[P-EM12] Coupling Processes in the Atmosphere-Ionosphere System

[PEM12-32] Causes of the abnormally strong easterly phase of the mesopause SAO during the March equinox of 2023 revealed by a new reanalysis data covering the entire middle atmosphere

*佐藤 薫¹、小新 大²、Suclupe Jose³、Chau Jorge, L³、Lima Lourivaldo, M⁴、Li Guozhu⁵、Rao S. Vijaya Bhaskara⁶、Ratnam M. Venkat⁷、Rodriguez Rodolfo⁸、Scipion Danny⁹ (1.東京大学大学院理学系研究科地球惑星科学専攻、2.NSF National Center for Atmospheric Research, USA、3.Leibniz-Institute of Atmospheric Physics at the University of Rostock, Germany、4.Universidade Estadual da Paraiba, Brazil、5.Beijing National Observatory of Space Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, China、6.Department of Physics, Sri Venkateswara University, India、7.National Atmospheric Research Laboratory, India、8.Universidad de Piura, Peru、9.Radio Observatorio de Jicamarca, Instituto Geofisico del Peru, Peru)

キーワード：equatorial mesopause semiannual oscillation 、wave-mean flow interaction、residual mean circulation 、extreme event、a new reanalysis JAWARA

During the March equinox of 2023, a strong easterly wind of about 80 m/s appeared at an altitude of about 82 km in the equatorial upper mesosphere, which is regarded as an enhancement of the mesopause semi-annual oscillation. In this study, a new reanalysis data available up to 110 km was used to investigate its momentum budget. The strong easterly acceleration was due to a similar contribution from resolved waves and parameterized gravity waves, but largely counteracted by an upward advection of westerly momentum. The significant anomaly in the mean winds was not restricted to the 82 km height, but also included strong westerly winds (about 50 m/s) at 65 km and easterly winds (about 40 m/s) at 42 km. The stratospheric quasi-biennial oscillation was westerly. The mean wind intensification at each height is explained by the acceleration due to upward propagating waves, which do not suffer from critical filtering below.