Alory G., G. Meyers, 2009: Warming of the upper equatorial Indian Ocean and changes in the heat budget (1960-99). J. Climate, 22, 93- 113.10.1175/2008JCLI2330.18c97aa54-9333-495f-9356-2fe8335d17bb94fc9a2d649e67233f1d745193aaa89dhttp%3A%2F%2Fwww.cabdirect.org%2Fabstracts%2F20093063975.htmlrefpaperuri:(a74657da3bb2b287c5ef241747f3fc13)http://www.cabdirect.org/abstracts/20093063975.htmlAbstract In the equatorial Indian Ocean, sea surface has warmed by 0.5°–1°C over the 1960–99 period, while waters have cooled at thermocline depth and the net atmospheric heat flux has decreased. Among a set of twentieth-century climate simulations from 12 coupled models, the Centre National de Recherches Météorologiques Coupled Global Climate Model version 3 (CNRM-CM3) reproduces key observed features of these changes. It is used to investigate changes in the heat budget of the upper equatorial Indian Ocean and identify mechanisms responsible for the warming. By comparing twentieth-century and control simulations, significant shifts in the mean balance of the heat budget between the preindustrial and the 1960–99 periods can be identified. The main cause of the surface warming is a decrease in the upwelling-related oceanic cooling. It occurs in the thermocline dome region because of a slowdown of the wind-driven Ekman pumping. The observed decrease in net heat flux is a negative feedback driven by evaporation, which is enhanced by the equatorial warming and associated strengthening of trade winds.
Baquero-Bernal A., M. Latif, and S. Legutke, 2002: On dipolelike variability of sea surface temperature in the tropical Indian Ocean. J. Climate, 15, 1358- 1368.10.1175/1520-0442(2002)015<1358:ODVOSS>2.0.CO;2e56975e98a91c5b196dbb95888db5218http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F27265657_On_dipolelike_variability_of_sea_surface_temperature_in_the_tropical_Indian_Oceanhttp://www.researchgate.net/publication/27265657_On_dipolelike_variability_of_sea_surface_temperature_in_the_tropical_Indian_OceanThe aim of this study is to investigate the differences on ultrastructure of the cochleae caused by different classic musical opuses with different intonations. Guinea pigs were grouped into 3, one of which was the control and the other two were the experimental groups. While the first group, which was the control, was not exposed to any music, the second group was exposed to classic musical opuses with extensive intervals (40 decibel) and third group was exposed to classical music opuses with strained intonations (60 decibel) for 6 h a day with 15 min-intervals for totally 10 days. Cochleae tissue samples were taken from the guinea pigs at the end of the tenth day. They were examined at the electron microscopic level. In addition to compansatris processes on the cochleae, thickening on the stereocilias of hair cells and basal membranes and proliferation on the synaptic terminalles of afferent nerves caused by extensive intonations were observed. Extremely obvious degenerative differences such as damage in neuroepitelial cells, nerves and synaptic terminalles as well as componsatris processes caused by strained intonations were determined. As a result of all these observations it was concluded that continuously listening to the strained intonations used in musical opuses has a very harmful effect on the auditory system.
Behera S. K., J. J. Luo, S. Masson, S. A. Rao, H. Sakuma, and T. Yamagata, 2006: A CGCM study on the interaction between IOD and ENSO. J. Climate, 19, 1688- 1705.10.1175/JCLI3797.1e324603d0f6fe9c5dae0272b3e665df8http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F232643274_A_CGCM_study_on_the_interaction_between_IOD_and_ENSOhttp://www.researchgate.net/publication/232643274_A_CGCM_study_on_the_interaction_between_IOD_and_ENSOAbstract An atmosphere–ocean coupled general circulation model known as the Scale Interaction Experiment Frontier version 1 (SINTEX-F1) model is used to understand the intrinsic variability of the Indian Ocean dipole (IOD). In addition to a globally coupled control experiment, a Pacific decoupled noENSO experiment has been conducted. In the latter, the El Ni09o–Southern Oscillation (ENSO) variability is suppressed by decoupling the tropical Pacific Ocean from the atmosphere. The ocean–atmosphere conditions related to the IOD are realistically simulated by both experiments including the characteristic east–west dipole in SST anomalies. This demonstrates that the dipole mode in the Indian Ocean is mainly determined by intrinsic processes within the basin. In the EOF analysis of SST anomalies from the noENSO experiment, the IOD takes the dominant seat instead of the basinwide monopole mode. Even the coupled feedback among anomalies of upper-ocean heat content, SST, wind, and Walker circulation over the Indian Ocean is reproduced. As in the observation, IOD peaks in boreal fall for both model experiments. In the absence of ENSO variability the interannual IOD variability is dominantly biennial. The ENSO variability is found to affect the periodicity, strength, and formation processes of the IOD in years of co-occurrences. The amplitudes of SST anomalies in the western pole of co-occurring IODs are aided by dynamical and thermodynamical modifications related to the ENSO-induced wind variability. Anomalous latent heat flux and vertical heat convergence associated with the modified Walker circulation contribute to the alteration of western anomalies. It is found that 42% of IOD events affected by changes in the Walker circulation are related to the tropical Pacific variabilities including ENSO. The formation is delayed until boreal summer for those IODs, which otherwise form in boreal spring as in the noENSO experiment.
