Convective Intensity, Morphology, Rainfall Production, and Evolution of Madden-Julian Oscillation over the Central Indian Ocean

This study investigates convective evolution and environmental transitions over the Central Indian Ocean (CIO) where the convective envelope of the Madden-Julian Oscillation (MJO) usually initiates. This work aims to better understand physical processes key to the MJO initiation. This study first analyzes C-band shipborne radar and radiosonde observations collected from the R/V Roger Revelle during the 2011-2012 DYNAMO (Dynamics of the MJO) field campaign over the CIO. Radar data are grouped into precipitation features (PFs). Based on this dataset, we quantify the MJO convection as a function of MJO phase, including convective population, intensity, morphology (depth, size, and organization), and rainfall contributions by systems of different morphology. We also connect evolution of these quantities to changes in environmental conditions over the CIO for physical reasoning, including tropospheric moisture, sea surface temperature (SST), convective available potential Energy (CAPE), and vertical wind shear. Results from the above analysis are supportive of the “discharge-recharge” MJO hypothesis. Our results indicate shallow-deep-organized convective evolution during MJO initiation, and the role of convective moistening. This study further examines MJO convective evolution using long-term (14 years) TRMM (Tropical Rainfall Measuring Mission) satellite measurements. Analysis of TRMM data is also based on PFs. In this case, we can compare the MJO convective evolution (e.g., convective intensity and morphology) during the relative short-term time span (DYNAMO) with that of the long-term TRMM climatology.