Atmosphere (2) ...

The temperatures at the cloud tops of Neptune are about -216 degrees C, slightly warmer than for Uranus. Neptune is further from the Sun, but has an internal energy source that produces almost 2.7 times as much energy as that incident from the Sun.
Clouds of Condensed Methane
The clouds themselves are probably condensed methane, and the features in them can be seen to change on timescales of a few hours. Presumably the greater activity observed in the atmosphere of Neptune relative to Uranus is because of the internal heat source, but we understand few of the details. Neptune has less haze in its upper atmosphere than Uranus, and this may also play a role in allowing us to see more easily activity that is obscured on Uranus by the haze.

High Cirrus on Neptune
The top right image shows Neptune as photographed by Voyager 2 about two hours before its closest approach in 1989. The distance from Neptune is 157,000 km and the resolution of the image is about 11 kilometers. The blue color is again because of methane. The stringy, light colored features are cirrus clouds floating high in Neptune's atmosphere.
High Velocity Winds
Neptune has wind speeds as great as 1700 km/hr, which is comparable to the large wind speeds observed on Saturn. Similar to Uranus, the winds near the equator blow in the opposite direction of the rotation (retrograde), while the winds nearer the poles blow in the same (prograde) direction. It is not understood why Uranus and Neptune have this reversed wind pattern relative to Jupiter and Saturn, although generally the belt and zone patterns suggest that the atmospheric circulation for all the Jovian planets is dominated by effects coming from the high rotational velocity of the planet.

The Atmospheric Storms
The Voyager 2 flyby in 1989 revealed strong winds, bright, high-altitude clouds, and two large dark spots attributed to long-lived giant storm systems. The largest dark storm system, called the "Great Dark Spot", is shown in the image adjacent left.

The Great Dark Spot is comparable in size to the Earth and, like Jupiter's Red Spot, it is a southern hemisphere anticyclone, spinning counter-clockwise with a period of 16 hours; thus, it is a region of high pressure. The source of vertical atmospheric motion leading to the high pressure system is not well understood.

Dark Spot / Red Spot

Although the Great Dark Spot had many similarities with Jupiter's Great Red Spot, there is at least one important difference associated with the contrasting wind flows on Jupiter and Neptune. The Red Spot is a storm being rolled between winds flowing in opposite directions north or south of it, but the Great Dark Spot had winds blowing in the same direction north and south of it.

Stability of Anticyclones on Neptune
More recent Earth-based observations indicate that the Great Dark Spot observed by Voyager has disappeared, but other similar (but smaller) spots have appeared. This suggests that large anticyclonic disturbances are much less stable on Neptune than on Jupiter.