Carbon monoxide (CO) is a toxic gas and one of the major pollutants of urban air. Beijing is a megacity with a population of more than 21 million; and Moscow, more than 12 million. But what has been the trend of change in the CO total column amount in these two megacities during recent decades? And what about Eurasia? The answers to these questions were recently sought from an analysis of long-term ground-based measurements and satellite observations. The findings are published in Advances in Atmospheric Sciences.

The scientists leading the study—Professor WANG Pucai from the Institute of Atmospheric Physics, Chinese Academy of Sciences, and Professor G. S. GOLITSYN from the Institute of Atmospheric Physics, Russian Academy of Sciences—and colleagues, carried out more than 10 years of measurements of the CO total column amount using high-resolution infrared spectrometers in Beijing, Moscow, and their respective suburban stations. Based on the collected dataset, the CO total column amounts and their trends of change in the two megacities were obtained. Additionally, the trend of change in the CO total column amount in midlatitude regions of Eurasia was also determined from satellite-based high-resolution infrared spectrometers, the measurements from which were validated with the ground-based measurements.

The team found a decreasing trend (1.14% ± 0.87% yr^-1) in the CO total column amount (1998–2014) at the urban site of Beijing. However, at the Moscow site, it decreased remarkably by 3.73% ± 0.39% yr^-1, in which a sharp decrease took place before 2007. A slight decrease (0.4%–0.6% yr^-1) in the CO total column amount was detected over the midlatitude regions of Eurasia, while a reduction of 0.9%–1.2% yr^-1 was found in Southeast Asia.

The team pointed out that the use of clean energy and changes with respect to forest fires are the main reasons for these decreasing trends. Also highlighted was that the CO total column amounts in heavily polluted areas were seriously underestimated by IASI MetOp-A and AIRSv6 data, when compared with the ground measurements.

Reference

Wang, P. C., and Coauthors, 2018: Long-term trends of carbon monoxide total columnar amount in urban areas and background regions: ground- and satellite-based spectroscopic measurements. Adv. Atmos. Sci., 35(7), https://doi.org/10.1007/s00376-017-6327-8 .

Contact: LIN Zheng, jennylin@mail.iap.ac.cn