Comparison and evaluation of remote sensing indices for agricultural drought monitoring over Kazakhstan

Drought has a significant impact on the Kazakhstan's agricultural economy, which is the world's largest wheat flour exporting country. Remote sensing provides an efficient tool for monitoring agricultural drought in a wide range. Hundreds of remote sensing drought indices have been developed during the past decades. Some of them have been widely used over the world as an indispensable indicator in drought monitoring systems. However, the applicability of those indices in Kazakhstan, the largest country in Central Asia has not been tested, especially for agricultural drought monitoring. In this study, the most common remote sensing drought indices in current running systems of drought monitoring are compared and evaluated. The response of those indices to the soil drought is validated based on remote sensing soil moisture data. In addition, the effectiveness of remote sensing indices in agricultural drought monitoring is assessed according to agricultural product yield data from the past 15 years (2004-2018). Results indicate that remote sensing drought indices can generally reflect serious drought events in the study area, but the consistency of different types of indices is poor. Compared with annual statistics of agricultural product yield, remote sensing drought index better reflects the long-term change of agricultural drought in Kazakhstan.