11:45 AM - 12:00 PM
[PEM13-23] What causes the Antarctic Mesospheric Cooling during 2019 SH SSW?
Keywords:Sudden Stratospheric Warming (SSW), Anthropogenic emission of CO2 , Mesosphere Cooling, Meteor Radar , Planetary Waves
Sudden stratosphere warmings (SSWs) very rarely occur in the southern hemisphere (SH) polar region due to its geographical condition. During 2019 minor SSW in the SH the polar stratosphere temperature and planetary wave (PW) improvement are found to be unusual from the history for 40 years, hence, we named it as “Extremely-Rare SSW”. We found unusual cooling of polar mesosphere during the SSW and the possible reasons have been discussed in the present work. Usually, Carbon dioxide (CO2) warms the Earth's surface due to the absorption of solar radiation, however, it shows a cooling effect above the stratopause through infrared emission. In addition, ozone (O3) depletion due to anthropogenic emission of greenhouse gases results in a cooling effect in the stratosphere and mesosphere. Using the ground-based meteor radar (MR) and MLS satellite observations the Antarctic mesosphere temperature response to the 2019 minor SSW was observed. The polar mesopause cooled to 26 K in response to 66 K warming in the stratosphere. We have noted the weakening of gravity wave (GW) activity and upward propagation of 10-day planetary waves (PWs) during the SSW. We also observed the enhancement in Carbon monoxide (CO), and fall in O3 during the peak SSW. We further observed a distinct feature of the mesosphere cooling due to the combined effect of PWs, CO2 infrared cooling, and O3 depletion, rather than the usual adiabatic cooling by GWs. The wavelet spectra of the temperature and meridional winds show the existence PWs in the temperature and meridional winds from 32 to 80 km consistently, which in turn suggests that the chemical tracers caused mesosphere cooling are uplifted from the lower atmosphere through the PWs and meridional circulation in the SH.
Our observations reveal that the greenhouse gases, especially CO2 emitted by anthropogenic or natural disaster sources in the lower atmosphere, propagate upward by the PWs, and becomes one of the major drivers of the mesospheric temperature variability in the SH polar region. Though the less land surface area over the SH, the CO2 emission is mainly originating from the Australian wildfires, and Southern Ocean outgassing. Further, the tropical contents are a major source of CO2 emission, since CO2 has a long photochemical lifetime, which transports poleward and upward through the meridional circulation (Brewer-Dobson Circulation) and affects the mesosphere. Thus the 2019 SSW effect may not be limited to the Antarctic mesosphere, but it may have extended to the other tropical and NH latitudes.
Our observations reveal that the greenhouse gases, especially CO2 emitted by anthropogenic or natural disaster sources in the lower atmosphere, propagate upward by the PWs, and becomes one of the major drivers of the mesospheric temperature variability in the SH polar region. Though the less land surface area over the SH, the CO2 emission is mainly originating from the Australian wildfires, and Southern Ocean outgassing. Further, the tropical contents are a major source of CO2 emission, since CO2 has a long photochemical lifetime, which transports poleward and upward through the meridional circulation (Brewer-Dobson Circulation) and affects the mesosphere. Thus the 2019 SSW effect may not be limited to the Antarctic mesosphere, but it may have extended to the other tropical and NH latitudes.