The first six Chebyshev polynomial coefficients (i.e., A00, A01, A10, A11, A02, A20) were derived from monthly mean geopotential height over East Asia for the period 1951-1983. Spectral analysis of these coefficients ...The first six Chebyshev polynomial coefficients (i.e., A00, A01, A10, A11, A02, A20) were derived from monthly mean geopotential height over East Asia for the period 1951-1983. Spectral analysis of these coefficients reveals relative maxima of power in the frequency bands of 200 months (- 16.7 years), 25 months (the quasi-biennial oscillation), 5-6 months, and 2-3 months. Cross-spectral characteristics between Chebyshev coefficients and the Southern Oscillation Index (SOI) were also explored. Coherence spectrum for the zonal and meridional circulation index (A01 and A 10) with the SOI was significant near 4 years, the QBO, and 2-3 months. Some physical explanations were offered for the spatial linkages (i.e., teleconnections) between the SO and atmospheric circulation anomalies overEast Asia.展开更多
A method for evaluating the fluctuation of the reverberation envelope is proposed and examined through simulation and real data in this paper.This method is different from the coefficient of variation which is only a ...A method for evaluating the fluctuation of the reverberation envelope is proposed and examined through simulation and real data in this paper.This method is different from the coefficient of variation which is only a function of the first and second order moment of the reverberation statistical model.By using the standard variance of the mean square derivate(MSD) of the reverberation envelope,the paper shows that the reverberation fluctuation is a function of the bandwidth of the emitted signal,and that a large value of the square variance means little fluctuation of the reverberation envelope.Theoretical studies show that the standard variance is proportional to the bandwidth of the emitted signal,so we conclude that less time width or larger bandwidth of the transmitted signal produces less fluctuation.Simulation and real active sonar data processing are used to verify this conclusion.展开更多
文摘The first six Chebyshev polynomial coefficients (i.e., A00, A01, A10, A11, A02, A20) were derived from monthly mean geopotential height over East Asia for the period 1951-1983. Spectral analysis of these coefficients reveals relative maxima of power in the frequency bands of 200 months (- 16.7 years), 25 months (the quasi-biennial oscillation), 5-6 months, and 2-3 months. Cross-spectral characteristics between Chebyshev coefficients and the Southern Oscillation Index (SOI) were also explored. Coherence spectrum for the zonal and meridional circulation index (A01 and A 10) with the SOI was significant near 4 years, the QBO, and 2-3 months. Some physical explanations were offered for the spatial linkages (i.e., teleconnections) between the SO and atmospheric circulation anomalies overEast Asia.
基金supported by the Foundation of Underwater Information Processing and Control National Key Lab (Grant No. 9140C2304090-60C23)the Foundation of National Defense Basement Research(Grant No. 9140A5030409HK0337)
文摘A method for evaluating the fluctuation of the reverberation envelope is proposed and examined through simulation and real data in this paper.This method is different from the coefficient of variation which is only a function of the first and second order moment of the reverberation statistical model.By using the standard variance of the mean square derivate(MSD) of the reverberation envelope,the paper shows that the reverberation fluctuation is a function of the bandwidth of the emitted signal,and that a large value of the square variance means little fluctuation of the reverberation envelope.Theoretical studies show that the standard variance is proportional to the bandwidth of the emitted signal,so we conclude that less time width or larger bandwidth of the transmitted signal produces less fluctuation.Simulation and real active sonar data processing are used to verify this conclusion.
