Reduction in commercial flights due to COVID-19 leading to less accurate weather forecasts

Date:
July 17, 2020
Source:
American Geophysical Union
Summary:
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 finds the world lost 50 to 75 percent
of its aircraft weather observations between March and May of this
year, when many flights were grounded due to the pandemic.



FULL STORY ========================================================================== 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 AGU's journal Geophysical Research Letters finds the
world lost 50-75% of its aircraft weather observations between March
and May of this year, when many flights were grounded due to the pandemic.

Aircraft typically inform weather forecasts by recording information
about air temperature, relative humidity, air pressure and wind along
their flight path.

With significantly fewer planes in the sky this spring, forecasts of
these meteorological conditions have become less accurate and the impact
is more pronounced as forecasts extend further out in time, according
to the study, which is part of an ongoing special collection of research
in AGU journals related to the current pandemic.

Weather forecasts are an essential part of daily life, but inaccurate
forecasts can also impact the economy, according to Ying Chen, a senior research associate at the Lancaster Environment Centre in Lancaster,
United Kingdom and lead author of the new study. The accuracy of
weather forecasts can impact agriculture as well as the energy sector
and stability of the electrical grid.

Wind turbines rely on accurate forecasts of windspeed and energy companies depend on temperature forecasts to predict what the energy load will be
each day as people crank up their air conditioning.

"If this uncertainty goes over a threshold, it will introduce unstable
voltage for the electrical grid," Chen said. "That could lead to
a blackout, and I think this is the last thing we want to see in
this pandemic." The regions most impacted by the reduction in weather forecasts have been those with normally heavy air traffic, like the United States, southeast China and Australia, as well as isolated regions like
the Sahara Desert, Greenland and Antarctica. Western Europe is a notable exception: its weather forecasts have been relatively unaffected despite
the number of aircraft over the region dropping by 80-90%.



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

"It's a good lesson which tells us we should introduce more observation
sites, especially in the regions with sparse data observations," Chen
said. "This will help us to buffer the impacts of this kind of global
emergency in the future." Chen also found precipitation forecasts
around the world have not been significantly affected, because rainfall forecasts have been able to rely on satellite observations. But March,
April and May have been relatively dry this year in most of the world,
so Chen cautions that precipitation forecasts could potentially suffer
as the hurricane and monsoon seasons arrive.

Comparing forecasts Forecast models are more accurate when a greater
number of meteorological observations are taken into account, and the
number of observations is greatly diminished when fewer planes are
in the air, as was the case in March-May of this year. The Aircraft Meteorological Data Relay program includes over 3,500 aircraft and 40 commercial airlines, which typically provide over 700,000 meteorological reports a day.



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

He found 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 dropped off, forecast accuracy in several regions that rely on
aircraft observations had actually improved by up to 1.5 degrees Celsius
(35 degrees Fahrenheit) over previous years. But in March-May 2020, when flights were reduced by 50-75% compared to February, that improvement
in accuracy vanished.

Chen found western Europe was the only region with normally high flight
traffic that did not suffer remarkably reduced accuracy in temperature forecasts. He attributed this to over 1,500 meteorological stations that
form a dense data collection network in the area.

However, European weather was particularly unvarying over the March-May
2020 time period, making it easier to forecast with less data, according
to Jim Haywood, a professor of atmospheric science at the University of
Exeter, United Kingdom, who was not involved with the new study. Haywood suspects this played a role in the persisting accuracy of western European forecasts in addition to the network of ground observation points.

The longer forecasters lack aircraft data, the more weather forecasts will
be impacted, according to the study. While precipitation forecasts have
so far been unaffected, scientists' ability to catch early warning signs
of extreme weather events this summer could suffer. In the long term,
the study results suggest sources of weather data should be diversified, especially in observation-sparse areas and areas that rely heavily on commercial flights, according to Chen.


========================================================================== Story Source: Materials provided by American_Geophysical_Union. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Ying Chen. COVID‐19 Pandemic Imperils Weather
Forecast. Geophysical
Research Letters, 2020; DOI: 10.1029/2020GL088613 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200717101026.htm

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