Coupled Simulations of the 2016 Summer BSISO Event over the Maritime Continent

During the summer of 2016, a Boreal Summer Intraseasonal Oscillation (BSISO) event was observed over Southeast Asia, the South China and Philippine seas. Precipitation anomalies associated with this BSISO event propagate northward at a speed of 1 degree per day from July to August. This BSISO event was selected as a research target by the PISTON (Propagation of Intra-Seasonal Tropical Oscillations) modeling team in advance of the field campaign.

To understand the dynamical processes of this BSISO event, coupled numerical simulations of one full BSISO life cycle are conducted to explore multiscale interaction in the atmosphere and air-sea interaction. The coupled modeling system inherited from Chen et al. (2013) is configured to couple the Weather Research and Forecasting Model (WRF) model and the Hybrid Coordinate Ocean Model (HYCOM). It is shown that the 2 month long coupled simulations reasonably capture large-scale northward propagation of this BSISO event, as well as prominent diurnal variations of precipitation at the large islands in this region. Coupled simulations with altered air-sea interaction and uncoupled simulations with prescribed sea surface temperature are further conducted. Results from these experiments confirm the importance of air-sea interaction in determining BSISO amplitude and propagation speed.