Vegetation monitoring with surface bi-directional reflectivities in MODIS near-IR and mid-IR channels

This paper proposed to study a Vegetation Index (VI) with surface bi-directional reflectivities in MODIS near-IR and mid-IR channels. Considering the fact that the observations in mid-IR at satellite altitude during daytime consist of a combination of both reflected radiance due to sun irradiance and emitted radiance from both the surface and the atmosphere, a brief description of estimating the land surface bi-directional reflectivity in mid-IR channels from MODIS data was given. Sensitivity analysis of the vegetation index with regard to the variations of horizontal visibility was performed. The results showed that the proposed vegetation index is much less sensitive to haze in the atmosphere than the Normalized Difference Vegetation Index (NDVI). In addition, in order to compare the traditional NDVI with the new VI, NDVI and VI were calculated using MODIS data acquired over a region of Western Europe (Spain), for cloud-free days, covering a period of one month, July, 2006. The result of this comparison indicated that the proposed new vegetation index is feasible to descript the properties of vegetation and to determine the classification of vegetation, especially in the areas covered by dense smoke or industrial pollution.