Bjerknes J., 1969: Atmospheric teleconnections from the equatorial Pacific. Mon. Wea. Rev., 97, 163- 172.10.1175/1520-0493(1969)097<0163:ATFTEP>2.3.CO;296e8f63f-f22c-4793-816c-0525274d0af3d99667c470b8e221952789ed1bd6b4a7http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F243781719_Atmospheric_Teleconnections_from_the_Equatorial_PACIFIC1refpaperuri:(20704598911cca9eea64a71df5188422)http://www.researchgate.net/publication/243781719_Atmospheric_Teleconnections_from_the_Equatorial_PACIFIC1Abstract The “high index” response of the northeast Pacific westerlies to big positive anomalies of equatorial sea temperature, observed in the winter of 1957–58, has been found to repeat during the major equatorial sea temperature maxima in the winters of 1963–64 and 1965–66. The 1963 positive temperature anomaly started early enough to exert the analogous effect on the atmosphere of the south Indian Ocean during its winter season. The maxima of the sea temperature in the eastern and central equatorial Pacific occur as a result of anomalous weakening of the trade winds of the Southern Hemisphere with inherent weakening of the equatorial upwelling. These anomalies are shown to be closely tied to the “Southern Oscillation” of Sir Gilbert Walker.
Cai W., X. T. Zheng, E. Weller, M. Collins, T. Cowan, M. Lengaigne, W. D. Yu, and T. Yamagata, 2013: Projected response of the Indian Ocean Dipole to greenhouse warming. Nature Geoscience, 6, 999- 1007.10.1038/ngeo200917ecaa5e9a5fd74d76f64f696346adb8http%3A%2F%2Fwww.nature.com%2Fngeo%2Fjournal%2Fv6%2Fn12%2Fabs%2Fngeo2009.htmlhttp://www.nature.com/ngeo/journal/v6/n12/abs/ngeo2009.htmlNatural modes of variability centred in the tropics, such as the El Nino/Southern Oscillation and the Indian Ocean Dipole, are a significant source of interannual climate variability across the globe. Future climate warming could alter these modes of variability. For example, with the warming projected for the end of the twenty-first century, the mean climate of the tropical Indian Ocean is expected to change considerably. These changes have the potential to affect the Indian Ocean Dipole, currently characterized by an alternation of anomalous cooling in the eastern tropical Indian Ocean and warming in the west in a positive dipole event, and the reverse pattern for negative events. The amplitude of positive events is generally greater than that of negative events. Mean climate warming in austral spring is expected to lead to stronger easterly winds just south of the Equator, faster warming of sea surface temperatures in the western Indian Ocean compared with the eastern basin, and a shoaling equatorial thermocline. The mean climate conditions that result from these changes more closely resemble a positive dipole state. However, defined relative to the mean state at any given time, the overall frequency of events is not projected to change - but we expect a reduction in the difference in amplitude between positive and negative dipole events.
Cai W., A. Santoso, G. J. Wang, E. Weller, X. L. Wu, K. Ashok, Y. Masumoto, and T. Yamagata, 2014: Increased frequency of extreme Indian Ocean Dipole events due to greenhouse warming. Nature, 510, 254- 258.10.1038/nature13327249199200f8f4226ba85becb48ec0ff069d9200fhttp%3A%2F%2Fmed.wanfangdata.com.cn%2FPaper%2FDetail%2FPeriodicalPaper_PM24919920http://med.wanfangdata.com.cn/Paper/Detail/PeriodicalPaper_PM24919920The Indian Ocean dipole is a prominent mode of coupled ocean-atmosphere variability, affecting the lives of millions of people in Indian Ocean rim countries. In its positive phase, sea surface temperatures are lower than normal off the Sumatra-Java coast, but higher in the western tropical Indian Ocean. During the extreme positive-IOD (pIOD) events of 1961, 1994 and 1997, the eastern cooling strengthened and extended westward along the equatorial Indian Ocean through strong reversal of both the mean westerly winds and the associated eastward-flowing upper ocean currents. This created anomalously dry conditions from the eastern to the central Indian Ocean along the Equator and atmospheric convergence farther west, leading to catastrophic floods in eastern tropical African countries but devastating droughts in eastern Indian Ocean rim countries. Despite these serious consequences, the response of pIOD events to greenhouse warming is unknown. Here, using an ensemble of climate models forced by a scenario of high greenhouse gas emissions (Representative Concentration Pathway 8.5), we project that the frequency of extreme pIOD events will increase by almost a factor of three, from one event every 17.3-墆ears over the twentieth century to one event every 6.3 ears over the twenty-first century. We find that a mean state change--with weakening of both equatorial westerly winds and eastward oceanic currents in association with a faster warming in the western than the eastern equatorial Indian Ocean--facilitates more frequent occurrences of wind and oceanic current reversal. This leads to more frequent extreme pIOD events, suggesting an increasing frequency of extreme climate and weather events in regions affected by the pIOD.
