A Survey of Large-Scale Precipitation Tracked Systems over the Maritime Continent: Composite Dynamic and Thermodynamic Structures

The maritime continent (MC) straddles the Equator and divides the Indo-Pacific warm pool into the Indian Ocean and the western Pacific. The eastward propagation of the Madden-Julian Oscillation (MJO) is often hindered by the MC—the so-called MC “barrier effect.” The east Asian and Australian monsoons also affect the MC. Precipitation over the MC has a pronounced diurnal cycle due to the geography of large islands separated by narrow seas and shallow throughflows, and the precipitation is often organized in to large scale systems such as MJO envelopes and monsoonal systems. While many studies have focused on the seasonal and diurnal cycle of rain over the MC, there has not yet been a comprehensive survey of large-scale (e.g., spanning thousands of km lasting longer than a week) precipitation systems over the MC. The multi decade record of satellite derived merged rain products such as the TRMM Multisatellite Precipitation Analysis (TMPA) now makes such a survey possible. In this study, the method of Large-scale Precipitation Tracking (LPT), which has previously been used for tracking active MJO envelopes, is generalized for various Large-scale Precipitation Tracked systems (“LPT systems”) throughout the year from 1998 – 2018. These LPT systems include: active MJO envelopes, Rossby-like waves, and monsoonal systems. Three-dimensional composite wind, vorticity, divergence, moisture, and temperature will be presented for each type of LPT system over the MC, along with the within group variability/diversity. These composites will then be compared with suppressed precipitation days and days when there was significant precipitation, but it was at a scale too small to be part of an LPT system.