2025 Data (Information)

Modulation of Stratosphere-to-Troposphere Transport of Ozone by North Pacific Weather Patterns

Lee, Jaewon

Stratosphere-to-troposphere transport (STT) of ozone is a major natural source of tropospheric ozone and is tightly linked to both stratospheric and tropospheric circulations. However, the complex interactions of drivers make it challenging to understand the subseasonal variability of STT. In this study, we apply a weather pattern perspective to address the midlatitude internal variability of STT over western North America, the strongest global hotspot. Six weather patterns are identified using self-organizing maps applied to year-round 500 hPa geopotential height anomalies from a nudged WACCM6 simulation. Extreme STT occurs preferentially in the pattern with a deep trough south of Alaska, which resembles the Pacific Trough regime. A larger ozone source and an aligned strong jet lead to frequent intrusions in this specific pattern. This framework is able to explain the ENSO impact on STT variability and its temporal evolving preference. It also suggests potential predictability of stratospheric intrusion through weather patterns.