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1.
Effect of chlorophyll-a spatial distribution on upper ocean temperature in the central and eastern equatorial Pacific 总被引：1，自引：0，他引：1
Effect of the spatial distributions of chlorophyll-a concentration on upper ocean temperature and currents in the equatorial Pacific is investigated through a set of numerical experiments by using an ocean general circulation model. This study indicates that enhanced meridional gradient of chlorophyll-a between the equator and off-equatorial regions can strengthen zonal circulation and lead to a decrease in equatorial sea surface temperature （SST）. However, the circulation changes by themselves are not effective enough to affect SST in the equatorial cold tongue （CT） region. The comparison between the experiments indicates that the CT SST are more sensitive to chlorophyll-a distribution away from the equator. The off-equatorial chlorophyll-a traps more solar radiation in the mixed layer, therefore, the temperature in the thermoeline decreases. The cold water can then be transported to the equator by the meridional circulation within the mixed layer. Furthermore, the relation among CT SST, the surface heat flux, and the equatorial upwelling are discussed. The study implies the simulation biases of temperature on the equator are not only related to the local ocean dynamics but also related to some deficiency in simulating off-equatorial processes. 相似文献
2.
Phytoplankton pigments (e.g., chlorophyll-a) absorb solar radiation in the upper ocean and induce a pronounced radiant heating effect (chlorophyll effect) on the climate. However, the ocean chlorophyll-induced heating effect on the mean climate state in the tropical Pacific has not been understood well. Here, a hybrid coupled model (HCM) of the atmosphere, ocean physics and biogeochemistry is used to investigate the chlorophyll effect on sea surface temperature (SST) in the eastern equatorial Pacific; a tunable coefficient, α, is introduced to represent the coupling intensity between the atmosphere and ocean in the HCM. The modeling results show that the chlorophyll effect on the mean-state SST is sensitively dependent on α (the coupling intensity). At weakly represented coupling intensity (0 ≤ α < 1.01), the chlorophyll effect tends to induce an SST cooling in the eastern equatorial Pacific, whereas an SST warming emerges at the strongly represented coupling intensity (α ≥ 1.01). Thus, a threshold exists for the coupling intensity (about α = 1.01) at which the sign of SST responses can change. Mechanisms and processes are illustrated to understand the different SST responses. In the weak coupling cases, indirect dynamical cooling processes (the adjustment of ocean circulation, enhanced vertical mixing, and upwelling) tend to dominate the SST cooling. In the strong coupling cases, the persistent warming induced by chlorophyll in the southern subtropical Pacific tends to induce cross-equatorial northerly winds, which shifts to anomalous westerly winds in the eastern equatorial Pacific, consequently reducing the evaporative cooling and weakening indirect dynamical cooling; eventually, SST warming maintains in the eastern equatorial Pacific. These results provide new insights into the biogeochemical feedback on the climate and bio-physical interactions in the tropical Pacific.
相似文献3.
东太平洋冷舌区海表面温度日变化特征的模拟研究 总被引：1，自引：0，他引：1
本文通过分辨太阳辐射日变化, 利用中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室 (LASG/IAP) 气候系统海洋环流模式 (LICOM), 模拟了东太平洋冷舌区海表面温度 (SST) 的日变化特征并研究了弱混合对其影响。采用理想的太阳辐射日变化强迫上层垂向分辨率为10 m的海洋模式LICOM, 模拟出了SST日变化一些特征, 同时海洋的上层流场也产生明显日变化。模拟的SST日变化振幅水平分布与观测接近, 且受太阳辐射日变化振幅水平分布调制。在赤道中东太平洋区, 模拟的SST日变化振幅 (约为0.3～0.4℃) 比观测偏小约0.1～0.2℃。模拟的SST日变化峰值出现在15～16 时 (当地标准时间), 落后于太阳辐射峰值2～3个小时, 接近观测。进一步减弱混合后, 模拟的日变化振幅增加约0.1℃, 更接近观测。这说明在东太平洋冷舌区SST日变化主要受太阳辐射日变化和垂直混合影响。此外, 混合减小后, 在太阳辐射日变化调制下, 平均态 (如混合层、温度和流场) 也出现明显变化。在赤道东太平洋冷舌区北侧, 弱混合导致混合层变浅, 变浅使热量堆积进而使平均SST升高约0.3℃; 在赤道东太平洋冷舌南侧, 经向平流加强导致平均SST降低约0.2℃。 相似文献
4.
