| 21 Jul 2026
cSINGV v1.0: Development and evaluation of a 1.5 km coupled atmosphere-ocean-wave modelling system for the Western Maritime Continent
Abstract. This study presents cSINGV v1.0, a high-resolution (1.5 km) regional coupled atmosphere–ocean–wave modelling system developed for the Western Maritime Continent (WMC). The system integrates a convection-permitting atmospheric model (SINGV) with newly configured ocean (NEMO) and wave (WAVEWATCH III) components within a unified coupling framework based on the Regional Coupled Suite and OASIS3-MCT coupler. The primary contribution of this work lies in the development of a fully coupled system enabling two-way interactions between atmosphere, ocean, and waves at kilometre scale. The ocean and wave components are specifically configured and optimised for the WMC, a region characterised by complex coastlines, shallow seas, and strong air–sea interactions.
The model is evaluated using a six-month simulation (January–June 2019) against multiple observational and reanalysis datasets. The ocean and wave components show good agreement with reference datasets, with sea surface temperature errors generally below 0.5 °C and significant wave height errors around 0.2 m. The influence of coupling is assessed by comparing the coupled and uncoupled atmospheric configurations. Results show that coupling improves the spatial organisation of precipitation, the diurnal cycle over the ocean, and the offshore propagation of convection, while differences in near-surface atmospheric variables remain modest. Process-based analysis indicates that these improvements are primarily linked to enhanced latent heat flux driven by thermodynamic air–sea feedbacks associated with sea surface temperature variability. Case studies of Sumatra squall events further indicate that coupling can influence the organisation and persistence of eastward-propagating convection, with the magnitude of this impact depending on the dominant convective regime. Overall, cSINGV provides a physically consistent framework for representing coupled processes in the WMC and offers a useful platform for investigating air–sea–wave interactions at convection-permitting scales.
General comments
The manuscript describes the UK Met Office regional coupled modelling suite configured for the Singapore region and highlights the performance for the first half of 2019. Two-way coupling improved precipitation and the diurnal cycle over the oceans compared to an atmosphere-only simulation. The focus lies in understanding air-sea interactions and their impact on regional weather, particularly on momentum transfer and large-scale precipitation. The structure of the manuscript could see a few improvements, mainly for readability, clarity, and focus. One major concern is the role of both tuning and evaluation of ocean-only and wave-only components, specifically the wave part for Betamax with a value of 1.75 (Appendix A). It contradicts the primary objective, "the development of a fully coupled system enabling two-way interaction" (line 15-16). The parameter is significantly higher than the Met Office value of 1.39 and is equivalent to that from an ERA5-driven wave hindcast (Alday et al., 2021, https://doi.org/10.1016/j.ocemod.2021.101848). The Miles-Janssen-type wind input is known to significantly increase wave feedback to the atmosphere through the Charnock coefficient in two-way coupled simulations and reduce surface wind speed. In addition, the manuscript could benefit from a clearer description of the coupled system and its components, to support the results of fully coupled and atmosphere-only (uncoupled) simulations presented in section 4. If the coupled system is valid, then surface variables and diagnostics will improve and agree well with observations. On the ocean side, similar concerns as for the waves. "Sensitivity experiments were conducted to optimise configuration choices, including light penetration schemes and bulk forcing formulations, resulting in improved SST representation […]" on lines 156-157 sideline any form of coupling feedback entirely. The total water-side stress is equivalent to the air-side stress only if the wave field is in equilibrium, ie., the sum of wind input, dissipation and nonlinear interaction is zero. Most of the time, the wave field is not in equilibrium, which means that the air-side stress differs from the water-side stress. Atmosphere-wave-ocean coupler should take care of the flux exchange in the wave boundary layer, i.e., similar to Figure 8 in Breivik et al. (2015, https://doi.org/10.1002/2014JC010565).
Specific comments