Characteristics of the South China Sea and Maritime Continent Boreal Winter Subseasonal Peak Precipitation and Its Predictability

Tropical South China Sea (SCS)-Maritime Continent (MC) is one of the precipitation centers in the tropics during the boreal winter half-year (NDJFMA). The abundant winter rainfall amount over this region involves multiple-scale phenomena such as the annual cycle, cold surges, ENSO, Madden-Julian Oscillation (MJO), and convectively coupled equatorial waves (CCEWs). Understanding how the above-mentioned climate systems modulate the major precipitation events will help us to understand the features of precipitation variability in the SCS-MC region and improve subseasonal-to-seasonal (S2S) prediction. In this study, we first identify the subseasonal peak precipitation event based on CMORPH daily rainfall data. The peak event is defined as a successive 3 pentads of which the accumulated rainfall amount is the highest of the winter-half-year in terms of 15-day accumulated rainfall. The result suggests that the MJO and CCEWs have strong influences on the timing and intensity of the peak precipitation, while the terrain effect can overwhelm the large-scale modulation. The analysis result is applied to assess the predictability of the peak event during two winters (2016/17 and 2017/18) of the South China Sea Two Island Monsoon Experiment (SCSTIMX) using the SubX/EMC-GEFS dataset. The peak event predictability, in particular, the influence of tropical and extratropical waves and terrain effect will be discussed.