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In this investigation a statistical analysis of the characteristics ofmesospheric inversion layers (MILs) over tropical regions is presented. Thisstudy involves the analysis of 16 years of lidar observations recorded atRéunion (20.8° S, 55.5° E) and 21 years of lidarobservations recorded at Mauna Loa (19.5° N, 155.6° W)together with SABER observations at these two locations. MILs appear in 10and 9.3 % of the observed temperature profiles recorded by Rayleigh lidarat Réunion and Mauna Loa, respectively. The parameters defining MILs show asemi-annual cycle over the two selected sites with maxima occurring near theequinoxes and minima occurring during the solstices. Over both sites, themaximum mean amplitude is observed in April and October, and this correspondsto a value greater than 35 K. According to lidar observations, the maximumand minimum mean of the base height ranged from 79 to 80.5 km and from 76 to77.5 km, respectively. The MILs at Réunion appear on average ∼ 1 kmthinner and ∼ 1 km lower, with an amplitude of ∼ 2 K higherthan Mauna Loa. Generally, the statistical results for these two tropicallocations as presented in this investigation are in fairly good agreementwith previous studies. When compared to lidar measurements, on average SABERobservations show MILs with greater amplitude, thickness and base altitudesof 4 K, 0.75 and 1.1 km, respectively. Taking into account the temperatureerror by SABER in the mesosphere, it can therefore be concluded that themeasurements obtained from lidar and SABER observations are in significantagreement. The frequency spectrum analysis based on the lidar profiles andthe 60-day averaged profile from SABER confirms the presence of thesemi-annual oscillation where the magnitude maximum is found to coincide withthe height range of the temperature inversion zone. This connection betweenincreases in the semi-annual component close to the inversion zone is inagreement with most previously reported studies over tropics based onsatellite observations. Results presented in this study confirm through theuse of the ground-based Rayleigh lidar at Réunion and Mauna Loa that thesemi-annual oscillation contributes to the formation of MILs over thetropical region

annales geophysicae

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)