Seasonal and Diurnal Variations of Surface Ozone at Ieodo in the East China Sea

Abstract. Ieodo Ocean Research Station (IORS), a research tower (~ 40 m a.s.l.) for atmospheric and oceanographic observations, is located in the East China Sea (32.07° N, 125.10° E). The IORS is almost equidistant from South Korea, China, and Japan and, therefore, it is an ideal place to observe Asian outflows without local emission effects. The average ozone concentrations were 51.8 ± 15.9 ppbv during June 2003–December 2010. The seasonal variation of ozone was distinct, with a summer minimum (37.8 ppbv) and a spring maximum (61.1 ppbv), and was largely affected by seasonal wind pattern over East Asia. The fractional contribution of ozone at IORS could be attributed to six well distinguished air masses that were classified by the cluster analysis of backward trajectories. Marine air from the Pacific Ocean represents a relatively clean background air with a lowest ozone level of 32.2 ppbv in summer. In spring and winter the influence of Chinese outflows was dominant with higher ozone concentrations of 61.6 and 49.3 ppbv, respectively. This study confirms that the influence of Chinese outflows was the main factor determining O3 levels at IORS, of which extent was apt to be changed by meteorological state, particularly at a long-term scale.

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Variations of surface ozone at Ieodo Ocean Research Station in the East China Sea and the influence of Asian outflows

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-12611-2015 ◽

2015 ◽

Vol 15 (21) ◽

pp. 12611-12621 ◽

Cited By ~ 8

Author(s):

J. Han ◽

B. Shin ◽

M. Lee ◽

G. Hwang ◽

J. Kim ◽

...

Keyword(s):

East China Sea ◽

Surface Ozone ◽

East China ◽

Research Station ◽

The East China Sea ◽

Ozone Level ◽

Air Masses ◽

China Sea ◽

The Pacific ◽

Marine Air

Abstract. Ieodo Ocean Research Station (IORS), a research tower (~ 40 m a.s.l.) for atmospheric and oceanographic observations, is located in the East China Sea (32.07° N, 125.10° E). The IORS is almost equidistant from South Korea, China, and Japan and, therefore, it is an ideal place to observe Asian outflows without local emission effects. The seasonal variation of ozone was distinct, with a minimum in August (37 ppbv) and two peaks in April and October (62 ppbv), and was largely affected by the seasonal wind pattern over east Asia. At IORS, six types of air masses were distinguished with different levels of O3 concentrations by the cluster analysis of backward trajectories. Marine air masses from the Pacific Ocean represent a relatively clean background air with a lowest ozone level of 32 ppbv, which was most frequently observed in summer (July–August). In spring (March–April) and winter (December–February), the influence of Chinese outflows was dominant with higher ozone concentrations of 62 and 49 ppbv, respectively. This study confirms that the influence of Chinese outflows was the main factor determining O3 levels at IORS and its extent was dependent on meteorological state, particularly at a long-term scale.

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