Characteristics of the Intraseasonal Oscillation in the Equatorial Mesosphere and Lower Thermosphere Region Revealed by Satellite Observation and Global Analysis by the JAGUAR Data Assimilation System

Abstract Climatological features of the intraseasonal oscillation (ISO) in equatorial mesosphere and lower thermosphere were analyzed using temperature data from Aura Microwave Limb Sounder (MLS) global analysis a assimilation satellite observations, including MLS, over 15 years. Based on spectral analyses, fluctuations with period 15–90 days extracted as ISO component. First, an empirical orthogonal function (EOF) was performed for components zonal mean MLS region 10°S–10°N, 68–85 km, where amplitudes are found to be maximized. The structure anomalies winds estimated assuming gradient wind balance examined by regression first second principal EOFs. It is shown that phases propagate downward vertical wavelength 25–30 km above height 60 signal synchronized observed even middle high latitude regions both hemispheres. Second, used examine driving mechanism ISO. confirmed time series agreed well radar which not assimilation. Results suggest small‐scale phenomena, such gravity waves necessarily represented parameterization meridional advection angular momentum, mainly contribute drive