The coronavirus is also playing with the weather forecast

Weather forecasts have become less accurate during the COVID-19 pandemic due to the reduction in commercial flights, according to new research.

A new study in the AGU journal Geophysical research charts It finds that the world lost between 50 and 75% of the meteorological observations of its planes between March and May of this year, when many flights were interrupted due to the pandemic.

Aircraft generally report weather forecasts by recording information on air temperature, relative humidity, air pressure, and wind along their flight path. With significantly fewer planes in the sky this spring, the forecasts for these weather conditions have become less accurate and the impact is more pronounced as the forecasts extend over time, according to the study, which is part of A special collection of ongoing research in AGU journals related to the current pandemic.

Weather forecasting is an essential part of everyday life, but inaccurate forecasting can also affect the economy, according to Ying Chen, a senior research fellow at the Lancaster Environment Center in Lancaster, UK, and lead author of the new study. The accuracy of weather forecasts can affect agriculture as well as the energy sector and the stability of the electricity grid. Wind turbines rely on accurate wind speed forecasts, and power companies rely on temperature forecasts to predict what the energy load will be each day as people turn on their air conditioning.

“If this uncertainty exceeds a threshold, it will introduce an unstable voltage to the power grid,” said Chen. “That could lead to a blackout, and I think this is the last thing we want to see in this pandemic.”

The regions most affected by the reduction in weather forecasts have been those with normally heavy air traffic, such as the United States, Southeast China and Australia, as well as isolated regions such as the Sahara desert, Greenland and Antarctica. Western Europe is a notable exception: its weather forecasts have not been affected, despite the fact that the number of aircraft in the region fell by 80-90%.

This was surprising, Chen said. Chen suspects the region has been able to avoid inaccuracies because it has a densely populated network of ground-based weather stations and balloon measurements to make up for the lack of aircraft.

“It is a good lesson that tells us that we should introduce more observation sites, especially in regions with little data observation,” Chen said. “This will help us cushion the impacts of this type of global emergency in the future.”

Chen also found that rainfall forecasts worldwide have not been significantly affected, because rainfall forecasts may have been dependent on satellite observations. But March, April, and May have been relatively dry this year in most parts of the world, so Chen cautions that precipitation forecasts could potentially suffer as the hurricane and monsoon seasons come.

Forecast comparison

Forecast models are more accurate when more meteorological observations are taken into account, and the number of observations decreases considerably when there are fewer aircraft in the air, as was the case in March-May this year. The Aircraft Weather Data Relay Program is comprised of more than 3,500 aircraft and 40 commercial airlines, which generally provide more than 700,000 weather reports per day.

When Chen compared the accuracy of the weather forecasts from March to May 2020 with the same periods in 2017, 2018, and 2019, he found that the 2020 forecasts were less accurate for temperature, relative humidity, wind speed, and air pressure. This despite the fact that in February, before flights were significantly affected, weather forecasts were more accurate than in previous years.

It found that surface pressure and wind speed forecasts were unaffected in the short term (1-3 days) but were less accurate for the longer term (4-8 days) forecasts included in the study. In February, before the number of flights was reduced, forecast accuracy in several regions dependent on aircraft observations had actually improved to 35 degrees Fahrenheit (1.5 degrees Celsius) in previous years. But in March-May 2020, when flights were down 50-75% compared to February, that improvement in accuracy disappeared.

Chen discovered that Western Europe was the only region with normally high flight traffic that did not suffer significantly reduced accuracy in temperature forecasts. He attributed this to more than 1,500 weather stations that form a dense data collection network in the area.

However, the European climate was particularly unchanged during the period from March to May 2020, making it easier to forecast with less data, according to Jim Haywood, professor of atmospheric science at the University of Exeter, UK, who did not participated in the new study Haywood suspects that this played a role in the persistent accuracy of western European forecasts, in addition to the network of ground observation points.

According to studies, the longer the aircraft data is missing, the more weather forecasts will be affected. While precipitation forecasts so far have not been affected, scientists’ ability to detect early warning signs of extreme weather events this summer could be affected. In the long term, the study results suggest that meteorological data sources should diversify, especially in areas with little observation and areas that are highly dependent on commercial flights, according to Chen.