[A-OS10] Continental Oceanic Mutual Interaction - Planetary Scale Material Circulationn

[AOS10-04] An ocean-atmosphere wave number-4 pattern in the southern subtropics

*Swadhin Behera¹, Balaji Senapati², Mihir Dash² (1.Application Laboratory, JAMSTEC, 3173-25 Showa-machi, Yokohama 236-0001, 2.Centre for Oceans, Rivers, Atmosphere and Land Sciences, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal, India)

Keywords:wave number 4 , coupled, ocean and atmosphere

A stationary zonal wavenumber-4 (W4) pattern is revealed in Southern subtropics from an empirical orthogonal function analysis in the sea surface temperature (SST) anomalies. A thermodynamic coupling of atmosphere and the upper ocean helps in generating the W4 pattern, which later terminates due to the breaking of the ocean-atmosphere positive feedback. This W4 pattern is found to be seasonally phase-locked to the austral summer (persists up to mid-autumn) and independent of other known tropical and extra-tropical climate phenomena. During the positive phase of the W4 event, the cold SST anomaly develops over the south- eastern and -western side (SE-NW) of Australia creating an anomalous divergence circulation. It favours the moisture transport towards the southeastern region of the continent. Consequently, the specific humidity increases and causes an above-normal rainfall in a SE-NW axis over Australia. An opposite process is seen in case of a negative W4 event.