资源环境科技发展态势分析平台

A key contribution of the analysis is the use of new satellite data offering unprecedented skills to observe the horizontal distribution of lowermost tropospheric ozone over East Asia on a daily basis, with a multispectral approach called IASI + GOME2 (combining Infrared Atmospheric Sounding Interferometer observations in the IR and Global Ozone Monitoring Experiment-2 measurements in the UV). These satellite observations are in good agreement with ozonesondes, with low mean biases (3 %), a precision of about 16 %, a correlation coefficient of 0.85 and practically the same standard deviation for a comparison based on 2 years of data from 46 launching stations distributed worldwide, during all seasons. A similar agreement is also found over East Asia. Moreover, IASI + GOME2 offers a unique capacity for observing the evolution of near-surface ozone during pollution outbreaks (with 5 % bias and 0.69 correlation), according to a comparison with surface in situ measurements during two major ozone events over several Japanese islands. Single-band ozone retrievals, such as those from IASI in the thermal infrared, do not capture such variability.

Using IASI + GOME2, we show that (i) ozone pollution plumes are transported by an anticyclonic circulation around the Yellow Sea from the NCP to northern China, Korea and Japan, collocated with carbon monoxide plumes; (ii) over northern China the plume splits into two pollution filaments with one mixing with freshly emitted pollutants; and (iii) ozone is produced every day of the event, accounting for an enhancement in concentration during transport across East Asia of up to  ∼ 84 % with respect to that produced over NCP. This estimation is done according to monotonically increasing values during 7 days of the ratio of ozone to carbon monoxide enhancements within the transported pollution plumes from about  ∼ 0.25 over the NCP to  ∼ 0.46 over the Pacific south of Japan.