Abstract
Abstract. Observations show strong correlations between large-scale ozone and temperature variations in the tropical lower stratosphere across a wide range of timescales. We quantify this behavior using monthly records of ozone and temperature data from Southern Hemisphere Additional Ozonesonde (SHADOZ) tropical balloon measurements (1998–2016), along with global satellite data from Aura microwave limb sounder and GPS radio occultation over 2004–2018. The observational data demonstrate strong in-phase ozone–temperature coherence spanning sub-seasonal, annual and interannual timescales, and the slope of the temperature–ozone relationship (T / O3) varies as a function of timescale and altitude. We compare the observations to idealized calculations based on the coupled zonal mean thermodynamic and ozone continuity equations, including ozone radiative feedbacks on temperature, where both temperature and ozone respond in a coupled manner to variations in the tropical upwelling Brewer–Dobson circulation. These calculations can approximately explain the observed (T / O3) amplitude and phase relationships, including sensitivity to timescale and altitude, and highlight distinct balances for “fast” variations (periods < 150 d, controlled by transport across background vertical gradients) and “slow” coupling (seasonal and interannual variations, controlled by radiative balances).
Highlights
Large-scale ozone and temperature variations in the tropical lower stratosphere exhibit strong correlations across a range of timescales. This behavior is well known for the annual cycle in the lower stratosphere (Chae and Sherwood, 2007; Randel et al, 2007) and for interannual variations linked to the quasi-biennial oscillation (QBO) (e.g., Hasebe et al, 1994; Baldwin et al, 2001; Witte et al, 2008; Hauchecorne et al, 2010) and El Niño–Southern Oscillation (ENSO; Randel et al, 2009)
Calculations have shown that the radiative effects of ozone feed back onto and enhance temperature variations, and this topic has been well studied in relation to the annual cycle in the tropical lower stratosphere (Chae and Sherwood, 2007; Fueglistaler et al, 2011; Ming et al, 2017; Gilford and Solomon, 2017) and by Forster et al (2007) and Polvani and Solomon (2012) for decadal-scale trends
Observations show strong correlations between ozone and temperature in the tropical lower stratosphere, and calculations show that the ozone radiative feedbacks significantly enhance temperatures, e.g., by ∼ 30 % for the annual cycle (e.g., Ming et al, 2017)
Summary
Large-scale ozone and temperature variations in the tropical lower stratosphere exhibit strong correlations across a range of timescales. The dominant mechanism for strong ozone–temperature correlations in the tropical lower stratosphere is relatively simple: namely, variations in upwelling (i.e., fluctuations in the tropical Brewer–Dobson circulation) acting on the strong background vertical gradients of both ozone and potential temperature, leading to correlated variability This behavior was quantified from observations and model simulations in Abalos et al (2012, 2013), highlighting the control of upwelling for forcing transient variations in temperature, ozone and other trace species with strong vertical gradients, such as carbon monoxide (CO). Our goal is to explain the salient features of temperature–ozone (T –O3) coupling from observations in a relatively simple framework, including the frequency and altitude dependences of the (T / O3) amplitude and phase relationships These results are a complement to the recent analyses of Birner and Charlesworth (2017) and Charlesworth et al (2019), based on a very different model
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