Abstract
Abstract. The stratospheric circulation determines the transport and lifetime of key trace gases in a changing climate, including water vapor and ozone, which radiatively impact surface climate. The unusually warm El Niño–Southern Oscillation (ENSO) event aligned with a disrupted Quasi-Biennial Oscillation (QBO) caused an unprecedented perturbation to this circulation in 2015–2016. Here, we quantify the impact of the alignment of these two phenomena in 2015–2016 on lower stratospheric water vapor and ozone from satellite observations. We show that the warm ENSO event substantially increased water vapor and decreased ozone in the tropical lower stratosphere. The QBO disruption significantly decreased global lower stratospheric water vapor and tropical ozone from early spring to late autumn. Thus, this QBO disruption reversed the lower stratosphere moistening triggered by the alignment of the warm ENSO event with westerly QBO in early boreal winter. Our results suggest that the interplay of ENSO events and QBO phases will be crucial for the distributions of radiatively active trace gases in a changing future climate, when increasing El Niño-like conditions and a decreasing lower stratospheric QBO amplitude are expected.
Highlights
The lower stratosphere (10–25 km) is a key region in a changing climate
Our results suggest that the interplay of El Niño–Southern Oscillation (ENSO) events and Quasi-Biennial Oscillation (QBO) phases will be crucial for the distributions of radiatively active trace gases in a changing future climate, when increasing El Niño-like conditions and a decreasing lower stratospheric QBO amplitude are expected
Based on an established multiple regression method applied to Aura MLS observations and Chemical Lagrangian Model of the Stratosphere (CLaMS) model simulations, we found that both the most recent El Niño and the QBO
Summary
The lower stratosphere (10–25 km) is a key region in a changing climate. Transport, mixing and chemistry in this region regulate the amount of key greenhouse gases, such as water vapor and ozone, which radiatively impact temperatures both locally (e.g., Forster and Shine, 2002) and globally (e.g., Forster and Shine, 1999; Solomon et al, 2010; Riese et al, 2012; Dessler et al, 2013). Water vapor mainly originates from the troposphere and its stratospheric concentration is controlled by the tropical cold point tropopause temperatures (Holton and Gettelman, 2001; Hu et al, 2016) and production from methane oxidation (le Texier et al, 1988; Dessler et al, 1994). The amount of stratospheric water vapor is thereby modulated by the coldest temperatures experienced by air parcels ascending through the tropical tropopause layer (TTL) (e.g., between 14 and 19 km; Fueglistaler et al, 2009; Fueglistaler, 2012; Schoeberl and Dessler, 2011). Stratospheric water vapor is the primary source of stratospheric hydrogen oxide radicals, which drive important gas-phase ozone loss cycles, and it strongly influences heterogeneous chemistry on cold sulfate aerosol and the formation
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