本文利用1958～2018年期间海表面温度（SST）异常和湍流热通量异常变化的关系,探讨了其与北太平洋年代际振荡（PDO）相关的年际和年代际时间尺度上在不同海域的海气相互作用特征。结果表明:在年际尺度上,黑潮—亲潮延伸区（KOE）表现为显著大气强迫海洋,赤道中东太平洋表现为显著海洋强迫大气;在年代际尺度上,PDO北中心表现为大气强迫海洋,加利福尼亚附近则表现为显著海洋强迫大气。进一步分析表明:加利福尼亚附近区域是北太平洋准12年振荡的关键区域之一,与PDO准十年的周期类似,加利福尼亚附近的冷（暖）海温对应其上有反气旋（气旋）型环流,赤道中太平洋海水上翻和北太平洋东部副热带区域经向风应力的变化是北太平洋准12年振荡的另外两个重要环节。 相似文献
5.
Impacts of an improved low-level cloud scheme on the eastern Pacific ITCZ-cold tongue complex 总被引：1，自引：0，他引：1
A statistically-based low-level cloud parameterization scheme is introduced, modified, and applied in the Flexible coupled General Circulation Model (FGCM-0). It is found that the low-level cloud scheme makes improved simulations of low-level cloud fractions and net surface shortwave radiation fluxes in the subtropical eastern oceans off western coasts in the model. Accompanying the improvement in the net surface shortwave radiation fluxes, the simulated distribution of SSTs is more reasonably asymmetrical about the equator in the tropical eastern Pacific, which suppresses, to some extent, the development of the double ITCZ in the model. Warm SST biases in the ITCZ north of the equator are more realistically reduced, too. But the equatorial cold tongue is strengthened and extends further westward, which reduces the precipitation rate in the western equatorial Pacific but increases it in the ITCZ north of the equator in the far eastern Pacific. It is demonstrated that the low-level cloud-radiation feedback would enhance the cooperative feedback between the equatorial cold tongue and the ITCZ. Based on surface layer heat budget analyses, it is demonstrated that the reduction of SSTs is attributed to both the thermodynamic cooling process modified by the increase of cloud fractions and the oceanic dynamical cooling processes associated with the strengthened surface wind in the eastern equatorial Pacific, but it is mainly attributed to oceanic dynamical cooling processes associated with the strengthening of surface wind in the central and western equatorial Pacific. 相似文献
6.
Using an intermediate ocean–atmosphere coupled model (ICM) for the tropical Pacific, we investigated the role of the ocean dynamical thermostat (ODT) in regulating the tropical eastern Pacific sea surface temperature (SST) under global warming conditions. The external, uniformly distributed surface heating results in the cooling of the tropical eastern Pacific “cold tongue,” and the amplitude of the cooling increases as more heat is added but not simply linearly. Furthermore, an upper bound for the influence of the equatorially symmetric surface heating on the cold tongue cooling exists. The additional heating beyond the upper bound does not cool the cold tongue in a systematic manner. The heat budget analysis suggests that the zonal advection is the primary factor that contributes to such nonlinear SST response. The radiative heating due to the greenhouse effect (hereafter, RHG) that is obtained from the multi-model ensemble of the Climate Model Intercomparison Project Phase III (CMIP3) was externally given to ICM. The RHG obtained from the twentieth century simulation intensified the cold tongue cooling and the subtropical warming, which were further intensified by the RHG from the doubled CO2 concentration simulation. However, the cold tongue cooling was significantly reduced and the negative SST response region was shrunken toward the equator by the RHG from the quadrupled CO2 concentration simulation, while the subtropical warming increased further. A systematic RHG forced experiment having the same spatial pattern of RHG from doubled CO2 concentration simulation with different amplitude of forcing revealed that the ocean dynamical response to global warming tended to enhance the cooling in the tropical eastern Pacific by virtue of meridional advection and upwelling; however, these cooling effects could not fully compensate a given RHG warming as the external forcing becomes larger. Moreover, the feedback by the zonal thermal advection actually exerted the warming over the equatorial region. Therefore, as the global warming is intensified, the cooling over the eastern tropical Pacific by ODT and the negative SST response area are reduced. 相似文献
7.
