[A-AS12] Atmospheric Chemistry

[AAS12-05] Return to the decade-ago level of tropospheric nitrogen dioxide pollution in East Asia

*Hitoshi Irie¹, Takuya Muto¹, Syuichi Itahashi², Jun-ichi Kurokawa³, Itsushi Uno⁴ (1.Chiba University, 2.Central Research Institute of Electric Power Industry, 3.Asia Center for Air Pollution Research, 4.Kyushu University)

Keywords:NO2, trend, East Asia, OMI

Long-term (2005-2015) tropospheric nitrogen dioxide (NO₂) column data recorded by the satellite-borne Ozone Monitoring Instrument (OMI) in East Asia were analyzed to investigate annual trends quantitatively and their potential causes. We found an evident decrease in the NO2 level over China after 2011 and then a return to the 2005 level in 2015. The grid-basis trend analysis implies that the rapid decrease occurred on a provincial or larger spatial scale and was likely due to a nationwide action such as the widespread use of denitrification units. Other prominent features were seen in Japan. Despite a significant substitution from nuclear to thermal power after 2011 as a consequence of a massive earthquake off the Pacific coast of northern Japan, the NO₂ level continued to decrease for both periods (2005-2011 and 2011-2015). The decrease contributed to a return to the decade-ago level of tropospheric NO₂ pollution in East Asia.