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An atmospheric tide is a movement of the atmosphere analogous to the tides of the Earth's oceans. In addition to tides due to gravity, it also includes significant tides due to thermal heating (thermal tide), e.g., from the Sun, which consists of flows away from the warmest spot and toward the coolest spot. In fact, the Earth's atmospheric tide is primarily thermal.
Atmospheric thermal tides have the interesting property that though normal tides tend to slow rotation (in relation to the position of the orbiting body causing the tide, eventually tidal locking), an atmospheric thermal tide affects rotation in the opposite direction, i.e., increases it when a normal tide would slow it. Theoretically, the opposing forces might balance so the rotation remains the same. This opposite push happens because the heated atmosphere under the influence of the host star is less dense, and as that less-dense atmosphere is carried away by the planet's rotation, the more dense portion of the atmosphere on the other side is pulled on by the host star. When this was first conceived it was thought the Earth might be in such a balance. Some theories of Venus's unexpected rotation attribute it to influence of its thermal tide.
It has been suggested that life, through its influence on atmosphere (e.g., supplying oxygen) affects the scale height of the atmosphere, thus could have an effect on thermal tide and the planet's rotation.