Interannual variability of the Arabian Sea Warm Pool: observations and governing mechanisms

Rao, R. R.; Jitendra, V.; Girishkumar, M. S.; Ravichandran, M.; Ramakrishna, S. S. V. S.

doi:10.1007/s00382-014-2243-0

Cited by 28 publications

(20 citation statements)

References 110 publications

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“…These results are consistent with those of previous studies, which found a deeper freshwater pool and barrier layer to be associated with a stronger ASMWP (Rao et al, ). Observational studies based on the ARMEX program found that ASMWP temperatures could exceed 30 °C (Sengupta et al, ).…”

Section: Resultssupporting

confidence: 94%

“…As ERA5's moisture flux and surface latent heat fluxes are strongly related, it follows that surface fluxes, especially moisture and latent heat fluxes, are largely responsible for the drop off of monsoon strength. This is consistent with previous studies of the ASMWP, which found surface heat fluxes to place a critical role in the development of the ASMWP, especially in increasing the strength of the ASMWP (Rao et al, ; Sengupta et al, ). It is worth noting that the BLTA also decreases at the same time as the moisture flux trend decreases, which may have contributed to the decrease in monsoon strength.…”

Section: Resultssupporting

confidence: 93%

“…These results are consistent with those of previous studies, which found a deeper freshwater pool and barrier layer to be associated with a stronger ASMWP (Rao et al, 2015). Observational studies…”

Section: 1029/2019jc015592supporting

confidence: 93%

“…Both La Niñas and negative IOD phases were found to support increased moisture over India, whereas El Niños and positive IOD phases were found to inhibit this. These findings are complicated by more recent research, which found that the ASMWP was more developed during El Niños than during La Niñas (Rao et al, 2015). As ENSO and IOD are both found to influence the strength and timing of the second downwelling Kelvin wave's arrival in the Bay of Bengal and the subsequent coastal Kelvin wave that interacts with the EICC, it is evident that the influences of both ENSO and IOD on both the ASMWP and MOK will be more complex (Rao et al, 2010).…”

Section: Introductionmentioning

confidence: 95%

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The Role of Salinity in the Southeastern Arabian Sea in Determining Monsoon Onset and Strength

2020

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In this study, we examine the role of freshwater transported from the Bay of Bengal into the southeastern Arabian Sea (SEAS) in determining both the timing of monsoon onset and the strength of the ensuing monsoon. To do this, we use a combination of satellite-derived salinity data and reanalysis products from 1980 to 2016 in order to discuss seasonal, interannual, subdecadal, and long-term decadal variability in various atmospheric and oceanic contributors such as ocean heat content, freshwater transport, ERA5 instantaneous moisture flux, mixed layer depth, and barrier layer thickness. The salt budget in the SEAS reveals the dominance of meridional freshwater advective transport that brings in variability in salinity and thus in salinity stratification, as well as in mixed layer processes. We find that these parameters exhibit the prevalence of a long-term decadal variability (with trends of increasing/decreasing phases over a 15-year duration) over which interannual (3-year trend) and intradecadal (7-year trend) variability trends are superimposed. The patterns of both the 3-and 7-year trends follow each other closely, and relatively high amplitudes are seen in the 3-year trends. The long-term decrease in moisture flux and freshwater transport into the SEAS along with a rise in ocean heat content over a 15-year duration after 1994 contributed to a lack of strong monsoons in recent years; the prevailing interannual and intradecadal variability in these parameters associated with the Indian Ocean Dipole and El Niño Southern Oscillation events favored weaker and normal monsoons after 1994. Plain Language SummaryThe timing and intensity of the southwest monsoon is difficult to forecast and has been the subject of a great deal of research. In particular, the genesis of a monsoon onset vortex over the southeastern Arabian Sea (SEAS) encompassing the Arabian Sea Mini Warm Pool has received increased attention for the role it plays on the onset of the southwest monsoon. In our study, we examine how the low salinity waters transported from the Bay of Bengal (both along the east coast of India and from the southern Bay of Bengal) into the SEAS region influence the strength and timing of the ensuing southwest monsoon. Our finding is that this low salinity water has a significant impact on barrier layer formation in the SEAS and the vertical thermal structure of the Arabian Sea Mini Warm Pool. Further examination of subdecadal, decadal, and long-period decadal trends from 1980 to 2016 shows that instantaneous moisture fluxes and zonal winds over the SEAS have decreased substantially, and barrier layer thickness has increased since 1994 in association with the increasing trend in ocean heat content and contributed to the lack of strong southwest monsoons after 1994.

