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Fuzzy logic to fog rescue
- Scientists work on forecast plan that could reduce chaos

New Delhi, Dec. 25: Nerves were near snapping-point this morning at Delhi airport, fogged out since last night and unable to operate any flight for hours. From ministers to stars to common people, hundreds were holed up in the airport with the mercury outside plunging to a low of 6.2 degrees Celsius.

The options are limited in fighting thick fog that descends without notice but if a scientific gamble pays off, the chaos could be controlled through forecasts that allow more reaction ' and rescheduling ' time.

Scientists at the Centre for Mathematical Modelling and Computer Simulation in Bangalore have teamed up with a software company to produce fog forecasts 12 to 24 hours in advance, much earlier than those currently available.

The government laboratory in Bangalore was in the spotlight early this year when it drew the ire of the Indian meteorological establishment through its independent rain forecasts.

Physicist Prashant Goswami at the centre is gambling that fuzzy logic, the technology that can run washing machines, control robot motion and track stock exchanges, might also be able to deliver reliable fog forecasts.

While fog physics is well understood, reliable forecasts have eluded weather scientists. Now, with a Rs 1-crore grant from the Council of Scientific and Industrial Research (CSIR), the Bangalore centre has worked out a new technique that combines an element of artificial intelligence ' fuzzy logic ' with conventional weather forecasting.

The centre and its industrial partner ' the software company ' will conduct a reliability analysis tomorrow to check the accuracy of their experimental fog forecasts, a crucial step before a decision on whether the model is ready for launch for public use.

A senior official said it is too early to predict whether or when the new technique would be ready for routine applications.

“It’s in an experimental stage. But if it is proven to work, we’d like to see it take off as a commercial venture,” CSIR director-general Raghunath Mashelkar told The Telegraph.

While the centre will focus on the development of the technique, the software company will help get a product ready for commercial use.

Successful fog forecasts have eluded meteorologists because, unlike most other weather events, fog is a ground-hugging phenomenon.

“Fog is a shallow atmospheric event, concentrated just 100 metres from the ground,” said Akhilesh Gupta, a scientist at the National Centre for Medium Range Weather Forecasting (NCMRWF) in New Delhi, independently pursuing fog forecasts.

The routine forecasts currently delivered to airports are issued just before visibility begins to drop and are not early enough for effective action, Gupta said.

Whether fog will form over a city depends on the values of three weather parameters: humidity, temperature and wind speed. Several combinations of these can produce fog. But fog thickness and duration also depends on tiny particles of pollutants.

Based on weather data alone, the NCMRWF last year began to generate rudimentary fog forecasts for internal evaluation. While this approach has shown some successes, Gupta said, it is far from ready for routine operational forecasts.

At the Bangalore centre, Goswami is trying to reduce uncertainties in fog prediction with the help of fuzzy logic -- a mathematical technique to handle imprecise concepts.

Goswami plans to use weather data to generate conventional forecasts of humidity, temperature and wind, and feed the results into software modules based on fuzzy logic. “These modules are designed to improve accuracy of forecasts,” he said.

Earlier this year, the centre had published on its web site separate monsoon forecasts for June, July and August for specific parts of India, drawing criticism from the Indian meteorological establishment, which does not issue monthly forecasts.

The department of science and technology had then arm-twisted the centre into removing the forecasts from its web site on the ground that the Indian Meteorological Department (IMD) was the lone official weather forecaster.

An investigation of trends in winter visibility over airports conducted by the IMD had indicated a steady worsening of fog conditions in northern India over the past two decades. During the 1970s, airports reported less than seven days of poor visibility from December to February.

By the late 1990s, several airports reported 60 to 80 days of poor visibility during this 90-day period.

Reliable fog forecasts will help airline operations as well as farming practices. Light irrigation of crops just before the onset of fog will protect the plants, said Gupta. “But forecasts need to be early enough for effective action.”

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