Statistical analysis of the mesospheric inversion layers over two symmetrical tropical sites: Réunion (20.8° S, 55.5° E) and Mauna Loa (19.5° N, 155.6° W)

Abstract

Abstract. In this investigation a statistical analysis of the characteristics of mesospheric inversion layers (MILs) over tropical regions is presented. This study involves the analysis of 16 years of lidar observations recorded at Réunion (20.8° S, 55.5° E) and 21 years of lidar observations recorded at Mauna Loa (19.5° N, 155.6° W) together with SABER observations at these two locations. MILs appear in 10 and 9.3 % of the observed temperature profiles recorded by Rayleigh lidar at Réunion and Mauna Loa, respectively. The parameters defining MILs show a semi-annual cycle over the two selected sites with maxima occurring near the equinoxes and minima occurring during the solstices. Over both sites, the maximum mean amplitude is observed in April and October, and this corresponds to a value greater than 35 K. According to lidar observations, the maximum and minimum mean of the base height ranged from 79 to 80.5 km and from 76 to 77.5 km, respectively. The MILs at Réunion appear on average ∼ 1 km thinner and ∼ 1 km lower, with an amplitude of ∼ 2 K higher than Mauna Loa. Generally, the statistical results for these two tropical locations as presented in this investigation are in fairly good agreement with previous studies. When compared to lidar measurements, on average SABER observations show MILs with greater amplitude, thickness and base altitudes of 4 K, 0.75 and 1.1 km, respectively. Taking into account the temperature error by SABER in the mesosphere, it can therefore be concluded that the measurements obtained from lidar and SABER observations are in significant agreement. The frequency spectrum analysis based on the lidar profiles and the 60-day averaged profile from SABER confirms the presence of the semi-annual oscillation where the magnitude maximum is found to coincide with the height range of the temperature inversion zone. This connection between increases in the semi-annual component close to the inversion zone is in agreement with most previously reported studies over tropics based on satellite observations. Results presented in this study confirm through the use of the ground-based Rayleigh lidar at Réunion and Mauna Loa that the semi-annual oscillation contributes to the formation of MILs over the tropical region.

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

“…Among future research, a statistical study is needed to explore MILs and both GWs and planetary waves in the middle atmosphere and simulated MILs in climate model WACCM in the tropics. Indeed, MILs are frequently observed on Lidar observations over La Réunion [24]. Moreover, planetary wave breaking is also known as another important cause for the formation of lower MILs, which was not the case in the present study.…”

“…Statistical studies using lidar data from the Haute-Provence Observatory [17] in midlatitudes and the Maïdo Observatory [24] show the ubiquity of MILs and the need to clarify the different processes involved. The variability of MILs above La Réunion is dominated by a semi-annual cycle with a maximum occurrence in late austral winter in October-November [24], as previously reported in [25] for tropical regions. In the northern tropics, amplitudes of MILs are revealed to be underestimated [26]; in particular, Ramesh et al [27] identified three tropical MILs of different natures on the same night.…”

Long‐Term Trends in Tropical (10°N–15°N) Middle Atmosphere (40–110 km) CO2 Cooling

“…The semiannual variation in the CO 2 heating can be related to the mesospheric semiannual oscillation due to gravity wave breaking, and it needs further investigation. Further, the lower mesospheric inversion layers (MILs) occur due to mesospheric semiannual oscillation in the height region of ~65–85 km with peak amplitudes during equinoxes over tropics (e.g., Bègue et al, ; Gan et al, ; Siva Kumar et al, ; Zhang et al, ). These lower MILs are accompanied by cold layers at the bottom, which again show semiannual variation with stronger amplitudes at spring equinox than at autumn equinox (Figure d).…”

Surface Temperature Trend Estimation over 12 Sites in Guinea Using 57 Years of Ground-Based Data

“…For instance, from a study on a temperature trend analysis in South Africa, it was highlighted that temperature can, directly and indirectly, impact the livelihood of inhabitants of the country and the natural environment as a whole [10]. Temperature has been the subject of several studies on different atmospheric layers according to various research interests [3,[11][12][13][14][15][16][17][18][19][20][21][22]. Ahmed et al [23] used statistical analyses (Fourier test analysis, t-test analysis and Mann-Kendall test analysis) for determining the trend in the annual and seasonal temperature time-series at fifteen weather stations within the Ontario Great Lakes Basin for the period 1941-2005.…”