Mesospheric OH Climate Assessment (MOHCA)

Two remotely-operated optical spectrometers (SPEX and FTS) and a scanning radiometer (UWOSCR) observe the nocturnal hydroxyl (OH) airglow emissions over Davis station Antarctica to monitor long-term trends and variability in temperature and wave activity of the high-latitude upper-atmosphere. All instruments were successfully operated over the 2021 winter observing season which was the 27th consecutive year of continuous measurements at Davis.
Critically for long-term climate records, the instruments continue to be meticulously calibrated. Climate model simulations predict a dramatic cooling response in the high-latitude upper-atmosphere with global increases in greenhouse gases.
In addition to the long-term trends, we find evidence in the residual winter mean temperatures of an oscillation over an approximately 3.5–4.5-year cycle with a peak-to-peak amplitude of 3–4 K. We have dubbed this the quasi-quadrennial (QQO) oscillation and it has not been previously reported. This feature was investigated in the context of the global temperature, pressure, wind, and surface fields using satellite, meteorological reanalysis, sea surface temperature, and sea ice concentration data sets
These results were published in two papers in 2020. "Analysis of 24 years of mesopause region OH rotational temperature observations at Davis, Antarctica – Part 1: long-term trends" (https://acp.copernicus.org/articles/20/6379/2020/) and "Analysis of 24 years of mesopause region OH rotational temperature observations at Davis, Antarctica – Part 2: Evidence of a quasi-quadrennial oscillation (QQO) in the polar mesosphere" (https://acp.copernicus.org/articles/20/8691/2020/)
These measurements are available from the Australian Antarctic Data Centre and integrated into the global Network for Detection of Mesospheric Change (NDMC) coordinated by DLR in Germany.

Two remotely-operated optical spectrometers (SPEX and FTS) and a scanning radiometer (UWOSCR) observe the nocturnal hydroxyl (OH) airglow emissions over Davis station Antarctica to monitor long-term trends and variability in temperature and wave activity of the high-latitude upper-atmosphere. All instruments were successfully operated over the 2020 winter observing season (mid-Feb to end-Oct, ~260 nights) which was the 26th consecutive year of continuous measurements at Davis.
The SPEX made observations on a total of 255 nights yielding 241 nightly average temperatures that pass selection criteria. The FTS measured OH spectra on 269 nights and UWOSCR sampled OH images on 264 nights.
Critically for long-term climate records, the instruments continue to be meticulously calibrated and performance remained excellent during this season.
Climate model simulations predict a dramatic cooling response in the high-latitude upper-atmosphere with global increases in greenhouse gases. In the latest re-analysis of Davis hydroxyl temperature trends the winter average temperature continues to cool at rate of ~1.2° per decade with a solar cycle response of ~4.3° per 100 solar flux units. A maximum seasonal cooling of 3.1 K/decade is also measured for the Antarctic spring (30 day average centered early September). These measurements are available from the Australian Antarctic Data Center and integrated into the global Network for Detection of Mesospheric Change (NDMC) coordinated by DLR in Germany.
This work resulted in 2 peer reviewed publications, 2 popular articles and 2 oral presentation in this reporting period :-
1. https://acp.copernicus.org/articles/20/6379/2020/ - Analysis of 24 years of mesopause region OH rotational temperature observations at Davis, Antarctica – Part 1: long-term trends
2. https://acp.copernicus.org/articles/20/8691/2020/ - Analysis of 24 years of mesopause region OH rotational temperature observations at Davis, Antarctica – Part 2: Evidence of a quasi-quadrennial oscillation (QQO) in the polar mesosphere
3. https://theconversation.com/carbon-emissions-are-chilling-the-atmosphere-90km-above-antarctica-at-the-edge-of-space-143271
4. COSMOS https://cosmosmagazine.com/earth/climate/cosmos-qa-cooling-of-the-upper-atmosphere/
5. COSPAR oral presentation (online) Observations of a quasi-quadrennial oscillation (QQO) in the polar mesosphere.
6. COSPAR oral presentation (online) Observations of OH airglow from ground, aircraft, and satellite.

Two remotely-operated optical spectrometers (SPEX and FTS) and a scanning radiometer (UWOSCR) observe the nocturnal hydroxyl (OH) airglow emissions over Davis station Antarctica to monitor long-term trends and variability in temperature and wave activity of the high-latitude upper-atmosphere. All instruments were successfully operated over the 2017 winter observing season (mid-Feb to end-Oct, ~260 nights) which was the 23rd consecutive year of continuous measurements at Davis.
The SPEX made observations on a total of 257 nights yielding 236 nightly average temperatures that pass selection criteria. The FTS measured OH spectra on 269 nights and UWOSCR sampled OH images on 264 nights. A paper on the gravity wave trends from UWOSCR observations entitled "A climatological study of short-period gravity waves and ripples at Davis Station, Antarctica (68°S, 78°E) during the (austral winter February-October) period 1999-2013" was accepted by JGR.
Critically for long-term climate records, the instruments continue to be meticulously calibrated and performance remained excellent during this season.
Climate model simulations predict a dramatic cooling response in the high-latitude upper-atmosphere with global increases in greenhouse gases. In the latest re-analysis of Davis hydroxyl temperature trends the winter average temperature continues to cool at ~1° per decade with a solar cycle response of ~4° per 100 solar flux units. A maximum seasonal cooling of 3.1 K/decade is also measured for the Antarctic spring (30 day average centred early September).

These measurements are available from the Australian Antarctic Data Centre and integrated into the global Network for Detection of Mesospheric Change (NDMC) coordinated by DLR in Germany.

