RSS published a spatially explicit and transferable approach to mapping drought with remote sensing this month. All the model's input variables are available at no cost and at a global extent, making it transferable to any area of interest on the planet with comparable results. The paper describes how our method was run and calibrated over a study site in USA (chosen for the country's rich availability of data), before being tested in South Africa and Zimbabwe.
The figure displayed here shows the model outputs for months in a drought year (2012) and during a non-drought year (2014), and gives an example of how well the modeled results match the spatial patterns seen in the reference (US Drought Monitor's map for the same time period).
Access the full publication here