Tracking air-sea exchange and upper-ocean variability in the Indonesian-Australian basin during the onset of the 2018/19 Australian summer monsoon

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2020-08-01
Authors
Feng, Ming
Duan, Yongliang
Wijffels, Susan E.
Hsu, Je-Yuan
Li, Chao
Wang, Huiwu
Yang, Yang
Shen, Hong
Liu, Jianjun
Ning, Chunlin
Yu, Weidong
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10.1175/BAMS-D-19-0278.1
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Abstract
Sea surface temperatures (SSTs) north of Australia in the Indonesian–Australian Basin are significantly influenced by Madden–Julian oscillation (MJO), an eastward-moving atmospheric disturbance that traverses the globe in the tropics. The region also has large-amplitude diurnal SST variations, which may influence the air–sea heat and moisture fluxes, that provide feedback to the MJO evolution. During the 2018/19 austral summer, a field campaign aiming to better understand the influences of air–sea coupling on the MJO was conducted north of Australia in the Indonesian–Australian Basin. Surface meteorology from buoy observations and upper-ocean data from autonomous fast-profiling float observations were collected. Two MJO convective phases propagated eastward across the region in mid-December 2018 and late January 2019 and the second MJO was in conjunction with a tropical cyclone development. Observations showed that SST in the region was rather sensitive to the MJO forcing. Air–sea heat fluxes warmed the SST throughout the 2018/19 austral summer, punctuated by the MJO activities, with a 2°–3°C drop in SST during the two MJO events. Substantial diurnal SST variations during the suppressed phases of the MJOs were observed, and the near-surface thermal stratifications provided positive feedback for the peak diurnal SST amplitude, which may be a mechanism to influence the MJO evolution. Compared to traditionally vessel-based observation programs, we have relied on fast-profiling floats as the main vehicle in measuring the upper-ocean variability from diurnal to the MJO time scales, which may pave the way for using cost-effective technology in similar process studies.
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Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Bulletin of the American Meteorological Society 101(8), (2020): E1397-E1412, https://doi.org/10.1175/BAMS-D-19-0278.1.
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Feng, M., Duan, Y., Wijffels, S., Hsu, J., Li, C., Wang, H., Yang, Y., Shen, H., Liu, J., Ning, C., & Yu, W. (2020). Tracking air-sea exchange and upper-ocean variability in the Indonesian-Australian basin during the onset of the 2018/19 Australian summer monsoon. Bulletin of the American Meteorological Society, 101(8), E1397-E1412.
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