Spontaneous formation of equatorial jets in freely decaying shallow water turbulence

Results of high-resolution, long time integrations of the shallow water equ ations in spherical geometry are presented. Final quasi-steady states of th e freely decaying evolution are found, characterized by the emergence of ro bust equatorial jets and by the breaking of cyclone-anticyclone symmetry. I t is shown that these two phenomena are intimately related and that global prevalence of anticyclonic vorticity necessarily leads to the formation of a westward (retrograde) equatorial jet. (C) 1999 American Institute of Phys ics. [S1070-6631(99)02505-2].