Influence of Indian Ocean Dipole on Poleward Propagation of Boreal Summer Intraseasonal Oscillations

Ajayamohan, R. S.; Rao, Suryachandra A.; Yamagata, Toshio

doi:10.1175/2008jcli1758.1

Cited by 70 publications

(54 citation statements)

References 53 publications

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“…It seems however that this flow anomaly over the Arabian Sea remains quite poorly correlated to DMI (r *0.20) resulting in little overall influence of the IOD on the Indian rainfall. Another possible reason for the weak correlations may be due to the asymmetry in the respective impact of the positive and negative IODs on summer monsoon intraseasonal Oscillations over India (Ajayamohan et al 2008). Finally, results are relatively similar when considering the entire South Asian monsoon over land and ocean (ISAS), with slightly weaker biases (Fig.…”

Section: Indian Summer Monsoonmentioning

confidence: 79%

The Indo-Australian monsoon and its relationship to ENSO and IOD in reanalysis data and the CMIP3/CMIP5 simulations

et al. 2013

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A large spread exists in both Indian and Australian average monsoon rainfall and in their interannual variations diagnosed from various observational and reanalysis products. While the multi model mean monsoon rainfall from 59 models taking part in the Coupled Model Intercomparison Project (CMIP3 and CMIP5) fall within the observational uncertainty, considerable model spread exists. Rainfall seasonality is consistent across observations and reanalyses, but most CMIP models produce either a too peaked or a too flat seasonal cycle, with CMIP5 models generally performing better than CMIP3. Considering all North-Australia rainfall, most models reproduce the observed Australian monsoon-El Niño Southern Oscillation (ENSO) teleconnection, with the strength of the relationship dependent on the strength of the simulated ENSO. However, over the Maritime Continent, the simulated monsoon-ENSO connection is generally weaker than observed, depending on the ability of each model to realistically reproduce the ENSO signature in the Warm Pool region. A large part of this bias comes from the contribution of Papua, where moisture convergence seems to be particularly affected by this SST bias. The Indian summer monsoon-ENSO relationship is affected by overly persistent ENSO events in many CMIP models. Despite significant wind anomalies in the Indian Ocean related to Indian Ocean Dipole (IOD) events, the monsoon-IOD relationship remains relatively weak both in the observations and in the CMIP models. Based on model fidelity in reproducing realistic monsoon characteristics and ENSO teleconnections, we objectively select 12 ''best'' models to analyze projections in the rcp8.5 scenario. Eleven of these models are from the CMIP5 ensemble. In India and Australia, most of these models produce 5-20 % more monsoon rainfall over the second half of the twentieth century than during the late nineteenth century. By contrast, there is no clear model consensus over the Maritime Continent.

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Section: Indian Summer Monsoonmentioning

confidence: 79%

The Indo-Australian monsoon and its relationship to ENSO and IOD in reanalysis data and the CMIP3/CMIP5 simulations

et al. 2013

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“…The meridional vertical structure of composite MISO in both the periods (1979–1988 and 2001–2010) is shown in Figure . The vertical structure of the composite MISO is created based on the methodology adopted by previous studies [ Jiang et al ., ; Ajayamohan et al ., ]. First, a latitude time diagram of positive MISO precipitation anomalies averaged over 70°E–95°E is plotted for each year (figure not shown).…”

Section: Observational Resultsmentioning

confidence: 99%

“…A phase composite of the MISO is computed at each reference latitude over which the maximum positive precipitation anomalies occur. Since these composite structures bear a close resemblance, we further made a composite of these structures with respect to the maximum convection center [ Jiang et al ., ; Ajayamohan et al ., ]. From Figure , clearly, during the recent decade, the amplitude of vorticity, divergence, specific humidity, and vertical velocity have strengthened to the north of the convection.…”

