Note on use of NDVI
The CDI monitoring tool explores the use of three climatic conditions that influence drought conditions. This includes rainfall, temperature and the Normalised Vegetation Drought Index (NVDI) which is a proxy of soil moisture. The NDVI is a dimensionless index that describes the difference between visible and near-infrared reflectance of vegetation cover and can be used to estimate the density of greenness on an area of land.
Since the beginning of 2021, there has been a poor correlation of the NDVI and the ground information, therefore resulting to false values of CDI. In this regard, the use of NDVI in generating CDI values has been halted. Meanwhile, SWALIM is in the process of looking for alternative component to represent soil moisture in place of NDVI
The current values of CDI shown on the map does not include the NDVI values rather a combination of temperature and rainfall.
List of Acronyms
CDI: Combined Drought Index
PDI: Precipitation Drought Index
TDI : Temperature Drought Index
NDVI : Normalized Difference Vegetation Index
RFE : Rainfall Estimates