A budget analysis of NO x column losses over the Korean peninsula

In this study, the chemical and physical losses of nitrogen oxides (NO_x) over the Korean peninsula were discussed in order to better understand the effects of the NO_x losses on the tropospheric NO₂ columns. Initially, it was found that the physical loss processes due to dry and wet depositions had almost negligible impacts on the NO_x loss processes over the Korean peninsula. In contrast, the hourly NO_x chemical column losses were large at ??10¹⁴ molecules cm^?2 h^?1. The amounts of NO_x removed for 1 hour account for approximately 33?C35% of the episode-averaged tropospheric NO₂ columns during summer over the Korean peninsula. The NO_x chemical column loss rates were 24.1?C70.9 times larger than the NO_x physical column loss rates. In a budget analysis of the NO_x chemical column losses, HNO₃ formation via the reaction of OH + NO₂ had the largest contribution toward the NO_x chemical losses (42?C55% during fall and winter seasons; 76?C77% during spring; 92?C93% during summer). Large amounts of NO_x were also removed by heterogeneous nitrate formation via N₂O₅ condensation during the cold seasons (42?C56%) over the Korean peninsula. The columnar NO_x chemical losses took place mainly due to the two chemico-physical reaction processes, and also showed seasonal variations. PAN (Peroxyacetyl Nitrate) is another NO₂ reservoir of potential importance. If the influence of the PAN-related chemistry on the NO_x budget is considered, it can result in an approximate 69% increase in the NO_x chemical column loss during summer. Such increases in the amounts of NO_x removed for 1 hour due to the formation of PAN were equivalent to 56?C58% of the episode-averaged tropospheric NO₂ columns during summer over the Korean peninsula. Such active NO_x chemical losses during summer are another main factor for the tropospheric NO₂ columns exhibiting their smallest values during summer.