BEIJING, April 13 (Xinhua) -- Chinese researchers reported their first attempt to measure the vertical carbon dioxide distribution by using a non-dispersive infrared (NDIR) gas sensor, according to a recent study by the Chinese Academy of Sciences.

The miniaturized sensor, co-developed by experts from the academy's Institute of Atmospheric Physics and the University of Maryland, was carried in a giant aerostat, a helium-filled tethered balloon rising to 1,000 meters, to measure the vertical carbon dioxide distribution during a week-long experiment in January 2019, at a suburban site in Shijiazhuang, capital of north China's Hebei Province, also a city with serious air pollution.

Among all greenhouse gases, carbon dioxide accounts for the largest share. Since the 1970s, scientists have conducted long-term global monitoring of greenhouse gases. However, data of carbon dioxide in its vertical distribution are insufficient.

Compared with traditional instruments, such as high towers and aircraft, the use of gas sensors based on NDIR technology has a lower cost. "It enables researchers to achieve a more accurate assessment of the distribution and changes of the greenhouse gas concentration, which is crucial for the climate policy formulation and climate change predictions," said the institute researcher Han Pengfei, who led the study.

The study showed that the greenhouse gas concentration in the atmosphere within 1,000 meters displayed a decreasing trend with the increase in height. Furthermore, the levels of the vertical greenhouse gas concentration varied from morning to afternoon, which were affected by weather conditions and carbon dioxide emission sources, including human activities and the burning of fossil fuels.

The researchers also found that the sensor produced data consistent with the traditional method, indicating the instrument is feasible for high spatial density carbon dioxide monitoring, Han said.

The results were published in the journal Atmospheric and Oceanic Science Letters.

Hebei Province, together with its neighbors Beijing and Tianjin, topped China in carbon emissions intensity due to massive emissions of pollutants from factories and vehicles. Chinese scientists have intensified carbon dioxide monitoring efforts in this region in recent years, to offer anti-smog measures.

The institute has obtained data of carbon dioxide concentration by using greenhouse monitoring satellites from space, airships in the air and tower stations on the ground.

Researchers also installed monitoring instruments atop cars to acquire mobile measurements during the experiment last year.

According to Han, vertical measurements can be realized by using high towers, giant balloons and aircraft. However, the tower measurements are restricted by tower heights, which are generally lower than 500 meters. Though aircraft can measure greenhouse gases at higher altitudes, up to 13 km, they have a higher cost and a lower vertical resolution than a tethered balloon.

Compared with other vertical carbon dioxide observation methods, tethered balloons, therefore, are cheaper and easier to operate.

The study, using a sensor carried by a tethered balloon, will help us to understand the vertical distribution of carbon dioxide and provide data for the modeling of the greenhouse gas transport, Han said.