Re-evaluation of inter-annual variability using lidars Temperature extending over several decades of observation

Rayleigh lidars, in particular as part of the NDACC (Network for the Detection of Atmospheric Composition Change) network, have been observing the stratosphere and mesosphere (also known as the 'middle atmosphere' (MA)) with excellent vertical resolution for many years. Data from the lidars at the Observatoire de Haute-Provence (1978-2024), Table Mountain in California (1989-2024), Mauna Loa in Hawaii (2000-2024), Hohenpeissenberg (1987-2024) and Kühlungsborn (2012-2024) in Germany, Rio Grande in Argentina (2017-2024) and Réunion Island (1994-2024) have made it possible to obtain a unique dataset of temperature profiles between 30 and 80 km. This dataset makes it possible to establish a climatology of MA at several latitudes and over several decades.

Seasonal variations are represented by annual and semi-annual sinusoids. The behaviour of the amplitudes is similar at all sites: stable in the stratosphere, a decrease at the stratopause followed by a constant increase in the mesosphere; the opposite is true for the biannual amplitude, with a slight increase followed by stagnation in the mesosphere. The strength of the annual amplitudes measured at mid-latitudes is about 6 K in the stratosphere, with a decrease to 2 K in the stratopause, followed by an increase to 16 K in the mesosphere. These amplitudes are halved at tropical sites.

The temporal extent of the data series also allows us to analyse the response of the atmosphere to variations in solar activity, showing that these can cause variations of up to 3 K. The influence of the QBO (Quasi-Biennial Oscillation) produces variations that can exceed variations of about 1 K. There is also a general cooling of the atmosphere. We also observe a general cooling of the AM, which varies from site to site: for example, Reunion Island records a cooling of up to 3 K/decade in the mesosphere, while the Haute-Provence site measures a cooling of 1.5 K/decade.

These lidars have also been used to validate measurements made by limb observations from space. The main objective of this study is therefore to provide complete climatologies of the middle atmosphere from several points on the globe, in order to ensure continuity between several successive limb targeting missions. The production of temperature profiles from experiments such as GOMOS or OMPS shows that it is possible to obtain excellent precision in the measurement of temperature profiles. As the observations are made at different times of the day, atmospheric tides must also be taken into account.