The Indian South West Monsoon or Indian Summer Monsoon Rainfall (ISMR) is planet Earth’s most productive wet season. The monsoon generates over 80% of the annual rainfall across the country and is vital for the Indian Economy, being the main source of water for agriculture, and contributes about 17% to India’s Gross Domestic Product (GDP). Other than the 60% of the country’s workforce that depends on agriculture, Indian Monsoon is also important for traders dealing in food and cash crops as any shortfall can inject price volatility in the markets.
When the monsoon fails, GDP falls by almost 2-3%. It has a huge cost on the agricultural sector. Hence the title which means, if in some year due to poor Indian Monsoon, India imports food commodities; it sends global food prices spiraling upwards.
A good monsoon results in record harvests and poor monsoons results in agricultural production shortfalls and food commodity inflation. This is because 55% of India’s agriculture is still rain-fed. Production of crops like paddy, coarse cereals, pulses, oil seeds and cotton is mostly dependent on the four-month monsoon season starting June.
The rains also provide critical soil moisture that helps sustain production during the ensuing ‘Rabi’ sowing season. Last year though we had a pretty good South West Monsoon, the North East monsoon rainfall fell short by a whopping 40%. This means a significant portion of the farmland is currently devoid of any tangible moisture content.
Added to this, water levels of all major rivers in India are running low. As of 2012, the water level in the 80-odd major reservoirs across the country was 48.19 billion cubic centimetres, 83 per cent of last year’s storage during the same period and 31 per cent of the full-reservoir capacity. (On this I remember, there was an Integrated Watershed Development Programme (co-ordinated by MoRD), undertaken to look into efficient groundwater management and rain water harvesting, but did nothing except wasting taxpayers money, lol ! , like we didn’t know ! 😛)
It is obvious that there is not much of a buffer to tide over a bad monsoon season and hence our dependence on the South-West Monsoon is total, year after year, and if it fails in any year, its impact has far reaching consequence as was evident in 2002 and in 2009.
To add to this critical nature of Indian Monsoon, is the glaring guesswork being done by our weatherman ( read Indian Meteorological Department – IMD) [Almost on the lines of Bejan ‘Hyper’ Daruwala], which is giving tough time to our policy makers and rendering them defenseless to some difficult questions posed by media/public. (Like the one posed to Mr. Montek ‘DSE’ Povertywala, when he suggested that trend of income change is the same for all income groups, on the poverty line debate! How convenient? :p ).
Because of the confusing trends about Indian Monsoon performance this year(2012) and considering the tough questions he was asked in 2009, our beloved, ‘Toyota-Lexus driven pro-poor’ Shri Sharad Pawar is in a panic mode. Leaving nothing to ‘Meghdut‘ to shower his blessings, the minister has already issued advisories to all states and Union territories to prepare a contingency plan in the event of low rains, especially in drought-prone districts.
In all cabinet meetings and other discussions with the PM, our ministers must have been cribbing about ‘what a waste‘ our weather men(IMD) have been and how their ministry is almost helpless, if they know of ensuing drought only in June. So, whenever IMD have predicted above normal rainfall, those years India has faced drought (2002/2009). El-Nino (we will learn whats that , in some time) was found to be behind these droughts, almost suggesting El-Nino singing “LMFAO’S Sorry! for party rocking!“, staring at those IMD professionals.
Seeing all of this, there must have been a conscious decision taken in one of the cabinet meetings to upgrade our country’s ‘Monson Forecasting System’ and improve its skills to forecasts such events more accurately, in future.
Indian Monsoon Mission
Implementation of a new mission named “National Monsoon Mission” has been approved by the Cabinet Committee on Economic Affairs on 26th April’12 with an initial corpus of Rs 400 crores and a period of 5 yrs.
This programme is under Ministry of Earth Sciences(MoES) and is headed by Shri Vilasrao Deshmukh. (lol …We couldn’t care less! As if he knew anything remotely connected to Earth Sciences, except ofcourse attending all Bollywood Award functions and is seen more often in MMRDA Grounds than in Prithvi Bhavan, Delhi)
The main objective of this mission is:
“Setting up a ‘dynamic climatic model’ for an improved forecast of Indian Summer Monsoon Rainfall (ISMR)”
To meet this objective, we need to do the following things:
- Research institutions of MoES (namely IITM-Pune) will collaborate with foreign institutions (in this case it’s NOAA, USA) which have successfully developed a dynamic climatic model, then customize it to Indian Monsoon requirements and finally implement it for weather forecasting in future. The forecasting model that we have been chosen is called Coupled Forecasting System (CFS).