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Section: Resultssupporting

confidence: 94%

Section: Resultssupporting

confidence: 93%

Section: 1029/2019jc015592supporting

confidence: 93%

Section: Introductionmentioning

confidence: 95%

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The Role of Salinity in the Southeastern Arabian Sea in Determining Monsoon Onset and Strength

2020

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“…Vinaychandran et al (), however, concluded that, although the ASMWP impacts the onset vortex, it is not a sufficient condition for its formation. Rao et al () investigated the interannual variability of ASMWP variables in terms of their phase, amplitude, and spatial extent. Joseph () suggested a need to study the ASMWP and its impact on the Indian Summer Monsoon Rainfall (ISMR).…”

Section: Introductionmentioning

confidence: 99%

Heat content of the Arabian Sea Mini Warm Pool is increasing

Nagamani

Ali

Goñi

et al. 2015

Atmospheric Science Letters

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Sea surface temperature in the Arabian Sea Mini Warm Pool has been suggested to be one of the factors that affects the Indian summer monsoon. In this paper, we analyze the annual ocean heat content (OHC) of this region during 1993-2010, using in situ data, satellite observations, and a model simulation. We find that OHC increases significantly in the region during this period relative to the north Indian Ocean, and propose that this increase could have caused the decrease in Indian Summer Monsoon Rainfall that occurred at the same time.

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Characteristics of Marine Heat Extreme Evolution in the Northern Indian Ocean

Gupta,

Deogharia,

Sil

et al. 2024

Intl Journal of Climatology

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Marine Heat Extremes (MHEs) are events of anomalously high Sea Surface Temperature (SST) during which SST values exceed a certain pre‐defined threshold. These MHEs have profound influence over weather patterns, air‐sea interaction and the health of marine ecosystems. This study investigates the long‐term evolution of MHEs in the Northern Indian Ocean (NIO) from 1900 to 2020. We utilised two normalised indices, the Normalised Extreme Frequency Index (NEFI) for frequency and the Normalised Extreme Heat Index (NEHI) for the intensity of MHEs, to objectively compare the MHE attributes across different periods and regions of the NIO. The analysis reveals non‐linearly increasing NEFI, with the Western Equatorial Indian Ocean (WEIO) experiencing the fastest rise, followed by the Eastern Equatorial Indian Ocean (EEIO), Arabian Sea (AS) and Bay of Bengal (BoB). MHE intensity shows exponential growth, with its mean‐based regimes becoming shorter and shifting more frequently. A new regime has been emerging since the last decade. Analysis of the spatial extent of the MHEs indicates that the WEIO is the fastest‐growing region of the NIO. Similar observations were found upon removing sub‐decadal variabilities, which include the potential effects of El Niño‐Southern Oscillation and Indian Ocean Dipole, highlighting the long‐term warming associated with global warming. The study also links the increasing mean SST to the rising frequency and intensity of MHEs, which is predominantly driven by the net surface heat‐flux, which is a combined effect of local and pantropical air‐sea interaction. The surface warming is outpacing subsurface warming, thereby strengthening thermal stratification over time, potentially impacting vertical mixing and upwelling, which can, in turn, lead to further surface warming.

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Interannual variability of the Arabian Sea Warm Pool: observations and governing mechanisms

Cited by 28 publications

References 110 publications

The Role of Salinity in the Southeastern Arabian Sea in Determining Monsoon Onset and Strength

The Role of Salinity in the Southeastern Arabian Sea in Determining Monsoon Onset and Strength

Heat content of the Arabian Sea Mini Warm Pool is increasing

Characteristics of Marine Heat Extreme Evolution in the Northern Indian Ocean

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