利用NOAA数据分析中国地区植被覆盖变化周期

Analyze the Vegetation Cover Variation Cycle of China from NOAA Data

对中国地区连续数年的改进的高解析度传感器(AVHRR)均一化植被指数(NDVI)时间序列数据进行研究,利用时间序列谐波分析(HANTS)算法对NDVI数据进行去云处理,同时计算NDVI时间序列的特征分量,用以分析地表植被覆盖的生长周期性变化特性,从而了解地表植被覆盖情况。研究HANTS之后提取出的NDVI傅里叶特征分量,得知0频率表明了全年植被覆盖率均值,1、2频率谐波分量简明地描述了观测点的全年与半年幅值与相位值;1频率谐波的幅值表明了全年中植被生产率的变化,1频率谐波的相位值表明了植被绿度的时间变化快慢;2频率谐波表示的是半年的植被覆盖强度以及时间变化率。

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＂ harmonic indicates the variability of vegetation cover over the year. The phase of the 1st harmonic summarized the timing of vegetation green-up. The 2nd harmonic indicates the strength and timing of any biannual signal.