Coronavirus Could Disrupt Weather Monitoring

The drop in airline travel caused by the coronavirus pandemic has sharply reduced the amount of atmospheric data routinely gathered by commercial airliners, the World Meteorological Organization said Thursday, adding that it was “concerned about the increasing impact” on weather forecasts worldwide.

The agency said data on temperature, wind and humidity from airplane flights, collected by sensors on the planes and transmitted in real time to forecasting organizations around the world, has been cut by nearly 90 percent in some regions.

In the United States, data has declined by 75 percent during the pandemic, according to the National Oceanic and Atmospheric Administration. Under the observational program, established in the 1960s, data from 3,500 aircraft operated by Delta, United, American and Southwest, and by the cargo carriers United Parcel Service and FedEx, is transmitted directly to National Weather Service forecasting operations.

Christopher Vaccaro, a NOAA spokesman, said the decline “does not necessarily translate into a reduction in forecast accuracy since National Weather Service meteorologists use an entire suite of observations and guidance to produce an actual forecast.” That includes data from satellites, radar and other land- and sea-based instruments and radiosondes, small instruments that are launched into the upper atmosphere on a daily schedule and provide data as they descend.

But fewer than 200 radiosondes are launched each day. Observations from aircraft have been far more abundant, said William R. Moninger, a retired NOAA physicist who now works at the Cooperative Institute for Research in Environmental Sciences at the University of Colorado. Not every airplane supplies data, but those that do transmit readings as often as every few seconds, depending on altitude, he said.

At this time last year, Dr. Moninger said, aircraft in the United States provided nearly 600,000 observations a day. Now, with far fewer flights, on a recent day in April there were 180,000 observations, he said.

The observational data is fed into weather service computer models that forecast conditions anywhere from several hours to days ahead. Dr. Moninger and some colleagues are currently studying whether short-term forecasts have been affected. “The short answer is we haven’t seen an unequivocal impact yet,” he said, noting they have yet to complete their analysis.

The World Meteorological Organization, an arm of the United Nations that coordinates a global observing system for 193 member nations, said that in addition to aircraft data, surface-based weather observations have been affected in some parts of the world, including Africa and Central and South America, where many weather instruments are not automated and must be visited regularly to obtain readings.

The agency said that automated instruments should continue to function well for some time, but that if the pandemic is prolonged, lack of maintenance and repair may become a problem.

The agency said some countries, especially in Europe, were launching more radiosondes to partially make up for the loss of aircraft data.

National weather agencies “are facing increasingly severe challenges as a result of the coronavirus pandemic, especially in developing countries,” said Petteri Taalas, the agency’s director-general, in a statement.

“As we approach the Atlantic hurricane season, the Covid-19 pandemic poses an additional challenge, and may exacerbate multi-hazard risks at a single country level,” he added.

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