The difference in sunrise and sunset low-latitude nitric oxide (NO) mixing ratios in the mesosphere and lower thermosphere (MLT) is shown to be consistent with a perturbation induced by the migrating diurnal tide. The vertical wind of the tide can induce factor of 2 changes over 12 hours at the equator. The vertical, latitudinal and temporal structure of NO perturbations closely matches the structure of vertical winds from a tidal model. In addition, previous observations of the seasonal and interannual variation in the tidal wind appear to correlate with NO variations. ¿ 2000 American Geophysical Union