Assimilated Taiwan Ocean Prediction (ATOP)

& Climate Research at NCU

by

Leo Oey lyooey@ncu.edu.tw

March 2012

Goals

• Build a data -assimilated ocean prediction system for the North Pacific Ocean with focus on the Kuroshio and the marginal seas around Taiwan ATOP

• Conduct air-sea coupled research based on ATOP & the Weather Research and Forecasting (WRF) Model to study processes that range from short (e.g. typhoons), seasonal, to inter-annual (e.g. ENSO) and inter-decadal (e.g. PDO) time scales, also with focus on the climate in the western North Pacific & Taiwan

• Help to foster future Taiwan’s scientists to conduct and publish oceanic and atmospheric modeling and data-analysis research

ATOP Research Highlights

IHOS@NCU is developing an ocean current and wave prediction model: the Assimilated Taiwan Ocean Prediction (ATOP) system that will include also air-sea (with typhoons) and air-sea-ice coupling, as well as biogeochemical processes. Three recent publications and an example of the simulated SST over the North Pacific Ocean are given below.

•Chang, Y.-L. & L.-Y. Oey, 2012: The Philippines-Taiwan Oscillation: Monsoon-Like Interannual Oscillation of the Subtropical-Tropical Western North Pacific Wind System and Its Impact on the Ocean. J. Climate, 25, 1597-1618. PDF Format.  Download PTO Data (text file) here.•Chang, Y.-L., and L.-Y. Oey, 2011: Interannual and seasonal variations of Kuroshio transport east of Taiwan inferred from 29 years of tide-gauge data, Geophys. Res. Lett., 38, L08603, doi:10.1029/2011GL047062.•Fujisaki, A. and L.‐Y. Oey, 2011: Formation of ice bands by winds, J. Geophys. Res., 116, C10015, doi:10.1029/2010JC006655.

ATOP sea-surface temperature (SST) on Jun/06/1988 during the developing stage of the strong 88-89 La Niña when waters as cold as 19oC is simulated in the eastern equatorial Pacific in excellent agreement with observation (http://www.pmel.noaa.gov/tao/elnino/la-nina-story.html#). ATOP also simulates a beautiful meandering Kuroshio that separates off the eastern coast of Japan, as well as the intrusion of very warm waters (SST≈31oC) into the South China Sea through the Luzon Strait. (From Lu, H.-F. & L.-Y. Oey, 2011: Instability waves and eddies of the Subtropical Counter Current in the North Pacific Ocean, Manuscript in preparation).

Shown here is the planned ATOP region at medium grid resolution (~5km) in the western North Pacific Ocean

ATOP will include realistic topography, winds, tides, rivers, surface evaporative and precipitation fluxes, waves, data assimilations, and with options to nest very-high resolution (10~1000m) near the coast around Taiwan. A main goal is to include air-sea coupling for typhoon and climate research and, in cooperation with other scientists, we envision to also incorporate ecology, biology, chemistry, sediment, and hydrology.

ATOP for the Western North Pacific

Ocean’s Topography & Major Currents in the Western North

Pacific ATOP Region

South China Sea

East China Sea

Japan Sea

meters

Kuroshio

North Equatorial Current

Mindanao Current

Eddies

Eddies

Typhoon

Scientific Questions:• What are the roles of SI and MLI in eddies?• The turbulence they produce: how do they compare against those by e.g. Langmuir cells and wave-

breaking?• How are these eddies coupled to winds that drive SI & MLI’s, what are the coupled responses in the PBL ~

troposphere, and physical-biological responses?• Is PTO a coupled response? The answer is probably yes, but how is it related to small-scale physics +

eddies & coupled atmosphere, and how is it related to interannual variations of monsoon troughs and perhaps to typhoon intensity and frequency?

• What are the coupled responses to regional marginal seas, and their possible feedbacks to the climate system – e.g. ITF?

The Role of Ocean, eddies and their Coupling with the Atmosphere in Regulating Sea-Surface Fluxes and Western North Pacific Climate