Effect of ENSO on the Ozone Valley over the Tibetan Plateau Based on the WACCM4 Model

Abstract

El Niño-Southern Oscillation (ENSO) is the most significant global ocean–atmosphere coupled signal in the tropical Pacific Ocean, and it can affect the stratosphere. However, the ENSO-related dynamical processes that influence the ozone valley during summer are still not well understood and are under-investigated. In this study, we used the ERA5 and MERRA-2 reanalysis data from 1979 to 2021 combined with numerical simulations to analyze the mechanisms through which ENSO affects the ozone valley over the Tibetan Plateau in the upper troposphere and the lower stratosphere (UTLS) in summer. The results showed that the two cores of the ozone valley in UTLS were more evident in the summer following La Niña than in the summer following El Niño. At low latitudes, negative O3 anomalies in UTLS were observed in the summer following El Niño and positive O3 anomalies were observed in the summer following La Niña. At middle latitudes, negative O3 anomalies in UTLS were found near 60°E in the summer following El Niño, while negative anomalies were found at 40°E and 120°E in the summer following La Niña. The analysis of the flow and vorticity fields suggested that the field anomalies can cause vertical motion, which in turn leads to the mixing of different ozone concentrations and affects the ozone valley in UTLS over the Tibetan Plateau. In particular, the warming of the Indian Ocean sea-surface temperature (SST) in the summer following El Niño enhances the South Asian High (SAH) through two-stage thermal adaptation, leading to ozone anomalies at low latitudes in the ozone-valley region. These conclusions were verified by a simulation using the WACCM4 model, the results of which were consistent with the original observations.

The Impact of Different Types of El Niño Events on the Ozone Valley of the Tibetan Plateau Based on the WACCM4 Mode

“…Researchers have extensively studied the phenomenon and causes of the ozone valley over the TP [21][22][23][24][25][26][27]. Guo Dong et al [22] found that the center of the ozone valley is located near the tropopause, with an intensity of approximately −15 DU, and the other sub-strong center is located in the upper stratosphere with an intensity of −8 DU.…”

Gravity wave analysis and stratosphere-troposphere exchange during Typhoon Molave (2020)

“…Tropical cyclones play an important role in STE (Emanuel 2005;Merrill 1988) as demonstrated by many previous studies on typhoon-induced STE processes. First of all, ozone is one of the most important trace components in the atmosphere and can be used as a tracer to reflect physical processes such as Quasi-biennial oscillation, El Niño-Southern Oscillation (Chang et al 2022;Li et al 2023), and is easy to be depleted by reacting with other substances (Feng et al 2023). Moreover, STE is of great significance to the change of O3 content between the stratosphere and troposphere, so study the variation of O3 content in the stratosphere and troposphere can characterize the role of typhoons on STE.…”