IMD’s Rainfall Forecasting Model- Relevance for UPSC Exam
- GS Paper 1: Important Geophysical phenomena such as earthquakes, Tsunami, Volcanic activity, cyclones, etc.;
IMD’s Rainfall Forecasting Model- Context
- The southwest monsoon has officially ended in India with 87.4 cm of rainfall between June and September, or just 0.7% short of the historical average of 88 cm.
IMD’s Rainfall Forecasting Model- Monsoon in 2021
- Rainfall deficit: By August end, India was staring at an all-India monsoon rainfall deficit of nearly 9%.
- This was primarily due to monsoon rain in August, usually the second rainiest month, being short by 24%.
- However, September rainfall (35% more than the monthly normal) was so munificent that it completely closed the deficit and was well beyond the IMD’s expectations.
- IMD Predictions:
- Initial Prediction: IMD forecasted “normal” rains with “a tendency towards the positive side”.
- Latest prediction: IMD maintained that the overall monsoon rainfall while still “normal” would be towards the lower end.
- Previous Trends: Monsoon 2021 capped a rare three years of healthy rain.
- In 2020, India received 109% of the long period average (LPA) and in 2019, 110% of the LPA.
- Since 1996, 1997 and 1998, India has not got three consecutive years of normal or above normal rain.
Monsoon 2021- Geographical Distribution and Associated Impacts
- Geographical distribution: Much of the rain was focused on southern India, with large parts of northeast and eastern India receiving below normal rainfall, but this is not concerning for two reasons-
- The base level of monsoon rains is higher in the northeastern regions than in the rest of India and
- The region also gets the retreating monsoon which normally commences by October end.
- Associated Impact:
- Three years of good rains have boosted storage in India’s key reservoirs.
- Proved erratic for agriculture: This is due to failure of monsoon during Kharif sowing season (July & August) and excess rains in September (causing crop damage due to excessive moisture).