Dynamics and Prediction of the Boreal Summer Instraseasonal Oscillation in the Maritime Continent
Abstract
We propose a project that will investigate the dynamics of the boreal summer intraseasonal oscillation (BSISO) as it propagates northwards and eastwards through the South China Sea (SCS), Philippines, and adjacent regions of the maritime continent (MC) and Western North Pacific. The project will focus on the synoptic- and mesoscale convective disturbances within the planetary-scale BSISO, and on interactions with both the land surface and upper ocean. We propose a project that will investigate the dynamics of the boreal summer intraseasonal oscillation (BSISO) as it propagates northwards and eastwards through the South China Sea (SCS), Philippines, and adjacent regions of the maritime continent (MC) and Western North Pacific. The project will focus on the synoptic- and mesoscale convective disturbances within the planetary-scale BSISO, and on interactions with both the land surface and upper ocean. The questions of primary interest will be the following: 1. What happens to the BSISO when it reaches the MC, and the SCS/Philippines in particular? What are the roles of land-sea contrasts, orography, air-sea heat exchange, and ocean coupling? 2. What mesoscale and synoptic-scale structures exist within the BSISO envelope, and how do these contribute to the planetary-scale propagation of the BSISO? How do these structures interact with the ocean and with the islands? 3. What are the relative roles of thermal and mechanical forcing in orographic convection over the MC, and how does each influence the BSISO? 4. What are the interactions between the climatology, the diurnal cycle and the intraseasonal variations associated with the BSISO? Do model biases in either the time-mean climatology or the diurnal cycle cause poor simulation of intraseasonal variability, or are errors on these time scales independent? Our methods will be: 1. Case studies to examine the synoptic- and mesoscale structures of individual BSISO events as they are manifest in the SCS and Philippines region in northern summer; 2. High-resolution regional simulations using a cloud system-resolving regional model, to study MJO/BSISO interactions with diurnal and orographic convection, as well as ocean coupling with a coupled version of the model. 3. Analysis of the ensemble forecast dataset from the Seasonal to Subseasonal (S2S) project, focusing on the SCS and Philippines, complemented by output from the new Navy NAVGEM-HYCOM system as available, to determine how variations in key processes across the ensembles are related to BSISO forecast skill. 4. Once field observations are available, close analysis of those observations to constrain and validate the simulations (both global and regional) of both the MJO and, especially, local convective processes in the MC. This combination of approaches will lead to an improved understanding of the BSISO’s propagation mechanisms, its smaller-scale manifestations in the complex local geography of the SCS and Philippines. This will lead to a greater understanding of the factors which determine whether individual events propagate through the region or do not, and whether global and regional models are able to successfully predict that propagation or its absence. Accurate simulation of the BSISO is a prerequisite to good intraseasonal forecasts in the tropics, and this project will build the foundation for improvements in those forecasts
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Nov 23, 2016
- Source ID
- N000141613073
Entities
People
- Adam Sobel
Organizations
- Office of Naval Research
- Trustees of Columbia University in the City of New York
- United States Navy