共查询到20条相似文献，搜索用时 78 毫秒
1.
The tropical Indian Ocean experiences an interannual mode of climatic variability, known as the Indian Ocean Dipole (IOD). The signature of this variability in ocean salinity is hypothesized based on modeling and assimilation studies, on account of scanty observations. Soil Moisture and Ocean Salinity (SMOS) satellite has been designed to take up the challenge of sea surface salinity remote sensing. We show that SMOS data can be used to infer the pattern of salinity variability linked with the IOD events. The core of maximum variability is located in the central tropical basin, south of the equator. This region is anomalously salty during the 2010 negative IOD event, and anomalously fresh during the 2011 positive IOD event. The peak-to-peak anomaly exceeds one salinity unit, between late 2010 and late 2011. In conjunction with other observational datasets, SMOS data allow us to draw the salt budget of the area. It turns out that the horizontal advection is the main driver of salinity anomalies. This finding is confirmed by the analysis of the outputs of a numerical model. This study shows that the advent of SMOS makes it feasible the quantitative assessment of the mechanisms of ocean surface salinity variability in the tropical basins, at interannual timescales. 相似文献
2.
Interannual modulation of mesoscale eddy activity at the intraseasonal timescale in the southeastern tropical Indian Ocean
and its relation to the Indian Ocean dipole mode (IOD) events are investigated using results from a high-resolution ocean
general circulation model. The model reproduces observed characteristics of the intraseasonal variability and its interannual
modulation fairly well, with large variances of the intraseasonal variability during the 1994 and 1997/1998 IOD events. Large
negative temperature anomaly off the coasts of Java and the Lesser Sunda Islands in boreal summer, due to seasonal variation
and interannual anomaly, extended further to the east in 1994, and the associated strong Indonesian throughflow enhanced the
baroclinic instability in the upper layer, generating anomalously large mesoscale eddy activity. The eddy heat transport,
in turn, significantly affected decaying phase of the 1994 IOD event. On the other hand, the development of the cold region
off the Java Island associated with the 1997/1998 IOD event occurred in boreal winter, causing weaker baroclinic instability
and hence weaker eddy activity off Java. This led to little influence on the heat budget in the southeastern tropical Indian
Ocean for the 1997/1998 IOD event. 相似文献
3.
XiaoYuan Hong HaiBo Hu XiuQun Yang Yuan Zhang GuoQiang Liu Wei Liu 《中国科学:地球科学(英文版)》2014,57(11):2616-2627
Both the tropical Indian and tropical Pacific Oceans are active atmosphere-ocean interactive regions with robust interannual variability, which also constitutes a linkage between the two basins in the mode of variability. Using a global atmosphereocean coupled model, we conducted two experiments(CTRL and PC) to explore the contributions of Indian Ocean interannual sea surface temperature(SST) modes to the occurrence of El Ni?o events. The results show that interannual variability of the SST in the Indian Ocean induces a rapid growth of El Ni?o events during the boreal autumn in an El Ni?o developing year. However, it weakens El Ni?o events or even promotes cold phase conversions in an El Ni?o decaying year. Therefore, the entire period of the El Ni?o is shortened by the interannual variations of the Indian Ocean SST. Specifically, during the El Ni?o developing years, the positive Indian Ocean Dipole(IOD) events force an anomalous Walker circulation, which then enhances the existing westerly wind anomalies over the west Pacific. This will cause a warmer El Ni?o event, with some modulations by ocean advection and oceanic Rossby and Kelvin waves. However, with the onset of the South Asian monsoon, the Indian Ocean Basin(IOB) warming SST anomalies excite low level easterly wind anomalies over the west tropical Pacific during the El Ni?o decaying years. As a result, the El Ni?o event is prompted to change from a warm phase to a cold phase. At the same time, an associated atmospheric anticyclone anomaly appears and leads to a decreasing precipitation anomaly over the northwest Pacific. In summary, with remote forcing in the atmospheric circulation, the IOD mode usually affects the El Ni?o during the developing years, whereas the IOB mode affects the El Ni?o during the decaying years. 相似文献
4.
