A research team led by Prof. SI Fuqi from Anhui Institute of Optics and Fine Mechanics (AIOFM), Hefei Institutes of physical Science (HFIPS) of Chinese Academy of Sciences (CAS) developed a new method to retrieve the tropospheric ozone profiles. The corresponding results were published in the journal Science of the Total Environment.
Ozone, which participated in the chemical conversion process of various atmospheric pollution, is a typical secondary pollutant especially in urban area. The accurate monitoring of surface ozone concentration and vertical distribution is important to strengthen the prevention and control of ozone pollution. Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS), a passive optical monitoring technology, can realize the retrieval of multi-component trace gases. However, due to the strong absorption of stratospheric ozone, it makes the retrieval of tropospheric ozone profiles by MAX-DOAS technology a very challenging task.
In this research, Associate Prof. LUO Yuhan and Dr. QIAN Yuanyuan from AIOFM innovatively employed MAX-DOAS measurements to retrieve tropospheric ozone profiles. They applied the methods in a SCIATRAN radiative transfer model to determine the influence of stratospheric absorption on the retrieval of these profiles.
Thanks to the optimal estimation algorithm, researchers accurately obtained the absorption of troposphere ozone and reliable troposphere ozone profiles.
The inversion method was accurate, according to the team. They obtained tropospheric ozone concentrations during the PRIDE-GBA Campaign with it.
The team retrieved ozone differential slant column densities with the "time-interpolated zenith spectrum" as the reference spectrum. By subtracting the simulated stratospheric ozone differential slant column densities, they calculated the precise tropospheric ozone differential slant column densities, which was simulated from the SCIATRAN model.
"We compared the observed ozone profile and surface ozone concentrations with Lidar and in-situ measurements," concluded LUO, "the results were highly correlated, with correlation coefficients of 0.75 and 0.81, respectively".
This study expanded the application scenarios of the MAX-DOAS instrument and provided a new solution for studying the mechanism of tropospheric ozone formation.
Combined with the retrieved NO2 and HCHO profiles using the MAX-DOAS measurements, the mechanisms of regional tropospheric ozone pollution can be analyzed more accurately. Meanwhile, the cost of observation and instrument maintenance will be greatly reduced.
This work was supported by the National Natural Science Foundation of China (Grant No.41941011 and 41676184) and the Youth Innovation Promotion Association of CAS (Grant No. 2020439).
