Response Differences of MODIS-NDVI and MODIS-EVI to Climate Factors

To evaluate and provide an appropriate theoretical direction for research into climate-vegetation interactions using meteorological station data at different time scales, we examined differences between the Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) and their responses to climate factors. We looked for correlations between data extracted from MOD13Q1 remote sensing images and meteorological station data for the two indexes. The results showed that even though NDVI and EVI are derived from the same remote sensing image, their response to climate factors was significantly different. In the same meteorological station, the correlation coefficients for NDVI, EVI and climate factors were different; correlation coefficients between NDVI, EVI and climate factors varied with meteorological station. In addition, there was a lag effect for responses of NDVI to average minimum temperature, average temperature, average vapor pressure, minimum relative humidity, extreme wind speed, maximum wind speed, average wind speed and average station air-pressure. EVI had a lag only for average minimum temperature, average vapor pressure, extreme wind speed, maximum wind speed and average station air-pressure. The lag period was variable, but most were in the -3 period. Different vegetation types had different sensitivities to climate. The correlation between meteorological stations and vegetation requires more attention in future research.