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Weighing the monsoon winds for El Niño

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Ignoring the torpor of the summer heat, the India Meteorological Department has dusted off the statutory paragraphs that give us in the sub-continent a first indication of what monsoon for the year may be like. The result this year, both scintillating pages, has been made that much more gripping by the inclusion of El Niño. The IMD’s treatment of the normal variables whose interplay determine the nature of any monsoon is perfunctory – which is surprising as the regional and international earth observation networks spare no detail and tend to inundate us with data and analysis.

Clouds and wind, land and farm. The equation that all rural districts make at this time of the year, but which is becoming more difficult with every year that climate change strengthens its grip.

Clouds and wind, land and farm. The equation that all rural districts make at this time of the year, but which is becoming more difficult with every year that climate change strengthens its grip.

But the IMD, especially for the south-west monsoon, has always preferred to be spartan. Perhaps there is some philosophical dictum that us non-meteorologists have yet to grasp, and if so then the only criticism we may be permitted, if the IMD had its way, its to ask for more such teaching. But the IMD does not have its way, and we publics whose monies support its work must continue to demand from the recalcitrant department better, much better, application and communication of its work.

The official release, ‘Long Range Forecast For the 2014 Southwest Monsoon Season Rainfall’, is delivered to us by the IMD, Ministry of Earth Sciences (MoES). There is the usual paragraph claiming a profundity of observation and of the IMD being a standard-bearer of superior method. “Operational models are critically reviewed regularly and further improved through inhouse research activities,” says the IMD. But what we still have, in a tradition that is probably three generations old, is the two stage forecast (one in April, the second in June). [Here is the release in Hindi.]

I think this proves how out of step the IMD – and the Ministry of Earth Sciences (grand title isn’t it?) – is with what citizens of India experience in their villages, towns, fields and hills. For, the south-west monsoon no longer arrives in the first week of June, and it no longer begins to depart by mid-September. Climate change began to alter that comfortable rhythm years ago, but the IMD’s forecasting grindstone is the same, never mind how many new earth observation satellites India pelts into orbit.

IMD_monsoon_2014_probability

With all these provisos, stated and implicit, what has the IMD told us?

First, that the “experimental ensemble forecast based on IMD seasonal forecast model (SFM) indicates that the rainfall during the 2014 monsoon season (June to September) averaged over the country as a whole is likely to be 88% ± 5% of long period average (LPA)”. This means that in places it could be as low as 83% of the average, and no more than 92% of the average. Combine this with the assessments about the 2014 El Niño and we can see why, far from being satisfied that the IMD is considering both the monsoon and El Niño, we ought to monitor independently both and force the IMD to become more responsive.

Second, that “the experimental forecast based on the coupled dynamical model forecasting system suggest that the monsoon rainfall during the 2014 monsoon season (June to September) averaged over the country as a whole is likely to be 96% ± 5% of long period model average (LPMA)”. This is a more hopeful set, but also shows that the IMD, by telling us of two different scenarios from two models, is hedging its forecast, which is not what its job is.

Third, the IMD has said “the experimental five category probability forecasts for the 2014 monsoon season rainfall over the country as a whole using the experimental dynamical prediction system are 33% (deficient), 20% (below normal), 24% (normal), 6% (above normal) and 17% (excess)”. This means, using this ‘probability’, that a normal monsoon for 2014 has only a 1-in-4 chance whereas a deficient monsoon (that is, total rain less than 90% of the long period average) has a 1-in-3 chance.

This is a prognosis that stands between serious and grim, for a 10% drift towards the lower side of an expected average, for any of our 36 agro-meteorological regions, can spell ruin for farmers and severe hardship for water consumers. How have central and state governments prepared for such a forecast? We have no information, most likely because there has been no preparation (there are contingency plans for the chronically drought-prone districts, but these are normally triggered when there is an official declaration by  the state government that there are conditions of drought in parts of the state). Elections or no elections, El Niño cares not, and it is up to the state governments to make preparations for a monsoon 2014 whose delivery of water already looks uncertain.

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India lowers its 2011 monsoon forecast

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India’s meteorological department has issued its second long range forecast for the 2011 monsoon and has lowered its estimate. Rainfall will be 95% of the 50-year average in the June-September season, which are the monsoon months. In April, the Indian Meteorological Department predicted a monsoon that would be 98% of the long-term average. Normal precipitation is considered to be 96%-104% percent of the long-term average.

