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Monsoon variations

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Hindu Business Line reports on the growing concern over the monsoon in the country:

The Food Minister, Mr K.V. Thomas, is expected to announce tomorrow steps such as sale of surplus wheat and rice through rations shops and open market to tackle any food price rise in the wake of drought-like situation in some parts of the country.

The Food Ministry is also considering relaunching sale of imported pulses and cooking oils through public distribution system with increased subsidy.

Mr Thomas is expected to unveil the measures tomorrow following direction from the Prime Minister’s Office, sources said.

The minister is likely to announce various initiatives planned by the government to ensure sufficient supply of foodgrains and other essential commodities.

Prices of food items such as sugar, pulses, cooking oils and vegetables have risen during the past few weeks amid concern over deficient monsoon and its likely adverse impact on kharif crop production.

Overall, monsoon rain is deficient by 22 per cent so far with Karnataka, Maharashtra, Gujarat and Rajasthan being the worst affected States.

Gloom and doom is in the air, as Reuters summarizes:

India’s crucial monsoon rains are now expected to be below average, the government said on Monday, turning to contingency plans as rainfall has been about a fifth below normal so far and recent rains have not been enough to ease concerns.

The monsoon lost momentum last week, falling 22 percent short of averages and raising the risk of a drought year in one of the world’s leading producers of grains and sugar just as global prices hit record highs and domestic food prices soar.

The government scaled down the weather office’s latest forecast of rains at 96 percent of a 50-year average towards 92 percent of the average — still avoiding classification as a drought.

“The progress of the monsoon so far has not allayed earlier concerns,” the statement from the prime minister’s office said. “The intensity and spread of rainfall over the next week or so needs to be watched carefully,” it added.

Distribution is key and poor rains have slowed the speed of planting crops such as rice, cereals, pulses and oilseeds including soybean, but areas under cane, mainly grown in irrigated regions, have been higher than in the previous year.

Monsoon rains irrigate 55 percent of India’s farmlands. The four-month season accounts for 75 percent of the country’s annual rainfall and half of that is usually delivered in June and July.

Financial tabloids like Livemint have been driven to delve into the history and procedures of India’s department of meteorology:

Like many institutions founded in the early days of British rule in India, IMD [India Meteorological Department] was based in Kolkata. It was headed by Henry Francis Blanford, a paleontologist, weather watcher and member of the Royal Geographical Society. For the next 113 years, headed by men from Gilbert Walker, considered by many to be the “brightest meteorologist ever”, to S.K. Banerji, the first Indian boss of the organization, from British rule through independence, IMD would attempt to predict the future, for the ears of the government only.

That day in 1988, under then director general S.M. Kulshrestha, India’s weather office dropped its habitual veil of secrecy and went public with its prediction that the monsoon rains that year would be “excellent”. It was right. Rainfall was indeed above average that summer. Since then, the Met department, as it is popularly known across the country, has lost its reputation as a reliable soothsayer—if it ever had one.

Even in 1988, IMD wasn’t exactly the embodiment of accuracy: for instance, it told the government that rains would be normal in 1986. They were 13% below normal. It said the loss would be made up in 1987, which ended up seeing India’s worst drought.

The crucial fact about monsoon forecasts comes later in the same article:

Since then, the weather office has weathered the phenomenon called El Nino, once a minor variable and now an entire equation unto itself; two reworkings and an abandonment of its trusted weather models; and lay and scientific criticism of its forecasts. It has also promised to abandon its century-old reliance on statistics-based forecasting for the emerging global trend of so-called dynamical forecasting.

Serious questions are being raised about purely statistical modelling of monsoon. Nature notes:

Timothy DelSole and Jagadish Shukla at George Mason University in Fairfax, Virginia, found no significant statistical relationship between summer monsoon rainfall in India and sea surface temperatures surrounding the country in May of each year from 1960 to 2005. They analysed predictions made by five coupled ocean–atmosphere climate models based on the same temperature data and period, and found that the models were better than the statistical methods at predicting rainfall.

The paper itself was published in Geophysical Research Letters and says:

After more than one hundred years of statistical forecasting and fifty years of climate model development, this paper shows that the skill of predicting Indian monsoon rainfall with coupled atmosphere-ocean models initialized in May is statistically significant, and much higher than can be predicted empirically from May sea surface temperatures (SSTs). The superior skill of dynamical models is attributed to the fact that slowly evolving sea surface temperatures are the primary source of predictability, and to the fact that climate models produce more skillful predictions of June-September sea surface temperatures. The recent apparent breakdown in SST-monsoon relation can be simulated in coupled models, even though the relation is significant and relatively constant on an ensemble mean basis, suggesting that the observed breakdown could be due, in large part, to sampling variability.

