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Upper Troposphere – Lower Stratosphere Circulation and Ozone Patterns Driven by ENSO and PDO in South America

Authors: Brandi Gamelin*, University of California - Santa Barbara
Topics: Climatology and Meteorology
Keywords: ENSO, PDO, Ozone, South America, tropopause
Session Type: Paper
Presentation File: No File Uploaded

The El Niño-Southern Oscillation (ENSO) is a well-known Pacific Ocean forcing which drives atmospheric variability around the globe. Less understood are the influences of the ENSO teleconnection on upper troposphere-lower stratosphere (UTLS) ozone. Consequently, this work investigates the interannual – interdecadal relationships between UTLS ozone patterns in South America and El Niño events during the recent PDO phases. MERRA-2 reanalysis data is used to identify the primary modes of variability, and a principal component analysis (PCA) is applied to UTLS austral spring detrended ozone anomalies. The results show a weak tri-pole indicating a possible response to El Niño driven Rossby Wave trains. Furthermore, several mechanisms are influencing UTLS circulation related to El Nino, for example, jet stream position, geopotential height variability, and vertical velocity variability. However, the influence of El Niño on UTLS ozone patterns varies based on the recent PDO phases. Results show that during the last two PDO phases: 1980-1997 (warm PDO) and 1998-2012 (cool PDO), the El Niño teleconnection does not appear to modulate ozone patterns during the warm PDO. However, during the cool PDO, UTLS circulation and ozone patterns are strongly modulated by El Niño. Additionally, the strength of the ENSO teleconnection may be modulated by the location of the Pacific Ocean warm pool - Modoki vs. traditional El Niño, during the cool PDO Modoki is prevalent. These results are likely due to the influence of El Niño induced Rossby wave trains in South America driving enhanced deep convection and perturbing UTLS temperatures and ozone.

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