- Implementation of this CFS model will be done on an experimental basis for the first few years. Thereon the research institutions will work with NOAA, USA to improve the skill of this CFS model for more accurate long range forecasts of monsoon rainfall. While all this is being done, it will be Business-As-Usual (BAU) for IMD, which provides forecasts for ISMR, using old forecasting model.
- To help us with our research on improvement of forecasting skills of CFS Model, India will have to build working partnership between the academic/R&D organisations and operational agencies, both national and international.
The National Monsoon Mission will be undertaken through two sub-missions on two different time scales:
a. Seasonal and extended range prediction system (16 days to one season) – co-ordinated by Indian Institute of Tropical Meteorology (IITM)
b. Short to medium range prediction system (up to 15 days) – co-ordinated by National Centre for Medium Range Weather Forecasting (NCMRWF)
The Indian National Center for Ocean Information Services (INCOIS) will provide the ocean observations for assimilation and the India Meteorological Department (IMD) will implement the research outcome of the efforts in operational mode.
Please see below an indicative flow of how this monsoon mission must been approved. This is off-topic, but nevertheless informative.
What is a weather forecasting model?
Weather is a result of many different physical phenomena. Indian Monsoon is affected by many such physical processes (we call them predictors) and in order to correctly forecast how the monsoon will behave, we need to understand the correlation these predictors with the monsoon and for that we take help of a model. So a weather forecast model is nothing but a set of mathematical equations, in which we input observed values of the predictors and get certain results, which we then interpret and forecast the behaviour of monsoon for a particular year i.e. how much of rain – when and where.
The current IMD weather forecasting model is based on a statistical platform (called Ensemble) that uses 16 predictors in an empirical relationship with the total quantum of monsoon rainfall over the entire country.
Historical data over a sample period (1951-1987) have been used to identify 16 predictor variables that have significant influence on the Indian Summer Monsoon Rainfall (ISMR) behaviour.
Some of the predictors (indicative and not exhaustive) used by IMD are shown in below diagram.
IMD has assigned weight to these individual predictors, based on their significance to Indian Monsoon (this is again based on historical data study) and measures their value, as they occur, from December to May. These observed values (of predictors) are then fed into the model, which does complex number crunching and comes up with a weather forecast for the season. IMD develops several such models using different statistical methods – “multiple regression”, “projection pursuit regression”, and then takes an average of them to arrive at the final value. They call this Long Period Average (LPA) as it’s the average for long time of the monsoon season.
IMD issues operational long range forecasts for the southwest monsoon rainfall in two stages. First stage forecast is issued in April (this year on 26th April) and the second stage forecast is issued in June.
This statistical model is stated to have an inherent error window of 4% on either side because of its statistical nature (remember normal distribution). Over the years the skill of these models in predicting the monsoon has gone down, especially after they replaced 4 out of the original 16 parameters with new ones (remember in 2002 and again in 2009, IMD had predicted normal monsoon, when actually India was hit by drought).
The need for a new weather forecasting model
Realising all of these issues and pressure from Government to improve its forecasting skills, IITM,Pune collaborated with NOAA, USA to build something called a coupled dynamic climate model, the Coupled Forecasting System (CFS).
One inherent methodological difference in the new dynamic model is the fact that it will consider data for the current year and take into account any change in the relationship between predictors that it will use for weather forecast.
For example, let’s say, historically the relationship between temperature between the Bay of Bengal and land is one of the determinants of monsoon. In the past week, there has been an emergence of a tornado in this region that changes the relationship of sea and land. The old model would have simply ignored that and would have considered just the historical data. On the contrary the new model will take this development into account and hence the name ‘dynamic’.
All of this implies that different mathematical formula will be applied to capture the interaction of different physical phenomena. These formulas will divide the world into tens of thousands of grids of 100 sq km each and each grid will have its own set of predictors. Each year, fresh values will be entered for each of these predictors for each grid and the supercomputer will crunch through millions of calculations to solve the mathematical formula and project the amount of rainfall India will get in that year.
A summarised comparison of the current statistical model and the proposed coupled dynamic climate model is shown in picture below.
Having said all this, many meteorologists have agreed, that weather forecasting in tropical conditions is very difficult because here things develop quite rapidly and have no prior signals. At the moment, the most disheartening fact is that globally, the success rate of the new model is not very different from the old model. A statistical model’s success rate is about 22% as compared to 24% of the dynamic model.
This new dynamic climatic model has already been adopted by IITM, Pune and they are running it on experimental basis for last couple of years. Meanwhile the IITM folks are also doing something called a ‘hind cast’ wherein we use historical data to see if the new model correctly “predicts” the monsoon for a particular year. For instance, we can feed the predictor observed values for backdated year like 2009 and see the prediction by this new system. That is a different thing that it did not predict the drought of 2009 in India and so far the new model’s performance for predicting the monsoon/drought over India has been a mixed one.
