Detection of intraseasonal oscillations in the Bay of Bengal using altimetry

Atmospheric Science Letters

Bulusu Subrahmanyam¹  Corinne B. Trott¹ 

[1] School of the Earth, Ocean, and Environment University of South Carolina Columbia South Carolina;

关键词: altimetry;    Bay of Bengal;    intraseasonal oscillations;    Madden‐Julian oscillation;   

DOI  :  10.1002/asl.920

来源: DOAJ

【 摘 要 】

Abstract Air–sea and mixed layer dynamics in the Bay of Bengal (BoB) respond strongly to Intraseasonal Oscillations (ISOs) that primarily operate on three observed time scales: the 30–90 day Madden‐Julian Oscillation, the 10–20 day quasi‐biweekly oscillation, and the synoptic‐scale 3–7 day oscillation of the monsoon trough. In this research, we focus on local and basin‐wide signals, zonal and meridional propagation, and variability of ISOs with respect to the strength of the summer monsoon season over a multi‐decadal period (1993–2016). For the first time, this study examines the relationship between larger‐ and shorter‐period ISOs in SLA and shows the usefulness of altimetry data in Indian monsoon studies. We compare ISOs in SLA during years with summer monsoons of varying strengths, finding notably stronger circulation and larger amplitude of all ISOs in years with stronger summer monsoons theorized in part to be due to the first‐baroclinic mode forcing from low‐level winds (R2 values of 0.61, 0.67, and 0.64 in the northern, central, and southern Bay, respectively), although it is important to note the influence of other local forcings, such as mesoscale eddies and coastal Kelvin waves. We demonstrate that 30–90 day variability of SLA is initially forced by equatorial processes and strengthened by local processes in the BoB, as higher‐amplitude SLA ISOs were consistently observed in the southern and eastern Bay. Local processes like coastal Kelvin waves were found to strongly influence the 10–20 day quasi‐biweekly signal, as was seen in the high‐amplitude 10–20 day SLA ISOs found in the eastern BoB. The synoptic signal also revealed a zonal pattern consistent with coastal Kelvin wave intensification and eddy generation.

【 授权许可】

Unknown