Two remotely operated optical spectrometers (SPEX and FTS) and a scanning radiometer (UWOSCR) observe the nocturnal hydroxyl (OH) airglow emissions over Davis station Antarctica to monitor long-term trends and variability in temperature and wave activity of the high-latitude upper-atmosphere. The 2016 season was the 22nd year of continuous measurements at Davis, and all instruments operated successfully over the winter observing period (mid-Feb to end-Oct). The SPEX observed on 266 nights yielding 239 nightly average temperatures that pass selection criteria. The FTS measured OH spectra on 283 nights and UWOSCR sampled OH images on 271 nights. A paper on the gravity wave trends from UWOSCR observations was submitted to JGR.
Critically for long-term climate records, the instruments continue to be meticulously calibrated. Improvements in the optical alignment of the SPEX scanning spectrometer in Feb-15 optimized the instrument for the 2015 observing season and this excellent alignment continues through to 2017.
Climate model simulations predict a dramatic cooling response in the high-latitude upper-atmosphere due to global increases in greenhouse gases. In the latest re-analysis of Davis hydroxyl temperature results, a winter average cooling response of 1.08±0.55K/decade is measured over the 22 years, coupled with a solar cycle response of 4.14±0.99K/100sfu. A maximum seasonal cooling of 3.30±1.09 K/decade is also measured for the Antarctic spring (30 day average centred early September).
These measurements are available from the Australian Antarctic DataCentre and integrated into the global Network for Detection of Mesospheric Change (NDMC) coordinated by DLR in Germany.

Two remotely operated optical spectrometers (SPEX and FTS) and a radiometer (UWOSCR) at Davis station Antarctica observe the nocturnal hydroxyl airglow emissions to monitor long-term trends and variability in temperature and wave activity of the high-latitude upper-atmosphere. The 2015 season was the 21st year of continuous measurements at Davis. A successful year with all possible night samples for the SPEX and UWOSCR, but an electronic component failure resulted in a 45 day gap (OCt-Nov) in the FTS record until a new part could be shipped to Davis.
Critically for long-term climate records, the instruments continue to be meticulously calibrated. Improvements in the optical alignment of the SPEX scanning spectrometer in Feb-15 optimized the instrument for the 2015 observing season and this excellent alignment continues through into 2016.
Climate model simulations predict a dramatic cooling response in the high-latitude upper-atmosphere due to global increases in greenhouse gases. In the latest re-analysis of Davis hydroxyl temperature results, a winter average cooling response of 1.33±0.6K/decade is measured over the 21 years, coupled with a solar cycle response of 4.26±0.98K/100sfu. A maximum seasonal cooling of 4.05±1.07 K/decade is also measured for the Antarctic spring (30 day average centred early September).
These measurements are available from the Australian Antarctic DataCentre and integrated into the global Network for Detection of Mesospheric Change (NDMC) coordinated by DLR in Germany.

Two remotely operated optical spectrometers, a radiometer and an airglow camera at Davis station Antarctica observe the nocturnal hydroxyl airglow emissions to monitor long-term trends and variability in temperature and wave activity of the high-latitude upper-atmosphere. The 2014 season was the 20th year of continuous measurements at Davis and was successfully completed with all possible nights sampled. Critically for long-term climate records, the instruments continue to be meticulously calibrated. Improvements in the optical alignment of the scanning spectrometer in Feb-15 have optimized the instrument for the 2015 observing season. Climate model simulations predict a dramatic cooling response in the high-latitude upper-atmosphere due to global increases in greenhouse gases. In the latest re-analysis of these temperature results a winter average cooling response of 1.6±0.6K/decade is measured for Davis over the 20 years, coupled with a solar cycle response of 4.2±0.9K/100sfu. A maximum seasonal cooling of 4.2±1.2 K/decade is also measured for the Antarctic spring (during August and September). These measurements are integrated into the global Network for Detection of Mesospheric Change (NDMC) coordinated by DLR in Germany. Presentations on the updated Davis results were given at the 6th NDMC meeting in May 2014.

This project includes a number of spectrometers, radiometers and cameras at Davis station Antarctica designed to cost effectively monitor long-term change and variability in the high-latitude upper-atmosphere using the nocturnal hydroxyl airglow emissions. The observing program continued successfully over 2013 and into the 2014 winter season which marks 2 decades of continuous measurements. Six nights of measurements were lost when the sky-viewing hatch on the roof of the observatory was blown off in a blizzard on 10-Jun-2013. The instruments continue to be meticulously calibrated, as is critical for long-term climate records. A cooling response in the upper atmosphere is expected from climate model simulations due to global increases in CO2. A winter average cooling response of 1.4±0.7K/decade is measured for Davis over 19 years, coupled with a solar cycle response of 4.3±0.9K/100sfu. A maximum seasonal cooling of 4.2±1.4 K/decade is also measured for the Antarctic spring (during August and September). These measurements are integrated into the global Network for Detection of Mesospheric Change (NDMC) coordinated by DLR in Germany. Three presentations on the updated Davis results were given at the 6th NDMC meeting in May 2014.

Operation of the hydroxyl airglow spectrometers at Davis station was achieved successfully over the 2012 winter observing season, adding to an 18 year continuous record of winter hydroxyl layer rotational temperatures from 1994 (the longest in the southern hemisphere). Primary instrument calibrations were undertaken in Nov-12 and Feb-13, response correction curves calculated and applied to the spectral analysis to derive atmospheric temperatures. A total of 32111 spectra were processed for 2012. Trend analysis of the 4152 nightly average temperatures in this dataset contributed to the paper “Antarctic climate change and the environment: an update” [Turner et al, 2013] published in Polar Record and provided for the IPCC 5th Assessment Report. Temperature comparison studies with other ground based observations , satellite profiles and model results continue with colleagues in the Network for Detection of Mesospheric Change (http://wdc.dlr.de/ndmc/)