A composite of the effects of major sudden stratospheric warming events on carbon dioxide radiative cooling in the mesosphere-lower-thermosphere

TL;DR

This study investigates how major sudden stratospheric warming events affect CO₂ radiative cooling in the mesosphere-lower thermosphere, revealing temperature and transport-driven variations during these events.

Contribution

It provides the first composite analysis of SSW-induced changes in CO₂ radiative cooling in the MLT region from 2005 to 2020, linking dynamical changes to radiative effects.

Findings

CO₂ radiative cooling decreases during mesospheric cooling in SSW events

Cooling is associated with temperature perturbations and oxygen transport

Cooling enhances during the recovery stage of SSW events

Abstract

The major sudden stratospheric warming (SSW) events strongly influence the mean structure of the entire atmosphere, from the troposphere to the thermosphere. These events disrupt the compositional and thermal structure of the mesosphere and lower thermosphere (MLT), causing spatiotemporal variations in the concentration of trace species of this region. Currently, the role of dynamical changes during SSW events on radiative cooling in the MLT region is not well understood. An investigation of the SSW-induced changes in CO$_2$ radiative cooling in the MLT region is presented by examining the changes in the dynamics and transport of key species, such as CO$_2$ and atomic oxygen (O). A composite analysis has been performed to understand these changes during the major SSW events that occurred between 2005 and 2020. The variation of trace species is found to be associated with the change in vertical residual circulation. The results also show that CO$_2$ radiative cooling decreases during the mesospheric cooling that occurs during the stratospheric warming over the polar region. During the recovery stage of the SSW event, the CO$_2$ radiative cooling enhances in the mesosphere. These variations in CO$_2$ radiative cooling are mainly caused by temperature perturbations and oxygen transport in the MLT region. The contribution of temperature change and transport have also been investigated in detail.