Interannual variability in the Biannual Rossby waves in the tropical Indian Ocean and its relation to Indian Ocean Dipole and El Nino forcing 总被引：1，自引：0，他引：1
The interannual variability of the tropical Indian Ocean is studied using Simple Ocean Data Assimilation (SODA) sea surface
height anomalies (SSHA) and Hadley Centre Ice Sea Surface Temperature anomalies. Biannual Rossby waves (BRW) were observed
along the 1.5° S and 10.5° S latitudes during the Indian Ocean Dipole (IOD) years. The SODA SSHA and its BRW components were
comparable with those of Topex/Poseidon. The phase speed of BRW along 1.5° S is −28 cm/s, which is comparable with the theoretical
speed of first mode baroclinic (equatorially trapped) Rossby waves. This is the first study to show that no such propagation
is seen along 1.5° S during El Nino years in the absence of IOD. Thus the westward propagating downwelling BRW in the equatorial
Indian Ocean is hypothesized as a potential predictor for IOD. These waves transport heat from the eastern equatorial Indian
Ocean to west, long before the dipole formation. Along 10.5° S, the BRW formation mechanisms during the El Nino and IOD years
were found to be different. The eastern boundary variations along 10.5° S, being localized, do not influence the ocean interior
considerably. Major portion of the interannual variability of the thermocline, is caused by the Ekman pumping integrated along
the characteristic lines of Rossby waves. The study provides evidence of internal dynamics in the IOD formation. The positive
trend in the downwelling BRW (both in SODA and Topex/Poseidon) is of great concern, as it contributes to the Indian Ocean
warming. 相似文献
5.
Two modes of dipole events in tropical Indian Ocean 总被引：1，自引：0，他引：1
By analyzing the distributions of subsurface temperature and the surface wind stress anomalies in the tropical Pacific and
Indian Oceans during the Indian Ocean Dipole (IOD) events, two major modes of the IOD and their formation mechanisms are revealed.
(1) The subsurface temperature anomaly (STA) in the tropical Indian Ocean during the IOD events can be described as a “<”
-shaped and west-east-oriented dipole pattern; in the east side of the “<” pattern, a notable tongue-like STA extends westward
along the equator in the tropical eastern Indian Ocean; while in the west side of the “<” pattern, the STA has opposite sign
with two centers (the southern one is stronger than the northern one in intensity) being of rough symmetry about the equator
in the tropical mid-western Indian Ocean. (2) The IOD events are composed of two modes, which have similar spatial pattern
but different temporal variabilities due to the large scale air-sea interactions within two independent systems. The first
mode of the IOD event originates from the air-sea interaction on a scale of the tropical Pacific-Indian Ocean and coexists
with ENSO. The second mode originates from the air-sea interaction on a scale of the tropical Indian Ocean and is closely
associated with changes in the position and intensity of the Mascarene high pressure. The strong IOD event occurs when the
two modes are in phase, and the IOD event weakens or disappears when the two modes are out of phase. Besides, the IOD events
are normally strong when either of the two modes is strong. (3) The IOD event is caused by the abnormal wind stress forcing
over the tropical Indian Ocean, which results in vertical transports, leading to the upwelling and pileup of seawater. This
is the main dynamic processes resulting in the STA. When the anomalous easterly exists over the equatorial Indian Ocean, the
cold waters upwell in the tropical eastern Indian Ocean while the warm waters pileup in the tropical western Indian Ocean,
hence the thermocline in the tropical Indian Ocean is shallowed in the east and deepened in the west. The off-equator component
due to the Coriolis force in the equatorial area causes the upwelling of cold waters and the shallowing of the equatorial
India Ocean thermocline. On the other hand, the anomalous anticyclonic circulations and their curl fields located on both
sides of the equator, cause the pileup of warm waters in the central area of their curl fields and the deepening of the equatorial
Indian Ocean thermocline off the equator. The above three factors lead to the occurrence of positive phase IOD events. When
anomalous westerly dominates over the tropical Indian Ocean, the dynamic processes are reversed, and the negative-phase IOD
event occurs.
Supported by National Natural Science Foundation of China (Grant No. 40776013), National Basic Research Program of China (Grant
No. 2006CB403601) and the Knowledge Innovation Project of Chinese Academy of Sciences (Grant No. KZCX-SW-222) 相似文献
6.
