Abstract
The distinct winter temperature difference between the eastern South China Sea (ESCS) and western South China Sea (WSCS) has a crucial impact on regional air–sea interactions. By utilizing satellite and reanalysis data, the zonal contrasting winter thermal conditions and their formation mechanisms are investigated. The second empirical orthogonal function (EOF) mode of winter sea surface temperature (SST) anomalies is responsible for this east–west contrasting temperature pattern (EWCTP), with warming (cooling) in the ESCS (WSCS) and cooling (warming) in the WSCS (ESCS) during the positive (negative) phase events. A mixed layer heat budget analysis reveals that the net heat flux plays a primary role in the WSCS. In the ESCS, the temperature variation is instead mainly dominated by the horizontal heat advection term. In the positive phase events, an anomalous cyclonic circulation promotes an eastern boundary current (EBC) anomaly, which enhances the northward heat transport and thus warms the ESCS. In contrast, an anomalous anticyclonic circulation pattern weakens the heat transport by the southward EBC anomaly and cools the ESCS in the negative phase events. The water exchange through the Mindoro Strait and the vertical entrainment term also contribute to the ESCS SST anomalies. Further analyses show that although there are many EWCTP events that co-occur with the central Pacific El Niño-Southern Oscillation (CP ENSO) events, they have a complex relationship. The EWCTP could appear without CP ENSO events and some CP ENSO events do not lead to the EWCTP. It is because of the different temperature state in the WSCS and ESCS during October–December months and the different contributions of net heat flux and ocean processes to the temperature changes during October–February months.
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Data availability
The SODA3.4.2 dataset is obtained from http://www.soda.umd.edu/. OISST_v2 is from website http://apdrc.soest.hawaii.edu/data/data.php. Geostrophic current data is from http://marine.copernicus.eu/services-portfolio/access-to-products/?option=com_csw&view=details&product_id=SEALEVEL_GLO_PHY_L4_REP_OBSERVATIONS_008_047. ERA- Interim wind data is from https://apps.ecmwf.int/datasets/data/interim-full-moda/levtype=sfc/. TropFlux data product is download from https://incois.gov.in/tropflux/.
Code availability
The program codes in this study is finished by software Matlab and Python.
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Acknowledgements
We appreciate the anonymous reviewers for their helpful comments and thoughtful suggestions to improve this paper. The data used in this study are appreciated. The SODA3.4.2 dataset is obtained from http://www.soda.umd.edu/. OISST_v2 is from website http://apdrc.soest.hawaii.edu/data/data.php. Geostrophic current data is from http://marine.copernicus.eu/services-portfolio/access-to-products/?option=com_csw&view=details&product_id=SEALEVEL_GLO_PHY_L4_REP_OBSERVATIONS_008_047. ERA-Interim wind data is from https://apps.ecmwf.int/datasets/data/interim-full-moda/levtype=sfc/. TropFlux data product is download from https://incois.gov.in/tropflux/. This research was supported by the National Natural Science Foundation of China (42076209, 41776025, 41606030 and 41776026), Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) (GML2019ZD0306), and the Rising Star Foundation of the South China Sea Institute of Oceanology (NHXX2019WL0101), the National Natural Science Foundation of China (41776026), the Pearl River S&T Nova Program of Guangzhou (201906010051), the Science and Technology Planning Project of Guangzhou City, China (202102080363), and the Nation Key Research and Development Program (2011YFA0603201).
Funding
This research was supported by the National Natural Science Foundation of China (42076209, 41776025, 41606030 and 41776026), Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) (GML2019ZD0306), and the Rising Star Foundation of the South China Sea Institute of Oceanology (NHXX2019WL0101), the National Natural Science Foundation of China (41776026), the Pearl River S&T Nova Program of Guangzhou (201906010051), the Science and Technology Planning Project of Guangzhou City, China (202102080363) and the Nation Key Research and Development Program (2011YFA0603201).
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Conceptualization and methodology is provided by ZL, LZ. and QW; ZL analyzed the data and wrote the manuscript; all authors reviewed, edited and approved the final manuscript.
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Liang, Z., Zeng, L., Wang, Q. et al. Interpretation of interannual variability of the zonal contrasting thermal conditions in the winter South China Sea. Clim Dyn 58, 1439–1457 (2022). https://doi.org/10.1007/s00382-021-05968-6
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DOI: https://doi.org/10.1007/s00382-021-05968-6