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| Keerthi, M. G.; Lengaigne, M.; Drushka, K.; Vialard, J.; De Boyer Montegut, Clement; Pous, Stephane; Levy, M.; Muraleedharan, P. M.. |
| In this paper, we use an observational dataset built from Argo in situ profiles to describe the main large-scale patterns of intraseasonal mixed layer depth (MLD) variations in the Indian Ocean. An eddy permitting (0.25A degrees) regional ocean model that generally agrees well with those observed estimates is then used to investigate the mechanisms that drive MLD intraseasonal variations and to assess their potential impact on the related SST response. During summer, intraseasonal MLD variations in the Bay of Bengal and eastern equatorial Indian Ocean primarily respond to active/break convective phases of the summer monsoon. In the southern Arabian Sea, summer MLD variations are largely driven by seemingly-independent intraseasonal fluctuations of the... |
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| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00332/44335/45788.pdf |
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| Praveen Kumar, B.; Vialard, J.; Lengaigne, M.; Murty, V. S. N.; Foltz, G. R.; Mcphaden, M. J.; Pous, S.; De Boyer Montegut, Clement. |
| Sea-surface temperature interannual anomalies (SSTAs) in the thermocline ridge of the southwestern tropical Indian Ocean (TRIO) have several well-documented climate impacts. In this paper, we explore the physical processes responsible for SSTA evolution in the TRIO region using a combination of observational estimates and model-derived surface layer heat budget analyses. Vertical oceanic processes contribute most to SSTA variance from December to June, while lateral advection dominates from July to November. Atmospheric fluxes generally damp SSTA generation in the TRIO region. As a result of the phase opposition between the seasonal cycle of vertical processes and lateral advection, there is no obvious peak in SSTA amplitude in boreal winter, as previously... |
| Tipo: Text |
Palavras-chave: Thermocline ridge of the Indian Ocean; Surface temperature interannual variability; ENSO; IOD. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00185/29642/28051.pdf |
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| Currie, J. C.; Lengaigne, M.; Vialard, Jerome; Kaplan, David; Aumont, Olivier; Naqvi, S. W. A.; Maury, Olivier. |
| The Indian Ocean Dipole (IOD) and the El Nino/Southern Oscillation (ENSO) are independent climate modes, which frequently co-occur, driving significant interannual changes within the Indian Ocean. We use a four-decade hindcast from a coupled biophysical ocean general circulation model, to disentangle patterns of chlorophyll anomalies driven by these two climate modes. Comparisons with remotely sensed records show that the simulation competently reproduces the chlorophyll seasonal cycle, as well as open-ocean anomalies during the 1997/1998 ENSO and IOD event. Results suggest that anomalous surface and euphotic-layer chlorophyll blooms in the eastern equatorial Indian Ocean in fall, and southern Bay of Bengal in winter, are primarily related to IOD forcing.... |
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| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00166/27749/25945.pdf |
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| Samson, G.; Masson, S.; Lengaigne, M.; Keerthi, M. G.; Vialard, J.; Pous, Stephane; Madec, G.; Jourdain, N. C.; Jullien, Swen; Menkes, C.; Marchesiello, P.. |
| This paper presents the NOW regional coupled ocean-atmosphere model built from the NEMO ocean and WRF atmospheric numerical models. This model is applied to the tropical Indian Ocean, with the oceanic and atmospheric components sharing a common 1/4 degrees horizontal grid. Long experiments are performed over the 1990-2009 period using the Betts-Miller-Janjic (BMJ) and Kain-Fritsch (KF) cumulus parameterizations. Both simulations produce a realistic distribution of seasonal rainfall and a realistic northward seasonal migration of monsoon rainfall over the Indian subcontinent. At subseasonal time scales, the model reasonably reproduces summer monsoon active and break phases, although with underestimated rainfall and surface wind signals. Its relatively high... |
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| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00349/46036/45703.pdf |
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| Akhil, V. P.; Lengaigne, M.; Vialard, J.; Durand, F.; Keerthi, M. G.; Chaitanya, A. V. S.; Papa, F.; Gopalakrishna, V. V.; De Boyer Montegut, Clement. |
| Recent observational studies provided preliminary insights on the interannual variability of Bay of Bengal (BoB) Sea Surface Salinity (SSS), but are limited by the poor data coverage. Here, we describe the BoB interannual SSS variability and its driving processes from a regional eddy-permitting ocean general circulation model forced by interannually varying air-sea fluxes and altimeter-derived discharges of major rivers over the past two decades. Simulated interannual SSS variations compare favorably with both in situ and satellite data and are largest in boreal fall in three regions: the northern BoB, the coastal region off east India, and the Andaman Sea. In the northern BoB, these variations are independent from those in other regions and mostly driven... |
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| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00360/47134/47083.pdf |
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| Nidheesh, A. G.; Lengaigne, M.; Vialard, J.; Izumo, T.; Unnikrishnan, A. S.; Meyssignac, B.; Hamlington, B.; De Boyer Montegut, Clement. |
| We examine the consistency of Indo-Pacific decadal sea level variability in 10 gridded, observation-based sea level products for the 1960–2010 period. Decadal sea level variations are robust in the Pacific, with more than 50% of variance explained by decadal modulation of two flavors of El Niño–Southern Oscillation (classical ENSO and Modoki). Amplitude of decadal sea level variability is weaker in the Indian Ocean than in the Pacific. All data sets indicate a transmission of decadal sea level signals from the western Pacific to the northwest Australian coast through the Indonesian throughflow. The southern tropical Indian Ocean sea level variability is associated with decadal modulations of ENSO in reconstructions but not in reanalyses or in situ data... |
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| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00395/50593/51290.pdf |
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| Dutheil, Cyril; Bador, M.; Lengaigne, M.; Lefèvre, J.; Jourdain, N. C.; Vialard, J.; Jullien, Swen; Peltier, A.; Menkes, C.. |
| The South Pacific Convergence Zone (SPCZ) is poorly represented in global coupled simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5), with trademark biases such as the tendency to form a “double Intertropical convergence zone” and an equatorial cold tongue that extends too far westward. Such biases limit our confidence in projections of the future climate change for this region. In this study, we use a downscaling strategy based on a regional atmospheric general circulation model that accurately captures the SPCZ present-day climatology and interannual variability. More specifically, we investigate the sensitivity of the projected rainfall response to either just correcting present-day CMIP5 Sea Surface Temperature (SST) biases or... |
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Palavras-chave: Regional climate models; South Pacific Convergence Zone; Precipitation; Sea Surface Temperature. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00484/59603/62636.pdf |
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| Mignot, J.; Swingedouw, D.; Deshayes, Julie; Marti, O.; Talandier, Claude; Seferian, R.; Lengaigne, M.; Madec,. |
| This study analyses the impact on the oceanic mean state of the evolution of the oceanic component (NEMO) of the climate model developed at Institut Pierre Simon Laplace (IPSL-CM), from the version IPSL-CM4, used for third phase of the Coupled Model Intercomparison Project (CMIP3), to IPSL-CM5A, used for CMIP5. Several modifications have been implemented between these two versions, in particular an interactive coupling with a biogeochemical module, a 3-band model for the penetration of the solar radiation, partial steps at the bottom of the ocean and a set of physical parameterisations to improve the representation of the impact of turbulent and tidal mixing. A set of forced and coupled experiments is used to single out the effect of each of these... |
| Tipo: Text |
Palavras-chave: Ocean modelling; Parameterizations; Climate model; Coupled ocean biogeochemistry. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00170/28102/26612.pdf |
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