Nicolas Reul Severine Fournier Jaqueline Boutin Olga Hernandez Christophe Maes Bertrand Chapron Gaël Alory Yves Quilfen Joseph Tenerelli Simmon Morisset Yann Kerr Susanne Mecklenburg Steven Delwart 《Surveys in Geophysics》2014,35(3):681-722
While it is well known that the ocean is one of the most important component of the climate system, with a heat capacity 1,100 times greater than the atmosphere, the ocean is also the primary reservoir for freshwater transport to the atmosphere and largest component of the global water cycle. Two new satellite sensors, the ESA Soil Moisture and Ocean Salinity (SMOS) and the NASA Aquarius SAC-D missions, are now providing the first space-borne measurements of the sea surface salinity (SSS). In this paper, we present examples demonstrating how SMOS-derived SSS data are being used to better characterize key land–ocean and atmosphere–ocean interaction processes that occur within the marine hydrological cycle. In particular, SMOS with its ocean mapping capability provides observations across the world’s largest tropical ocean fresh pool regions, and we discuss from intraseasonal to interannual precipitation impacts as well as large-scale river runoff from the Amazon–Orinoco and Congo rivers and its offshore advection. Synergistic multi-satellite analyses of these new surface salinity data sets combined with sea surface temperature, dynamical height and currents from altimetry, surface wind, ocean color, rainfall estimates, and in situ observations are shown to yield new freshwater budget insight. Finally, SSS observations from the SMOS and Aquarius/SAC-D sensors are combined to examine the response of the upper ocean to tropical cyclone passage including the potential role that a freshwater-induced upper ocean barrier layer may play in modulating surface cooling and enthalpy flux in tropical cyclone track regions. 相似文献
7.
An intermediate ocean-atmosphere coupled model is developed to simulate and predict the tropical interannual variability. Originating from the basic physical framework of the Zebiak-Cane(ZC) model, this tropical intermediate couple model(TICM) extends to the entire global tropics, with a surface heat flux parameterization and a surface wind bias correction added to improve model performance and inter-basin connections. The model well reproduces the variabilities in the tropical Pacific and Indian basins. The simulated El Ni?o-Southern Oscillation(ENSO) shows a period of 3–4 years and an amplitude of about 2°C, similar to those observed. The variabilities in the Indian Ocean, including the Indian Ocean basin mode(IOBM) and the Indian Ocean Dipole(IOD), are also reasonably captured with a realistic relationship to the Pacific. However, the tropical Atlantic variability in the TICM has a westward bias and is overly influenced by the tropical Pacific. A 47-year hindcast experiment using the TICM for the period of 1970–2016 indicates that ENSO is the most predictable mode in the tropics. Skillful predictions of ENSO can be made one year ahead, similar to the skill of the latest version of the ZC model, while a "spring predictability barrier" still exists as in other models. In the tropical Indian Ocean, the predictability seems much higher in the west than in the east. The correlation skill of IOD prediction reaches 0.5 at a 5-month lead, which is comparable to that of the state-of-the-art coupled general circulation models. The prediction of IOD shows a significant "winter-spring predictability barrier", implying combined influences from the tropical Pacific and the local sea-air interaction in the eastern Indian Ocean. The TICM has little predictive skill in the equatorial Atlantic for lead times longer than 3 months, which is a common problem of current climate models badly in need of further investigation. 相似文献
8.
利用1979-2009年NCEP第二套大气再分析资料和ERSST海温资料,分析南海夏季风爆发时间的年际和年代际变化特征,考察南海夏季风爆发早晚与南大洋海温之间的联系.主要结果为:(1)南海夏季风爆发时间年际和年代际变化明显,1979-1993年与1994-2009年前后两个阶段爆发时间存在阶段性突变;(2)南海夏季风爆发时间与前期冬季(12-1月)印度洋-南大洋(0-80°E,75°S-50°S)海温、春季(2-3月)太平洋-南大洋(170°E -80°W,75°S-50°S)海温都存在正相关关系,当前期冬、春季南大洋海温偏低(高)时,南海夏季风爆发偏早(晚).南大洋海温信号,无论是年际还是年代际变化,都对南海夏季风爆发具有一定的预测指示作用;(3)南大洋海温异常通过海气相互作用和大气遥相关影响南海夏季风爆发的迟早.当南大洋海温异常偏低(偏高)时,冬季南极涛动偏强(偏弱),同时通过遥相关作用使热带印度洋-西太平洋地区位势高度偏低(偏高)、纬向风加强(减弱),热带大气这种环流异常一直维持到春季4、5月份,位势高度和纬向风异常范围逐步向北扩展并伴随索马里越赤道气流的加强(减弱),从而为南海夏季风爆发偏早(偏晚)提供有利的环流条件.初步分析认为,热带大气环流对南大洋海气相互作用的遥响应与半球际大气质量重新分布引起的南北涛动有关. 相似文献
9.
