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1.
M. Pontaud J.-P. Céron M. Kimoto F. Pluviaud L. Terray A. Vintzileos 《Climate Dynamics》2000,16(12):917-933
The interannual variability over the tropical Pacific and a possible link with the mean state or the seasonal cycle is examined
in four coupled ocean-atmosphere general circulation models (GCM). Each model is composed of a high-resolution ocean GCM of
either the tropical Pacific or near-global oceans coupled to a moderate-resolution atmospheric GCM, without using flux correction.
The oceanic subsurface is considered to describe the mean state or the seasonal cycle through the analytical formulations
of some potential coupled processes. These coupled processes characterise the zonal gradient of sea surface temperature (hereafter
SST), the oceanic vertical gradient of temperature and the equatorial upwelling. The simulated SST patterns of the mean state
and the interannual signals are generally too narrow. The grid of the oceanic model could control the structure of the SST
interannual signals while the behaviour of the atmospheric model could be important in the link between the oceanic surface
and the subsurface. The first SST EOFs are different between the coupled models, however, the second SST EOFs are quite similar
and could correspond to the return to the normal state while that of the observations (COADS) could favour the initial anomaly.
All the models seem to simulate a similar equatorial wave-like dynamics to return to the normal state. The more the basic
state is unstable from the coupled processes point of view, the more the interannual signal are high. It seems that the basic
state could control the intensity of the interannual variability. Two models, which have a significant seasonal variation
of the interannual variance, also have a significant seasonal variation of the instability with a few months lag. The potential
seasonal phase locking of the interannual fluctuations need to be examined in more models to confirm its existence in current
tropical GCMs.
Received: 30 July 1999 / Accepted: 25 April 2000 相似文献
2.
G. A. Meehl P. R. Gent J. M. Arblaster B. L. Otto-Bliesner E. C. Brady A. Craig 《Climate Dynamics》2001,17(7):515-526
Historically, El Nino-like events simulated in global coupled climate models have had reduced amplitude compared to observations.
Here, El Nino-like phenomena are compared in ten sensitivity experiments using two recent global coupled models. These models
have various combinations of horizontal and vertical ocean resolution, ocean physics, and atmospheric model resolution. It
is demonstrated that the lower the value of the ocean background vertical diffusivity, the greater the amplitude of El Nino
variability which is related primarily to a sharper equatorial thermocline. Among models with low background vertical diffusivity,
stronger equatorial zonal wind stress is associated with relatively higher amplitude El Nino variability along with more realistic
east–west sea surface temperature (SST) gradient along the equator. The SST seasonal cycle in the eastern tropical Pacific
has too much of a semiannual component with a double intertropical convergence zone (ITCZ) in all experiments, and thus does
not affect, nor is it affected by, the amplitude of El Nino variability. Systematic errors affecting the spatial variability
of El Nino in the experiments are characterized by the eastern equatorial Pacific cold tongue regime extending too far westward
into the warm pool. The time scales of interannual variability (as represented by time series of Nino3 SSTs) show significant
power in the 3–4 year ENSO band and 2–2.5 year tropospheric biennial oscillation (TBO) band in the model experiments. The
TBO periods in the models agree well with the observations, while the ENSO periods are near the short end of the range of
3–6 years observed during the period 1950–94. The close association between interannual variability of equatorial eastern
Pacific SSTs and large-scale SST patterns is represented by significant correlations between Nino3 time series and the PC
time series of the first EOFs of near-global SSTs in the models and observations.
Received: 17 April 2000 / Accepted: 17 August 2000 相似文献
3.
Contrasting Impacts of South and North Tropical Indian Ocean Sea Surface Temperature Anomalies on East Asian Summer Climate 
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Using observational data and model simulations,the author find that the North Indian Ocean(NIO)sea surface temperature(SST)anomalies can trigger an eastward atmospheric Kelvin wave propagating into the equatorial western Pacific,inducing an anomalous anticyclone over the subtropical Northwest Pacific(NWP)and resulting in prominent summer climate anomalies in the East Asia-Northwest Pacific(EANWP)region.However,the response of tropospheric temperatures and atmospheric Kelvin waves to the South Indian Ocean(SIO)SST anomalies is weak;as a result,the impact of the SIO SST anomalies on the EANWP summer climate is weak.The contrasting impacts of NIO and SIO SST anomalies on the EANWP summer climate is possibly due to the different mean state of SSTs in the two regions.In summer,the climatological SSTs in the NIO are higher than in the SIO,leading to a stronger response of atmospheric convection to the NIO SST anomalies than to the SIO SST anomalies.Thus,compared with the SIO SST anomalies,the NIO SST anomalies can lead to stronger tropospheric air temperature anomalies and atmospheric Kelvin waves to affect the EANWP summer climate. 相似文献
4.
