NDDI - Normalized Difference Drought Index

NDDI Normalized Difference Drought Index

The Normalized Difference Drought Index (NDDI) is a drought monitoring and early warning tool that is used to assess the severity and duration of drought conditions. It is a vegetation-based index that uses satellite imagery to measure the difference between the near-infrared (NIR) and visible (VIS) bands of light reflected by vegetation.

NDDI is calculated as:

In which Normalized Vegetation Index is calculated as follow: 

And normalized difference water index: 

where NDVI is the Normalized Difference Vegetation Indexand NDWI is the Normalized Difference Water Index

The NDDI values range from -1 to 1, with negative values indicating moisture stress and positive values indicating healthy vegetation. The closer the value is to -1, the more severe the drought conditions are.

NDDI is particularly useful in areas where rainfall data is limited or unreliable, as it provides a more accurate and timely assessment of drought conditions. It can be used to monitor drought conditions in near real-time and is widely used in agriculture, water management, and natural resource management.

References:

Gu, Y., Brown, J. F., Verdin, J. P., & Wardlow, B. (2007). A five‐year analysis of MODIS NDVI and NDWI for grassland drought assessment over the central Great Plains of the United States. Geophysical research letters, 34(6).