Using MODIS Land Surface Temperature and Normalized Difference Vegetation Index products for monitoring drought in the southern Great Plains, USA

A near-real time drought monitoring approach is developed using Terra-Moderate Resolution Imaging Spectoradiometer (MODIS) Normalized Difference Vegetation Index (NDVI) and Land Surface Temperature (LST) products. The approach is called Vegetation Temperature Condition Index (VTCI), which integrates land surface reflectance and thermal properties. VTCI is defined as the ratio of LST differences among pixels with a specific NDVI value in a sufficiently large study area; the numerator is the difference between maximum LST of the pixels and LST of one pixel; and the denominator is the difference between maximum and minimum LSTs of the pixels. VTCI is lower for drought and higher for wet conditions. The ground-measured precipitation data from a study area covering parts of the states of Texas and Oklahoma in the southern Great Plains, USA, are used to validate the drought monitoring approach. Linear correlation analysis between VTCI, and total monthly precipitation and departure from normal monthly precipitation shows that VTCI is not only closely related to recent rainfall events but also related to past rainfall amounts, and indicates that VTCI might be a better and a near-real time drought monitoring approach.