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
5.
A general circulation model is used to simulate the atmospheric response to a prescribed, idealized time varying warm sea surface temperature anomaly (SSTA) in the equatorial Pacific characteristic of ENSO events. The model incorporates the full seasonal cycle and an ensemble of five anomaly simulations, each of 14 months duration, is performed and the results compared with those from a ten year control simulation involving climatological SSTs. In a test of the model, simulated perturbations to precipitation patterns are compared with the analysis by Ropelewski and Halpert which identifies regions where precipitation perturbations are associated with the ENSO cycle. Strong and statistically significant perturbations are simulated throughout much of the equatorial Pacific and the Australian region which agree with the analysis. Perturbations over the Americas and the Indian sub-continent show part agreement with observations, while elsewhere, at more remote and high latitude locations, there is less agreement, providing some indication of model limitations in simulating the hydrological cycle. Over the equatorial Pacific most of the anomalous precipitation is accounted for by moisture flux convergence. Only in the vicinity of the maximum anomaly, located in the eastern Pacific, do warmer SSTs contribute to the perturbed circulation. Elsewhere, anomalous wind speeds mainly determine anomalous heat fluxes. As a result, the large scale perturbations to wind, moisture and precipitation appear to be forced indirectly, rather than directly as assumed in simple ocean-atmosphere models. 相似文献
6.
The response of the upper-ocean temperatures and currents in the tropical Pacific to the spatial distribution of chlorophyll-a and its seasonal cycle is investigated using a coupled atmosphere-ocean model and a stand-alone oceanic general circulation model.The spatial distribution of chlorophyll-a significantly influences the mean state of models in the tropical Pacific.The annual mean SST in the eastern equatorial Pacific decreases accompanied by a shallow thermocline and stronger currents because of shallow penetration depth of solar radiation.Equatorial upwelling dominates the heat budget in that region.Atmosphere-ocean interaction processes can further amplify such changes. The seasonal cycle of chlorophyll-a can dramatically change ENSO period in the coupled model.After introducing the seasonal cycle of chlorophyll-a concentration,the peak of the power spectrum becomes broad,and longer periods(>3 years) are found.These changes led to ENSO irregularities in the model. The increasing period is mainly due to the slow speed of Rossby waves,which are caused by the shallow mean thermocline in the northeastern Pacific. 相似文献
7.
Based on a novel design of coupled model simulations where sea surface temperature (SST) variability in the equatorial tropical Pacific was constrained to follow the observed El Niño—Southern Oscillation (ENSO) variability, while rest of the global oceans were free to evolve, the ENSO response in SSTs over the other ocean basins was analyzed. Conceptually the experimental setup was similar to discerning the contribution of ENSO variability to interannual variations in atmospheric anomalies. A unique feature of the analysis was that it was not constrained by a priori assumptions on the nature of the teleconnected response in SSTs. The analysis demonstrated that the time lag between ENSO SST and SSTs in other ocean basins was about 6 months. A signal-to-noise analysis indicated that between 25 and 50 % of monthly mean SST variance over certain ocean basins can be attributed to SST variability over the equatorial tropical Pacific. The experimental setup provides a basis for (a) attribution of SST variability in global oceans to ENSO variability, (b) a method for separating the ENSO influence in SST variations, and (c) understanding the contribution from other external factors responsible for variations in SSTs, for example, changes in atmospheric composition, volcanic aerosols, etc. 相似文献
8.