Section: Observational Resultsmentioning

confidence: 99%

Modulation of monsoon intraseasonal oscillations in the recent warming period

et al. 2014

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The Indian Ocean sea surface temperature (SST) during the boreal summer has shown a significant warming of 0.3°C in the recent decade (2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010) compared to a former decade (1979)(1980)(1981)(1982)(1983)(1984)(1985)(1986)(1987)(1988), and it is most pronounced in the central tropical Indian Ocean. By using reanalysis and satellite-derived data sets, we investigated how the monsoon intraseasonal oscillation (MISO) over the South Asian summer monsoon (ASM) region has been influenced by the recent warming in the Indian Ocean. It is found that the MISO variance has increased over the ASM region in the recent period compared with the earlier decade. It is also noted that the characteristic northward propagation of the MISO has slowed over 2001-2010, resembling more of a standing oscillation near the equator. Mechanisms implicated in the observed MISO changes are explored by conducting several model sensitivity experiments with an atmospheric general circulation model. The model experiments suggest that the mean SST increase over the Indian Ocean, and the associated changes in the air-sea interaction, the increased mean moisture convergence, and changes in the large-scale circulation are responsible for the changes in the characteristics of the MISO. The influence of the recent Indian Ocean warming on the MISO characteristics must be understood fully since they determine the seasonal amount of rainfall over the Indian subcontinent. An examination of future projections of the MISO using the MPI-ESM-LR model from the Coupled Model Intercomparison Project phase 5 archive also gives consistent result.

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“…Studies show that the IOZM is most significantly correlated with the local Hadley cell, which influences the Asian monsoons (Slingo and Annamalai 2000). The IOZM has been noted to influence MJO activity as well (Rao et al 2007;Ajayamohan et al 2008). Kug et al (2009) showed that the high-frequency atmospheric variability in the Indian Ocean is modulated by IOZM events and that MJO and synoptic eddies become significantly energetic during negative IOZM events.…”

Section: B Mjo-monsoon Relationsmentioning

confidence: 99%

The Madden–Julian Oscillation in CCSM4

et al. 2011

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This study assesses the ability of the Community Climate System Model, version 4 (CCSM4) to represent the Madden-Julian oscillation (MJO), the dominant mode of intraseasonal variability in the tropical atmosphere. The U.S. Climate Variability and Predictability (CLIVAR) MJO Working Group's prescribed diagnostic tests are used to evaluate the model's mean state, variance, and wavenumber-frequency characteristics in a 20-yr simulation of the intraseasonal variability in zonal winds at 850 hPa (U850) and 200 hPa (U200), and outgoing longwave radiation (OLR). Unlike its predecessor, CCSM4 reproduces a number of aspects of MJO behavior more realistically.The CCSM4 produces coherent, broadbanded, and energetic patterns in eastward-propagating intraseasonal zonal winds and OLR in the tropical Indian and Pacific Oceans that are generally consistent with MJO characteristics. Strong peaks occur in power spectra and coherence spectra with periods between 20 and 100 days and zonal wavenumbers between 1 and 3. Model MJOs, however, tend to be more broadbanded in frequency than in observations. Broad-scale patterns, as revealed in combined EOFs of U850, U200, and OLR, are remarkably consistent with observations and indicate that large-scale convergence-convection coupling occurs in the simulated MJO.Relations between MJO in the model and its concurrence with other climate states are also explored. MJO activity (defined as the percentage of time the MJO index exceeds 1.5) is enhanced during El Niñ o events compared to La Niñ a events, both in the model and observations. MJO activity is increased during periods of anomalously strong negative meridional wind shear in the Asian monsoon region and also during strong negative Indian Ocean zonal mode states, in both the model and observations.

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Influence of Indian Ocean Dipole on Poleward Propagation of Boreal Summer Intraseasonal Oscillations

Cited by 70 publications

References 53 publications

The Indo-Australian monsoon and its relationship to ENSO and IOD in reanalysis data and the CMIP3/CMIP5 simulations

The Indo-Australian monsoon and its relationship to ENSO and IOD in reanalysis data and the CMIP3/CMIP5 simulations

Modulation of monsoon intraseasonal oscillations in the recent warming period

The Madden–Julian Oscillation in CCSM4

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