Characteristics of Gravity Wave-Excited Disturbances Observed in HFSWR Ocean-Ionosphere System During Typhoons

In this study, the intricate gravity wave-excited disturbances in the ocean-ionosphere system is investigated using the high-frequency surface wave radar (HFSWR) data measured during typhoons. To address the nonstationarity of HFSWR echoes during typhoons, a multilayer denoising preprocessing model based on local mean decomposition is introduced. For qualitative analysis of the disturbance relationship between the ocean and ionosphere at smaller time scales, a fuzzy equivalence coefficient based on HFSWR chaotic attractors is designed, integrating fuzzy set theory. To maximize the presentation of the disturbance characteristics excited by gravity waves, an adaptive optimization method based on the fuzzy equivalence coefficients of HFSWR chaotic attractors is constructed. In summary, an adaptive fuzzy evaluation method based on HFSWR chaotic attractors to characterize the nonlinear evolution process of HFSWR oceanic-ionospheric echoes excited by gravity waves is proposed in this paper. Disturbance features in HFSWR oceanic echoes that exhibit the same evolution trends as traveling ionospheric disturbances (TIDs) excited by gravity waves are successfully identified in this study, thus confirming the presence of gravity wave-excited disturbances in HFSWR ocean-ionosphere system. Experimental studies also demonstrate the validity of the proposed adaptive fuzzy evaluation approach.