The extremal spatial dependence of significant wave height in the South China sea

The extremal spatial dependence of significant wave height (HS) in the South China Sea (SCS) is discussed by combining altimeter observations of ocean satellites and ERA5 reanalysis dataset from the period 2011-2023. A spatial conditional extremes (SCE) model allowing different classes of extremal dependence is established, which uses a reliable Markov chain Monte Carlo (MCMC) scheme to realize the parameter inference. In this work, four transects are selected in the northern South China Sea (NSCS) and the central South China Sea (CSCS) respectively, which are approximately southwest-northeast (SW-NE) and northwest-southeast (NW-SE), and the HS data is transformed to the standard Laplace scale. The model fitting results show that the extremal dependence characteristics of different regions and directions in the SCS are different. The mean dependence of HS in NSCS decays faster than in CSCS, and the mean dependence on NW-SE transects decays faster than SW-NE transects. In general, the SW-NE transect in CSCS is observed a longer-range extremal dependence, which is potentially related to the storm direction in the SCS.