Clement A., P. DiNezio, and C. Deser, 2011: Rethinking the Ocean's role in the Southern Oscillation. J. Climate, 24, 4056-4072, doi: 10.1175/2011JCLI3973.1.10.1175/2011JCLI3973.182f8056aef71f5eeef5565eefb2890cchttp%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2010AGUFMGC44A..03Chttp://adsabs.harvard.edu/abs/2010AGUFMGC44A..03CAbstract The Southern Oscillation (SO) is usually described as the atmospheric component of the dynamically coupled El Ni09o–Southern Oscillation phenomenon. The contention in this work, however, is that dynamical coupling is not required to produce the SO. Simulations with atmospheric general circulation models that have varying degrees of coupling to the ocean are used to show that the SO emerges as a dominant mode of variability if the atmosphere and ocean are coupled only through heat and moisture fluxes. Herein this mode of variability is called the thermally coupled Walker (TCW) mode. It is a robust feature of simulations with atmospheric general circulation models (GCMs) coupled to simple ocean mixed layers. Despite the absence of interactive ocean dynamics in these simulations, the spatial patterns of sea level pressure, surface temperature, and precipitation variability associated with the TCW are remarkably realistic. This mode has a red spectrum indicating persistence on interannual to decadal time scales that appears to arise through an off-equatorial trade wind–evaporation–surface temperature feedback and cloud shortwave radiative effects in the central Pacific. When dynamically coupled to the ocean (in fully coupled ocean–atmosphere GCMs), the main change to this mode is increased interannual variability in the eastern equatorial Pacific sea surface temperature and teleconnections in the North Pacific and equatorial Atlantic, though not all coupled GCMs simulate this effect. Despite the oversimplification due to the lack of interactive ocean dynamics, the physical mechanisms leading to the TCW should be active in the actual climate system. Moreover, the robustness and realism of the spatial patterns of this mode suggest that the physics of the TCW can explain some of the primary features of observed interannual and decadal variability in the Pacific and the associated global teleconnections.
DiNezio P. N., A. C. Clement, and G. A. Vecchi, 2010: Reconciling differing views of tropical Pacific climate change. Eos, Trans. Amer. Geophys.Union, 91, 141- 142.10.1029/2010EO160001e9a847ea3e50b910b57f3cd49275988bhttp%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F2010EO160001%2Fabstracthttp://onlinelibrary.wiley.com/doi/10.1029/2010EO160001/abstractRecent analyses of global warming projections simulated with global climate models (GCMs) suggest that the tropical Pacific does not become El Ni&ntilde;o- or La Ni&ntilde;a-like in response to increased greenhouse gases (GHGs). Rather, the physical mechanisms that drive tropical Pacific climate change depart substantially from the El Ni&ntilde;o-Southern Oscillation (ENSO) analogy often invoked for interpreting future climate changes [e.g., Knutson and Manabe, 1995; Meehl and Washington, 1996; Cane et al., 1997; Collins et al., 2005; Meehl et al., 2007; Lu et al., 2008; Cox et al., 2004] and past climate changes [e.g. Lea et al., 2001; Koutavas et al., 2002]. This presents an opportunity for reconciling theory, models, and observations. An ENSO analogy typically is invoked for interpreting tropical Pacific climate change because if an external forcing introduces some east-west asymmetry, this asymmetry can be amplified in the same way as interannual perturbations are, through the positive ocean-atmosphere Bjerknes feedback. This then would lead to an altered mean state of the tropical Pacific resembling El Ni&ntilde;o or La Ni&ntilde;a [ Dijkstra and Neelin, 1995]. For instance, the model projections used for the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) anticipate tropical Pacific climate change in response to increased GHGs that has been described as El Ni&ntilde;o&mdash;like [ Meehl et al., 2007]. These models project robust enhanced equatorial warming [ Liu et al., 2006; DiNezio et al., 2009] and a weakening of the overturning atmosphere circulation across the tropical Pacific, i.e., the Walker circulation [ Vecchi and Soden, 2007], both of which occur during El Ni&ntilde;o events. However, these experiments also show a shoaling and sharpening of the equatorial thermocline [ Vecchi and Soden, 2007; DiNezio et al., 2009] (Figure 1a). This is in contrast to El Ni&ntilde;o events, when the thermocline response is heavily dominated by a relaxed tilt (Figure 1b).
Huang P. Y., Y. Xue, H. Wang, W. Q. Wang, and A. Kumar, 2012: Mixed layer heat budget of the El Niño in NCEP climate forecast system. Climate Dyn., 39, 365- 381.10.1007/s00382-011-1111-466e0c2c8-9cf7-4b21-b02e-d7769f2ea2295a2c85d6992080204bd8b492cdf38aeehttp%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fq82h348760000g30%2Frefpaperuri:(1e2ccc9a8b305995b71960f92910bbbd)http://www.springerlink.com/content/q82h348760000g30/The mechanisms controlling the El Ni01±o have been studied by analyzing mixed layer heat budget of daily outputs from a free coupled simulation with the Climate Forecast System (CFS). The CFS is operational at National Centers for Environmental Prediction, and is used by Climate Prediction Center for seasonal-to-interannual prediction, particularly for the prediction of the El Ni01±o and Southern Oscillation (ENSO) in the tropical Pacific. Our analysis shows that the development and decay of El Ni01±o can be attributed to ocean advection in which all three components contribute. Temperature advection associated with anomalous zonal current and mean vertical upwelling contributes to the El Ni01±o during its entire evolutionary cycle in accordance with many observational, theoretical, and modeling studies. The impact of anomalous vertical current is found to be comparable to that of mean upwelling. Temperature advection associated with mean (anomalous) meridional current in the CFS also contributes to the El Ni01±o cycle due to strong meridional gradient of anomalous (mean) temperature. The surface heat flux, non-linearity of temperature advection, and eddies associated with tropical instabilities waves (TIW) have the tendency to damp the El Ni01±o. Possible degradation in the analysis and closure of the heat budget based on the monthly mean (instead of daily) data is also quantified.
Iskand ar, I., W. Mardiansyah, D. Setiabudidaya, A. K. Affand i, F. Syamsuddin, 2014: Surface and subsurface oceanic variability observed in the eastern equatorial Indian Ocean during three consecutive Indian Ocean dipole events: 2006-2008. AIP Conference Proceedings 1617,48, doi: 10.1063/1.4897101.
