They are also known as blocking highs or blocking anticyclones. In winter anticyclones bring cold dry weather. Morning frosts are also common during winter anticyclones. Sir Francis Galton first discovered anticyclones in the 1860s. Between depressions there are often small mobile anticyclones that bring periods of fair weather. Between depressions there are often small mobile anticyclones that bring periods of fine weather. North Asia was covered by other anticyclones that belong to that giant arctic airmass. This difference was because the ice sheets in Europe produced extensive anticyclones above them. Between depressions, there are often small mobile anticyclones that bring periods of fair weather. However Jupiter has two anticyclones that are somewhat different from all others. Effects of surface-based anticyclones include clearing skies as well as cooler, drier air. Most observed extraterrestrial vortices have been seen in large cyclones, or anticyclones. In contrast to anticyclones, the Jovian cyclones tend to be small, dark and irregular structures. High-pressure systems are alternatively referred to as anticyclones. Different anticyclones located in one zone tend to merge when they approach each other.