of these predictive skills in the multi-model ensemble is higher than that in a single-model ensemble. 相似文献
12.
北太平洋海温异常的空间模态及其与东亚环流异常的关系 总被引：2，自引：0，他引：2
运用英国气象局全球海温和NCEP/NCAR 再分析逐月资料, 分析了1979年以来北太平洋夏季海温异常的主要模态, 并探讨了海温异常的空间分布与东亚环流异常的关系。结果表明: 北太平洋夏季海温主要存在两种模态, 当太平洋热带地区西高东低 (西低东高), 西太平洋到黑潮区海温偏高 (低), 东南太平洋的海温偏低 (高) 时, 东亚贝加尔湖南侧地区为显著的正 (负) 高度异常。进一步分析发现这种环流异常与北太平洋西部海温异常引起的辐合辐散有关, 北太平洋西部近大陆海域海温异常偏暖 (冷), 对应上空为异常的上升 (下沉) 运动, 因质量的连续性使贝加尔湖南侧地区低层辐散 (辐合) 异常, 有利于该地区异常反气旋性环流的加强 (减弱)。 相似文献
13.
东海黑潮暖舌的演变及其对我国气温的影响 总被引：1，自引：1，他引：0
利用高分辨率的海温分析资料模式资料,分析了黑潮暖舌与我国气温的关系,初步探讨了太平洋年代际振荡(PDO)等造成黑潮暖舌变化的可能原因。结果表明,冬季和春季东海黑潮暖舌存在明显的年际和年代际变化。暖舌在1996/1997年发生了一次突变,此前暖舌处在偏冷的状态,之后转为偏暖的状态。我国冬季和春季气温存在一定的年代际变化,1997年之后,冬季除东北和新疆外,气温有所偏高,而春季气温全国表现为一致的显著偏高。冬季和春季气温对黑潮暖舌存在邻(域)响应。冬季东海黑潮暖舌指数与冬季我国东部气温存在正相关,并且这一相关性能够延续到次年春季。冬季黑潮暖舌指数与我国4月海陆热力差异指数也存在显著的正相关。当冬季暖舌偏强(弱)时,4月海陆热力差异指数偏高(低),即东亚地区海陆热力差异偏大(小)。春季黑潮暖舌指数与春季我国中部及南方地区气温也存在正相关,当春季黑潮暖舌偏强(弱)时,上述地区气温将偏高(低)。PDO和黑潮暖舌之间的相互作用存在一个反馈机制。西风的增强,可通过使海洋向大气释放热量增加和向南的埃克曼(Ekman)输送,降低北太平洋中部的SST,而这一地区SST的降低对应着PDO的暖位相。增强的负风应力旋度在北太平洋副热带流涡中强迫出的向南斯维尔德鲁普(Sverdrup)流也偏强,而向北流动的东海黑潮的增强正是补偿了这一向南的海流。黑潮增强后经过两个月将大量热量输送至北太平洋中部,增强了这一地区的SST,而这对应着PDO的冷位相。 相似文献
14.
利用麻省理工学院海洋环流模式研究了风应力输入到海洋中的能量的气候变率特征。结果表明:风应力输入到海洋中的能量对气候变化有显著的响应。在北大西洋涛动(North Atlantic Oscillation,NAO)正位相的年份,风应力输入到海洋中的能量的大值区北移且加强,主要由于暴风路径的北移和天气尺度大气扰动的加强导致;同样,在南半球环状模(Southern Annular Mode,SAM)正位相年份输入到南大洋的能量大值区南移并加强,且输入到南极大陆沿岸流中的能量也有显著增加。经验正交函数分解分析结果表明:NAO主导了风应力输入到北大西洋区域的能量变化。SAM解释了南大洋区域风应力输入能量的第一模态,第二、三模态解释了受ENSO(El Niňo-Southern Oscillation)影响的情况。最近几十年,在南大洋区域,风应力及其输入能量的年代际变化都有所增强,而在北半球的中高纬度区域有所下降。 相似文献
15.