Lau N. C., M. J. Nath, 2004: Coupled GCM simulation of atmosphere-ocean variability associated with zonally asymmetric SST changes in the tropical Indian Ocean. J. Climate, 17, 245- 265.25c7cc27-9aab-4636-a241-35b8a65a0e8c8ad5418080b187a917b1712436b60bb6http%3A%2F%2Fadsabs.harvard.edu%2Fcgi-bin%2Fnph-data_query%3Fbibcode%3D2004JCli...17..245L%26db_key%3DAST%26link_type%3DABSTRACTrefpaperuri:(4878e8e2f2c675393b2a0ad97b63ac8b)/s?wd=paperuri%3A%284878e8e2f2c675393b2a0ad97b63ac8b%29&filter=sc_long_sign&tn=SE_xueshusource_2kduw22v&sc_vurl=http%3A%2F%2Fadsabs.harvard.edu%2Fcgi-bin%2Fnph-data_query%3Fbibcode%3D2004JCli...17..245L%26db_key%3DAST%26link_type%3DABSTRACT&ie=utf-8
Li T., Y. S. Zhang, E. Lu, and D. L. Wang, 2002: Relative role of dynamic and thermodynamic processes in the development of the Indian Ocean dipole: An OGCM diagnosis. Geophys. Res. Lett., 29,2110, doi: 10.1029/2002GL015789.10.1029/2002GL0157892353721b5d06e3b3b98ad12d04b222fbhttp%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F2002GL015789%2Fcitedbyhttp://onlinelibrary.wiley.com/doi/10.1029/2002GL015789/citedby[1] The relative role of oceanic dynamics and surface heat fluxes in the initiation and development of the Indian Ocean dipole was investigated by analyzing results from an oceanic general circulation model. The model was forced by observed surface wind stress and heat flux fields for 1958-1997. The results show that it was capable of reproducing observed dipole events over the tropical Indian Ocean. The diagnosis of the mixed-layer heat budget indicates that the SST anomaly (SSTA) in the east pole is primarily induced by anomalous surface latent heat flux and vertical temperature advection, whereas in the west pole it is mainly caused by meridional and vertical temperature advection anomalies. In both regions shortwave radiation anomalies tend to damp the SSTA. The ocean Rossby waves are essential in linking the anomalous wind and SST off Sumatra and subsurface temperature variations in southwest Indian Ocean.
Li T., B. Wang, C. P. Chang, and Y. S. Zhang, 2003: A theory for the Indian Ocean dipole-zonal mode. J. Atmos. Sci., 60, 2119- 2135.10.1175/1520-0469(2003)060<2119:ATFTIO>2.0.CO;29c6729e7-986b-4adb-805a-0e091142ea68f4568f9f4b02dd1773f6e8246185db86http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F228906248_A_theory_for_the_Indian_Ocean_Dipole_Zonal_Mode%3Fev%3Dauth_pubrefpaperuri:(5f5a63bc4a8c6ac12e3c371cb185f0ef)http://www.researchgate.net/publication/228906248_A_theory_for_the_Indian_Ocean_Dipole_Zonal_Mode?ev=auth_pubABSTRACT Four fundamental differences of air-sea interactions between the tropical Pacific and Indian Oceans are identified based on observational analyses and physical reasoning. The first difference is represented by the strong contrast of a zonal cloud-SST phase relationship between the warm and cool oceans. The in-phase cloud- SST relationship in the warm oceans leads to a strong negative feedback, while a significant phase difference in the cold tongue leads to a much weaker thermodynamic damping. The second difference arises from the reversal of the basic-state zonal wind and the tilting of the ocean thermocline, which leads to distinctive effects of ocean waves. The third difference lies in the existence of the Asian monsoon and its interaction with the adjacent oceans. The fourth difference is that the southeast Indian Ocean is a region where a positive atmosphere- ocean thermodynamic feedback exists in boreal summer. A conceptual coupled atmosphere-ocean model was constructed aimed to understand the origin of the Indian Ocean dipole-zonal mode (IODM). In the model, various positive and negative air-sea feedback processes were considered. Among them were the cloud-radiation-SST feedback, the evaporation-SST-wind feedback, the thermocline-SST feedback, and the monsoon-ocean feedback. Numerical results indicate that the IODM is a dynamically coupled atmosphere-ocean mode whose instability depends on the annual cycle of the basic state. It tends to develop rapidly in boreal summer but decay in boreal winter. As a result, the IODM has a distinctive evolution characteristic compared to the El Nino. Sensitivity experiments suggest that the IODM is a weakly damped oscillator in the absence of external forcing, owing to a strong negative cloud-SST feedback and a deep mean thermocline in the equatorial Indian Ocean. A thermodynamic air-sea (TAS) feedback arises from the interaction between an anomalous atmospheric anticyclone and a cold SST anomaly (SSTA) off Sumatra. Because of its dependence on the basic-state wind, the nature of this TAS feedback is season dependent. A positive feedback occurs only in northern summer when the southeasterly flow is pronounced. It becomes a negative feedback in northern winter when the northwesterly wind is pronounced. The phase locking of the IODM can be, to a large extent, explained by this seasonal- dependent TAS feedback. The biennial tendency of the IODM is attributed to the monsoon-ocean feedback and the remote El Nino forcing that has a quasi-biennial component. In the presence of realistic Nino-3 SSTA forcing, the model is capable of simulating IODM events during the last 50 yr that are associated with the El Nino, indicating that ENSO is one of triggering mechanisms. The failure of simulation of the 1961 and 1994 events suggests that other types of climate forcings in addition to the ENSO must play a role in triggering an IODM event.