So why invest so much for such a small difference? Well, the new dynamic climate model is based on a more rigorous approach and much more fundamental science. So if Indian scientists can adapt and improve this model, the country will have a much better prediction system. Collaboration with NOAA, USA and the “National Monsoon Mission” is exactly for doing that.
Some Science and Geography concepts, anomalies in them and its effect on ISMR
♦ Conservation of Angular Momentum & Coriolis Effect
Conservation of Angular Momentum states that for any rotating object, the product of its
mass X angular velocity X radius should be constant.
Please see the diagram below. As you see Earth’s velocity at equator is maximum and it decreases towards pole.
Now, let’s consider a particle of air on Earth(Shown by black dots on the above diagram). Since, mass of Earth is constant; the only things which would change are its angular velocity and radius. Since as we move towards poles, radius decreases and so to conserve the ‘angular momentum’, the particle’s angular velocity should increase. This causes deflection of the particle from its straight path, due to increased angular velocity and causes it to bend in circular path. This deflection of particle is called ‘Coriolis Effect’.
Coriolis Effect causes deflection in clockwise direction in Northern hemisphere and anti-clockwise in Southern hemisphere.
These are the dominant tropical winds, which blows from east-pacific region (i.e South America) to west-pacific region (SE Asia) during normal time. This is cause of major weather activities in the tropical region.
Sun heats the surface of sea, in the equatorial region, the most. So we have warm Sea Surface Temperature (SST) area developed. The trade winds are very strong winds and when it blows from east to west, it carries along with itself these warm SSTs along with itself to the SE Asia region. This causes huge rains in that area.
(Remember the tropical forest regions in Indonesia which supports rubber plantation due to this wet weather. Infact my friends say, its always hot and humid weather in Singapore and rains almost throughout the year. Poor them! 😦 )
La-Nina has usually helped the SW Indian Monsoon in past.
See diagram below, the red region is the accumulation of hot SSTs in the SE Asian/Australia region and the opposite side of pacific (South America) we have cold water rising to the top, a phenomenon called upswelling. This brings all nutrients and planktons to the top and is good for fish and the fishing industry there.
♦ El Nino
In every 2-3 year, the normal trade wind travelling from east to west pacific region gets weakened. Due to this the SSTs couldn’t go to the west pacific region, causing little to no rainfall in that area and in contrast heavy rainfall in east pacific (i.e. South America Region). This anomaly is called El Nino.
For the purpose of measurements of changes in atmospheric air-pressure due to El-Nino anomaly, meteorologists have adopted two places on Earth, one in east pacific – Tahiti Island (T) and the other in west pacific – Darwin, Australia (D) region as standard indexes (Just like for measurement of time, we have adopted an atomic clock in Greenwich London and measured all world clocks with it).
In normal circumstances T is the high pressure area and D is the low pressure area and hence the air pressure difference [T-D] is always positive. But it has been observed that during El-Nino, this pressure feature gets reversed (or rather oscillated) and the pressure difference between [T-D] goes negative. This is what we can Southern Oscillation, as the pressure difference oscillates between positive and negative values and since it’s almost always associated with an El-Nino, we call it El-Nino Southern Oscillation or ENSO.
El-Nino has been responsible for bringing drought in Indian subcontinent, several times in past, and this is so because as it draws all moisture laden air from west(SE Asia) to east pacific region(South America). The connection of El-Nino and La-Nina with Indian Monsoon is called ‘teleconnection’.
♦ Indian Ocean Dipole (IOD)
The IOD is see-sawing of sea-surface temperatures (SSTs) from the west to the east of the Indian Ocean. When the west gets warmer (positive IOD) it helps the Indian monsoon and vice versa. When IOD turns negative, it adversely affects rainfall within the Indian sub-continent by sucking up the thermal convection of sea water away from the mainland. Neutral IOD would mean the SSTs in west and east Indian Ocean is same and this causes average to normal monsoon in Indian Subcontinent.
Unlike the El Nino-La Nina tele-connection with ISMR, the impact from an IOD is more direct and immediate to a concurrent Indian monsoon.
Based on studies and past observations, following trend has emerged:
So, we see that IOD acts as a wild-card for the Indian Summer Monsoon Rainfall. Should it swing positive, India can look forward to a bountiful monsoon – a third in the row. On the other hand, should it shift to its negative mode, India may be placed in more than a spot of bother. If the IOD retains its neutral status coinciding with a neutral ENSO, the chances are we are heading for a normal-normal monsoon.
Enjoy and please leave your comments ! 🙂