长江流域夏季降水及其与海温的滞后相关 总被引：7，自引：0，他引：7
基于月平均台站降水资料分析了中国东部降水的气候特征。由于其降水分布在空间和时间上的复杂性，为便于研究其与海温的关联，特别是海温对降水的影响，根据台站间降水变化在季节变化和年际变化以及与海温相关的一致性，将中国东部区域分成四个子区域。以长江流域的降水为代表，分析了海温对降水的超前相关。给出了主要影响海区和它们的超前时间。综合各影响海区海温和超前时间建立的回归方分析表明：回归降水和观测降水的相关系数大于０．８５。回归的平方根误差是其标准差的６０％和平均雨量的１５％。另外还分析了海温与降水相关与环流变化的一致性。 相似文献
9.
Time sclice experiments are performed with the atmospheric GCM ARPEGE, developed at Météo-France, to study the impact to increases in the atmospheric carbon dioxide. This spectral model runs at T42 horizontal resolution with 30 vertical layers including a comprehensive tropospheric and stratospheric resolution and a prognostic parameterization of the ozone mixing ratio. The model is forced in a 5-year control run by climatological SSTs and sea-ice extents in order to obtain an accurate simulation of the present-day climate. Two perturbed runs are performed using SSTs and sea-ice extents for doubled CO2 concentration, obtained from transient runs performed by two coupled atmospheric-oceanic models run at the Max Planck Institute (MPI) in Hamburg and the Hadley Centre (HC). A global surface temperature warming of 1.6 K is obtained with the MPI SST anomalies and 1.9 K with the HC SST anomalies. The precipitation rate increases by 4.2% (and 4.7%). The features obtained in the stratosphere (a cooling increasing with the altitude and an increase in the ozone mixing ratio) are not sensitive to the oceanic forcing. On the contrary, the anomalies in the troposphere such as a warming increasing with altitude, an acceleration of westerly jets and a raised cloud height, depend on the oceanic forcing imposed in the two perturbed runs. Special attention is given to continental areas where the impact of the oceanic forcing is studied over eight regions around the globe. Regions sensitive to oceanic forcing such as Europe are identified in contrast with areas where the patterns are driven by land-surface physical processes, such as over continental Asia. Finally, the Köppen classification is applied to the climate simulated in the three experiments. Both doubled CO2 runs show the same predominance of global warming over precipitation changes in the Kbppen analyses. 相似文献
10.
The Kuroshio Extension region is characterized by energetic oceanic mesoscale and frontal variability that alters the air–sea fluxes that can influence large-scale climate variability in the North Pacific. We investigate this mesoscale air-sea coupling using a regional eddy-resolving coupled ocean–atmosphere (OA) model that downscales the observed large-scale climate variability from 2001 to 2007. The model simulates many aspects of the observed seasonal cycle of OA coupling strength for both momentum and turbulent heat fluxes. We introduce a new modeling approach to study the scale-dependence of two well-known mechanisms for the surface wind response to mesoscale sea surface temperatures (SSTs), namely, the ‘vertical mixing mechanism’ (VMM) and the ‘pressure adjustment mechanism’ (PAM). We compare the fully coupled model to the same model with an online, 2-D spatial smoother applied to remove the mesoscale SST field felt by the atmosphere. Both VMM and PAM are found to be active during the strong wintertime peak seen in the coupling strength in both the model and observations. For VMM, large-scale SST gradients surprisingly generate coupling between downwind SST gradient and wind stress divergence that is often stronger than the coupling on the mesoscale, indicating their joint importance in OA interaction in this region. In contrast, VMM coupling between crosswind SST gradient and wind stress curl occurs only on the mesoscale, and not over large-scale SST gradients, indicating the essential role of the ocean mesocale. For PAM, the model results indicate that coupling between the Laplacian of sea level pressure and surface wind convergence occurs for both mesoscale and large-scale processes, but inclusion of the mesoscale roughly doubles the coupling strength. Coupling between latent heat flux and SST is found to be significant throughout the entire seasonal cycle in both fully coupled mode and large-scale coupled mode, with peak coupling during winter months. The atmospheric response to the oceanic mesoscale SST is also studied by comparing the fully coupled run to an uncoupled atmospheric model forced with smoothed SST prescribed from the coupled run. Precipitation anomalies are found to be forced by surface wind convergence patterns that are driven by mesoscale SST gradients, indicating the importance of the ocean forcing the atmosphere at this scale. 相似文献
11.
