Altimetry-derived ocean thermal structure reconstruction for the Bay of Bengal cyclone season
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Altimetry-derived ocean thermal structure reconstruction for the Bay of Bengal cyclone season Fangjie Yu 1,2 & Xuan Zhang 1 & Xin Chen 1 & Ge Chen 1,2 Received: 24 October 2018 / Accepted: 9 September 2020 / Published online: 21 September 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The ocean thermal structure (OTS) is a significant element that affects tropical cyclone (TC) intensities, as energy drawn from the ocean fuels TCs. Satellite altimetry can be used to derive the OTS for TC research. The cooling of sea surface temperature (SST) caused by TCs is closely related to the OTS and differs according to differences in the OTS in different regions. However, the accuracy of existing methods in spatially describing the OTS is not sufficient. To overcome the limited resolution and accuracy of current OTS-derived methods, a ridge regression model is proposed for the Bay of Bengal (RRBOB) in this paper to derive isotherms for 47 layers (D5–D28) from satellite altimetry data and from in situ Argo thermal profiles. RRBOB improves the derivation accuracy by allowing small deviations to achieve higher precision than unbiased estimators. Compared with in situ observations, most errors are limited to within 20%. The accuracy of the derivations is within a reasonable range, and no significant biases are observed. Although the ridge regression derivation method has limitations in predicting the temperature inversion, which occurs in the northern of the BOB during the periods of post monsoon and winter, the derivation can characterize the subsurface OTS in detail in most regions. The ability to monitor the subsurface ocean will improve seasonal predictions of TCs. Keywords Ocean thermal structure . Tropical cyclones . Tropical cyclone–ocean interaction . Ridge regression derivation
1 Introduction Tropical cyclones (TCs) are known to have strong thermal impacts on oceans. During the passage of TCs, the strong wind stress on the sea surface causes entrainment mixing and dynamic upwelling, followed by a decrease in the sea surface temperature (SST) (Mei and Pasquero 2013; Morey et al. 2006; Price 1981; Zhan and Wang 2016; Zhang et al. 2016). This negative feedback is a key part of the process of TC strengthening (Androulidakis et al. 2016; Hegde et al. 2016; Lin et al. 2009; Mei and Pasquero 2013). This phenomenon not only reduces the contrast between ocean and atmospheric temperatures but also significantly reduces the TC oceanic energy supply transferred by heat flux (Gallacher Responsible Editor: Pierre F.J. Lermusiaux * Ge Chen [email protected] 1
College of Information Science and Engineering, Ocean University of China, Qingdao, People’s Republic of China
2
Laboratory for Regional Oceanography and Numerical Modeling, Qingdao National Laboratory for Marine Science and Technology, Qingdao, People’s Republic of China
et al. 1989; Morey et al. 2006; Reynolds 1993; Yang et al. 2016). The cooling of SSTs caused by TCs is closely related to the ocean thermal structure (OTS) and varies according to
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