An Examination of Circulation Characteristics in the Luzon Strait and the South China Sea Using High‐Resolution Regional Atmosphere‐Ocean Coupled Models

Abstract

Sea surface winds and water transports through the Luzon Strait (LS) are two main factors that force the circulations in the South China Sea (SCS). Typically, a sandwich‐like inflow‐outflow‐inflow structure in the LS and a corresponding three‐layer cyclonic‐anticyclonic‐cyclonic circulation structure in the SCS have been identified. In this study, the impact of model resolution on the simulation of SCS circulations is investigated through examining the circulation features in different resolution coupled models of the Asia‐Pacific Regional Coupled Prediction (AP‐RCP) system at the Qingdao Pilot National Laboratory for Marine Science and Technology (QNLM). The AP‐RCP system of QNLM consists of a 9‐km resolution Regional Ocean Model System (ROMS) coupled with a 27‐km resolution Weather Forecast and Research (WRF) atmosphere model (9v27) and a 3‐km ROMS coupled with a 9‐km WRF (3v9). Results show that compared to the 9‐km case, the 3‐km resolution ocean model can distinctly depict the topography of Bashi Channel and Luzon Trough, thus simulating the deep circulations of the LS more accurately. In addition, with more mesoscale air‐sea interactions, the 3v9 model has better simulation of Kuroshio structure and strength as well as upper layer SCS circulations than the 9v27 model. Our results affirm that due to better representation of complex topography at the LS and eddy‐current interactions in the Kuroshio area, the enhanced‐resolution coupled model can simulate the LS overflow and Kuroshio intrusion more accurately, which may help to improve the simulation and prediction for SCS circulations and mesoscale activities once the observations are sufficient in the future.

Volume and Heat Transport in the South China Sea and Maritime Continent at Present and the End of the 21st Century

“…This sheared vertical structure (i.e., inflow in the upper layer accompanied by outflow in the intermediate layer) is more pronounced in winter at approximately 20°N. This sheared vertical structure is somewhat similar to a few earlier studies investigating the annual structure of the Luzon Strait (e.g., Jiang et al., 2020; Qu, 2002), however three‐layer structure along the cross‐section (e.g., Zhu et al., 2019) is not pronounced. The Kuroshio intrusion enters the SCS carrying warmer and saltier water from the western Pacific Ocean (e.g., Nan et al., 2015 ).…”

“…Consequently, there are several regional ocean model‐based simulations to study SCS dynamics and Luzon transport, such as, with Modular Ocean Model version‐2 at 1/4° (Qu et al., 2004), and Princeton Ocean Model at ¼‐2° (Hsin et al., 2012; Wei et al., 2009). Of late, with the availability of better computing resources, higher resolution regional model studies have also been initiated over SCS (Fang et al., 2005; Jiang et al., 2020; Li et al., 2019; Liang et al., 2019; Liu & Gan, 2017; Nan et al., 2013).…”

“…Consequently, there are several regional ocean model-based simulations to study SCS dynamics and Luzon transport, such as, with Modular Ocean Model version-2 at 1/4° (Qu et al, 2004), and Princeton Ocean Model at ¼-2° (Hsin et al, 2012;Wei et al, 2009). Of late, with the availability of better computing resources, higher resolution regional model studies have also been initiated over SCS (Fang et al, 2005;Jiang et al, 2020;Li et al, 2019;Liang et al, 2019;Liu & Gan, 2017;Nan et al, 2013). However, all these studies are either focused on a short period of simulation, the northern SCS (e.g., Jilan, 2004), SCS-averaged layer circulation (e.g., Gan et al, 2016), the ITF region, the Kuroshio region, or different aspects of SCS that are unrelated to SCS transport.…”

Contourite processes associated with the overflow of Pacific Deep Water within the Luzon Trough: Conceptual and regional implications

“…2-5). No observation of cross-trough variations in the along-trough flow has been reported for the main Luzon Trough, yet a numerical simulation revealed the presence of the counter-current in the northern and middle Luzon Trough (Jiang et al, 2020). The occurrence and behaviour of the OPDW counter-current urgently call for long-term, cross-trough observations of the Luzon Trough.…”

Distribution and microbial degradation of dissolved organic carbon in the northern South China Sea

“…These basin-wide surface circulation gyres effectively isolate the interior SCS from the influence of land runoff. Moreover, the Kuroshio intrusion through the Luzon Strait located at the northeastern rim also has an important impact on the circulation in the northern SCS, which is stronger in winter and weaker in summer (Nan et al, 2015;Jiang et al, 2020). Under the influence of seasonal atmospheric and oceanic forcing, the oceanic biogeochemistry in the SCS varies in space and time.…”