基于美国哥伦比亚大学Lamont—Doherty地球观象台LDEO（Lamont—DohertyEarth Observatory）海表温度资料和NCEP／NCAR再分析风场资料,分析了1997／1998年El Nino3期间西太平洋暖池海表温度和西风距平的时间演变特征,同时也分析了东太平洋暖池海表温度和北风距平的时间演变特征。结果表明,1997／1998年El Nino3事件期间,西太平洋暖池海表温度变化及异常西风和东太平洋暖池海表温度变化及异常北风都与Nino3指数变化密切相关。将东、西太平洋暖池及异常北风、西风一并结合起来考虑,进一步研究了1997／1998年El Nino3事件发生、发展的可能机制：异常西风驱动西太平洋暖池东端暖水向东伸展直接有利于赤道东太平洋海表温度增加;异常西风激发东传的暖Kelvin波对东太平洋的冷上升流有抑制作用,从而有利于赤道东太平洋海表温度增加;东传的异常西风可以通过埃克曼漂流效应将赤道两侧的海表暖水向赤道辐合从而加强了赤道附近的下沉流,也有利于赤道东太平洋赤道附近海表温度增加。几乎与此同时,北风距平通过产生北风吹流将东太平洋暖池暖水由北向南输送至赤道附近直接导致Nino3区海表温度增加。上述增温因素的叠加作用共同导致了1997／1998年El Nino事件迅速发生、异常强大。 相似文献
8.
P. Braconnot F. Hourdin S. Bony J. L. Dufresne J. Y. Grandpeix O. Marti 《Climate Dynamics》2007,29(5):501-520
The simulation of the mean seasonal cycle of sea surface temperature (SST) remains a challenge for coupled ocean–atmosphere
general circulation models (OAGCMs). Here we investigate how the numerical representation of clouds and convection affects
the simulation of the seasonal variations of tropical SST. For this purpose, we compare simulations performed with two versions
of the same OAGCM differing only by their convection and cloud schemes. Most of the atmospheric temperature and precipitation
differences between the two simulations reflect differences found in atmosphere-alone simulations. They affect the ocean interior
down to 1,000 m. Substantial differences are found between the two coupled simulations in the seasonal march of the Intertropical
Convergence Zone in the eastern part of the Pacific and Atlantic basins, where the equatorial upwelling develops. The results
confirm that the distribution of atmospheric convection between ocean and land during the American and African boreal summer
monsoons plays a key role in maintaining a cross equatorial flow and a strong windstress along the equator, and thereby the
equatorial upwelling. Feedbacks between convection, large-scale circulation, SST and clouds are highlighted from the differences
between the two simulations. In one case, these feedbacks maintain the ITCZ in a quite realistic position, whereas in the
other case the ITCZ is located too far south close to the equator. 相似文献
9.
副热带东太平洋低云对LASG耦合环流模式FGCM-0中"双ITCZ"的影响 总被引：8，自引：0，他引：8
与其他耦合环流模式一样,LASG耦合模式FGCM-0也存在虚假的“双ITCZ”。为了认识FGCM-0中“双ITCZ”,首先研究了FGCM-0的大气分量模式,剧INCAR(美国国家大气研究中心)的公用气候模式CCM3对秘鲁和加利福尼亚沿岸低云以及低层大气整体稳定度的模拟能力。发现：尽管CCM3模拟的低层大气整体稳定度与利用NCEP(美国国家环境预报中心)再分析资料分析的结果较一致,但模拟的低云量比ISCCP(国际卫星云气候计划)观测值显偏少。利用ISCCP低云量与由NCEP再分析温度场分析的低层整体稳定度之间的回归关系,修改了CCM3中低云参数化方案,并用于敏感性试验,以研究副热带东太平洋低云对FGCM-0中“双ITCZ”的影响。结果发现,修改的方案能显增强对低云量的模拟,秘鲁沿岸冷海域低云量增加能显减弱赤道以南热带东太平洋海表面温度(SST)的暖偏差,但同时也将使赤道冷舌增强、向西伸展更远;加利福尼亚沿岸低云量增加可以有效减弱赤道以北ITCZ区SST暖偏差。为了检验秘鲁沿岸SST与低云间的正反馈,又实施了一个控制秘鲁沿岸SST的敏感性试验,结果表明：控制秘鲁沿岸SST抑制其增暖,对自东南太平洋向西北至中、西赤道太平洋广大区域产生的影响,与增加秘鲁沿岸低云量产生的影响相似。 相似文献
10.
