A. Sánchez-Lavega, T. Del Rio-Gaztelurrutia, R. Hueso, J.M. Gomez-Forrellad, J.F. Sanz-Requena, J. Legarreta, E. Garcia-Melendo, F. Colas, J. Lecacheux, L.N. Fletcher, D. Barrado-Navascues, D. Parker, T. Akutsu, T. Barry, J. Beltran, S. Buda, B. Combs, F. Carvalho, P. Casquinha, M. Delcroix, S. Ghomizadeh, C. Go, J. Hotershall, T. Ikemura, G. Jolly, A. Kazemoto, T. Kumamori, M. Lecompte, P. Maxson, F.J. Melillo, D.P. Milika, E. Morales, D. Peach, J. Phillips, J.J. Poupeau, J. Sussenbach, G. Walker, S. Walker, T. Tranter, A. Wesley, T. Wilson, K. Yunoki
Convective storms occur regularly in Saturn-atmosphere. Huge storms known as Great White Spots, which are ten times larger than the regular storms, are rarer and occur about once per Saturnian year (29.5 Earth years). Current models propose that the outbreak of a Great White Spot is due to moist convection induced by water. However, the generation of the global disturbance and its effect on Saturn's permanent winds have hitherto been unconstrained by data, because there was insufficient spatial resolution and temporal sampling to infer the dynamics of Saturnweather layer (the layer in the troposphere where the cloud forms). Theoretically, it has been suggested that this phenomenon is seasonally controlled. Here we report observations of a storm at northern latitudes in the peak of a weak westward jet during the beginning of northern springtime, in accord with the seasonal cycle but earlier than expected. The storm head moved faster than the jet, was active during the two-month observation period, and triggered a planetary-scale disturbance that circled Saturn but did not significantly alter the ambient zonal winds. Numerical simulations of the phenomenon show that, as on Jupiter, Saturn's winds extend without decay deep down into the weather layer, at least to the water-cloud base at pressures of 10-12-bar, which is much deeper than solar radiation penetrates. © 2011 Macmillan Publishers Limited. All rights reserved.
Departamento de Fisica Aplicada i, Escuela Técnica Superior de Ingenieria, Universidad Del Pais Vasco, 48013 Bilbao, Alameda Urquijo s/n, Spain; Esteve Duran Observatory Foundation, 08553 Seva, Spain; Universidad Europea Miguel de Cervantes, 47012 Valladolid, C/Padre Julio Chevalier, Spain; Departamento de Ingenieria de Sistemas y Automática, EUITI, Universidad Pais Vasco, 48012 Bilbao, Plaza de la Casilla 3, Spain; Institut de Ciències de l'Espai (CSIC-IEEC), Campus UAB, Facultat de Ciències, E-08193 Bellaterra, 2a pl., Spain; Institut de Mécanique Céleste et de Calcul des Ephémérides, Observatoire de Paris, UMR 8028 CNRS, 75014 Paris, 77 av. Denfert-Rochereau, France; Observatoire de Paris, LESIA, 92195 Meudon Cedex, 5, Place Jules Janssen, France; Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, Oxford OX1 3PU, Parks Road, United Kingdom; Observatorio de Calar Alto, Centro Astronómico Hispano Alemán, MPIA-CSIC, 04004 Almeria, Spain; Association of Lunar and Planetary Observers (ALPO), Coral Gables, FL 33156, 12911 Lerida Street, United States; ALPO-Japan (Kansai Branch) 520-0242, Honkatata Otsu-city, Shiga, 4-8-11, Japan; 406 Bromide Street, Broken Hill, NSW 2880, Australia; 12511 Rossell, Castellon, Dr Jose Prades n.7, Spain; 31 Raglan Street, St Kilda East, Melbourne 3183, Australia; Buena Vista, GA 31803, 606 Frank Powell Road, United States; Centro de Estudos Do Universo, 17380-000 Brotas, Brazil; Quinta do Anjo, 2850-745 Palmela, Rua Gil Eanes lte. 216, 2u dto, Portais da Arrábida, Portugal; 31170 Tournefeuille, 2, rue de l'Ardache, France; Physics Department, University of San Carlos, Nasipit, Talamban, 6000 Cebu City, Philippines; Brisbane, QLD 4163, 21 Tarcutta Street Cleveland, Australia; Gilbert, AZ 85296, 848 S. Rosemont Ct., United States; Slough, SL1 9BN, 51, Frogmore Close, United Kingdom; Surprise, AZ 85374, 17109 N. Eureka Trail, United States; Holtsville, NY 11742, Glen-Hollow Dr., United States; Sellicks Beach, SA 5174, Capri Crescent, Australia; Aguadilla, 00603, HC2 PO Box 20031, Puerto Rico; Selsey, West Sussex, PO200BW, 28 North Road, United Kingdom; Mt Pleasant, SC 29464, 1280 Johnnie Dodds Blvd., United States; 91470 Pecqueuse, 6 Grande Rue, France; 3991 VE Houten, Meekrap-oord 3, Netherlands; Macon, GA 31210, 632 Byars Drive, United States; Manchester, NH 03104, 294 Myrtle Street, United States; Kurri Kurri, NSW 2327, 8 Ellalong Street, Australia; Campbell, ACT 2612, PO Box 409, Australia; Alpharetta, GA 30022, 5755 North Point Parkway, United States