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
12.
Interactions between the tropical and subtropical northern Pacific at decadal time scales are examined using uncoupled oceanic and atmospheric simulations. An atmospheric model is forced with observed Pacific sea surface temperatures (SST) decadal anomalies, computed as the difference between the 2000–2009 and the 1990–1999 period. The resulting pattern has negative SST anomalies at the equator, with a global pattern reminiscent of the Pacific decadal oscillation. The tropical SST anomalies are responsible for driving a weakening of the Hadley cell and atmospheric meridional heat transport. The atmosphere is then shown to produce a significant response in the subtropics, with wind-stress-curl anomalies having the opposite sign from the climatological mean, consistent with a weakening of the oceanic subtropical gyre (STG). A global ocean model is then forced with the decadal anomalies from the atmospheric model. In the North Pacific, the shallow subtropical cell (STC) spins down and the meridional heat transport is reduced, resulting in positive tropical SST anomalies. The final tropical response is reached after the first 10 years of the experiment, consistent with the Rossby-wave adjustment time for both the STG and the STC. The STC provides the connection between subtropical wind stress anomalies and tropical SSTs. In fact, targeted simulations show the importance of off-equatorial wind stress anomalies in driving the oceanic response, whereas anomalous tropical winds have no role in the SST signal reversal. We further explore the connection between STG, STC and tropical SST with the help of an idealized model. We argue that, in our models, tropical SST decadal variability stems from the forcing of the Pacific subtropical gyre through the atmospheric response to ENSO. The resulting Ekman pumping anomaly alters the STC and oceanic heat transport, providing a negative feedback on the SST. We thus suggest that extratropical atmospheric responses to tropical forcing have feedbacks onto the ocean dynamics that lead to a time-delayed response of the tropical oceans, giving rise to a possible mechanism for multidecadal ocean-atmosphere coupled variability. 相似文献
13.
E. Roeckner J. M. Oberhuber A. Bacher M. Christoph I. Kirchner 《Climate Dynamics》1996,12(11):737-754
The interannual variability associated with the El Ni?o/Southern Oscillation (ENSO) cycle is investigated using a relatively
high-resolution (T42) coupled general circulation model (CGCM) of the atmosphere and ocean. Although the flux correction is
restricted to annual means of heat and freshwater, the annual as well as the seasonal climate of the CGCM is in good agreement
with that of the atmospheric model component forced with observed sea surface temperatures (SSTs). During a 100-year simulation
of the present-day climate, the model is able to capture many features of the observed interannual SST variability in the
tropical Pacific. This includes amplitude, lifetime and frequency of occurrence of El Ni?o events and also the phase locking
of the SST anomalies to the annual cycle. Although the SST warming during the evolution of El Ni?os is too confined spatially,
and the warming along the Peruvian coast is much too weak, the patterns and magnitudes of key atmospheric anomalies such as
westerly wind stress and precipitation, and also their eastward migration from the western to the central equatorial Pacific
is in accord with observations. There is also a qualitative agreement with the results obtained from the atmospheric model
forced with observed SSTs from 1979 through 1994. The large-scale dynamic response during the mature phase of ENSO (December
through February) is characterized by an eastward displacement and weakening of the Walker cell in the Pacific while the Hadley
cell intensifies and moves equatorward. Similar to the observations, there is a positive correlation between tropical Pacific
SST and the winter circulation in the North Pacific. The deepening of the Aleutian low during the ENSO winters is well captured
by the model as well as the cooling in the central North Pacific and the warming over Canada and Alaska. However, there are
indications that the anomalies of both SST and atmospheric circulation are overemphasized in the North Pacific. Finally, there
is evidence of a coherent downstream effect over the North Atlantic as indicated by negative correlations between the PNA
index and the NAO index, for example. The weakening of the westerlies across the North Atlantic in ENSO winters which is related
to a weakening and southwestward displacement of the Icelandic low, is in broad agreement with the observations, as well as
the weak tendency for colder than normal winters in Europe.
Received: 31 October 1995 / Accepted: 29 May 1996 相似文献
14.
