Evolution of the Diurnal Cycle of Tropical Rainfall Associated with the Madden–Julian Oscillation

This study evaluates the impact of the Madden-Julian oscillation on the diurnal cycle of tropical rainfall and cloud populations by analyzing data from the TOGA radar aboard R/V Roger Revelle. The data was collected during the DYNAMO field campaign which investigated MJO initiation processes and cloud evolution. Rain rate and rain type data were examined to understand the diurnal cycle observed by the TOGA radar. The mean hourly time series of rainfall during the overall field campaign displayed a stronger afternoon maximum in comparison to the climatological diurnal cycle that has been documented by satellite-based rain estimates and S-Polka radar. The diurnal cycle during the MJO enhanced phase shows a strong afternoon maximum when compared to S-PolKa radar. Large differences were observed in the time series of the diurnal cycles between the two MJO events that occurred during the observed period. These results indicate that the diurnal cycle of rainfall depends on the geography and synoptic conditions within each MJO event.