Lu J., B. Zhao, 2012: The role of oceanic feedback in the climate response to doubling CO2. J. Climate, 25, 7544- 7563.10.1175/JCLI-D-11-00712.193a5cff1-16c3-4939-aa94-b27ed480b7527f84e61ea2906fab8df3b57fdf63206ahttp%3A%2F%2Fconnection.ebscohost.com%2Fc%2Farticles%2F83356226%2Frole-oceanic-feedback-climate-response-doubling-co2refpaperuri:(bde8d1a3c7754784fe5aaf0ed0d552b0)http://connection.ebscohost.com/c/articles/83356226/role-oceanic-feedback-climate-response-doubling-co2Abstract Two suites of partial coupling experiments are devised with the upper-ocean dynamics version (UOM) of the CCSM3 to isolate the effects of the feedbacks from the change of the wind-driven ocean circulation and air–sea heat flux in the global climate response to the forcing of doubling CO 2 . The partial coupling is achieved by implementing a so-called overriding technique, which helps quantitatively partition the total response in the fully coupled model to the feedback component in question and the response to external forcing in the absence of the former. By overriding the wind stress seen by the ocean and the wind speed through the bulk formula for evaporation, the experiments help to reveal that (i) the wind–evaporation–SST (WES) feedback is the main formation mechanism for the tropical SST pattern under the CO 2 forcing, verifying the hypothesis proposed by Xie et al.; (ii) the weakened tropical Pacific wind is shown in this UOM model not to be the cause for the enhanced equatorial Pacific warming, as one might expect from the thermocline and Bjerknes feedbacks; (iii) WES is also the leading mechanism for shaping the tropical precipitation response in the ocean; and (iv) both the wind-driven ocean dynamical feedback and the WES feedback act to increase the persistence of the southern annular mode (SAM) and the increased time scale of the SAM due to these feedbacks manifests itself in the response of the jet shift to an identical CO 2 forcing, in a manner conforming to the fluctuation–dissipation theorem.
Luo Y. Y., Q. Y. Liu, and L. M. Rothstein, 2009: Simulated response of North Pacific Mode Waters to global warming. Geophys. Res. Lett., 36,L23609, doi: 10.1029/2009GL040906.10.1029/2009GL040906263773f58656265a816fc286db80caa2http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F2009GL040906%2Fabstracthttp://onlinelibrary.wiley.com/doi/10.1029/2009GL040906/abstract[1] This study investigates the response of the Mode Waters in the North Pacific to global warming based on a set of Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) models. Solutions between a present-day climate and a future, warmer climate are compared. Under the warmer climate scenario, the Mode Waters are produced on lighter isopycnal surfaces and are significantly weakened in terms of their formation and evolution. These changes are due to a more stratified upper ocean and thus a shoaling of the winter mixing depth resulting mainly from a reduction of the ocean-to-atmosphere heat loss over the subtropical region. The basin-wide wind stress may adjust the Mode Waters indirectly through its impact on the surface heat flux and subduction process.
Luo Y. Y., J. Lu, F. K. Liu, and W. Liu, 2014: Understanding the El Niño-like oceanic response in the tropical Pacific to global warming. Climate Dyn., doi: 10.1007/s00382-014-2448-2.10.1007/s00382-014-2448-259c083a503e7461b20d9d16105c4911fhttp%3A%2F%2Flink.springer.com%2F10.1007%2Fs00382-014-2448-2http://link.springer.com/10.1007/s00382-014-2448-2The enhanced central and eastern Pacific SST warming and the associated ocean processes under global warming are investigated using the ocean component of the Community Earth System Model (CESM), Parallel Ocean Program version 2 (POP2). The tropical SST warming pattern in the coupled CESM can be faithfully reproduced by the POP2 forced with surface fluxes computed using the aerodynamic bulk formula. By prescribing the wind stress and/or wind speed through the bulk formula, the effects of wind stress change and/or the wind-evaporation-SST (WES) feedback are isolated and their linearity is evaluated in this ocean-alone setting. Result shows that, although the weakening of the equatorial easterlies contributes positively to the El Nino-like SST warming, 80% of which can be simulated by the POP2 without considering the effects of wind change in both mechanical and thermodynamic fluxes. This result points to the importance of the air-sea thermal interaction and the relative feebleness of the ocean dynamical process in the El Nino-like equatorial Pacific SST response to global warming. On the other hand, the wind stress change is found to play a dominant role in the oceanic response in the tropical Pacific, accounting for most of the changes in the equatorial ocean current more&raquo; system and thermal structures, including the weakening of the surface westward currents, the enhancement of the near-surface stratification and the shoaling of the equatorial thermocline. Interestingly, greenhouse gas warming in the absence of wind stress change and WES feedback also contributes substantially to the changes at the subsurface equatorial Pacific. Further, this warming impact can be largely replicated by an idealized ocean experiment forced by a uniform surface heat flux, whereby, arguably, a purest form of oceanic dynamical thermostat is revealed. 芦less