Ping Huang Pengfei Wang Kaiming Hu Gang Huang Zhihua Zhang Yong Liu Bangliang Yan 《大气科学进展》2014,31(5):1136-1146
This study introduces a new global climate model--the Integrated Climate Model （ICM）--developed for the seasonal prediction of East Asian-western North Pacific （EA-WNP） climate by the Center for Monsoon System Research at the Institute of Atmospheric Physics （CMSR, IAP）, Chinese Academy of Sciences. ICM integrates ECHAM5 and NEMO2.3 as its atmospheric and oceanic components, respectively, using OASIS3 as the coupler. The simulation skill of ICM is evaluated here, including the simulated climatology, interannual variation, and the influence of E1 Nifio as one of the most important factors on EA-WNP climate. ICM successfully reproduces the distribution of sea surface temperature （SST） and precipitation without climate shift, the seasonal cycle of equatorial Pacific SST, and the precipitation and circulation of East Asian summer monsoon. The most prominent biases of ICM are the excessive cold tongue and unrealistic westward phase propagation of equatorial Pacific SST. The main interannual variation of the tropical Pacific SST and EA-WNP climate E1 Nifio and the East Asia-Pacific Pattern--are also well simulated in ICM, with realistic spatial pattern and period. The simulated E1 Nifio has significant impact on EA-WNP climate, as in other models. The assessment shows ICM should be a reliable model for the seasonal prediction of EA-WNP climate. 相似文献
15.
ABSTRACT Using data from 17 coupled models and nine sets of corresponding Atmospheric Model Intercomparison Project （AMIP） results, we investigated annual and seasonal variation biases in the upper 50 m of the south-central equatorial Pacific, with a focus on the double-ITCZ bias, and examined the causes for the amplitude biases by using heat budget analysis. The results showed that, in the research region, most of the models simulate SSTs that are higher than or similar to observed. The simulated seasonal phase is close to that observed, but the amplitudes of more than half of the model results are larger than or equal to observations. Heat budget analysis demonstrated that strong shortwave radiation in individual atmospheric models is the main factor that leads to high SST values and that weak southward cold advection is an important mechanism for maintaining a high SST. For seasonal circulation, large surface shortwave radiation amplitudes cause large SST amplitudes. 相似文献
16.
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
17.
将时间滑动相关方法 STC(sliding temporal correlation)用于研究混沌系统和海洋环流模式的可信计算时间RCT(reliable computation time),Lorenz混沌系统的数值试验表明用STC求得的可预报时间和可信计算时间,与使用传统误差限方法所得结果一致,证明了其有效性。对海洋环流模式LICOM和NEMO的研究发现:1.当海洋模式以非耦合的方式运行时,试验的结果表明其海表温度SST的可信计算时间较长,平均达到6个月以上,这主要是由于海洋模式的运行过程中,采用恢复性边界条件使模拟结果不会太过偏离观测值。对于强迫场从1月开始的试验,LICOM模式的SST可信计算时间在赤道东太平洋和西北太平洋地区存在RCT低值区,其数值不超过2个月。而NEMO模式在赤道太平洋地区全是RCT高值区,NEMO模式的RCT低值区域出现在赤道外的太平洋和大西洋中纬度地区,强迫场从7月开始的试验,RCT纬向平均分布与1月有相反的形式。2.海洋模式以耦合方式运行时,由于去掉了恢复边界条件作用,海洋模式预报的SST可信计算时间明显减小,年平均RCT为1个月左右。按季节平均得到的RCT变化不大,在30~40天之间,RCT的大值区春季位于南半球,而秋季位于北半球,可达2个月以上。耦合模式中所模拟的500 h Pa高度场的RCT与单独运行的大气模式所得结果相差不大,仍在2周以内。3.无论是按季节平均还是按海区平均所得到的RCT分布,都在30~60天左右,只有极少数区域在特定季节可以达到80天以上,这说明在海气耦合模式中,由于计算不确定造成的可预报上限一般不超过2~3个月,这比使用资料分析得到可预报期限短很多,因此根据木桶原理,RCT可能是制约海气耦合模式SST预报能力的一个重要因素。 相似文献
18.
