Aircraft exhaust temperature

The machine exhaust is atmospheric air conditioning.

According to the British "New Scientist" magazine reported on August 7th, people can often see long tails left by airplanes passing through the air, but few people think that these tails not only have ornamental value, but also can play a wonderful "air conditioning" role. A recent study shows that the atomized tail gas left in the air by airplanes can change the weather, making it cooler during the day and warmer at night.

"9 1 1" creates research opportunities.

Scientists have found that the smoky tail gas formed by jet planes passing through the air will reflect sunlight during the day, reducing the heat absorbed by the earth; On the contrary, at night, this water vapor can inhibit the heat dissipation of the surface and keep the surface temperature. This reduces the temperature difference between day and night.

It has long been recognized that the atomized tail gas, or "condensation tail", staying at high altitude can become cirrus clouds under appropriate atmospheric conditions. However, the impact of this phenomenon on the weather has been difficult to measure effectively, because the world air transport, especially the flights in Europe and North America, has never stopped, and it is impossible for scientists to accurately monitor it.

Finally, a once-in-a-lifetime opportunity suddenly came to the researchers. The "9. 1 1" terrorist attack made countless people sad, but it also created an excellent opportunity to measure the actual temperature of the atmosphere-all domestic flights in the United States were grounded for three days. A research team from the University of Wisconsin seized the opportunity to measure the daily average maximum and minimum temperatures over North America on the "no-fly day" and compared them with the data recorded by 1977.

The exhaust turned the sky from sunny to cloudy.

The researchers found that if there is no flight in the air, the difference between the highest and lowest temperatures in a day is one degree more than that in flight, which means that the temperature difference on the "no-fly day" changes even more. This kind of influence is regional and generally involves only one or two countries.

But there are also special circumstances, such as the "tail gas explosion" produced in many flight situations, which can affect the entire east coast of the United States. Dr. Travis, one of the team members, pointed out: "I have seen many times that the' artificial cloud' formed by waste gas covers half the sky, and some abnormal conditions can even turn sunny days into cloudy days."

Satellite images show that as many as 50 kinds of waste gases often appear in the same area at the same time. In areas with many routes, aircraft exhaust emissions will be more frequent. Before and after "9. 1 1", the most obvious temperature changes were concentrated in the central and western, northeastern and western parts of the North Pacific. These are areas with dense air routes in the United States.

Greatly aggravate the greenhouse effect

According to Dr. Travis' analysis, aircraft usually produce exhaust gas at the cruising altitude of 9100 ~12000m. People usually think that there are more exhaust emissions from airplanes in places with many airports, which is not correct. In fact, it takes enough time for the plane to rise to a sufficient cruising altitude, so the high altitude between airports is the concentration of aircraft exhaust.

Besides, a plane can't be a climate. Researchers believe that the influence of aircraft exhaust on temperature must meet two conditions: first, there must be enough aircraft passing through the same atmosphere at the same time, and second, the atmosphere in this area can ensure the long-term existence of exhaust. However, scientists still don't know how many planes can produce this effect. They just estimate that they need at least 65,438+00 planes.

In fact, people began to pay attention to aircraft exhaust very early. The composition of jet exhaust contains a large number of atmospheric suspended particles composed of carbon black, sulfur dioxide, carbon dioxide and other substances, which will reduce the atmospheric ozone concentration and aggravate the greenhouse effect. Many scientists have suggested that it is urgent to control jet exhaust.