Using MODIS satellite image to observe long term drought

Soil moisture is an important factor for the exchange of water between the land surface and plant transpiration. It has tremendous effects on agriculture, the environment, the ecological system, weather and climate. It is hard to evaluate the long term land surface dryness by field investigations or a ground survey alone. It has been shown in the literature that using Moderate Resolution Imaging Spectroradiometer (MODIS) satellite images to observe the land surface water content is feasible. A simple land surface dryness index (Temperature - Vegetation Dryness Index, TVDI) can be calculated based on an empirical parameterization of the relationship between the Land Surface Temperature (LST) and the Normalized Difference Vegetation Index (NDVI). In general, the LST and NDVI can be obtained from MODIS products. Another index for monitoring the water condition of the land surface is the Normalized Multi-Band Drought Index (NMDI). Basically, the reflectance difference between two liquid water absorption channels in the short wave infrared (SWIR) is used to describe the moisture content with the near infrared (NIR) channel as the reference. In this study, by using satellite data on the dry season climate as a study case, the comparison of drought sensitivity between the TVDI and NMDI indices is carried out. The preliminary results archived by visual comparisons between TVDI and NMDI indicated that between the two datasets.