Sea level change nonlinear trend extraction method

Abstract

The invention relates to a sea level change nonlinear trend extraction method, which comprises the following steps of decomposing a sea level change time sequence by utilizing an empirical mode decomposition method to obtain an intrinsic mode function and a trend term with different frequencies; eliminating a low-frequency false component by using a modal function method, and marking and eliminating a high-frequency noise component by using a frequency divergence method; sequentially carrying out frequency spectrum analysis by adopting a Fourier method to obtain frequencies corresponding to the peak values in each component frequency spectrogram, removing the invalid frequencies according to a Nyquist theorem, and converting the frequencies into periods; obtaining all possible embedded calculation windows, through the singular spectrum analysis, taking the trend term of empirical mode decomposition as a reference, and selecting the trend term with the minimum difference as the final nonlinear trend of the sea level change. According to the method, the automatic selection of the optimal window and the automatic extraction of the optimal sea level change trend can be realized, the adaptability is good, the efficiency is high, the trend extraction is stable, and the influence of the time sequence length is small.

Description

technical field [0001] The invention relates to the technical field of sea level monitoring, in particular to a method for extracting nonlinear trends of sea level changes. Background technique [0002] At present, the methods for nonlinear trend extraction of sea level can be divided into two categories: modeling methods and non-modeling methods according to whether prior modeling is required. [0003] The modeling method assumes that the sea level change process conforms to the characteristics of a certain nonlinear function, so that the sea level change time series is fitted with a function to obtain a nonlinear trend; the non-modeling method decomposes the sea level change time series into several different scales , it is considered that each scale corresponds to a certain periodic component, and the largest scale signal is selected as the trend item. Both modeling methods and non-modeling methods still have various deficiencies. For example, the assumptions of modeling...

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Problems solved by technology

[0016] The present invention mainly solves the problems existing in the existing sea level change trend method; it provides a combination of empirical mode decomposition and singular spectrum analysis, which is less affected by the signal length and can greatly improve the calculation efficiency of sea level change nonlinear trend extraction A method with accuracy

[0017] Another purpose of the present invention is to solve the existing problems of the existing methods; provide a method for extracting the nonlinear trend of sea level change combined with empirical mode decomposition and singular spectrum analysis, which can overcome the shortcomings of the lack of adaptability of singular spectrum analysis, without the need for Manual intervention, the efficiency of the method is greatly improved under the condition of ensuring accuracy, and a nonlinear trend extraction method of sea level change that can handle any time series can be widely used in nonlinear trend extraction or downtrend analysis of various time series

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