Typhoon-enhanced BVOC and Pollutants Drive Highly Oxidized SOA Formation in Subtropical Evergreen Forests in Okinawa, Japan

Typhoon Khanun’s passage over Okinawa Island in July and August 2023 offered a valuable opportunity to investigate its influence on atmospheric composition, particularly biogenic volatile organic compounds (BVOCs) and secondary organic aerosols (SOA). While typhoons are recognized for transporting ozone from remote regions, Okinawa’s unique geographic location resulted in elevated ozone levels after the typhoon’s departure. This phenomenon was driven by strong southwesterly to northwesterly winds that transported polluted air masses from eastern China. The typhoon also triggered significant increases in BVOC emissions, notably monoterpenes. These emissions, coupled with the highly oxidizing conditions in the post-typhoon air mass, led to substantial SOA formation. Both OH and NO₃ radicals played crucial roles in oxidizing BVOCs, with NO₃ becoming increasingly important at night. This study emphasizes the intricate connection among meteorological events, forest ecosystems, and atmospheric chemistry. Continuous monitoring is essential to fully understand the impact of such natural disturbances on air quality and climate.