On the latitudinal variations of AO, SAO, and ISOs in the MLT temperatures

Analysis of two years of OH(3-1) rotational temperatures derived from the PRL Airglow InfraRed Spectrograph (PAIRS) at Ahmedabad (23°N, 72.6°E) reveals a clear presence of annual (AO) and semi-annual (SAO) oscillations, along with intraseasonal oscillations (ISOs) near an altitude of 87 km. Similar oscillations are also observed in SABER-derived temperatures centered over Ahmedabad. However, the NRLMSIS model captures only AO and SAO, failing to reproduce the observed ISOs. Notably, the 75-day oscillation is absent in both PAIRS and SABER temperatures over Ahmedabad, which motivated a broader investigation into the latitudinal distribution of these oscillations. A comprehensive analysis was carried out using longitudinally averaged SABER temperature data, organized at 10° latitude intervals from 80°N to 80°S. Lomb-Scargle spectral analysis was employed to extract the amplitudes of significant oscillations at each latitude band. The results show that the AO and SAO are present across all latitudes, with their amplitudes peaking at the poles and reaching a minimum near the equator, while SAO amplitudes show a secondary peak near the equator. ISOs exhibit strong latitude-dependent variations: the terannual oscillation (TAO) is prominent at low to mid-latitudes, the quarter-annual oscillation (QAO) appears at all latitudes with stronger amplitudes at high latitudes, the 75-day oscillation is confined to mid and high latitudes, and the 60-day oscillation is primarily observed at equatorial and low latitudes. These findings provide new observational evidence for the latitude-dependent amplitude variations of ISOs and quantify their characteristics using PAIRS and SABER temperature measurements in the MLT region.