MJO Energetics Associated with Equatorially Asymmetric Convective Heating

Symmetric and antisymmetric heat sources about the equator are of fundamental interests in tropical dynamics. In this talk they are exemplified with asymmetric convective heating contributing to the perturbation kinetic energy (PKE) of the Madden-Julian oscillation (MJO). Previous work on the time mean features of kinetic energy budget in the intraseasonal time scale over the equator strongly suggested that convective heating largely contributed to the generation of perturbation available potential energy (PAPE), which is then converted to the perturbation kinetic energy of MJO over the Indo-Pacific warm pool (e.g., Yanai et al., 2000). Using satellite IR brightness temperature and the ECMWF Interim Reanalysis from 1984 to 2005, the evolution of MJO PKE across the warm pool is examined along with generation of PAPE through predominantly equatorially symmetric and predominantly off-equatorial MJO convective signals extracted by Tung et al. (2014). The results reveal the importance of off-equatorial heating in maintaining the MJO in boreal winters. Furthermore, through vertical normal mode decomposition, the MJO appears to gain substantial PKE from PAPE generated through off-equatorial deep convection with stratiform anvils; the energy conversion remains uninterrupted across the Maritime Continent into West Pacific and the South Pacific Convergence Zone.

References:

Yanai, M., B. Chen, and W.-w. Tung, 2000: The Madden-Julian oscillation observed during the TOGA COARE IOP: Global view. J. Atmos. Sci., 57, 2374--2396

Tung, W.-w., D. Giannakis, and A. J. Majda, 2014: Symmetric and antisymmetric convection signals in the Madden-Julian oscillation. Part I: Basic modes in infrared brightness temperature. J. Atmos. Sci., in press.