Monsoon is referred to as the lifeline of India. It greatly influences the agriculture yield, economy, water resources, power generation and ecosystem.The accurate prediction of monsoon rainfall is a basic need for India but remains a challenge over the decades.
- Monsoon forecast models
- LPA method
- Indian monsoon mission
- Megha tropique satellite
- New models
Monsoon Forecast Models
- Monsoon has always been critical for India’s economy.
- If variations in monsoon rainfall are known well in advance, it would be possible to reduce the diverse impacts related to excess or deficient rainfall.
- A reliable monsoon forecast with sufficient lead time is essential for policy makers and farmers for planning and sowing of crops, as well as making long-lead plans for the future.
- There are several methods to assess the likelihood of Monsoon rainfall.
- Currently, IMD relies on an ensemble model for forecasting monsoon. This traditional model uses a statistical technique.
- It uses an average of 6 meteorological values correlated to the monsoon such as sea surface temperatures in the Pacific, and North Atlantic sea level pressure.
- These meteorological values are traditionally derived from century-old meteorological data linked to the historical performance of the monsoon.
- This model equates relationships of physical parameters, such as for instance sea surface temperatures, snowfall, the temperature of landmass etc with the actual observed rainfall in the past.
- India currently operates a global model on a 12-km grid size — that is, information is gathered every 12 km. This is the highest resolution ensemble system, and at present India has the best model in the world.
- However, this traditional approach has failed to predict monsoon recent decades (for instance in 2002 and 2004) leading meteorologists to call for a new, modern forecasting system.
Dynamical Monsoon Model
- The dynamical monsoon model simulates the weather on powerful computers (supercomputers) and extrapolates it over particular timeframes.
- This modern forecasting model is being tested at the Indian Institute of Tropical Meteorology (IITM), Pune.
- The dynamical monsoon model is also called the Coupled Forecast System version 2.
- So far it has achieved only 60% accuracy in forecasting the monsoon.
- This method is widely used in forecasting weather over a few days. But using it to forecast the annual monsoon over 3 or 4 months has proved difficult.
- LPA of rainfall is the rainfall recorded over a particular region for a given interval (like month or season) average over a long period like 30years, 50-years etc.
- It acts as a benchmark while forecasting the quantitative rainfall for that region for a specific month or season.
- For example, LPA of south west monsoon rainfall over Kerala for the months June, July, August and September are 556mm, 659mm, 427mm and 252mm respectively.
- Current LPA of all India south west monsoon rainfall based on the average rainfall over the period 1961 -2010 is 880.6mm.
Indian Monsoon Mission (NMM):
- The accurate prediction of monsoon rainfall remained a challenge for decades. The conventional forecast in use so far is based on the statistical approach and is low skilled in forecasting rainfall anomalies.
- Several new approaches (high resolution, super parameterizations, data assimilation etc.) developed in recent times have shown that the variability in tropics can be reasonably resolved
- The National Monsoon Mission (NMM) was envisaged in 2012 by the Ministry of Earth Sciences (MoES) to develop a dynamical coupled prediction system specially suited for the Indian region.
- The main objectives of NMM are to improve Seasonal and Intra-seasonal Monsoon Forecast and to improve Medium Range Forecast.
To achieve its objectives the NMM envisages to:
- Build a working partnership between the academic research and development organisations and the operational agency to improve the monsoon forecast skill;
- Set up a dynamical modelling framework for improving prediction skill of seasonal and extended range prediction system, and short and medium range prediction system; and,
- Set up the infrastructure and train manpower required to improve the prediction skill in all time scales.
- The main objective of the Megha-Tropiques mission is to study the convective systems that influence the tropical weather and climate.
- The satellite was launched in 2011 into a non-sun synchronous orbit (Low Earth Orbit), unlike other IRS spacecraft.
- Megha-Tropiques provides scientific data on the contribution of the water cycle to the tropical atmosphere, with information on condensed water in clouds, water vapour in the atmosphere, precipitation, and evaporation.
- The Megha-Tropiques is a unique satellite for climate research that also aids scientists seeking to refine prediction models.
- It is operated as part of a joint programme between the Indian Space Research Organisation (ISRO) and France′s Centre National d′Etudes Spaciales (CNES).
- This Megha-Tropiques satellite carries four payloads namely, MADRAS-a microwave imager, SAPHIR-scanning radiometer instrument, SCARAB-scanner for radiative budget and GPS occultation receiver for atmospheric studies.
- The India Meteorological Department (IMD) may introduce new monsoon models this year to better forecast changes in rainfall.
- Three different models would be tested this year. Two of them were dynamical models and one a statistical model.
The three models under consideration are:
- 12 global circulation models (dynamical) : The outputs these models would be combined into a single one
- a model that gauges rainfall based on the sea surface temperature in the tropics (developed by Prof. Sumant Nigam, University of Maryland, U.S.) and
- the statistical model based on climate variables observed during the pre-monsoon.
All of them are ‘ensembles’ meaning smaller models are combined to arrive at an average value.
Approach to the answer:
- Uses of Monsoon Forecast
- Mention different forecast models used by IMD
- Mention their strengths and weaknesses