Unexpected high contribution of in-cloud wet scavenging to nitrogen deposition induced by pumping effect of typhoon landfall in China

Abstract

Atmospheric nitrogen deposition has large eco-environmental effects such as ocean acidification, eutrophication in coastal areas. However, knowledge of the source and the pathway of N deposition in coastal areas is limited, especially during tropical storms, hindering the accurate quantification of how anthropogenic activities influence the ocean ecosystem. In this study, the Nested Air Quality Prediction Modeling System was used to investigate the wet deposition of N induced by typhoon Hagupit over eastern coastal China from an in- and below-cloud process perspective. Our results reveal for the first time an enhancement mechanism of N deposition related to the ‘pumping effect’ of the typhoon. Different from the non-typhoon conditions, air pollutants in the typhoon-affected regions were pumped into the higher altitudes and deposited via the in-cloud scavenging process in the moving path of the typhoon-affected regions. This study updates our understanding of the source–receptor relationship on atmospheric wet deposition caused by tropical cyclones.

Severe level of photochemical oxidants (Ox) over the western coast of Japan during autumn after typhoon passing

“…Typhoons are usually associated with hazards, such as strong winds, storm surges, and rainfall, that can cause considerable damage and disruption. Although such a strong wind field could simply result in good ventilation and reduce air pollutant concentrations, several studies have reported that typhoons degraded air quality in terms of PM 2.5 17 , 18 , O x 19 , 20 , and deposition 21 , 22 . Because the O x warning issued in September 2020 occurred in a remote area of Goto Island, westernmost Nagasaki Prefecture, the horizontal distribution over East Asia should also be examined.…”