Tropical Cyclone Impacts on Madden-Julian Oscillation Convection over the Indian Ocean
The Madden-Julian Oscillation (MJO) can create favorable conditions for tropical cyclone (TC) genesis in the Indian Ocean. However, past work has not thoroughly investigated how TCs after genesis may influence MJO convection development, with TC-MJO convection interactions possibly having downstream implications on MJO forecasting. This work utilizes real and semi-idealized WRF simulations and long-term composite analysis to (1) broadly establish connections between Indian Ocean TCs and MJO convection development and (2) isolate specific TC impacts on MJO convection. Parcel back-trajectories and lower-tropospheric moisture budget analyses trace sources of dry air within the region, with the latter highlighting the importance of zonal moisture advection (i.e., WWB) for western MJO convection development and that meridional advection (e.g., TC) plays a non-negligible secondary role for western MJO convection changes. Experiments with simulated MJOs with and without a bogus TC vortex quantify TC impacts on equatorial horizontal moisture advection and the subsequent influences on MJO convection occurrence, depth, and intensity. With past work noting the importance of horizontal moisture advection to the MJO lifecycle over the Indian Ocean and with half of annual rainfall over the Maritime Continent being from MJO convection, MJO propagation changes resulting from TC impacts on horizontal moisture advection could significantly influence rainfall totals and forecasting for the Maritime Continent.
