Equatorial middle atmospheric chemical composition changes during sudden stratospheric warming events

Abstract

<p><strong>Abstract.</strong> Chemical composition data obtained from the Microwave Limb Sounder (MLS) and Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instruments onboard EOS-Aura and ENVISAT satellites are used to investigate the variation of ozone (O<sub>3</sub>), water vapor (H<sub>2</sub>O) and methane (CH<sub>4</sub>) volume mixing ratios (VMRs) in the height range 20–60 km over the equatorial region during the sudden stratospheric warmings (SSWs) of 2004, 2009 and 2012, the occurrence of which are identified using the ERA (European Center for Medium Range Weather Forecasting Reanalysis) Interim temperature and zonal wind data sets. It is found that the O<sub>3</sub> VMR shows increment whereas H<sub>2</sub>O VMR shows decrement during the SSW event and the possible reasons for these changes in the VMRs are investigated. In the upper stratosphere, the source of water vapor is oxidation of CH<sub>4</sub> which takes place either by hydroxyl (OH) or by atomic oxygen (O). However, the OH VMR available for the year 2009 SSW event does not show any significant variation. The decrease of zonal mean MLS temperature over the equator during the SSW suggests that the rate of the reaction of ozone production (O + O<sub>2</sub> ⟶ O</sub>3</sub> + M), which increases with decreasing temperature, shifts the O/O<sub>3</sub> ratio towards O<sub>3</sub>, resulting in the decrease of CH<sub>4</sub> oxidation and consequent decrease in water vapor.</p>

Morphology of ionospheric F2 region variability associated with sudden stratospheric warmings

“…Such SSW‐related ionospheric responses have also been observed at 7°S for major SSW event of 2006 [ Lima et al , ], at 30°S for 2013 SSW event [ Jonah et al , ] and even at midlatitudes of South American sector (2.8°N to 53.8°S) for 2009 major SSW [ Fagundes et al , ]. Further, reports of correlation between enhanced TEC and ozone density following SSW have also been reported [ Goncharenko et al , ; Nath and Sridharan , ].…”

A mid-latitude stratosphere dynamical index for attribution of stratospheric variability and improved ozone and temperature trend analysis

“…While I agree that wave activity proxies such as EP-flux divergence are difficult to calculate, one can try, for example, heat flux evaluated at 100hPa (e.g. Newman et al 2001), which is quite easy to calculate.…”

An upper-branch Brewer–Dobson circulation index for attribution of stratospheric variability and improved ozone and temperature trend analysis

“…As such, ozone and temperature have an inverse relationship in the equatorial stratosphere above 10 hPa, which in turn has a dependence on dynamics (Fusco and Salby, 1999;Mäder et al, 2007;Stolarski et al, 2012), although this is not always the case in the lower stratosphere (Zubov et al, 2013). Ultimately, then, dynamical perturbations at mid-to-high latitudes can directly influence the variability of ozone and temperature (Sridharan et al, 2012;Nath and Sridharan, 2015).…”