India’s agriculture-dependent population has been hoping for adequate rainfall to harvest good quantities of foodgrain and lentils for a second year and bring down inflation, which has led the Reserve Bank of India – the central bank – to raise rates for a 10th time in 15 months. Agriculture accounts for 14% of the economy and a reduced harvest can further lower rural incomes and send food inflation higher than it already is. Inflation in India is the highest among Asia’s major economies.

Bloomberg reported that the wholesale price index in India accelerated 9.06% in May after having increased 8.66% a month earlier, according to official data released on June 14. An index measuring wholesale prices of farm products including milk and lentils rose 8.96% in the week ended June 4 from a year earlier, according to the commerce ministry. India imported record quantities of sugar, lentils and oilseeds in 2009 following the weakest monsoon that year since 1972.

The IMD’s ‘long period’ is 1951-2000 and the department considers probabilities for the country (all-India) and four major regions: north-west India, central India, north-east India and south peninsula. “Over the four broad geographical regions of the country, rainfall for the 2011 Southwest Monsoon Season is likely to be 97% of its LPA over North-West India, 95% of its LPA over North-East India, 95% of its LPA over Central India and 94% of its LPA over South Peninsula, all with a model error of ± 8 %.”

The IMD also employs a six-parameter statistical forecasting system to prepare probability forecasts for five pre-defined rainfall categories. These are deficient (less than 90% of LPA), below normal (90-96% of LPA), normal (96-104% of LPA), above normal (104-110% of LPA) and excess (above 110% of LPA). The forecasted probabilities for the 2011 southwest monsoon season based on this system in percentage for the above 5 categories are 19%, 37%, 37%, 6% and 1%
respectively.

The department’s ‘Summary of the Update Forecasts for 2011 Southwest Monsoon Rainfall’ has said:

(1) Rainfall over the country as a whole for the 2011 southwest monsoon season (June to September) is most likely to be below normal (90-96% of LPA). Quantitatively, monsoon season rainfall for the country as a whole is likely to be 95% of the long period average with a model error of ±4%. The Long period average rainfall over the country as a whole for the period 1951-2000 is 89 cm.

(2) Rainfall over the country as a whole in the month of July 2011 is likely to be 93% of its LPA and that in the month of August is likely to be 94% of LPA both with a model error of ± 9 %.

(3) Over the four broad geographical regions of the country, rainfall for the 2011 Southwest Monsoon Season is likely to be 97% of its LPA over North-West India, 95% of its LPA over North-East India, 95% of its LPA over Central India and 94% of its LPA over South Peninsula, all with a model error of ± 8 %.

According to Reuters, government officials played down concerns that lower rainfall could fan inflation and dampen growth. “There is no need to press the panic button, as June rains are still above normal,” said Shailesh Nayak, the top civil servant in the ministry of earth sciences which controls the country’s weather office.

While rains could be slightly lower than normal in July, India’s chief forecaster said distribution was key. “There are chances the monsoon will pick up after July 15 once it covers the entire country,” said D. Sivananda Pai, director at the state-run National Climate Center. “Don’t go by the numbers, it is the distribution (of the rains) which we are still hoping to be good.” The weather office predicted 27 centimetres of rain in July compared with long-term average rainfall of 29 centimetres, and rains at 24 centimetres in August, when seeds start maturing, compared with long-term averages of 26 centimetres.

Weather office chief Ajit Tyagi remained optimistic. “Ninety five percent is a good forecast,” Tyagi said. “Had it been 90% of the long-term average then it would have been a cause for concern,” he said, adding that in the past slightly below normal monsoon rains had also seen adequate farm output because they were well distributed in the major crop growing regions.

Explaining climatic conditions over the equatorial Pacific and Indian Oceans, the department’s second long range said moderate to strong La Nina conditions that prevailed in the equatorial Pacific during mid-August 2010 to early February 2011 weakened during subsequent months and dissipated to neutral conditions around mid-May 2011. The latest forecasts from a majority of the dynamical and statistical models indicate strong probability for the present ENSO-neutral conditions to continue during the current monsoon season and the remaining part of 2011.

It is important to note that in addition to El Niño and La Niña events, other factors such as the Indian Ocean Sea surface temperatures (SSTs) have also significant influence on India monsoon. However, the latest forecasts do not suggest development of either a positive or a negative Indian Ocean Dipole event during the 2011 monsoon season. In the absence of strong monsoon forcing from both Pacific and Indian Oceans, intraseasonal variation may become more crucial during this southwest monsoon season and lead to increased uncertainty in the monsoon forecasts.