The El Ni o-Southern Oscillation(ENSO)phenomenon in the tropical Pacific has been a focus of ocean and climate studies in the last few decades.Recently,the short-term climate variability in the tropical Indian Ocean has attracted increasingly more attention,especially with the proposition of the Indian Ocean Dipole(IOD)mode.However,these phenomena are often studied separately without much consideration of their interaction.Observations reveal a striking out-of-phase relationship between zonal gradients of sea surface height anomaly(SSHA)and sea surface temperature anomaly(SSTA)in the tropical Indian and Pacific Oceans.Since the two oceans share the ascending branch of the Walker cells over the warm pool,the variation within one of them will affect the other.The accompanied zonal surface wind anomalies are always opposite over the two basins,thus producing a tripole structure with opposite zonal gradients of SSHA/SSTA in the two oceans.This mode of variability has been referred to as Indo-Pacific Tripole(IPT).Based on observational data analyses and a simple ocean-atmosphere coupled model,this study tries to identify the characteristics and physical mechanism of IPT with a particular emphasis on the relationships among ENSO,IOD,and IPT.The model includes the basic oceanic and atmospheric variables and the feedbacks between them,and takes into account the inter-basin connection through an atmospheric bridge,thus providing a valuable framework for further research on the short-term tropical climate variability. 相似文献
10.
Pramanik Saikat Sil Sourav Mandal Samiran Dey Dipanjan Shee Abhijit 《Ocean Dynamics》2019,69(11):1253-1271
Role of equatorial forcing on the thermocline variability in the Bay of Bengal (BoB) during positive and negative phases of the Indian Ocean Dipole (IOD) and El Niño Southern Oscillation (ENSO) was investigated using the Regional Ocean Modeling System (ROMS) simulations during 1988 to 2015. Two numerical experiments were carried out for (i) the Indian Ocean Model (IOM) with interannual open boundary conditions and (ii) the BoB Model (BoBM) with climatological boundary conditions. The first mode of Sea Surface Height Anomalies (SSHA) variability showed a west-east dipole nature in both IOM and altimetry observations around 11°N, which was absent in the BoBM. The vertical section of temperature along the same latitude showed a sharp subsurface temperature dipole with a core at ~ 100 m depth. The positive (negative) subsurface temperature anomalies were observed over the whole northeastern BoB during NIOD (PIOD) and LN (EN) composites due to stronger (weaker) second downwelling Kelvin Waves. During the negative phases of IOD and ENSO, the cyclonic eddy on the southwestern BoB strengthened due to intensified southward coastal current along the western BoB and local wind stress. The subsurface temperature dipole was at its peak during October–December (OND) with 1-month lag from IOD and was evident from the Argo observations and other reanalysis datasets as well. A new BoB dipole index (BDI) was defined as the normalized difference of 100-m temperature anomaly and found to be closely related to the frequency of cyclones and the surface chlorophyll-a concentration in the BoB.
相似文献11.
Using reanalysis data, the role of initial signals in the tropical Pacific Ocean in predictions of negative Indian Ocean Dipole (IOD) events were analyzed. It was found that the summer predictability barrier (SPB) phenomenon exists in predictions, which is closely related to initial sea temperature errors in the tropical Pacific Ocean, with type-1 initial errors presenting a significant west-east dipole pattern in the tropical Pacific Ocean, and type-2 initial errors showing the opposite spatial pattern. In contrast, SPB-related initial sea temperature errors in the tropical Indian Ocean are relatively small. The initial errors in the tropical Pacific Ocean induce anomalous winds in the tropical Indian Ocean by modulating the Walker circulation in the tropical oceans. In the first half of the prediction year, the anomalous winds, combined with the climatological winds in the tropical Indian Ocean, induce a basin-wide mode of sea surface temperature (SST) errors in the tropical Indian Ocean. With the reversal of the climatological wind in the second half of the prediction year, a west-east dipole pattern of SST errors appears in the tropical Indian Ocean, which is further strengthened under the Bjerknes feedback, yielding a significant SPB. Moreover, two types of precursors were also identified: a significant west-east dipole pattern in the tropical Pacific Ocean and relatively small temperature anomalies in the tropical Indian Ocean. Under the combined effects of temperature anomalies in the tropical Indian and Pacific oceans, northwest wind anomalies appear in the tropical Indian Ocean, which induce a significant west-east dipole pattern of SST anomalies, and yield a negative IOD event. 相似文献
12.
