Study on NDVI Periodic Change Characteristics of Inner Mongolia Grassland Based on Variational Mode Decomposition Algorithm

Based on the NDVI data of vegetation in Inner Mongolia from 1982 to 2015, variational mode decomposition (VMD) method, which has been well applied field signal decomposition, is introduced study periodicity index Mongolia. The VMD method used extract monthly and annual long time series cycle characteristics temperature precipitation same period April October 2015 results show that are important factors affecting growth vegetation, there 6.99 3.49 months oscillation for series; when central frequency same, amplitude increases with increase lag period. scale 16.95, 6.8a, 4.85a precipitation, 6.8a temperature. Residue component shows overall have shown a significant slow trend past 30 years. Although decline (p = 0.000), grassland still process continuous improvement.