Climate of Uranus
Uranus’s southern hemisphere in approximate natural colour (left) and in higher wavelengths (right), showing its faint cloud bands and atmospheric “hood” as seen by Voyager 2
The climate of Uranus is heavily influenced by both its lack of internal heat, which limits atmospheric activity, and by its extreme axial tilt, which induces intense seasonal variation. Uranus’s atmosphere is remarkably bland in comparison to the other gas giants which it otherwise closely resembles. When Voyager 2 flew by Uranus in 1986, it observed a total of ten cloud features across the entire planet. Later observations from the ground or by the Hubble Space Telescope made in the 1990s and the 2000s revealed bright clouds in the northern (winter) hemisphere. In 2006 a dark spot similar to the Great Dark Spot on Neptune was detected.
1 Banded structure, winds and clouds
1.1 Uranus Dark Spot
2 Seasonal variation
3 Circulation models
5 External links
Banded structure, winds and clouds
Uranus in 2005. Rings, southern collar and a light cloud in the northern hemisphere are visible.
In 1986 Voyager 2 discovered that the visible southern hemisphere of Uranus can be subdivided into two regions: a bright polar cap and dark equatorial bands (see figure on the right). Their boundary is located at about −45 degrees of latitude. A narrow band straddling the latitudinal range from −45 to −50 degrees is the brightest large feature on Uranus’s visible surface. It is called a southern “collar”. The cap and collar are thought to be a dense region of methane clouds located within the pressure range of 1.3 to 2 bar. Unfortunately Voyager 2 arrived during the height of Uranus’s southern summer and could not observe the northern hemisphere. However, at the end of 1990s and the beginning of the twenty-first century, when the northern polar region came into view, Hubble Space Telescope (HST) and Keck telescope initially observed neither a collar nor a polar cap in the northern hemisphere. So Uranus appeared to be asymmetric: bright near the south pole and uniformly dark in the region north of the southern collar. In 2007, however, when Uranus passed its equinox, the southern collar almost disappeared, whereas a faint northern collar emerged near 45 degrees of latitude. The visible latitudinal structure of Uranus is different from that of Jupiter and Saturn, which demonstrate multiple narrow and co