Coronavirus | Grounding of planes partially hits IMD’s weather data supply

Data relayed from aircraft on temperature and wind speed are used in dynamical models

April 04, 2020 05:57 pm | Updated April 05, 2020 09:29 am IST - New Delhi

The inputs sent by aircraft are important as they determine the initial conditions. File

The inputs sent by aircraft are important as they determine the initial conditions. File

The grounding of the country’s civilian aircraft has strangled a key source of weather data that the India Meteorological Department (IMD) uses for its forecasts. Officials, however, clarified that India’s annual monsoon forecast system was on track, with the first forecast scheduled to be issued in mid-April.

Also read | Why are monsoons difficult to predict?

Aircraft relay data about temperature and wind speed in the upper atmosphere to meteorological agencies the world over and this is used in the dynamical models, the ones which are run on super computers and relied on to give weather forecasts three days, or even two weeks ahead. “Inputs from aircraft are important for the dynamical models as it determines the initial conditions for these models,” D.S. Pai, chief forecaster, IMD Pune, told The Hindu. “However for the monsoon forecast, which is a long-term forecast, this isn’t significantly affected.”

Beginning mid-March, India began restricting incoming international flights into the country and by March 24 had imposed a total shutdown on domestic air travel as well.

This year, the IMD will likely rely on its traditional statistical forecast system — the workhorse, developed on the basis of historical data. India had begun to move away from this system and started to rely on its dynamical models as it better captures developing changes in the atmosphere. However, India’s dynamical models are still not as adept as meteorologists want them to be, for warning of a drought or extreme changes in monsoon rainfall. That, and limited data from aircraft as well as a general decline in land-based observations because of a shortage of manpower to send observations are forcing the agency’s hand.

Also read | Coronavirus lockdown lifts Delhi’s March air quality to 5-year high

“We need multiple observations from weather stations from all parts of the country,” said Madhavan Rajeevan, Secretary, Ministry of Earth Sciences (MoES). “Now that’s been reduced. But because weather services are an essential service we are working with reduced manpower,” he added. The IMD is a subsidiary of the MoES. A major factor for gauging the performance of the monsoon is the El Nino, a warming of the ocean waters in the equatorial Pacific Ocean. This data is measured by observational data buoys located in the sea and relayed via satellite. “This data isn’t affected so far,” Dr. Pai said. The IMD issues its first forecast for the June-September monsoon in April and updates it in June.

Aviation-generated data is also helpful to warn of developing thunderstorms or swings in temperatures that often begin at the heights aircraft traverse. “There are mathematical fixes that can be used to compensate for this. However, a lack of data for a prolonged period of time is a big loss for calculating weather trends and future climate patterns,” the IMD scientist added.

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