Updated Climatology of Mesospheric Temperature Inversions Detected by Rayleigh Lidar above Observatoire de Haute Provence, France, Using a K-Mean Clustering Technique

Abstract

A climatology of Mesospheric Inversion Layers (MIL) has been created using the Rayleigh lidar located in the south of France at L’Observatoire de Haute Provence (OHP). Using criteria based on lidar measurement uncertainties and climatological mean gravity wave amplitudes, we have selected significant large temperature anomalies that can be associated with MILs. We have tested a novel approach for classifying MILs based on a k-mean clustering technique. We supplied different parameters such as the MIL amplitudes, altitudes, vertical extension, and lapse rate and allowed the computer to classify each individual MIL into one of three clusters or classes. For this first proof of concept study, we selected k = 3 and arrived at three distinct MIL clusters, each of which can be associated with different processes generating MILs in different regimes. All clusters of MIL exhibit a strong seasonal cycle with the largest occurrence in winter. The four decades of measurements do not reveal any long-term changes that can be associated with climate changes and only show an inter-annual variability with a quasi-decadal oscillation.

Co‐Located Wind and Temperature Observations at Mid‐Latitudes During Mesospheric Inversion Layer Events

“…Here, in order to identify MIL events within the temperature profiles, we followed the method developed by Leblanc and Hauchecorne (1997) and Fechine et al (2008), which has been applied in numerous previous studies (e.g., Ardalan et al, 2022;Cutler et al, 2001;Leblanc et al, 1998). According to them, a MIL is identified when these three criteria are observed:…”

“…Here, in order to identify MIL events within the temperature profiles, we followed the method developed by Leblanc and Hauchecorne (1997) and Fechine et al. (2008), which has been applied in numerous previous studies (e.g., Ardalan et al., 2022; Cutler et al., 2001; Leblanc et al., 1998). According to them, a MIL is identified when these three criteria are observed: The MIL bottom must be at least 5 km above the stratopause and the MIL top below 90 km. The temperature perturbation must be significant relative to the measurement uncertainty, that is, Terr < ΔT. Finally, the temperature amplitude must be 2 σ larger than the temperature fluctuations expected by gravity waves at these altitudes.…”

Co-located wind and temperature observations at mid-latitudes during mesospheric inversion layer events

“…Here, in order to identify MIL events within the temperature profiles, we followed the method developed by Leblanc and Hauchecorne (1997) and Fechine et al (2008), which has been applied in numerous previous studies (e.g., Cutler et al, 2001;Leblanc et al, 1998;Ardalan et al, 2022). According to them, a MIL is identified when these three criteria are observed:…”

“…According to Mzé et al (2014), gravity waves are expected to generate perturbations of 1.6 K at 50 km and 4 K at 75 km. Afterward, we characterized each observed MIL by computing their amplitude, thickness, and gradient similarly to the method developed in Ardalan et al (2022) (see their Figure 2). Thus, for each observed temperature profile, our algorithm identified two altitudes: the altitude of the bottom MIL from which the temperature gradient reverses and the altitude of the top MIL where the temperature maximum is reached.…”

Case Study of a Mesospheric Temperature Inversion over Maïdo Observatory through a Multi-Instrumental Observation

“…These large-scale horizontal and persistent phenomena are suggested to arise due to various dynamics [16]. They are characterized by a minimum temperature with large deviations of several tens of Kelvins in the mesosphere with a strong positive lapse rate of the temperature above and a second maximum temperature [17]. However, several studies confirm that the breaking of GWs generates MILs [18][19][20].…”