东亚持续强冬季风影响赤道海表温度初始异常的数值试验研究 总被引：8，自引：0，他引：8
通过数值模拟和理论分析 ,文中指出在强东亚季风期间不仅在欧亚大陆和北印度洋出现强大的反气旋环流异常 ,而且通过海气相互作用在北太平洋西部和西北部形成异常气旋式流场 ;在其东南部产生异常反气旋式流场。在这种流场异常的驱动下赤道西太平洋西风加强 ,海面升高 ,海表温度上升 ,赤道中东印度洋和东太平洋东风加强 ,海面降低 ,海表温度下降。证明由于海表温度异常及海表温度变化趋势存在积分关系 ,因此持续的强东亚冬季风所强迫的沿赤道海表温度变化趋势的上述分布的强讯号可以在海洋中存在近一年之久 ,为尔后赤道太平洋 ENSO事件的可能发展提供初始条件 ,也为跨季度气候预测提供前期讯号 相似文献
11.
In the summers of 2003 and 2007, eastern China suffered similar climate disasters with severe flooding in the Huaihe River valley and heat waves in the southern Yangtze River delta and South China. Using SST data and outgoing longwave radiation (OLR) data from NOAA along with reanalysis data from NCEP/NCAR, the 2002/03 and 2006/07 El Ni(n)o episodes in the central Pacific and their delayed impacts on the following early summertime climate anomalies of eastern China were analyzed. The possible physical progresses behaved as follows: Both of the moderate E1 Ni(n)o episodes matured in the central equatorial Pacific during the early winter. The zonal wind anomalies near the sea surface of the west-central equatorial Pacific excited equatorial Kelvin waves propagating eastward and affected the evolution of the E1 Ni(n)o episodes. From spring to early summer, the concurring anomalous easterly winds in the central equatorial Pacific and the end of upwelling Kelvin waves propagating eastward in the western equatorial Pacific, favored the equatorial warm water both of the SST and the subsurface temperature in the western Pacific. These conditions favored the warm state of the western equatorial Pacific in the early summer for both cases of 2003 and 2007. Due to the active convection in the western equatorial Pacific in the early summer and the weak warm SST anomalies in the tropical western Pacific from spring to early summer, the convective activities in the western Pacific warm pool showed the pattern in which the anomalous strong convection only appeared over the southern regions of the tropical western Pacific warm pool, which effects the meridional shift of the western Pacific subtropical high in the summer. The physical progress of the delayed impacts of the E1 Nifio episodes in the central equatorial Pacific and their decaying evolution on the climate anomalies in eastern China were interpreted through the key role of special pattern for the heat convection in the tropical western Pacific warm pool and the response of the western North Pacific anomalous anticyclone. 相似文献
12.
The mechanisms responsible for the seasonal cycle in the tropical central and eastern Pacific sea surface temperature (SST)
are investigated using a coupled general circulation model. We find that the annual westward propagation of SST anomalies
along the equator is explained by a two-stage process. The first stage sets the phase of the variation at the eastern boundary.
The strengthening of the local Hadley Circulation in boreal summer leads to a strengthening of the northward winds that blow
across the equator. These stronger winds drive enhanced evaporation and entrainment cooling of the oceanic mixed layer. The
resulting change in SST is greatest in the east because the mixed layer is at its shallowest there. As the east Pacific SST
cools the zonal SST gradient in the central Pacific becomes more negative. This development signals the onset of the second
stage in the seasonal variation of equatorial SST. In response to the anomalous SST gradient the local westward wind stress
increases. This increase drives cooling of the oceanic mixed layer in which no single mechanism dominates: enhanced evaporation,
wind-driven entrainment, and westward advection all contribute. We discuss the role that equatorial upwelling plays in modulating
mixed layer depth and hence the entrainment cooling, and we highlight the importance of seasonal variations in mixed layer
depth. In sum these processes act to propagate the SST anomaly westward.
Received: 22 February 1999 / Accepted: 20 March 2000 相似文献
13.