Relationships were examined between variability in tropical Atlantic sea level and major climate indices with the use of TOPEX/POSEIDON altimeter and island tide gauge data with the aim of learning more about the external influences on the variability of the tropical Atlantic ocean. Possible important connections were found between indices related to the El Niño–Southern Oscillation (ENSO) and the sea levels in all three tropical regions (north, equatorial, and south), although the existence of only one major ENSO event within the decade of available altimetry means that a more complete investigation of the ENSO-dependence of Atlantic sea level changes has to await for the compilation of longer data sets. An additional link was found with the Indian Ocean Dipole (IOD) in the equatorial region, this perhaps surprising observation is probably an artifact of the similarity between IOD and ENSO time series in the 1990s. No evidence was obtained for significant correlations between tropical Atlantic sea level and North Atlantic Oscillation or Antarctic Oscillation Index. The most intriguing relationship observed was between the Quasi-Biennial Oscillation and sea level in a band centered approximately on 10°S. A plausible explanation for the relationship is lacking, but possibilities for further research are suggested. 相似文献
13.
Chen Fu Dongxiao Wang Lei Yang Yao Luo Fenghua Zhou Tilak Priyadarshana Jinglong Yao 《Ocean Dynamics》2018,68(6):689-699
Based on reanalysis data, we find that the Indian Ocean Dipole (IOD) plays an important role in the variability of wave climate in the equatorial Northern Indian Ocean (NIO). Significant wave height (SWH) in the equatorial NIO, especially over the waters southeast to Sri Lanka, exhibits strong interannual variations. SWH anomalies in the waters southeast to Sri Lanka correlate well with dipole mode index (DMI) during both summer and autumn. Negative SWH anomalies occur over the oceanic area southeast to Sri Lanka during positive IOD events and vary with different types of IOD. During positive prolonged (unseasonable) IOD, the SWH anomalies are the strongest in autumn (summer); while during positive normal IOD, the SWH anomalies are weak in both summer and autumn. Strong easterly wind anomalies over the southeast oceanic area of Sri Lanka during positive IOD events weaken the original equatorial westerly wind stress, which leads to the decrease in wind-sea waves. The longer wave period during positive IOD events further confirms less wind-sea waves. The SWH anomaly pattern during negative IOD events is nearly opposite to that during positive IOD events. 相似文献
14.
《中国科学:地球科学(英文版)》2015,(8)
Based on the merged satellite altimeter data and in-situ observations,as well as a diagnosis of linear baroclinic Rossby wave solutions,this study analyzed the rapidly rise of sea level/sea surface height(SSH)in the tropical Pacific and Indian Oceans during recent two decades.Results show that the sea level rise signals in the tropical west Pacific and the southeast Indian Ocean are closely linked to each other through the pathways of oceanic waveguide within the Indonesian Seas in the form of thermocline adjustment.The sea level changes in the southeast Indian Ocean are strongly influenced by the low-frequency westward-propagating waves originated in the tropical Pacific,whereas those in the southwest Indian Ocean respond mainly to the local wind forcing.Analyses of the lead-lag correlation further reveal the different origins of interannual and interdecadal variabilities in the tropical Pacific.The interannual wave signals are dominated by the wind variability along the equatorial Pacific,which is associated with the El Ni?o-Southern Oscillation;whereas the interdecadal signals are driven mainly by the wind curl off the equatorial Pacific,which is closely related to the Pacific Decadal Oscillation. 相似文献
15.
