In many parts of the world, predictions have become a lot less accurate due to COVID-19.

British researchers write this in the journal Geophysical Research letters . It has everything to do with the fact that air traffic came to a standstill between March and May. In one fell swoop, 50 to 75 percent of the weather stations mounted on aircraft also fell out of operation. And that leads to considerably less accurate predictions – certainly in areas where there is normally a lot of air traffic and in areas that are quite isolated. And as planes land longer, those predictions become less accurate, the researchers warn.

The importance of aircraft
Meteorologists can use various instruments to map and forecast the weather. For example, there are satellites and weather stations on the ground. Airplanes also play an important role by measuring temperature, air pressure and wind at flight height, among other things. And by collecting the same data in lower layers of air during takeoff and landing.

In total, there are approximately 40 commercial airlines worldwide – including KLM – that collect this data with about 3,500 aircraft and share it with meteorologists. Together, these planes usually account for some 700,000 meteorological observations per day. You can imagine that the loss of many of these flights has a huge impact on the data that meteorologists have at their disposal. And that is reflected in the predictions, the researchers say.

The research
In their study, they compared the accuracy of weather forecasts made in the period between March and May 2020 with those of weather forecasts made in the same period in 2017, 2018 and 2019. The research shows that the predictions in 2020 in terms of temperature, relative humidity, wind speed and air pressure were less accurate than in the years before. In the short term (1 to 3 days), the predictions of, for example, wind speed and air pressure at the surface were still fairly correct, but in the longer term (4 to 8 days) they were considerably less accurate in 2020 than in previous years. And that while the predictions in February of this year – shortly before air traffic came to a halt due to the pandemic – were even more accurate than in previous years.

Precipitation Precipitation
predictions remained fairly accurate. This is probably partly because it relies heavily on satellite data, the researchers say. But what probably also helped is that the months of March, April and May were quite dry in most of the world. The researchers cannot therefore rule out the possibility that precipitation forecasts will also become less accurate when the hurricane and monsoon seasons start.

We sometimes consult them all: the weather forecasts. But they are not only important for the general public, who want to check whether the bbq can be removed from the dust. Accurate weather forecasts are indispensable in many professions and, as such, of great economic importance. For example in the (sustainable) energy sector. Windmills rely heavily on accurate predictions of wind speed and direction. And energy companies use temperature predictions to predict how much energy people are expected to use to heat or cool their homes, for example. Accurate predictions are also of great value for agriculture.

From Greenland to Antarctica
The study also shows that the decrease in air traffic and thus the decrease in weather measurements did not lead to the same decreases in accuracy of the weather forecasts in all areas. For example, the weather measurements seem to be missed especially in areas where there is normally a lot of air traffic. Think of the US, but also the southeast of China and Australia. Also in isolated areas, such as the Sahara, Greenland and Antarctica, the weather forecasts were less accurate.

Western Europe
Strikingly enough, the weather forecasts in Western Europe, despite air traffic declining by 80 to 90 percent, seemed hardly affected. The researchers call this surprising, but think they can explain it. For example, the area has a very dense network of ground stations located on the ground. Many weather balloons are also used to measure at higher altitudes. In addition, however, it should be noted that the European weather was quite stable in the period March-May, which also makes it easier to predict the weather with less data.

What the research makes clear is that in many areas we are currently too dependent on aircraft for our meteorological data. “It’s a good lesson that tells us we need more observation points, especially in areas where data is scarce,” said researcher Ying Chen. “That can help protect us from the effects of such a global emergency in the future.”

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