Balkhash Lake Level Variations Monitored with Satellite Altimeter and Satellite Gravity Data

About 10 a(1992~2002) of TOPEX/Poseidon(T/P) and 6 a(2003~2008) Jason-1 altimetry data which have been corrected,edited,reduced and filtered,have been used to compute time series of lake level for Balkhash Lake.The time series is analyzed with Fourier transform and wavelet transformation,respectively.The mean periods are 1 007 d,364 d,313 d and 184 d.The amplitudes of annual and semiannual variations are 0.141 8 m and 0.035 m respectively based on the least square approach.The trend of water level variation of Balkhash Lake is +0.092 m/a,which indicates the water level is ascending.The gravity anomaly is also monitored with GRACE data.The mean change periods of gravity anomaly are 1 019 d,366 d and 186 d with Fourier transform and wavelet transformation,respectively.The amplitudes of annual and semiannual variations are 0.573 1 mGal and 0.091 8 mGal respectively based on the least square approach.The correlation coefficient and confidence level between water level change monthly and gravity anomaly is respectively 0.772 9 and 99%,which indicates the two kinds of data have a stronger correlation.Analysis of the correlation between NINO3.4 SST and water level change of Balkhash Lake shows NINO3.4 SST has a lag influence on the water variation of Balkhash Lake.When the lag is about 5 months,the correlation coefficient between them is max.