Ground-based observations of the long-term evolution and death of Saturn's 2010 Great White Spot

We report on the long-term evolution of Saturn’s sixth Great White Spot (GWS) event that initiated at northern mid-latitudes of the planet on December 5th, 2010 (Fletcher, L. et al. [2011]. Science 332, 1413–1417; Sanchez-Lavega, A. et al. [2011]. Nature 475, 71–74; Fischer, G. et al. [2011]. Nature 475, 75–77). We find from ground-based observations that the GWS formed a planetary-scale disturbance that encircled the planet in 50 days, covering the latitude band between 24.6 and 44.8N (planetographic) or about 22,000 km in meridional extent and 280,000 km in full zonal circumference length. The head of the GWS was located at an averaged latitude of 40.8 ± 1N in the peak of a westward jet and showed a mean linear drift in System III longitude of 2.793 deg/day, equivalent to a mean zonal velocity of u = � 27.9 m s � 1 , with maximum speed fluctuations around this mean of � 5.3 to +2.7 m s � 1 . The differ

[1]  E. Battaner,et al.  The nature of Saturn's atmospheric Great White Spots , 1987 .

[2]  T. Masaki.  Structure and Dynamics , 2002 .

[3]  Martin T. Dove.  Structure and Dynamics , 2003 .

[4]  R. West,et al.  Saturn's emitted power , 2010 .

[5]  A. Sanchez-Lavega,et al.  The Great White Spot and disturbances in Saturn's equatorial atmosphere during 1990 , 1991, Nature.

[6]  P. Zarka,et al.  Atmospheric Electricity at Saturn , 2008 .

[7]  G. Orton,et al.  Seasonal change on Saturn from Cassini/CIRS observations, 2004–2009 , 2010 .

[8]  J. F. Rojas,et al.  Saturn's cloud structure and temporal evolution from ten years of Hubble Space Telescope images (1994 2003) , 2005 .

[9]  C. Barnet,et al.  Hubble space telescope observations of the 1990 equatorial disturbance on Saturn: Images, albedos, and limb darkening , 1992 .

[10]  Timothy Edward Dowling,et al.  The Explicit Planetary Isentropic-Coordinate (EPIC) Atmospheric Model , 1998 .

[11]  C. C. Porco,et al.  A giant thunderstorm on Saturn , 2011, Nature.

[12]  J. F. Rojas,et al.  Discrete cloud activity in Saturn’s equator during 1995, 1996 and 1997 , 1999 .

[13]  D. Tholen,et al.  Report of the IAU/IAG Working Group on cartographic coordinates and rotational elements: 2006 , 2007 .

[14]  T. Dowling,et al.  Jupiter's 24° N highest speed jet: Vertical structure deduced from nonlinear simulations of a large-amplitude natural disturbance , 2005 .

[15]  A. Ingersoll,et al.  Analysis of a giant lightning storm on Saturn , 2007 .

[16]  P. Gierasch,et al.  Mapping potential vorticity dynamics on saturn: Zonal mean circulation from Cassini and Voyager data , 2009 .

[17]  J. F. Rojas,et al.  A strong decrease in Saturn's equatorial jet at cloud level , 2003, Nature.

[18]  J. Lecacheux,et al.  Temporal behavior of cloud morphologies and motions in Saturn's atmosphere , 1993 .

[19]  Agustin Sanchez-Lavega,et al.  Large-Scale Storms in Saturn's Atmosphere During 1994 , 1996, Science.

[20]  C. Barnet,et al.  Hubble space telescope observations of the 1990 equatorial disturbance on Saturn: Zonal winds and central Meridian albedos , 1992 .

[21]  R. West,et al.  Clouds and aerosols in Saturn's atmosphere , 1984 .

[22]  Y. Hayashi,et al.  Intermittent cumulonimbus activity breaking the three‐layer cloud structure of Jupiter , 2011 .

[23]  W. Kurth,et al.  Planetary Radio Emissions III , 1985 .

[24]  P. Stone.  The meteorology of the Jovian atmosphere , 1976 .

[25]  Cambridge,et al.  Lucky imaging: High angular resolution imaging in the visible from the ground , 2005, astro-ph/0507299.

