Standardised Precipitation Index:
The India Meteorological Department has analysed trends for precipitation and drought-like conditions over India using the ‘Standardised Precipitation Index’ (SPI).
- Standardised Precipitation Index estimates wet or dry conditions based on precipitation variables.
- The SPI calculation is based on the long-term precipitation record for a particular location and long-term period (longer than 30 years is desirable).
- This index is negative for drought and positive for wet conditions. As the dry or wet conditions become more severe, the index becomes more negative or positive respectively.
- It includes timescales of 1, 2, 3, 6, 9, 12, 24, 36, 48, 60 and 72 months.
