A giant thunderstorm on Saturn

Authors:
Publisher website
Google Scholar
Abstract
Six Great White Spot (GWS) events have been observed in the atmosphere of Saturn since 1876. These giant convective storms occur roughly once every Saturnian year (equal to 29.5 Earth years). The sixth GWS erupted in December 2010 and has been the subject of intense observation. Two papers in this issue present the details of some of these observations. Sánchez-Lavega et al. report that the storm developed at northern latitudes in the peak of a weak westward jet during early northern springtime. The storm head moved faster than the jet and triggered a disturbance that circled the planet. Numerical simulations show that Saturn's winds extend without decay deep down into the weather layer. Fischer et al. report that the storm reached a width of 10,000 kilometres within three weeks. Its lightning flash rates are an order of magnitude greater than those seen in previous storms, peaking at more than 10 flashes per second. Lightning discharges in Saturn’s atmosphere emit radio waves1 with intensities about 10,000 times stronger than those of their terrestrial counterparts2. These radio waves are the characteristic features of lightning from thunderstorms on Saturn, which last for days to months2. Convective storms about 2,000 kilometres in size have been observed in recent years at planetocentric latitude 35° south3,4,5 (corresponding to a planetographic latitude of 41° south). Here we report observations of a giant thunderstorm at planetocentric latitude 35° north that reached a latitudinal extension of 10,000 kilometres—comparable in size to a ‘Great White Spot’6,7—about three weeks after it started in early December 2010. The visible plume consists of high-altitude clouds that overshoot the outermost ammonia cloud layer owing to strong vertical convection, as is typical for thunderstorms. The flash rates of this storm are about an order of magnitude higher than previous ones, and peak rates larger than ten per second were recorded. This main storm developed an elongated eastward tail with additional but weaker storm cells that wrapped around the whole planet by February 2011. Unlike storms on Earth, the total power of this storm is comparable to Saturn’s total emitted power. The appearance of such storms in the northern hemisphere could be related to the change of seasons7, given that Saturn experienced vernal equinox in August 2009.

This publication has 26 references indexed in Scilit: