Mains Paper 1 : Geographical Features & Their Location |
- While releasing its monsoon forecast, the IMD expressed the projected rainfall in terms of Long Period Average (LPA), saying that it was expected to be 96% of LPA.
What is LPA of Monsoon
- The LPA for the season is calculated on the basis of the mean rainfall during the four-month monsoon season over the 50-year period from 1951-2010.
- It works out to an average of 89 cm for the country as a whole.
- This is the average rainfall recorded during the months from June to September, calculated during the 50-year period.
- It is kept as a benchmark while forecasting the quantitative rainfall for the monsoon season every year.
- When IMD forecasts the category of rainfall, be it for country, region or month, the forecast is based on these standardised figures calculated for a period of 50 years.
- As per the outputs obtained from the weather models, the rainfall is categorised as normal, below normal, or above normal.
Five Rainfall Distribution categories
- Normal or Near Normal: When per cent departure of actual rainfall is +/-10% of LPA, that is, between 96-104% of LPA
- Below normal: When departure of actual rainfall is less than 10% of LPA, that is 90-96% of LPA
- Above normal: When actual rainfall is 104-110% of LPA
- Deficient: When departure of actual rainfall is less than 90% of LPA
- Excess: When departure of actual rainfall is more than 110% of LPA
- 83 cm for East and Northeast India,
- 55 cm for Central India,
- 61 cm for South Peninsular India, and
- 50 for Northwest India, which put together, bring the all-India figure to 88.75 cm.