The determination of specific sea surface temperature (SST) patterns from large-scale gridded SST-fields has widely been done. Often principal component analysis (PCA) is used to condense the SST-data to major patterns of variability. In the present study SST-fields for the period 1950?C2003 from the area 20°S to 60°N are analysed with respect to SST-regimes being defined as large-scale oceanic patterns with a regular and at least seasonal occurrence. This has been done in context of investigations on seasonal predictability of Mediterranean regional climate with large-scale SST-regimes as intended predictors in statistical model relationships. The SST-regimes are derived by means of a particular technique including multiple applications of s-mode PCA. Altogether 17 stationary regimes can be identified, eight for the Pacific Ocean, five for the Atlantic Ocean, two for the Indian Ocean, and two regimes which show a distinct co-variability within different ocean basins. Some regimes exist, with varying strength and spatial extent, throughout the whole year, whereas other regimes are only characteristic for a particular season. Several regimes show dominant variability modes, like the regimes associated with El Ni?o, with the Pacific Decadal Oscillation or with the North Atlantic Tripole, whereas other regimes describe little-known patterns of large-scale SST variability. The determined SST-regimes are subsequently used as predictors for monthly precipitation and temperature in the Mediterranean area. This subject is addressed in Part II of this paper. 相似文献
16.
G.A. McBean 《大气与海洋》2013,51(3):576-595
Abstract The meridional heat flux in the North Pacific Ocean at 35°N is estimated primarily using hydrographic section data, following the method of Bryan (1962) and Bennett (1978). The meridional heat flux in the Kuroshio, computed using the Worthington and Kawai section across the current, was 1.76 PW (positive northward), with over 80% of the flux occurring in the upper 400 m. The large‐scale baroclinic heat flux across the rest of the section (145°? to North America) was —1.0 PW for the indopac (1976) section and —0.5 PW for the IOS‐72 section. The fluxes across the sections were also concentrated in the upper ocean with the upper 300 m accounting for over 75% of the flux. The mean horizontal barotropic gyre circulation results in little (0.1 PW) net heat flux because the northward‐moving water is only about 0.5°C warmer than the southward‐moving water. The contributions due to Ekman heat flux (—0.16 PW) and flow through the Japan Sea (0.13 PW) are also relatively small. The eddy heat flux is quite uncertain, but estimated to be about 0.3 PW. The total meridional heat flux, for the 1976 section, is calculated to be about 1.0 PW. The total is very dependent on the baroclinic heat flux in the highly variable Kuroshio region. The northward heat flux found in this study is more consistent with large‐scale atmospheric estimates and with Bryden et al. ‘s (1990) estimate for 24°? in the Pacific. 相似文献
17.
A global ocean temperature and altimeter data assimilation system for studies of climate variability 总被引：4，自引：0，他引：4
An ocean data assimilation (ODA) system which can assimilate both temperature and altimeter observations has been applied
to the global ocean and tested between January 1993–October 1996. A statistical method has been used to convert sea surface
height (SSH) anomalies observations from TOPEX/POSEIDON into synthetic temperature profiles. The innovative aspect of this
method is the introduction of time dependency in the correlations used to transform the altimeter observations into temperature
corrections. The assimilation system is based on a univariate variational optimal interpolation scheme applied to assimilate
both in situ and synthetic temperature profiles. In addition, a longer global analysis for the upper-ocean temperature starting
from January 1979 and ending November 1997, has been produced to examine the skill of sea temperature assimilation with a
rather simple and practical method. The temperature analysis shows encouraging improvement over a corresponding ocean simulation
when compared to independent (not assimilated) temperature data both at seasonal and interannual time scales. However, the
univariate data assimilation of hydrographic data does not result in an improvement of the velocity field. In fact the assimilation
of sparse in situ data can introduce unrealistic spatial variability in the temperature field which affects the velocity field
in a negative way. This deficiency is partially overcome when we also assimilate altimeter observations since the coverage
is complete and uniform for this data. In particular, our study shows that temperature corrections due to the altimeter signal
have a positive impact on the current system in the tropical Pacific.
