French, W. John R. and Mulligan, Frank J. and Klekociuk, Andrew R. (2020) Analysis of 24 years of mesopause region OH rotational temperature observations at Davis, Antarctica – Part 1: long-term trends. Atmospheric Chemistry and Physics, 20 (11). pp. 6379-6394. ISSN 1680-7324

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Abstract

The long-term trend, solar cycle response, and residual variability in 24 years of hydroxyl nightglow rotational temperatures above Davis research station, Antarctica (68◦ S, 78◦ E) are reported. Hydroxyl rotational temperatures are a layer-weighted proxy for kinetic temperatures near 87 km altitude and have been used for many decades to monitor trends in the mesopause region in response to increasing greenhouse gas emissions. Routine observations of the OH(6-2) band P-branch emission lines using a scanning spectrometer at Davis station have been made continuously over each winter season since 1995. Significant outcomes of this most recent analysis update are the following: (a) a record-low winter-average temperature of 198.3 K is obtained for 2018 (1.7 K below previous low in 2009); (b) a long-term cooling trend of −1.2 ± 0.51 K per decade persists, coupled with a solar cycle response of 4.3±1.02 K per 100 solar flux units; and (c) we find evidence in the residual winter mean temperatures of an oscillation on a quasi quadrennial (QQO) timescale which is investigated in detail in Part 2 of this work. Our observations and trend analyses are compared with satellite measurements from Aura/MLS version v4.2 level-2 data over the last 14 years, and we find close agreement (a best fit to temperature anomalies) with the 0.00464 hPa pressure level values. The solar cycle response (3.4 ± 2.3 K per 100 sfu), long-term trend (−1.3±1.2 K per decade), and underlying QQO residuals in Aura/MLS are consistent with the Davis observations. Consequently, we extend the Aura/MLS trend analysis to provide a global view of solar response and long-term trend for Southern and Northern Hemisphere winter seasons at the 0.00464 hPa pressure level to compare with other observers and models.

Item Type:	Article
Additional Information:	Cite as: John French, W.R., Mulligan, F.J. and Klekociuk, A.R. (2020) Analysis of 24 years of mesopause region OH rotational temperature observations at Davis, Antarctica - Part 1: Long-term trends. Atmospheric chemistry and physics, 20 (11), 6379-6394.
Keywords:	solar cycle response; Davis research station; solar cycle response
Academic Unit:	Faculty of Science and Engineering > Experimental Physics
Item ID:	15935
Identification Number:	https://doi.org/10.5194/acp-20-6379-2020
Depositing User:	Dr. Frank Mulligan
Date Deposited:	10 May 2022 14:44
Journal or Publication Title:	Atmospheric Chemistry and Physics
Refereed:	Yes
URI:	Publisher
Use Licence:	This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here

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