Passage of intraseasonal waves in the subsurface oceans

Krishnamurti, T. N.; Chakraborty, Arindam; Krishnamurti, Ruby; Dewar, William K.; Clayson, Carol Anne

doi:10.1029/2007gl030496

Cited by 12 publications

(5 citation statements)

References 31 publications

(45 reference statements)

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“…However, this SST anomaly is generated over the central and eastern equatorial Indian Ocean in phases 3-4 and moves northward in subsequent phases. An eastward movement of SST along the equator in the low-frequency intraseasonal timescale was documented in Krishnamurti et al (2007). But we do not observe clear indication of eastward movement over the equatorial Indian Ocean.…”

Section: ) Lf-iso and The Composite Structures Of Sst And Circulatiocontrasting

confidence: 81%

Space–Time Evolution of the Low- and High-Frequency Intraseasonal Modes of the Indian Summer Monsoon

Karmakar

Chakraborty

Nanjundiah

2017

Monthly Weather Review

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In this study, rainfall estimates by the Tropical Rainfall Measuring Mission are used to understand the spatiotemporal structures of convection in the intraseasonal time scale and their intensity during the boreal summer over South Asia. A quantitative analysis on how these intraseasonal modes modulate the central Indian rainfall is also provided. Two dominant modes of variability with periodicities of 10–20 and 20–60 days are found, with the latter strongly modulated by sea surface temperature. The 20–60-day mode shows northward propagation from the equatorial Indian Ocean linked with eastward-propagating modes of convective systems over the tropics. The 10–20-day mode shows a complex space–time structure with a northwestward-propagating anomalous pattern emanating from the Indonesian coast. This pattern is found to be interacting with a structure emerging from higher latitudes propagating southeastward, the development of which is attributed to the vertical shear of the zonal wind. The two modes exhibit profound variability in their intensity on the interannual time scale and they contribute a comparable amount to the daily rainfall variability in a season. The intensity of the 20–60 and 10–20-day modes shows a significantly strong inverse and direct relationship with the all-India June–September rainfall, respectively. This study establishes that the probability of the occurrence of substantial rainfall over central India increases significantly if the two intraseasonal modes simultaneously exhibit positive anomalies over the region. The results presented in this paper will provide a pathway to understand, using observations and numerical model simulations, intraseasonal variability and its relative contribution to the Indian summer monsoon. It can also be used for model evaluation.

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Section: ) Lf-iso and The Composite Structures Of Sst And Circulatiocontrasting

confidence: 81%

Space–Time Evolution of the Low- and High-Frequency Intraseasonal Modes of the Indian Summer Monsoon

Karmakar

Chakraborty

Nanjundiah

2017

Monthly Weather Review

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“…The paucity of subsurface observations has been partially resolved by Argo floats, which measure profiles of temperature (T) and salinity (S) as they drift in the ocean. The floats provide an unprecedented view of the subsurface ocean, and Argo data is being widely used for basic science as well as applications [e.g., Ravichandran et al , 2004; Iwasaka et al , 2006; Mathews et al , 2007; Krishnamurti et al , 2007]. Riser et al .…”

Section: Introductionmentioning

confidence: 99%

Intraseasonal response of mixed layer temperature and salinity in the Bay of Bengal to heat and freshwater flux

et al. 2010

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[1] Buoy and satellite data show pronounced subseasonal oscillations of sea surface temperature (SST) in the summertime Bay of Bengal. The SST oscillations are forced mainly by surface heat flux associated with the active break cycle of the south Asian summer monsoon. The input of freshwater (FW) from summer rain and rivers to the bay is large, but not much is known about subseasonal salinity variability. We use [2002][2003][2004][2005][2006][2007] observations from three Argo floats with 5 day repeat cycle to study the subseasonal response of temperature and salinity to surface heat and freshwater flux in the central Bay of Bengal. About 95% of Argo profiles show a shallow halocline, with substantial variability of mixed layer salinity. Estimates of surface heat and freshwater flux are based on daily satellite data sampled along the float trajectory. We find that intraseasonal variability of mixed layer temperature is mainly a response to net surface heat flux minus penetrative radiation during the summer monsoon season. In winter and spring, however, temperature variability appears to be mainly due to lateral advection rather than local heat flux. Variability of mixed layer freshwater content is generally independent of local surface flux (precipitation minus evaporation) in all seasons. There are occasions when intense monsoon rainfall leads to local freshening, but these are rare. Large fluctuations in FW appear to be due to advection, suggesting that freshwater from rivers and rain moves in eddies or filaments.

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“…Argo has revealed the local balances of evaporation minus precipitation in the salinity structure of the upper ocean (Durack et al, 2012, Helm et al, 2010, Hosoda et al, 2009, as well as longer term changes in subsurface water masses brought about by climate change (Zhang et al, 2008, Downes et al, 2009. Many operational centers are assimilating Argo data for seasonal predictions of the monsoon, El Niño, and the Indian Ocean Dipole mode (Oke and Schiller, 2007, Agarwal et al, 2008, Krishnamurti et al, 2007, Huang et al, 2008, Reddy et al, 2017. Though Argo observations are primarily intended to study seasonal-to-climate scale phenomena, the data are also used for other areas of research, such as cyclones and intra-seasonal variability.…”

Section: Argo Applicationsmentioning

confidence: 99%

Full Report. IndOOS-2: A roadmap to sustained observations of the Indian Ocean for 2020-2030

2019

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Argo is a global array of profiling floats that measure temperature and salinity over the upper 2000 m of the Ocean every 10 days. Here we present the status of Argo floats in the Indian Ocean and their applications, both operational and scientific. We also recommend future directions for Argo, like development of an array of floats with biogeochemical sensors (BGC-Argo) to measure and understand biogeochemical processes, increasing the number of floats in the equatorial Indian Ocean to better capture intraseasonal-to-interannual variability, and implementation of a Deep-Argo array to map heat and mass below 2000 m.

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Passage of intraseasonal waves in the subsurface oceans

Cited by 12 publications

References 31 publications

Space–Time Evolution of the Low- and High-Frequency Intraseasonal Modes of the Indian Summer Monsoon

Space–Time Evolution of the Low- and High-Frequency Intraseasonal Modes of the Indian Summer Monsoon

Intraseasonal response of mixed layer temperature and salinity in the Bay of Bengal to heat and freshwater flux

Full Report. IndOOS-2: A roadmap to sustained observations of the Indian Ocean for 2020-2030

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