用向量场奇异值分解方法分析了赤道太平洋区域风应力场与海表温度场年际异常的相关联系。结果表明,最主要的一对奇异向量与ENSO循环关系密切,其主要特征为赤道中、东太平洋风应力向赤道的异常辐合（辐散）与该区的SST异常升高（降低）准同步变化。对70和80年代的4次 El Ni?o事件中标准化风应力异常场的分析表明,它们均表现出赤道中、东太平洋的辐合。这一结果可能比用信风张弛描述ENSO循环中的环流异常更合理和更具代表性。 相似文献
14.
In the summers of 2003 and 2007, eastern China suffered similar climate disasters with
severe flooding in the Huaihe River valley and heat waves in the southern Yangtze River delta and
South China. Using SST data and outgoing longwave radiation (OLR) data from NOAA along with
reanalysis data from NCEP/NCAR, the 2002/03 and 2006/07 El Nino episodes in the central Pacific
and their delayed impacts on the following early summertime climate anomalies of eastern China
were analyzed. The possible physical progresses behaved as follows: Both of the moderate El Nino
episodes matured in the central equatorial Pacific during the early winter. The zonal wind anomalies
near the sea surface of the west-central equatorial Pacific excited equatorial Kelvin waves
propagating eastward and affected the evolution of the El Ni\~no episodes. From spring to early
summer, the concurring anomalous easterly winds in the central equatorial Pacific and the end
of upwelling Kelvin waves propagating eastward in the western equatorial Pacific, favored the
equatorial warm water both of the SST and the subsurface temperature in the western Pacific.
These conditions favored the warm state of the western equatorial Pacific in the early summer
for both cases of 2003 and 2007. Due to the active convection in the western equatorial Pacific
in the early summer and the weak warm SST anomalies in the tropical western Pacific from spring
to early summer, the convective activities in the western Pacific warm pool showed the pattern
in which the anomalous strong convection only appeared over the southern regions of the tropical
western Pacific warm pool, which effects the meridional shift of the western Pacific subtropical
high in the summer. The physical progress of the delayed impacts of the El Ni\~no episodes in the
central equatorial Pacific and their decaying evolution on the climate anomalies in eastern China
were interpreted through the key role of special pattern for the heat convection in the tropical
western Pacific warm pool and the response of the western North Pacific anomalous anticyclone. 相似文献
15.
D. J. Bernie E. Guilyardi G. Madec J. M. Slingo S. J. Woolnough J. Cole 《Climate Dynamics》2008,31(7-8):909-925
Coupled ocean atmosphere general circulation models (GCM) are typically coupled once every 24 h, excluding the diurnal cycle from the upper ocean. Previous studies attempting to examine the role of the diurnal cycle of the upper ocean and particularly of diurnal SST variability have used models unable to resolve the processes of interest. In part 1 of this study a high vertical resolution ocean GCM configuration with modified physics was developed that could resolve the diurnal cycle in the upper ocean. In this study it is coupled every 3 h to atmospheric GCM to examine the sensitivity of the mean climate simulation and aspects of its variability to the inclusion of diurnal ocean-atmosphere coupling. The inclusion of the diurnal cycle leads to a tropics wide increase in mean sea surface temperature (SST), with the strongest signal being across the equatorial Pacific where the warming increases from 0.2°C in the central and western Pacific to over 0.3°C in the eastern equatorial Pacific. Much of this warming is shown to be a direct consequence of the rectification of daily mean SST by the diurnal variability of SST. The warming of the equatorial Pacific leads to a redistribution of precipitation from the Inter tropical convergence zone (ITCZ) toward the equator. In the western Pacific there is an increase in precipitation between Papa new guinea and 170°E of up to 1.2 mm/day, improving the simulation compared to climatology. Pacific sub tropical cells are increased in strength by about 10%, in line with results of part 1 of this study, due to the modification of the exchange of momentum between the equatorially divergent Ekman currents and the geostropic convergence at depth, effectively increasing the dynamical response of the tropical Pacific to zonal wind stresses. During the spring relaxation of the Pacific trade winds, a large diurnal cycle of SST increases the seasonal warming of the equatorial Pacific. When the trade winds then re-intensify, the increase in the dynamical response of the ocean leads to a stronger equatorial upwelling. These two processes both lead to stronger seasonal basin scale feedbacks in the coupled system, increasing the strength of the seasonal cycle of the tropical Pacific sector by around 10%. This means that the diurnal cycle in the upper ocean plays a part in the coupled feedbacks between ocean and atmosphere that maintain the basic