Symmetric and antisymmetric signals in MJO deep convection . 1 Part II : Kinematics and thermodynamics

5 This paper studies the significance of MJO convection asymmetry through composites 6 of kinematic and thermodynamic fields associated with predominantly symmetric and pre7 dominantly antisymmetric MJO convection using ECMWF Interim Reanalysis. The MJO 8 events were identified based on the primary MJO modes extracted from the IR brightness 9 temperature in Part I of this work. The predominantly antisymmetric MJO convection is 10 established as a distinctly different signal from its symmetric counterpart. Its accompanying 11 200-hPa quadrupole anomalous circulation breaks down at initiation over Indian Ocean and 12 when the system passes through the Maritime Continent. The MJO convection takes on a 13 summertime-like antisymmetric pattern at initiation. It is therefore possible that antisym14 metric wave groups are critical for MJO initiation and maintenance. 15 The predominantly symmetric and antisymmetric convection signals also differ drastically 16 with respect to their propagation over the Maritime Continent. Before reaching the Maritime 17 Continent, symmetric MJO convection sustains the front-to-rear tilted cloud types near the 18 equator. Off the equator, the most enhanced cloud type is likely stratiform. Upon reaching 19 the Maritime Continent, the convection splits into two north-south branches separated by 20 dry air intrusion over the equator. The mid-tropospheric conversion of perturbation available 21 potential energy into kinetic energy due to convection is therefore interrupted over the path 22 along the equator. On the other hand, antisymmetric MJO convection often lacks the 23 systematic cloud-type transition around the equator. The MJO likely gains kinetic energy 24 from off-equatorial deep convection with stratiform anvils, which are not interrupted when 25 passing the Maritime Continent, and the energy conversion is maintained all the way to the 26 South Pacific Convergence Zone. 27