T aiwan S trait NOW cast s ystem N ational C enter for O cean R esearch Taiwan, ROC P01

promotion of cutting-edge oceanographic researchpromotion of cutting-edge oceanographic research promotion of the use of satellite remote-sensing technology in oceanographic researchpromotion of the use of satellite remote-sensing technology in oceanographic research Promotion of international collaboration in oceanographic researchPromotion of international collaboration in oceanographic research coordination of the use of oceanographic research vesselscoordination of the use of oceanographic research vessels establishment of an oceanographic databankestablishment of an oceanographic databank National Center for Ocean Research (NCOR) was established on August 1, 1997, by the National Science Council of Taiwan. The major missions of NCOR include Introduction to NCOR P02

Sen Jan and Yu-Huai Wang National Center for Ocean Research, Taiwan, R.O.C. Shenn-Yu Chao University of Maryland Center for Environmental Sciences, U.S.A. Dong-Ping Wang Marine Science Research Center, SUNY, Stony Brook, U.S.A. Development of a Nowcast System for the Taiwan Strait (TSNOW) P03

is necessary because 90% of Taiwan’s population, industry and economy lies in her west coastis necessary because 90% of Taiwan’s population, industry and economy lies in her west coast is based on the extensive hydrographic data acquired in the strait during the past two decadesis based on the extensive hydrographic data acquired in the strait during the past two decades is aimed for both practical and scientific applicationsis aimed for both practical and scientific applications takes a balanced approach relying equally on models and observationstakes a balanced approach relying equally on models and observations will have the capacity of real-time observational data assimilationwill have the capacity of real-time observational data assimilation The Taiwan Strait nowcast system P04

Taipei Kaohsiung Taichung Keelung Matsu Maopitou Dongshan Nowcast system model domain CY Rise KY Depression WC Depression P05

For TNOW, ”nowcast” is defined as time T = 0T = 24 hrs sea levels currents Definition of nowcast P06

Short-term Disaster warning Disaster warning Marine rescue Marine rescue Pollutant dispersion Pollutant dispersion prediction prediction Long-term Scientific study Scientific study Environmental Environmental policy making policy making Marine resources Marine resources management management ObservationsPredictionDemonstrationApplications Conceptual model for TSNOW P07WWW

1 st Stage: to establish the capability and demonstrate success in doing good hindcast for the barotropic tides 2 nd Stage: to incorporate wind-driven part in the model 3 rd Stage: to consider the seasonal/monthly mean circulation and baroclinic effect in the flow field Development of the TSNOW system P08

Observations To determine initial and boundary conditionsTo determine initial and boundary conditions To validate model resultsTo validate model results Tide-gage stations established by NCOR Tide-gage stations established by CWB P09 Mooring stations of bottom-mount ADCP

Velocities measured using SB-ADCP Observations Velocities acquired by long-term moored BM-ADCP SpringSummer Temperature SalinityTemperatureSalinity P10

Numerical model Model resolution Boundary conditions A 3D general circulation model with free surface is used for the nowcast system. The bottom slope is quite large and the baroclinic effect is strong in the Taiwan Strait, justifying the choice of a z-level model over a sigma-coordinate model (e.g., POM). Five major tidal constituents O1, K1, N2, M2 and S2 were run together in the model. P11

Observations -- real-time -- near real-time Malfunction? 2D adjoint model assimilating sea levels at 9 tide-gage stations Transfer function for harmonics derived from larger-domain 2D model Boundary conditions Complex 3D model Determination of boundary conditions No Yes Web P12

Determination of boundary conditions Take advantage of a larger-domain 2D tidal model results P13

Model simulated results P14

Black-observed Red -calculated Model validation – sea levels Kaohsiung Dongee P15

Model validation – tidal currents P16

Blue - ship-board ADCP measured velocities Red - model calculated velocities Model validation – tidal currents Errors of calculated speed: < 40% of measured speed. Errors of calculated current direction:  30º of measured directions. P17

Tidal Constituents M2S2N2K1O1 ADJM rms(cm) TSNOW -2D rms(cm) model skill TSNOW -ADJM rms(cm) model skill Assessment of model performance Define: P18

Penghu Islands Dongee Demonstration of model products P19

Summary In the first stage of model development, barotropic tides were successfully simulated in a hindcast mode. The model performed well as the open boundary conditions were determined using either an adjoint model or a larger-domain two-dimensional model results. The coexistence of a southward propagating Kelvin wave and a nearly standing wave respectively in the eastern and western halves of the Taiwan Strait has also been examined using the model. P20

Future work The two approaches of determining open boundary conditions will be adopted when the model is used in an operational mode. The wind-driven part, remote-controlled larger-scale circulation and buoyancy-driven circulation will be incorporated in the model step by step. The observational work will include strait-wide hydrographic surveys, current measurements using bottom-mounted ADCP moorings and real-time sea- level observations. P21

Thank you for your attention! P22