New maps show airplane contrails over the US dropped steeply in 2020

Travel restrictions and a drop in passengers caused a record number of flights to be grounded in 2020. The reduction in air travel cleared the skies of jets and fluffy white clouds.

MIT engineers mapped the contrails that were generated over the United States in 2020, and compared the results to prepandemic years. They found that on any given day in the last two years, there was a total area equal to Massachusetts and Connecticut combined. In 2020, this coverage fell by about 20 percent, like the U.S. flights.

The findings are proof that the mapping technique works. Their study is the first time researchers have captured the fine and ephemeral details of contrails over a large continental scale.

The researchers are using the technique to predict where the contrails are likely to form. The cloud-like formations play a significant role in global warming. The team is working with major airlines to forecast regions in the atmosphere where there may be contrails.

The technology can help divert planes in real time.

The results were published in the journal Environmental Research Letters. His co-authors at MIT include a graduate student, a research scientist, and a professor.

Training on the trail.

About half of the aviation industry contribution to global warming comes from carbon dioxide emissions. The other half is thought to be a result of the other half. The white tails are produced when the hot, humid exhaust of the plane mixes with the cool humid air in the atmosphere. The thin lines of the contrails quickly spread out and act as blankets that trap the Earth's outgoing heat.

A single contrail may not have much of a warming effect, but taken together they have a significant impact. The estimates of this effect are uncertain and are based on limited satellite data. Traditional computer vision programs that analyze data have a hard time distinguishing the differences between natural and artificial clouds.

The MIT team looked at images taken by NASA's GOES-16 satellite, which hovers over the same swath of the Earth, including the United States, taking continuous, high-resolution images.

The team first obtained about 100 images from the satellite and trained a group of people to label the images as either part of a contrail or not. They used the labeled dataset to train a computer-vision algorithm to see a cloud.

The researchers used about 100,000 satellite images to run the algorithm, each of which had a value of about 2 square kilometers. The images covered the contiguous U.S., along with parts of Canada and Mexico, and were taken about every 15 minutes.

The daily maps of contrails over the United States were generated by the algorithm. The major flight paths of most U.S. airlines were mirrored in these maps. The fact that planes landing and taking off around airports are not high enough in the atmosphere to form contrails is reflected in the appearance of holes around major airports.

When processing satellite imagery, this method resulted in recognizable flight routes, which is one piece of evidence that says this method really does capture contrails over a large scale.

There are cloudy patterns.

The researchers calculated the total area covered by the contrails based on the maps. The US took up about 43,000 square kilometers on an average day in the last two years. The coverage dropped by 20 percent in March of 2020. Air travel resumed through the year.

Daily and seasonal patterns were observed by the team. The morning and afternoon appeared to be the peak times for the contrails. As natural clouds are more likely to form in the afternoon, the program may have trouble distinguishing between them later in the day. It might be an indication of when the most contrails form. In the late winter and early spring, more of the air is naturally colder and more favorable for contrail formation.

The team has adapted the technique to predict where the contrails will form. It could take a significant chunk out of aviation's contribution to global warming by avoiding these regions.

It takes a long time to make aviation sustainable, and trail avoidance could be done in a few years. It is a short-term way of reducing the warming of aviation.

The team is working towards large-scale contrail avoidance using satellite observations.

More information: Vincent R Meijer et al, Contrail coverage over the United States before and during the COVID-19 pandemic, Environmental Research Letters (2022). DOI: 10.1088/1748-9326/ac26f0 Journal information: Environmental Research Letters

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