Delayed Atmospheric Temperature Response to ENSO SST： Role of High SST and the Western Pacific 总被引：1，自引：0，他引：1
Tropical zonally symmetric atmospheric warming occurs during ENSO’s warm phase, and lags the equa- torial east Pacific sea surface temperatures (SSTs) by 3–4 months. The role of the Indian and Atlantic oceans on the atmospheric delayed response has been pointed out by earlier studies. For 1951–2004, a regression analysis based on the observed SST data shows the western Pacific has a similarly important role as the Indian and Atlantic. Nevertheless, there is time mismatch of around 1–2 months between the zon... 相似文献
19.
ENSO dynamics and seasonal cycle in the tropical Pacific as simulated by the ECHAM4/OPYC3 coupled general circulation model 总被引：3，自引：0，他引：3
The new version of the atmospheric general circulation model (AGCM), ECHAM4, at the Max Planck Institute for Meteorology,
Hamburg, has been coupled to the OPYC3 isopycnic global ocean general circulation and sea ice model in a multi-century present-day
climate simulation. Non-seasonal constant flux adjustment for heat and freshwater was employed to ensure a long-term annual
mean state close to present-day climatology. This study examines the simulated upper ocean seasonal cycle and interannual
variability in the tropical Pacific for the first 100 years. The coupled model’s seasonal cycle of tropical Pacific SSTs is
satisfactory with respect to both the warm pool variation and the Central and Eastern Pacific, with significant errors only
in the cold tongue around April. The cold phase cold tongue extent and strength is as observed, and for this the heat flux
adjustment does not play a decisive role. A well-established South Pacific convergence zone is characteristic for the new
AGCM version. Apart from extending the southeast trades seasonal maximum to midbasin, wind stress pattern and strength are
captured. Overall the subsurface structure is consistent with the observed, with a pronounced thermocline at about 150 m depth
in the west and rising to the surface from 160 °W to 100 °W. The current system is better resolved than in some previous global
models and, on the whole, has the expected shape. The equatorial undercurrent is correctly positioned but the core is only
half as strong as observed. The north equatorial current and counter-current also have reduced maximum speeds but the April
minimum is captured. As with the companion publication from Roeckner et al. this study finds pronounced tropical Eastern and
Central Pacific interannual variability. Simulated and observed NINO3 sea surface temperature (SST) variability is represented
by a single, rather broadband, maximum of power spectral density, centered on about 28 months for the simulation and four
years for the observations. For simulation and observations, SST, windstress, and upper ocean heat content each exhibit a
single dominant large-scale amplitude and phase pattern, suggesting that the model captures the essential dynamics. The amplitude
of the essentially standing oscillation in SST in the NINO3 region attains the observed strength, but is weaker at the eastern
boundary. Anomalies of upper ocean heat content show off-equatorial westward and equatorial eastward propagation, the latter’s
arrival in the east of the basin coinciding with the SST anomalies. Equatorial wind stress anomalies near the date line provide
the appropriate forcing and clearly form a response to the anomalous SST.
Received: 14 June 1996 / Accepted: 11 November 1997 相似文献
20.
《大气与海洋》2013,51(4):263-283
Abstract A set of retrospective multi‐seasonal ensemble predictions based on a coupled global atmosphere‐ocean model is described. These predictions, designated as the first coupled Historical Forecasting Project or CHFP1, are produced with the climate model CGCM3.1 of the Canadian Centre for Climate Modelling and Analysis using a very simple initialization procedure in which model sea surface temperatures (SSTs) are nudged toward the observed values during a multi‐year period preceding the beginning of a forecast. This procedure, in addition to constraining initial SSTs to be close to observations, initializes equatorial Pacific zonal wind stress and thermocline depth with some skill. The ability of the subsequent forecasts to predict the evolution of SSTs, particularly in the equatorial Pacific, and surface air temperatures globally and in Canada is assessed. The results are compared with those of the second Historical Forecasting Project or HFP2, which uses a two‐tier strategy in which model SSTs are externally specified. Skill of CHFP1 forecasts, though generally modest, exceeds those of HFP2 in some cases, despite the larger multi‐model ensemble used in HFP2. CHFP1 represents an initial step in development directed toward a coupled operational seasonal prediction system for Canada. 相似文献