Murtugudde R., J. P. McCreary, and A. J. Busalacchi, 2000: Oceanic processes associated with anomalous events in the Indian Ocean with relevance to 1997-1998. J. Geophys. Res., 105, 3295- 3306.10.1029/1999JC90029422f1730243c534fde3a7e5d1cd099716http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F236846837_Oceanic_processes_associated_with_anomalous_events_in_the_Indian_Ocean_with_relevance_to_1997-1998._J_Geophys_Res_105_%28C2%29_3295-3306http://www.researchgate.net/publication/236846837_Oceanic_processes_associated_with_anomalous_events_in_the_Indian_Ocean_with_relevance_to_1997-1998._J_Geophys_Res_105_(C2)_3295-3306ABSTRACT An anomalous climatic event occurred in the Indian Ocean (IO) region during 1997-1998, which coincided with a severe drought in Indonesia and floods in parts of eastern Africa. Cool sea surface temperature anomalies (SSTAs) were present in the eastern IO along and south of the equator. Beginning in July 1997, warm SSTAs appeared in the western IO, and they peaked in February 1998. An ocean general circulation model is employed to investigate the dynamic and thermodynamic processes that caused the SSTAs associated with this and other similar IO events. The eastern cooling resulted from unusually strong upwelling along the equator and Sumatra. The Sumatran upwelling was forced both locally by the stronger alongshore winds and remotely by equatorial and coastal Kelvin waves. By the end of 1997, weakening of the winds and the associated reduction in latent heat loss led to the elimination of the cold SST anomalies in the east. The western warming was initiated by weaker Southwest Monsoon winds and maintained by enhanced precipitation forcing, which resulted in a barrier layer structure. Analysis of the mixed layer temperature equation indicates that a downwelling Rossby wave contribution was crucial for sustaining the warming into February 1998. It is tempting to suppose that the 1997 event was related to the El Ni&ntilde;o-Southern Oscillation (ENSO) event that took place in the Pacific at the same time. Indeed, weaker IO events occur quite regularly in the control run that evolve similarly to the 1997 event, and they are often but not always related to ENSO. We speculate that these events represent a natural mode of oscillation in the IO, which is externally forced by ENSO but also excited by ocean-atmosphere interactions internal to the IO.
Pacanowski R. C., S. G. H. Philander, 1981: Parameterization of vertical mixing in numerical models of tropical oceans. J. Phys. Oceanogr., 11, 1443- 1451.58df3873d0e400097a59d9bad08ae860http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1981JPO....11.1443P/s?wd=paperuri%3A%2868602b959a6762372e14dcad940a02c8%29&filter=sc_long_sign&tn=SE_xueshusource_2kduw22v&sc_vurl=http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1981JPO....11.1443P&ie=utf-8
Saji N. H., T. Yamagata, 2003: Structure of SST and surface wind variability during Indian Ocean dipole mode events: COADS observations. J. Climate, 16, 2735- 2751.10.1175/1520-0442(2003)016<2735:SOSASW>2.0.CO;298b491d65e37b09544743261573bc3e8http%3A%2F%2Fen.cnki.com.cn%2FArticle_en%2FCJFDTOTAL-JFJW200303008.htmhttp://en.cnki.com.cn/Article_en/CJFDTOTAL-JFJW200303008.htmABSTRACT A study of the detailed spatiotemporal characteristics of the Indian Ocean dipole (IOD) mode in SST and surface winds using available observations from 1958 till 1997 is reported. The analysis is used to address several of the controversial issues regarding the IOD.One key finding of this study is that interdecadal fluctuations contribute strongly to tropical Indian Ocean (TIO) SST variability; in SST anomalies (SSTA) interdecadal variance is as strong as interannual variance. Over both the western and eastern TIO, an accelerated warming of SST after the mid-1970s is apparent. The lack of anticorrelation between western and eastern TIO SSTA occurs only in this latter half of the analysis period.In order to examine the hypothesis that the IOD is a part of ENSO evolution in the TIO, the temporal characteristics of IOD indices have been compared with Ni&ntilde;o-3. On the basis of several quantitative comparisons that include wavelet and cross-wavelet analysis, several important differences between the two phenomena are reported. These differences are highlighted to argue that the IOD is not a part of ENSO evolution in the TIO. On the other hand, a striking similarity is found in the temporal structure of atmospheric and oceanic variability within the TIO that is suggestive of IOD arising from inherent coupled air-sea interactions in the TIO.ENSO events that do not co-occur with IOD have been isolated and their impacts on TIO SSTA and winds described. Similarly, the characteristics of IOD events that occur independently of ENSO are described. Based on the characteristics of these two groups a hypothesis is suggested through which both phenomena may interact. It is noted that ENSO events co-occurring with IOD events are much stronger compared to non-co-occurring events. On the other hand, IOD events that are independent of ENSO as well as those that co-occur with it appear to have the same strength.
Saji N. H., B. N. Goswami, P. N. Vinayachand ran, and T. Yamagata, 1999: A dipole mode in the tropical Indian Ocean. Nature, 401, 360- 363.10.1038/438541686210831d5bd363a994efe19550bc4fc1839b4http%3A%2F%2Fmed.wanfangdata.com.cn%2FPaper%2FDetail%2FPeriodicalPaper_PM16862108http://med.wanfangdata.com.cn/Paper/Detail/PeriodicalPaper_PM16862108For the tropical Pacific and Atlantic oceans, internal modes of variability that lead to climatic oscillations have been recognized, but in the Indian Ocean region a similar ocean-atmosphere interaction causing interannual climate variability has not yet been found. Here we report an analysis of observational data over the past 40 years, showing a dipole mode in the Indian Ocean: a pattern of internal variability with anomalously low sea surface temperatures off Sumatra and high sea surface temperatures in the western Indian Ocean, with accompanying wind and precipitation anomalies. The spatio-temporal links between sea surface temperatures and winds reveal a strong coupling through the precipitation field and ocean dynamics. This air-sea interaction process is unique and inherent in the Indian Ocean, and is shown to be independent of the El Nino/Southern Oscillation. The discovery of this dipole mode that accounts for about 12% of the sea surface temperature variability in the Indian Ocean--and, in its active years, also causes severe rainfall in eastern Africa and droughts in Indonesia--brightens the prospects for a long-term forecast of rainfall anomalies in the affected countries.
