Maintenance of Cyclonic Vortex During Monsoon Intraseasonal Oscillation: A View From Kinetic Energy Budget

Abstract

AbstractThe Monsoon intraseasonal oscillation (MISO) is the predominant variability over the tropical Indian Ocean during the Indian summer monsoon. A cyclonic vortex plays a critical role in the northward propagation of MISO. Here, we find that the pronounced intraseasonal kinetic energy accompanying the vortex is attributable to the barotropic energy gain from the background circulation. In particular, due to the phase shift between vortex and low‐level horizontal wind convergence, the covariance of the intraseasonal easterly and downdraft reinforces the intraseasonal kinetic energy before vortex. In contrast, the interaction between westerly and updraft nourishes the kinetic energy after vortex. Overall, the nonlinear processes across different scales are vital for the energy exchange during MISO, and this is dynamically different from that of Madden‐Julian oscillations. It implies that although these two major intraseasonal oscillations share the same spatiotemporal scales over the Indian Ocean, they are controlled by fundamentally different dynamical processes.