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ation the freency doa， particularly the case of earth， can potentially have a significant effect on its surface cliate syste through lar lation variation (cf berr 1988)

to give an overview of the long-ter 插n periodicity plaary orbital otion， we perford any fast fourier transforations (ffts) along the ti axis， and superposed the resultg periodgras to draw o-dsional ti–freency aps the specific approach to drag these ti–freency aps this paper is very siple – uch sipler than the wavelet analysis or laskars (1990， 1993) freency analysis

divide the low-pass filtered orbital data to any fragnts of the sa length the length of each data segnt should be a ultiple of 2 order to apply the fft

each fragnt of the data has a lar overlappg part: for exaple， when the ith data begs fro t=ti and ends at t=ti+t， the next data segnt rans fro ti+δt≤ti+δt+t， where δt?t we ntue this division until we reach a certa nuber n by which tn+t reaches the total tegration length

we apply an fft to each of the data fragnts， and obta n freency diagras

each freency diagra obtaed above， the strength of periodicity can be replaced by a grey-scale (or lour) 插rt

we perfor the replacent， and nnect all the grey-scale (or lour) 插rts to one graph for each tegration the horizontal axis of these new graphs should be the ti， ie the startg tis of each fragnt of data (ti， where i= 1，…， n) the vertical axis represents the period (or