  Observations have shown that there exists downward propagation of alternating
westward/eastward jets in Jupiter's equatorial stratosphere, with a
quasi-period between four and six years. This phenomenon is generally called
the quasi-quadrennial oscillation (QQO). Here, we simulate the QQO by injecting
isotropic small-scale thermal disturbances into a three-dimensional general
circulation model of Jupiter. It is found that the internal thermal disturbance
is able to excite a wealth of waves that generate the equatorial QQO and
multiple jet streams at middle and high latitudes of both hemispheres. The
dominant wave mode in generating the QQO-like oscillation is that with a zonal
wavenumber of 10. Inhomogeneous evolution of potential vorticity favors the
emergence of the off-equatorial zonal jets. The off-equatorial jets migrate to
the equator, strengthen the deep equatorial jets, and result in the prolonging
of the QQO-like oscillations.