A physical understanding of the monsoons could lead to long-term predictions as well, as Science Daily reported three years ago:

The [Potsdam Institute for Climate Impact Research] researchers now present a conceptual model that captures the self-amplification feedback. The basic equations show that there is a critical value of irradiation from the sun for a monsoon circulation to start. If irradiation falls below the critical value, for instance due to high air pollution, no conventional monsoon can develop. Above the critical value, one state with and one state without a monsoon circulation exist.

This allows for an abrupt transition to occur in one of two different ways. First, climatic shifts can push the system across the critical threshold. The transition would occur from one season to the other and last as long as the climatic shift prevails. The second possibility is abrupt transitions between the two stable states, when the system is — as current monsoon circulations are — in the bi-stable regime above the critical threshold. Within one rainy season weakening of monsoon winds and latent heat release could decrease the temperature difference between land and sea until the circulation is disrupted.

Pallav Bagla writes in the Hindu that the IMD, in its 137 years of existence, has never been able to predict a drought due to a failed monsoon. The reasons:

The southwest monsoon is that life giving phenomenon which releases on the Indian land mass 80 per cent of the total annual of 105 cm of rainfall that India receives. …Farming, especially crop sowing, is very dependent on the timing of the rainfall. In any given year, if rainfall climbs more than 10 per cent above a long-term monsoon average, floods ensue. If it declines more than 10 per cent below average, a drought is declared. Slippage in either direction brings misery. For example, a drought in 2002 shrank India’s GDP by an estimated 5.8 per cent.

It may come as a surprise but the monsoon arrives without fail and has never delivered less than 60 cm of rain in the last 137 years of official records. But its spatial and temporal variation is vast, a fact which befuddles scientists.

To put this in perspective, in the last 137 years the Indian weather office has never ever been able to predict a drought. Look at the basic statistics. In the last 100 years, more than 85 per cent of the time the monsoon has been normal. So the chances of a normal monsoon are always high. In the last two decades, the IMD has invariably only forecast “normal” monsoons despite the huge variations India has witnessed in bad years like the massive flooding of 1994, and the droughts of 1987, 2002, 2004 and 2009. Experts say a forecast is only good if it can pick up early signals and warn of impending hazards so that policymakers and farmers in particular can prepare for the worst while hoping for the best. To make a point in its self-praise, the IMD always points out that from 1989 to 2000, 11 years in a row, it predicted a “normal” monsoon and it “turned out to be normal.” But a closer examination reveals that more often than not, even in this “golden period” their prediction was also actually way off the estimated margin of error allowed in the model itself. The flaw possibly lies in the statistical model that the IMD uses to make its predictions. The current model is still not good enough. A numerical model considered more accurate is still cooking. Interestingly, for the 2012 season, the new numerical model imported from the United States actually predicts a surplus.

Interestingly, the world over, scientists find it very tough to forecast weather patterns months in advance, so in a way it is commendable that the IMD puts its reputation on the block and makes an operational monsoon forecast. Most others only do this as an academic exercise. According to India’s leading atmospheric scientist, J. Srinivasan of the Indian Institute of Science, “no agency in the world has ever been able to predict an ensuing drought or flood for the Indian region.” So should we not stop giving lollipops of a “normal” monsoon to the people?

The monsoon of 2011 was an eye-opener for forecasters. The IMD had forecast that it would be a bad monsoon with rains possibly being less than 90 per cent of the long-term average, but at the end of the season, the rains turned out in excess of the long period average. Hence, in a first of its kind admission as part its end of season report, it said that it was “not very accurate” in its forecasts. “The monsoon remains a scientific mystery,” admits Madhavan Rajeevan, a monsoon specialist, in the MoES, adding, “We are accumulating more questions than answers.”

Shailesh Nayak, a geologist and secretary in the MoES says, “understanding the monsoon will be major priority in the next five years.” In this new Monsoon Mission, efforts will be made to understand it using the numerical models developed by the United Kingdom Meteorological Office and the American model called Climate Forecast System developed by National Centers for Environmental Prediction (NCEP) that combine data from ocean, atmosphere and land for providing long range forecasting. Mr. Nayak admits that “current prediction capabilities are inadequate” and an effort will be made to improve high performance computing.

The Indian Institute of Tropical Meteorology, Pune will take the lead in deciphering the seasonal forecasts, while trying to predict the active and break periods of the monsoon. Mr. Nayak says the bottleneck is a shortage of trained scientists. According to his estimate, in the next five years India needs about 1,200 skilled meteorologists. There are only about 350 now.

The IMD has long resisted the move to incorporate physical understanding of the monsoon into its models, preferring to reply on purely statistical tools. The intellectual climate is now changing enough that it may have to adapt or die.

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Written by Arhopala Bazaloides

July 26, 2012 at 5:28 am

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