Vecchi G. A., B. J. Soden, 2007: Global Warming and the Weakening of the Tropical Circulation. J. Climate, 20, 4316- 4340.10.1175/JCLI4258.1a806368e-bebb-4d5b-ad72-296f452686b473c4454bd5c87d67e3bd17752bb3e9d7http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2006AGUFMOS11A1467Wrefpaperuri:(b30ccd0a9e8c71855c1ae5c8c7674dc2)http://adsabs.harvard.edu/abs/2006AGUFMOS11A1467WAbstract This study examines the response of the tropical atmospheric and oceanic circulation to increasing greenhouse gases using a coordinated set of twenty-first-century climate model experiments performed for the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). The strength of the atmospheric overturning circulation decreases as the climate warms in all IPCC AR4 models, in a manner consistent with the thermodynamic scaling arguments of Held and Soden. The weakening occurs preferentially in the zonally asymmetric (i.e., Walker) rather than zonal-mean (i.e., Hadley) component of the tropical circulation and is shown to induce substantial changes to the thermal structure and circulation of the tropical oceans. Evidence suggests that the overall circulation weakens by decreasing the frequency of strong updrafts and increasing the frequency of weak updrafts, although the robustness of this behavior across all models cannot be confirmed because of the lack of data. As the climate warms, changes in both the atmospheric and ocean circulation over the tropical Pacific Ocean resemble “El Ni09o–like” conditions; however, the mechanisms are shown to be distinct from those of El Ni09o and are reproduced in both mixed layer and full ocean dynamics coupled climate models. The character of the Indian Ocean response to global warming resembles that of Indian Ocean dipole mode events. The consensus of model results presented here is also consistent with recently detected changes in sea level pressure since the mid–nineteenth century.
Vinayachand ran, P. N., S. Iizuka, T. Yamagata, 2002: Indian Ocean dipole mode events in an ocean general circulation model. Deep-Sea Res., 49, 1573- 1596.10.1016/S0967-0645(01)00157-6d6074878926380e4f3ed2e4b753fc47bhttp%3A%2F%2Fwww.sciencedirect.com%2Fscience%2Farticle%2Fpii%2FS0967064501001576http://www.sciencedirect.com/science/article/pii/S0967064501001576The evolution of the dipole mode (DM) events in the Indian Ocean is examined using an ocean model that is driven by the NCEP fluxes for the period 1975-1998. The positive DM events during 1997, 1994 and 1982 and negative DM events during 1996 and 1984-1985 are captured by the model and it reproduces both the surface and subsurface features associated with these events. In its positive phase, the DM is characterized by warmer than normal SST in the western Indian Ocean and cooler than normal SST in the eastern Indian Ocean. The DM events are accompanied by easterly wind anomalies along the equatorial Indian Ocean and upwelling-favorable alongshore wind anomalies along the coast of Sumatra. The Wyrtki jets are weak during positive DM events, and the thermocline is shallower than normal in the eastern Indian Ocean and deeper in the west. This anomaly pattern reverses during negative DM events.During the positive phase of the DM easterly wind anomalies excite an upwelling equatorial Kelvin wave. This Kelvin wave reflects from the eastern boundary as an upwelling Rossby wave which propagates westward across the equatorial Indian Ocean. The anomalies in the eastern Indian Ocean weaken after the Rossby wave passes. A similar process excites a downwelling Rossby wave during the negative phase. This Rossby wave is much weaker but wind forcing in the central equatorial Indian Ocean amplifies the downwelling and increases its westward phase speed. This Rossby wave initiates the deepening of the thermocline in the western Indian Ocean during the following positive phase of the DM. Rossby wave generated in the southern tropical Indian Ocean by Ekman pumping contributes to this warming. Concurrently, the temperature equation of the model shows upwelling and downwelling to be the most important mechanism during both positive events of 1994 and 1997.
Yang H. J., F. Y. Wang, and A. D. Sun, 2009: Understanding the ocean temperature change in global warming: The tropical Pacific. Tellus A, 61, 371- 380.10.1111/j.1600-0870.2009.00390.x8d57b08b957ad60a1266b2b22ba01310http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1111%2Fj.1600-0870.2009.00390.x%2Fpdfhttp://onlinelibrary.wiley.com/doi/10.1111/j.1600-0870.2009.00390.x/pdfWe synthesized a mixed crystal of lanthanum-neodymium oxychloride (La Nd OCl) by the liquid pahse method. The change of the crystal structure with the Nd content was investigated by X-ray diffraction, Raman scattering and infrared absorption. We also studied the optical emission and the excitation spectra of the doped Ce and Nd ions in this material. Additional emission peaks from Nd ions in the visible region were observed.
