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Ship-based Observations of Atmospheric Boundary and Ocean Interactions near the Philippines during PISTON

The Madison-Julian Oscillation (MJO) is a major source of variability and predictability in the equatorial ocean. The Indian Ocean is usually referred to as the birthplace of the MJO. As the MJO propagates to the East it encounters the Maritime Continent (MC) where it may die out, propagate into the Pacific Ocean, and/or trigger the Boreal Summer Intraseasonal Oscillation (BSISO). The BSISO propagates from the equatorial Maritime Continent northward over the Philippine Archipelago. Intraseasonal atmospheric variability offers the possibility of better 10-day predictions, yet its predictability remains elusive. Furthermore, the local response of the atmosphere-oceanland system to intraseasonal and synoptic atmospheric variability is not understood. The local response involves terrain blocking the flow, diurnal land sea breezes that locally enhance and/or interrupt synoptic-scale waves, and different surface feedbacks between the mostly vegetated land surface and the ocean mixed layer. The MJO-barrier is poorly captured in climate models; the reason is hypothesized to be associated with conflicting land vs oceanic convective diurnal cycles. To address this, NOAA and partners (ONR, NASA, DOE) are planning a major field and modeling study in the MC called Propagation of IntraSeasonal Tropical Oscillations (PISTON).
We propose to make observations of ocean surface conditions, including fluxes of heat, moisture, and momentum, and the atmospheric boundary layer as part of PISTON in summer 2018 aboard a research vessel within the waters and the vicinity of the Philippine Archipelago. The research vessel permits us to sample different atmosphere-ocean interactions to incoming rain and wind events as a function of such parameters as distance offshore (0-300 km from shore), water depth, and island blocking of prevailing and anomalous wind. We expect nearshore diurnal circulations associated with the islands to superpose and interact with synoptic storm conditions propagating into the island regions.
We will measure the ocean wave state, sea surface temperature, and turbulent fluxes of sensible and latent heat and momentum across the atmosphere-ocean interface. A unique array of in situ and remote sensing instruments continuously measures turbulence and its effects on the momentum, heat, water, and salinity budgets. Together the observing systems proposed for the ship vertically profile temperature, moisture, and turbulent velocities from the ocean mixed layer, through the air-sea interface, atmospheric surface and planetary boundary layer, to shallow clouds. Our measurements will be a major contributor to high resolution modelling performed by research partners at Oregon State University (already funded for PISTON).

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