state and the timing of the seasonal cycle of SST and trade winds in the tropical Pacific. The Madden–Julian Oscillation (MJO) is examined by use of a large scale MJO index, lag correlations and composites of events. The inclusion of the diurnal cycle leads to a reduction in overall MJO activity. Precipitation composites show that the MJO is stronger and more coherent when the diurnal cycle of coupling is resolved, with the propagation and different phases being far more distinct both locally and to larger lead times across the tropical Indo-Pacific. Part one of this study showed that that diurnal variability of SST is modulated by the MJO and therefore increases the intraseasonal SST response to the different phases of the MJO. Precipitation-based composites of SST variability confirm this increase in the coupled simulations. It is argued that including this has increased the thermodynamical coupling of the ocean and atmosphere on the timescale of the MJO (20–100 days), accounting for the improvement in the MJO strength and coherency seen in composites of precipitation and SST. These results show that the diurnal cycle of ocean–atmosphere interaction has profound impact on a range of up-scale variability in the tropical climate and as such, it is an important feature of the modelled climate system which is currently either neglected or poorly resolved in state of the art coupled models. 相似文献
16.
Reduction of the thermocline feedback associated with mean SST bias in ENSO simulation 总被引：1，自引：1，他引：0
Baoqiang Xiang Bin Wang Qinghua Ding Fei–Fei Jin Xiouhua Fu Hyung-Jin Kim 《Climate Dynamics》2012,39(6):1413-1430
Associated with the double Inter-tropical convergence zone problem, a dipole SST bias pattern (cold in the equatorial central Pacific and warm in the southeast tropical Pacific) remains a common problem inherent in many contemporary coupled models. Based on a newly-developed coupled model, we performed a control run and two sensitivity runs, one is a coupled run with annual mean SST correction and the other is an ocean forced run. By comparison of these three runs, we demonstrated that a serious consequence of this SST bias is to severely suppress the thermocline feedback in a realistic simulation of the El Ni?o/Southern Oscillation. Firstly, the excessive cold tongue extension pushes the anomalous convection far westward from the equatorial central Pacific, prominently diminishing the convection-low level wind feedback and thus the air-sea coupling strength. Secondly, the equatorial surface wind anomaly exhibits a relatively uniform meridional structure with weak gradient, contributing to a weakened wind-thermocline feedback. Thirdly, the equatorial cold SST bias induces a weakened upper-ocean stratification and thus yields the underestimation of the thermocline-subsurface temperature feedback. Finally, the dipole SST bias underestimates the mean upwelling through (a) undermining equatorial mean easterly wind stress, and (b) enhancing convective mixing and thus reducing the upper ocean stratification, which weakens vertical shear of meridional currents and near-surface Ekman-divergence. 相似文献
17.
The role of halted "baroclinic modes" in the central equatorial Pacific is analyzed. It is found that dominant anomaly signals corresponding to "baroclinic modes" occur in the upper layer of the equatorial Pacific, in a two-and-a-half layer oceanic model, in assimilated results of a simple OGCM and in the ADCP observation of TAO. A second "baroclinic mode" is halted in the central equatorial Pacific corresponding to a positive SST anomaly while the first "baroclinic mode" propagates eastwards in the eastern equatorial Pacific. The role of the halted second "baroclinic mode" in the central equatorial Pacific is explained by a staged ocean-atmosphere interaction mechanism in the formation of El Nino: the westerly bursts in boreal winter over the western equatorial Pacific generate the halted second "baroclinic mode" in the central equatorial Pacific, leading to the increase of heat content and temperature in the upper layer of the central Pacific which induces the shift of convection from over the western equatorial Pacific to the central equatorial Pacific; another wider, westerly anomaly burst is induced over the western region of convection above the central equatorial Pacific and the westerly anomaly burst generates the first "baroclinic mode" propagating to the eastern equatorial Pacific, resulting in a warm event in the eastern equatorial Pacific. The mechanism presented in this paper reveals that the central equatorial Pacific is a key region in detecting the possibility of ENSO and, by analyzing TAO observation data of ocean currents and temperature in the central equatorial Pacific, in predicting the coming of an El Nino several months ahead. 相似文献
18.