Yu J. Y., K. M. Lau, 2004: Contrasting Indian Ocean SST variability with and without ENSO influence: A coupled atmosphere-ocean study. Meteor. Atmos. Phys.,90, 179-191, doi: 10.1007/s00703-004-0094-7.10.1007/s00703-004-0094-7625cd2fe-b4b9-4a33-a275-269797dfd50c9f0922fefc905bae499bd2781085b6fbhttp%3A%2F%2Flink.springer.com%2F10.1007%2Fs00703-004-0094-7refpaperuri:(7cab2393cf4c58c5bb0810a6502def6e)http://link.springer.com/10.1007/s00703-004-0094-7In this study, we perform experiments with a coupled atmosphere-ocean general circulation model (CGCM) to examine ENSO’s influence on the interannual sea-surface temperature (SST) variability of the tropical Indian Ocean. The control experiment includes both the Indian and Pacific Oceans in the ocean model component of the CGCM (the Indo-Pacific Run). The anomaly experiment excludes ENSO’s influence by including only the Indian Ocean while prescribing monthly-varying climatological SSTs for the Pacific Ocean (the Indian-Ocean Run). In the Indo-Pacific Run, an oscillatory mode of the Indian Ocean SST variability is identified by a multi-channel singular spectral analysis (MSSA). The oscillatory mode comprises two patterns that can be identified with the Indian Ocean Zonal Mode (IOZM) and a basin-wide warming/cooling mode respectively. In the model, the IOZM peaks about 3–5 months after ENSO reaches its maximum intensity. The basin mode peaks 8 months after the IOZM. The timing and associated SST patterns suggests that the IOZM is related to ENSO, and the basin-wide warming/cooling develops as a result of the decay of the IOZM spreading SST anomalies from western Indian Ocean to the eastern Indian Ocean. In contrast, in the Indian-Ocean Run, no oscillatory modes can be identified by the MSSA, even though the Indian Ocean SST variability is characterized by east–west SST contrast patterns similar to the IOZM. In both control and anomaly runs, IOZM-like SST variability appears to be associated with forcings from fluctuations of the Indian monsoon. Our modeling results suggest that the oscillatory feature of the IOZM is primarily forced by ENSO.
Zheng X. T., S. P. Xie, G. A. Vecchi, Q. Y. Liu, and J. Hafner, 2010: Indian Ocean dipole response to global warming: Analysis of ocean-atmospheric feedbacks in a coupled model. J. Climate, 23, 1240- 1253.10.1175/2009JCLI3326.186a5b86d97610a3eded00fbc6b4194dehttp%3A%2F%2Fwww.cabdirect.org%2Fabstracts%2F20103118386.htmlhttp://www.cabdirect.org/abstracts/20103118386.htmlLow-frequency modulation and change under global warming of the Indian Ocean dipole (IOD) mode are investigated with a pair of multicentury integrations of a coupled ocean09 tmosphere general circulation model: one under constant climate forcing and one forced by increasing greenhouse gas concentrations. In the unforced simulation, there is significant decadal and multidecadal modulation of the IOD variance. The mean thermocline depth in the eastern equatorial Indian Ocean (EEIO) is important for the slow modulation, skewness, and ENSO correlation of the IOD. With a shoaling (deepening) of the EEIO thermocline, the thermocline feedback strengthens, and this leads to an increase in IOD variance, a reduction of the negative skewness of the IOD, and a weakening of the IOD09 NSO correlation. In response to increasing greenhouse gases, a weakening of the Walker circulation leads to easterly wind anomalies in the equatorial Indian Ocean; the oceanic response to weakened circulation is a thermocline shoaling in the EEIO. Under greenhouse forcing, the thermocline feedback intensifies, but surprisingly IOD variance does not. The zonal wind anomalies associated with IOD are found to weaken, likely due to increased static stability of the troposphere from global warming. Linear model experiments confirm this stability effect to reduce circulation response to a sea surface temperature dipole. The opposing changes in thermocline and atmospheric feedbacks result in little change in IOD variance, but the shoaling thermocline weakens IOD skewness. Little change under global warming in IOD variance in the model suggests that the apparent intensification of IOD activity during recent decades is likely part of natural, chaotic modulation of the ocean09 tmosphere system or the response to nongreenhouse gas radiative changes.
Zheng X. T., S. P. Xie, Y. Du, L. Liu, G. Huang, and Q. Y. Liu, 2013: Indian Ocean dipole response to global warming in the CMIP5 multimodel ensemble. J. Climate, 26, 6067- 6080.10.1175/JCLI-D-12-00638.1217b6d62-44c0-4b96-b573-4e2e97f60adf041735ee362041f5e1f92012ac1b199ahttp%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2013JCli...26.6067Zrefpaperuri:(e607ff29921db99b0496d07bdde9439f)http://adsabs.harvard.edu/abs/2013JCli...26.6067ZAbstract The response of the Indian Ocean dipole (IOD) mode to global warming is investigated based on simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5). In response to increased greenhouse gases, an IOD-like warming pattern appears in the equatorial Indian Ocean, with reduced (enhanced) warming in the east (west), an easterly wind trend, and thermocline shoaling in the east. Despite a shoaling thermocline and strengthened thermocline feedback in the eastern equatorial Indian Ocean, the interannual variance of the IOD mode remains largely unchanged in sea surface temperature (SST) as atmospheric feedback and zonal wind variance weaken under global warming. The negative skewness in eastern Indian Ocean SST is reduced as a result of the shoaling thermocline. The change in interannual IOD variance exhibits some variability among models, and this intermodel variability is correlated with the change in thermocline feedback. The results herein illustrate that mean state changes modulate interannual modes, and suggest that recent changes in the IOD mode are likely due to natural variations.
Zhong A. H., H. H. Hendon, and O. Alves, 2005: Indian Ocean variability and its association with ENSO in a global coupled model. J. Climate, 18, 3634- 3649.