Water level Variations of Hulun Lake Monitored with TOPEX/POSEIDON and its Periods Analysis with Fourier Transformation and the Wavelet Transformation

摘要

About 10 years of TOPEX/POSEIDON (T/P) altimetric data which have been corrected, edited, reduced and filtered, have been used to compute a time series of lake levels of Hulun Lake in China. The time series is analyzed with the Fourier transformation and the wavelet transformation, respectively. The mean periods of lake level variations are 1493d, 73Id, 365d and 18Id. The seasonal variation is the main component, and the amplitudes of the annual and semiannual variations are 0.1882 m and 0.1434 m respectively in the least squares sense. So the annual period is the dominant part of the seasonal variation, and the semiannual part is the minor period. The trend of the water level variation of Hulun Lake within 1992-2002 is -0.0875 m/a, which indicates the water level of Hulun Lake is declining.