The role of halted “baroclinic modes” in the central equatorial Pacific is analyzed. It is found that dominant anomaly signals corresponding to “baroclinic modes” occur in the upper layer of the equatorial Pacific, in a two-and-a-half layer oceanic model, in assimilated results of a simple OGCM and in the ADCP observation of TAO. A second “baroclinic mode” is halted in the central equatorial Pacific corresponding to a positive SST anomaly while the first “baroclinic mode” propagates eastwards in the eastern equatorial Pacific. The role of the halted second “baroclinic mode” in the central equatorial Pacific is explained by a staged ocean-atmosphere interaction mechanism in the formation of El Ni?no: the westerly bursts in boreal winter over the western equatorial Pacific generate the halted second “baroclinic mode” in the central equatorial Pacific, leading to the increase of heat content and temperature in the upper layer of the central Pacific which induces the shift of convection from over the western equatorial Pacific to the central equatorial Pacific; another wider, westerly anomaly burst is induced over the western region of convection above the central equatorial Pacific and the westerly anomaly burst generates the first “baroclinic mode” propagating to the eastern equatorial Pacific, resulting in a warm event in the eastern equatorial Pacific. The mechanism presented in this paper reveals that the central equatorial Pacific is a key region in detecting the possibility of ENSO and, by analyzing TAO observation data of ocean currents and temperature in the central equatorial Pacific, in predicting the coming of an El Ni?no several months ahead. 相似文献
19.
The possibility of using a nonlinear empirical atmospheric model for hybrid coupled atmosphere-ocean modelling has been examined
by using a neural network (NN) model for predicting the contemporaneous wind stress field from the upper ocean state. Upper
ocean heat content (HC) from a 6-layer ocean model was a better predictor of the wind stress than the (observed or modelled)
sea surface temperature (SST). Our results showed that the NN model generally had slightly better skills in predicting the
contemporaneous wind stress than the linear regression (LR) model in the off-equatorial tropical Pacific and in the eastern
equatorial Pacific. When the wind stresses from the NN and LR models were used to drive the ocean model, slightly better SST
skills were found in the off-equatorial tropical Pacific and in the eastern equatorial Pacific when the NN winds were used
instead of the LR winds. Better skills for the model HC were found in the western and central equatorial Pacific when the
NN winds were used instead of the LR winds. Why NN failed to show more significant improvement over LR in the equatorial Pacific
for the wind stress and SST is probably because the relationship between the surface ocean and the atmosphere in the equatorial
Pacific over the seasonal time scale is almost linear.
Received: 2 March 1999 / Accepted: 13 July 2000 相似文献
20.
文中重点分析了中国科学院大气物理研究所LASG最新发展的全球大气环流谱模式(R42L9)与一全球海洋环流模式(T63L30)耦合形成的全球海洋-大气-陆面气候系统模式(GOALS/LASG)新版本已积分30 a的模拟结果,通过与多种观测资料的对比分析,讨论了赤道太平洋海表温度(SST)的年际变化及其纬向传播、赤道东太平洋SST异常与其他洋面SST变化之间的遥相关关系、赤道太平洋浅表层海温的年际变化特征等研究内容.结果表明,COALS模式模拟出了赤道太平洋SST异常出现不规则的年际变化特点;赤道东太平洋SST异常的向西传播过程;赤道太平洋混合层海温变化由西向东、由深层向浅层的传播过程;同时也模拟出了赤道东太平洋SST变化与赤道西太平洋以及与西南太平洋海温之间的反相关关系,与南印度洋和副热带大西洋SST之间的正遥相关关系等实际观测现象.但COALS模式也存在明显的不足,如对赤道东、中太平洋SST异常的年际变化幅度明显偏小,没能模拟出赤道东太平洋的SST变化比赤道中太平洋强的特点;赤道太平洋SST从东向西的传播速度明显比实际观测慢得多,但混合层海温极值变化由西向东的传播速度明显比实际情况快得多;没能模拟出赤道东太平洋SST变化同西北太平洋SST的负相关和北印度洋海温变化的正相关现象,因此也影响了对南亚、东南亚降水年际变化的模拟能力. 相似文献