Analyze the Vegetation Cover Variation Cycle of China from NOAA Data
利用NOAA数据分析中国地区植被覆盖变化周期

This paper applies the Harmonic Analysis of Time Series(HANTS) analysis to study the AVHRR Normalized Difference Vegetation Index(NDVI) time series images of China area.The HANTS algorithm can successfully reduce the cloud effect and at the same time output Fourier components.The Fourier components are used to analyze the variation characteristics of vegetation growing cycle and then study the vegetation cover in regional scale.Analyze the Fourier components of NDVI data after HANTS processing and find that the 0th-order harmonic,or the mean NDVI,indicates overall vegetation cover,and the first and second harmonics of the HANTS analysis concisely summarize the amplitude and phase of annual and biannual values of NDVI data.The amplitude of the 1~(st) harmonic indicates the variability of vegetation cover over the year.The phase of the 1~(st) harmonic summarized the timing of vegetation green-up.The 2~(nd) harmonic indicates the strength and timing of any biannual signal.