Ground-based resonance LiDAR has been used to study the morphology of the mesospheric potassium (K) and sodium (Na) layers from 2016 to 2024 at São José dos Campos (SJC; 23.1°S, 45.9°W). The seasonal variation of Na densities around 85–100 km altitude shows a pronounced minimum in summer and a flat maximum in equinox and winter. Otherwise, the K layer shows semiannual and annual behavior with a single maximum in winter. Spectral analysis of K and Na densities revealed oscillations with periods r