Interannual Variability in the Large-Scale Dynamics of the South Asian Summer Monsoon

Walker, J. M.; Bordoni, Simona; Schneider, Tapio

doi:10.1175/jcli-d-14-00612.1

Cited by 45 publications

(50 citation statements)

References 90 publications

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“…Although both the dynamic and thermodynamic components contribute to the IMR, the contribution of the dynamic part of the moisture flux is greater than the thermodynamic component for both the AMO and Atlantic tripole modes. This result is similar to the study by Walker et al (2015) showing that the dynamic part of the moisture flux is dominant, in general, on interannual timescale.…”

Section: Mechanism For Atlantic Tripole-monsoon Relationsupporting

confidence: 91%

Teleconnections of Indian monsoon rainfall with AMO and Atlantic tripole

Krishnamurthy

2015

Clim Dyn

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Section: Mechanism For Atlantic Tripole-monsoon Relationsupporting

confidence: 91%

Teleconnections of Indian monsoon rainfall with AMO and Atlantic tripole

Krishnamurthy

2015

Clim Dyn

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“…Following the approach of our previous work on the interannual variability of the SASM [ Walker et al , ], we define the SASM region as 10–30°N, 60–100°E (Figure S1, further details in the supporting information) and we analyze seasonal transitions in its large‐scale atmospheric moisture budget, given by

MFC = - \int_{0}^{p_{s}} \nabla_{p} \cdot (boldu q) \frac{normald p}{g} = P - E + \frac{∂w}{∂t}

where MFC is the horizontal moisture flux convergence integrated from the surface to the top of the atmosphere, ∇ p ·() the horizontal divergence in pressure coordinates, u = ( u , v ) the horizontal wind vector, q the specific humidity, P the precipitation rate, E the evaporation rate, and

w = \int_{0}^{p_{s}} q \frac{normald p}{g}

the total precipitable water. With negligible storage ∂ w / ∂ t (e.g., Figure a), the dominant balance in the SASM region is between MFC and net precipitation ( P ‐ E ).…”

Section: Sasm Onset and Withdrawal Indexmentioning

confidence: 58%

Onset and withdrawal of the large‐scale South Asian monsoon: A dynamical definition using change point detection

Walker

Bordoni

2016

Geophysical Research Letters

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We introduce an objective definition for onset and withdrawal of the South Asian summer monsoon (SASM), based on the large‐scale atmospheric moisture budget. The change point (CHP) index allows precise characterization of the different stages and timescales of the large‐scale SASM and is highly correlated with the local operational index, the monsoon onset over Kerala. The CHP‐based onset and withdrawal dates, which capture the expected seasonal transitions in rainfall and winds, correspond with regime changes in the SASM moisture budget between negative and positive net precipitation. Climatological composites reveal that the seasonal transitions in SASM sector mean precipitation and circulation closely resemble those of the zonal mean Hadley circulation. The CHP index at grid points within the SASM domain yields a robust definition of local onset and withdrawal dates, which are well correlated with the large‐scale index on interannual timescales, providing insight into the regional variability of the SASM.

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“…It confirms the dominant role of the dynamic processes in regulat- ing the precipitation change in SWC. Indeed, the interannual variation in the SASM net precipitation (within the Arabian Sea-Indian Subcontinent-BOB) is also dominated by the dynamic processes (Walker et al, 2015). This suggests that the dominant role played by the dynamic processes in regulating moisture transport and regional precipitation not only validates in SWC but prevails over a quite large area.…”

Section: Thermodynamic and Dynamic Control Of Moisture Transportmentioning

confidence: 99%

Tracing changes in atmospheric moisture supply to the drying Southwest China

et al. 2017

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Abstract. Precipitation over Southwest China (SWC) significantly decreased during 1979-2013. The months from July to September (JAS) contributed the most to the decrease in precipitation. By tracing moisture sources of JAS precipitation over the SWC region, it is found that most moisture originates in regions from the northern Indian Ocean to SWC and from South China Sea to SWC. The major moisture contributing area is divided into an extended west region, SWC, and an extended east region. The extended west region is mainly influenced by the South Asian summer monsoon (SASM) and the westerlies, while the extended east region is mainly influenced by the East Asian summer monsoon (EASM). The extended west, SWC, and extended east regions contribute 48.2, 15.5, and 24.5 % of the moisture for the SWC precipitation, respectively. Moisture supply from the extended west region decreased at a rate of −7.9 mm month −1 decade −1 , whereas that from the extended east increased at a rate of 1.4 mm month −1 decade −1 , resulting in an overall decrease in moisture supply. Further analysis reveals that the decline of JAS precipitation is mainly caused by change in the seasonal-mean component rather than the transient component of the moisture transport over the SWC region. In addition, the dynamic processes (i.e., changes in wind) rather than the thermodynamic processes (i.e., changes in specific humidity) are dominant in affecting the seasonal-mean moisture transport. A prevailing easterly anomaly of moisture transport that weakened moisture supply from the Indian Ocean is to a large extent responsible for the precipitation decrease over the SWC region.

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Interannual Variability in the Large-Scale Dynamics of the South Asian Summer Monsoon

Cited by 45 publications

References 90 publications

Teleconnections of Indian monsoon rainfall with AMO and Atlantic tripole

Teleconnections of Indian monsoon rainfall with AMO and Atlantic tripole

Onset and withdrawal of the large‐scale South Asian monsoon: A dynamical definition using change point detection

Tracing changes in atmospheric moisture supply to the drying Southwest China

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