Received: 28 May 2000 / Accepted: 6 November 2000 相似文献
18.
The inter-basin teleconnection between the North Atlantic and the North Pacific ocean–atmosphere interaction is studied using
a coupled ocean–atmosphere general circulation model. In the model, an idealized oceanic temperature anomaly is initiated
over the Kuroshio and the Gulf Stream extension region to track the coupled evolution of ocean and atmosphere interaction,
respectively. The experiments explicitly demonstrate that both the North Pacific and the North Atlantic ocean–atmosphere interactions
are intimately coupled through an inter-basin atmospheric teleconnection. This fast inter-basin communication can transmit
oceanic variability between the North Atlantic and the North Pacific through local ocean-to-atmosphere feedbacks. The leading
mode of the extratropical atmospheric internal variability plays a dominant role in shaping the hemispheric-scale response
forced by oceanic variability over the North Atlantic and Pacific. Modeling results also suggest that a century (two centuries)
long observations are necessary for the detection of Pacific response to Atlantic forcings (Atlantic response to Pacific forcing). 相似文献
19.
The ocean response to surface temperature transients is simulated with the use of the Hamburg large-scale geostrophic (LSG)
ocean general circulation model (OGCM). The transition, from the present to a climate corresponding to a doubling of the atmospheric
CO2 content, is compared with the reversed transition. For the Atlantic, the time scale for the deep ocean to adjust to the temperature
changes was similar for both transitions. In the Pacific, the time scale is shorter for the present to warm transition than
for the reverse case, a result of increased production of Antarctic bottom water (AABW) during the warm climate. While the
transition from cold to warm climate shows no secular variability, the reversed transition generates considerable variability
on time scales of 300–400 years. For the warm climate, oscillations with periods of 45 years are found in the Southern Ocean.
Results of principal oscillation pattern (POP) analysis indicate that these oscillations are due to interaction between convection
in the Southern Ocean and advected salinity anomalies in the Antarctic Circumpolar Current (ACC) and the Southern Pacific
Ocean.
Received: 19 September 1995 / Accepted: 15 March 1996 相似文献
20.
Sea surface temperature (SST) and salinity (SSS) time series from four ocean weather stations and data from an integration
of the GFDL coupled ocean-atmosphere model are analyzed to test the applicability of local linear stochastic theory to the
mixed-layer ocean. According to this theory, mixed-layer variability away from coasts and fronts can be explained as a ‘red
noise’ response to the ‘white noise’ forcing by atmospheric disturbances. At one weather station, Papa (northeast Pacific),
this stochastic theory can be applied to both salinity and temperature, explaining the relative redness of the SSS spectrum.
Similar results hold for a model grid point adjacent to Papa, where the relationships between atmospheric energy and water
fluxes and actual changes in SST and SSS are what is expected from local linear stochastic theory. At the other weather stations,
this theory cannot adequately explain mixed-layer variability. Two oceanic processes must be taken into account: at Panulirus
(near Bermuda), mososcale eddies enhance the observed variability at high frequencies. At Mike and India (North Atlantic),
variations in SST and SSS advection, indicated by the coherence and equal persistence of SST and SSS anomalies, contribute
to much of the low frequency variability in the model and observations. To achieve a global perspective, TOPEX altimeter data
and model results are used to identify regions of the ocean where these mechanisms of variability are important. Where mesoscale
eddies are as energetic as at Panulirus, indicated by the TOPEX global distribution of sea level variability, one would expect
enhanced variability on short time scales. In regions exhibiting signatures of variability similar to Mike and India, variations
in SST and SSS advection should dominate at low frequencies. According to the model, this mode of variability is found in
the circumpolar ocean and the northern North Atlantic, where it is associated with the irregular oscillations of the model’s
thermohaline circulation.
Received: 11 March 1996 / Accepted: 6 September 1996 相似文献