The weather pundit

Not surprisingly,when science and technology minister Jaipal Reddy announced last week in Delhi,in a hall packed with journalists eager for the news,that the monsoon this year is likely to be normal,it sent a sigh of relief among policymakers.

Why a good monsoon is important for the country,and getting the forecast right even more important,can be easily explained by a few facts: more than half of India’s 1.2-billion population is engaged in agriculture; about 55% arable land is dependent on monsoon rains,and agriculture contributes 15% to India’s nearly $2-trillion economy. Which is why before announcing its forecast for the monsoon,the IMD consults the food,agriculture and other ministries,as its impact on the economy is considerable.

Accuracy is the name of the game here and the met department has had its share of hits and misses. The year 2002 was a game changer,when the met department could not predict deficiency in the monsoon rainfall,forcing scientists to go in for a review of the methods of forecast being used.

Shailesh Nayak,secretary,earth sciences ministry,admits that the statistical model,being followed by the met department since decades,has been successful in predicting ‘mean or average rainfall’ across the country,but has failed in providing regional variations in rainfall pattern.

For instance,he says,last year’s deficiency in rainfall in parts of Gujarat,Maharashtra and Karnataka could not be captured because of deficiencies in this model. In April 2012,the IMD had predicted normal rainfall of 99% of LPA ( Long Period Average,the average countrywide annual rainfall of 89 cm during 1951-2000) for the four monsoon months,while the actual rainfall was only 92% of LPA,with many parts of the country,such as Maharashtra,Gujarat and Karnataka,facing drought-like conditions because of deficient rainfall. “The forecast for July rainfall over the country as a whole was an overestimate and that for rainfall during the second half of the monsoon season was an underestimate,” the IMD stated in its monsoon report of 2012.

The department has faced flak earlier too,for not accurately predicting deficient rainfall in 2003,2004,2007 and 2009. The IMD failed to foresee the worst drought in nearly four decades in 2009,predicting an average monsoon year,but the season ended with a rainfall deficit of 22%,making for the worst monsoon in nearly four decades. As a result,rice output fell and India had to import sugar,sending global prices to a 30-year high.

In 2007,in contrast to the forecast of below-average rainfall,the monsoon turned out to be above average.

Scientists argue that understanding variability in wind,pressure and temperature is not an easy process. “We need to constantly upgrade our computation capability to high-speed supercomputers for arriving at a more accurate weather forecast,” says Swati Basu,director,National Centre for Medium Range Weather Forecast (NCMRDF),a Noida-based organisation under the ministry of earth sciences.

Nayak tells FE that the department is planning to fully shift to the dynamic model of forecasting monsoon,which will help the IMD make short-term predictions too. “We will be able to make short-term forecasts using the dynamic model. Followed in the US,Europe and Japan,the model is being used across the globe for more localised forecasts. Within the next five to six years,we will move to this model.” The department has already started using this model since last year. The dynamic model depends more on the laws of physics and factors like formation of clouds,wind direction,etc,than purely math as used in the statistical method since the 1980s.

The IMD has also taken into account experimental forecasts. The model has been using data from premier national institutes like Space Applications Centre,Ahmedabad; Indian Institute of Science,Bangalore; Centre for Mathematical Modeling and Computer Simulation,Bangalore; and Centre for Development of Advanced Computing,Pune.

Besides,met scientists take into account experimental forecasts prepared by international institutes also,including the National Centers for Environmental Prediction,USA; International Research Institute for Climate and Society,USA; Meteorological Office,UK; Meteo France; the European Center for Medium Range Weather Forecasts,UK; Japan Meteorological Agency and Japan Agency for Marine,etc.

Recently,the met department joined hands with almost all the world’s major weather forecasters in its effort to accurately forecast monsoon rains in the next four years,raising prospects for a rise of up to 15% in farm output,says LS Rathore,director general,IMD. “Significant improvement in accuracy of weather forecast has been achieved by using latest technology—satellite,doppler weather radars,” says Rathore.

While NCMRDF provides information to the IMD on short-term weather forecast (five days in advance) on the temperature and weather conditions for 117 towns across the country,Pune-based Indian Institute of Tropical Meteorology (IITM) is the key organisation responsible for long-term weather forecasts for the country.

Meanwhile,all eyes are on the skies,as the country hopes for the met department to have got the ‘normal’ forecast right this year.

*Going commercial

while the IMD has been providing most of its weather forecast services free,the civil aviation ministry pays the IMD for getting weather reports for all airports across the country. The met department has also provided special weather services during the Kumbh Mela,Amarnath Yatra,Commonwealth Games and the ICC Cricket World Cup,to

name a few.

As for going commercial,IMD officials admit they do not have capacities to provide customised weather forecasting that would help agriculture and other sectors. “We need to develop our capacities for downscaling the existing data for special weather forecast services. We see a significant demand from sectors such as wind energy generation and transportation sector,” says Shailesh Nayak,secretary,ministry of earth sciences. Specialised weather forecast for cash crops,such as cotton,corn,sugar and others,is also being worked upon. But it would take a couple of years to develop technical capacities to generate such customised forecasts.

At present,the IMD provides short-term weather forecasts for 117 cities and towns in the country. These services have been used by sectors such as sports,event management,among others.

Hits & misses

* In 2012,normal rainfall of 99% of LPA was predicted,while actual rainfall was only 92% of LPA,with Maharashtra,Gujarat and Karnataka facing drought-like conditions.

* In 2009,the IMD failed to foresee the worst drought in nearly four decades,predicting an average monsoon year. But the season ended with a rainfall deficit of 22%.

* In 2007,in contrast to the forecast of below-average rainfall,the monsoon turned out to be above average.