[26]  R. Hueso,et al.  Depth of a strong jovian jet from a planetary-scale disturbance driven by storms , 2008, Nature.

[27]  A. Sánchez-Lavega,et al.  An Introduction to Planetary Atmospheres , 2010 .

[28]  E. García‐Melendo,et al.  Evolution of the cloud field and wind structure of Jupiter's highest speed jet during a huge disturbance , 2009 .

[29]  R. West,et al.  Cassini imaging of Saturn : Southern hemisphere winds and vortices , 2006 .

[30]  A. Genio,et al.  Saturn Atmospheric Structure and Dynamics , 2009 .

[31]  J. M. Gómez,et al.  The South Equatorial Belt of Jupiter, I: Its Life Cycle , 1996 .

[32]  J. F. Rojas,et al.  Saturn's Zonal Winds at Cloud Level , 1999 .

[33]  C. Barnet,et al.  The onset and growth of the 1990 equatorial disturbance on Saturn , 1992 .

[34]  R. Hueso,et al.  Deep winds beneath Saturn’s upper clouds from a seasonal long-lived planetary-scale storm , 2011, Nature.

[35]  J. Connerney,et al.  Atmospheric storm explanation of saturnian electrostatic discharges , 1983, Nature.

[36]  A. Ingersoll,et al.  Lightning storms on Saturn observed by Cassini ISS and RPWS during 2004–2006 , 2007 .

[37]  Ricardo Hueso,et al.  The international outer planets watch atmospheres node database of giant-planet images , 2010 .

[38]  Stefan Hippler,et al.  AstraLux - the Calar Alto 2.2-m telescope Lucky Imaging Camera , 2008, 0807.0504.

[39]  J. F. Rojas,et al.  Saturn's cloud morphology and zonal winds before the Cassini encounter , 2004 .

[40]  R. Hueso,et al.  A Three-Dimensional Model of Moist Convection for the Giant Planets: The Jupiter Case , 2001 .

[41]  T. Guillot,et al.  A model for large‐scale convective storms in Jupiter , 2002 .

[42]  D. Tholen,et al.  Report of the IAU Working Group on Cartographic Coordinates and Rotational Elements: 2009 , 2011 .

[43]  P. Zarka,et al.  Ground-based and spacecraft observations of lightning activity on Saturn , 2012 .

[44]  A. S. Lavega.  Motions in Saturn's atmosphere: Observations before Voyager encounters , 1982 .

[45]  H. Kuo.  DYNAMIC INSTABILITY OF TWO-DIMENSIONAL NONDIVERGENT FLOW IN A BAROTROPIC ATMOSPHERE , 1949 .

[46]  C. Barnet,et al.  A seasonal radiative-dynamic model of Saturn's troposphere , 1992 .

[47]  K. Sayanagi,et al.  Effects of a large convective storm on Saturn's equatorial jet , 2007 .

[48]  S. Pérez-Hoyos,et al.  Solar flux in Saturn's atmosphere: Penetration and heating rates in the aerosol and cloud layers , 2006 .

[49]  A. Sánchez‐Lavega.  Saturn's Great White Spots. , 1989, Chaos.

[50]  J. Pedlosky.  Geophysical Fluid Dynamics , 1979 .

[51]  V. Suomi,et al.  Some dynamical properties of vortex streets in Saturn's atmosphere from analyses of Voyager images , 1983 .

[52]  R. West,et al.  Detection of visible lightning on Saturn , 2010 .

[53]  C. Sotin,et al.  Thermal Structure and Dynamics of Saturn’s Northern Springtime Disturbance , 2011, Science.

[54]  J. Lecacheux,et al.  Cloud structure of Saturn’s 2010 storm from ground-based visual imaging , 2012 .

[55]  R. Hueso,et al.  A three-dimensional model of moist convection for the giant planets II: Saturn's water and ammonia moist convective storms , 2004 .

[56]  A. Sánchez-Lavega,et al.  Saturn’s zonal wind profile in 2004–2009 from Cassini ISS images and its long-term variability , 2011 .

[57]  R. Hueso,et al.  The jovian anticyclone BA: I. Motions and interaction with the GRS from observations and non-linear simulations , 2009 .

[58]  A. Ingersoll,et al.  Structure and dynamics of Saturn's atmosphere , 1984 .