南印度洋副热带偶极模（Subtropical Dipole Pattern,SDP）是印度洋存在的另一种很明显的偶极型海温差异现象,在年际和年代际尺度上均有十分明显的表现.而目前有关印度洋海气相互作用的研究主要集中在赤道印度洋地区,针对南印度洋地区的工作还比较少,特别是有关南印度洋海温与ENSO（El NiDo-Southern Oscillation）事件关系的研究.本文初步探讨了年际尺度上南印度洋副热带偶极型海温变化差异与ENSO事件的关系,发现SDP与ENSO事件有密切的联系,SDP事件就像连接正负ENSO位相转换的一个中间环节,SDP事件前后期ENSO的位相刚好完全相反.进一步,本文通过分析SDP事件前后期海温、高低层风、低层辐合辐散、高空云量和辐射等的变化特征研究了南印度洋偶极型海温异常在ENSO事件中的作用,结果表明：SDP在ENSO事件中的作用不仅涉及海气相互作用的正负反馈过程,还与热带和副热带大气环流之间的相互作用有关,特别是与东南印度洋海温变化所引起的异常纬向风由赤道印度洋向赤道太平洋传播的过程等有十分直接的关系;同时,SDP对ENSO事件的影响在很大程度上还依赖于大尺度平均气流随季节的变换. 相似文献
16.
Seasonal and interannual patterns of sea surface temperature in Banda Sea as revealed by self-organizing map 总被引：1，自引：0，他引：1
Seasonal and interannual variations of sea surface temperature (SST) in the Banda Sea are studied for the period of January 1985 through December 2007. A neural network pattern recognition approach based on self-organizing map (SOM) has been applied to monthly SST from the Advanced Very High Resolution Radiometer (AVHRR) Oceans Pathfinder. The principal conclusions of this paper are outlined as follows. There are three different patterns associated with the variations in the monsoonal winds: the southeast and northwest monsoon patterns, and the monsoon-break patterns. The southeast monsoon pattern is characterized by low SST due to the prevailing southeasterly winds that drive Ekman upwelling. The northwest monsoon pattern, on the other hand, is one of high SST distributed uniformly in space. The monsoon-break pattern is a transitional pattern between the northwest and southeast monsoon patterns, which is characterized by moderate SST patterns. On interannual time-scale, the SST variations are significantly influenced by the El Niño-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) phenomena. Low SST is observed during El Niño and/or positive IOD events, while high SST appears during La Niña event. Low SST in the Banda Sea during positive IOD event is induced by upwelling Kelvin waves generated in the equatorial Indian Ocean which propagate along the southern coast of Sumatra and Java before entering the Banda Sea through the Lombok and Ombai Straits as well as through the Timor Passage. On the other hand, during El Niño (La Niña) events, upwelling (downwelling) Rossby waves associated with off-equatorial divergence (convergence) in response to the equatorial westerly (easterly) winds in the Pacific, partly scattered into the Indonesian archipelago which in turn induce cool (warm) SST in the Banda Sea. 相似文献
17.
The characteristics and variability of the East India Coastal Current (EICC), the western boundary current in the Bay of Bengal (BoB) during the Indian Ocean Dipole (IOD) years between 2006 and 2012 have been investigated using the high-resolution Regional Ocean Modeling System (ROMS). The evolution of temperature, mixed layer depth (MLD), and seasonal basin scale circulation in the upper ocean simulated by the model agrees well with the observations. The EICC in BoB is characterized by a seasonal reversal flow: the poleward EICC during February?May and the equatorward EICC during August?December. A long-term simulation from 2006 to 2012 suggest that the circulation pattern, boundary current structure, and transport in the western BoB are completely different in positive and negative IOD years. As IOD is mainly phase-locked to the seasonal cycle with most significant influence in the Borel autumn, the equatorward EICC is affected during the IOD years. It is found that the strength of this EICC is ~?5 Sv in October 2010 and a weaker EICC dominated by the presence of eddies is observed in October 2006. We also quantified the local and remote forcing effects on the variability of EICC and found that the seasonal coastal Kelvin waves (KWs) play a dominant role in the development of the EICC. During positive IOD year 2006, due the absence of second downwelling KW, the EICC is completely disorganized and dominated by the eddies, whereas in the negative IOD year 2010, the strong second downwelling KW plays a key role in developing organized and stable EICC in the western BoB. 相似文献
18.
In this study, we have estimated the different sea level components (observed sea level from satellite altimetry, steric sea
level from in situ hydrography—including Argo profiling floats, and ocean mass from Gravity Recovery and Climate Experiment;
GRACE), in terms of regional and interannual variability, over 2002–2009. We compute the steric sea level using different
temperature (and salinity) data sets processed by different groups (SCRIPPS, CLS, IPRC, and NOAA) and first focus on the regional
variability in steric and altimetry-based sea level. In addition to El Nino–La Nina signatures, the observed and steric sea
level data show clear impact of three successive Indian Ocean Dipoles in 2006, 2007, and 2008 in the Indian Ocean. We next
study the spatial trend patterns in ocean mass signal by comparing GRACE observations over the oceans with observed minus
steric sea level. While in some regions, reasonably good agreement is observed, discrepancy is noticed in some others due
to still large regional trend errors in Argo and GRACE data, as well as to a possible (unknown) deep ocean contribution. In
terms of global mean, interannual variability in altimetry-based minus steric sea level and GRACE-based ocean mass appear
significantly correlated. However, large differences are reported when short-term trends are estimated (using both GRACE and
Argo data). This prevents us to draw any clear conclusion on the sea level budget over the recent years from the comparison
between altimetry-based, steric sea level, and GRACE-based ocean mass trends, nor does it not allow us to constrain the Glacial
Isostatic Adjustment correction to apply to GRACE-based ocean mass term using this observational approach. 相似文献
19.
The roles of surface heat flux and ocean heat transport convergence in determining Atlantic Ocean temperature variability 总被引：1，自引：0，他引：1
Jeremy P. Grist Simon A. Josey Robert Marsh Simon A. Good Andrew. C. Coward Beverly A. de Cuevas Steven G. Alderson Adrian L. New Gurvan Madec 《Ocean Dynamics》2010,60(4):771-790
The temperature variability of the Atlantic Ocean is investigated using an eddy-permitting (1/4°) global ocean model (ORCA-025) forced with historical surface meteorological fields from 1958 to 2001. The simulation of volume-averaged temperature and the vertical structure of the zonally averaged temperature trends are compared with those from observations. In regions with a high number of observations, in particular above a depth of 500 m and between 22° N and 65° N, the model simulation and the dataset are in good agreement. The relative contribution of variability in ocean heat transport (OHT) convergence and net surface heat flux to changes in ocean heat content is investigated with a focus on three regions: the subpolar and subtropical gyres and the tropics. The surface heat flux plays a relatively minor role in year-to-year changes in the subpolar and subtropical regions, but in the tropical North Atlantic, its role is of similar significance to the ocean heat transport convergence. The strongest signal during the study period is a cooling of the subpolar gyre between 1970 and 1990, which subsequently reversed as the mid-latitude OHT convergence transitioned from an anomalously weak to an anomalously strong state. We also explore whether model OHT anomalies can be linked to surface flux anomalies through a Hovmöller analysis of the Atlantic sector. At low latitudes, increased ocean heat gain coincides with anomalously strong northward transport, whereas at mid-high latitudes, reduced ocean heat loss is associated with anomalously weak heat transport. 相似文献
20.
This study explored the spatial patterns of winter predictability barrier (WPB)-related optimal initial errors and optimal precursors for positive Indian Ocean dipole (IOD) events, and the associated physical mechanisms for their developments were analyzed using the Simple Ocean Data Assimilation dataset. Without consideration of the effects of model errors on “predictions,” it was assumed that different “predictions” are caused by different initial conditions. The two types of WPB-related optimal initial errors are almost opposite for the start months of July (–1) and July (0), although they both present a west-east dipole pattern in the tropical Indian Ocean, with the maximum errors located at the thermocline depth. Bjerknes feedback and ocean waves play important roles in the growth of prediction errors. These two physical mechanisms compete during July–December and ocean waves dominate during January–June. The spatial patterns of optimal precursors and the physical mechanisms for their developments are similar to those of WPB-related optimal initial errors. It is worth noting that large values of WPB-related optimal initial errors and optimal precursors are concentrated within a few locations, which probably represent the sensitive areas of targeted observations for positive IOD events. The great similarities between WPB-related optimal initial errors and optimal precursors suggest that were intensive observations performed over these areas, this would not only reduce initial errors and thus, prediction errors, but it would also permit the detection of the signal of IOD events in advance, greatly improving the forecast skill of positive IOD events. 相似文献