Online Drought Indicators and Indices

Vegetation Health Index (VHI)


Index name: Vegetation Health Index (VHI).

Ease of use: Green.

Origins: The result of work done by Kogan with NOAA in the United States.

Characteristics: One of the first attempts to monitor and identify drought-related agricultural impacts using remotely sensed data. AVHRR data in the visible, infrared and near-infrared channels are all used to identify and classify stress to vegetation due to drought.

Input parameters: AVHRR satellite data.

Applications: Used to identify and monitor droughts affecting agriculture around the world.

Strengths: Coverage over the entire globe at a high resolution.

Weaknesses: The period of record for satellite data is short.

Resources: The calculations and sample case studies are given in the literature. VHI maps can be found online at


Kogan, F.N., 1990: Remote sensing of weather impacts on vegetation in non-homogeneous areas. International Journal of Remote Sensing, 11:1405–1419.

Kogan, F.N., 1997: Global drought watch from space. Bulletin of the American Meteorological Society, 78:621–636.

Kogan, F.N., 2001: Operational space technology for global vegetation assessments. Bulletin of the American Meteorological Society, 82(9):1949–1964.

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