The formation and dynamics of cold-dome northeast of Taiwan. Mao-Lin Shen, Yu-Heng Tseng and Sen Jan 2014/8/21. Outline. Introduction Numerical model Observation Numerical results Mechanism analysis Conclusion. Introduction (1/3).
Mao-Lin Shen, Yu-Heng Tseng and Sen Jan
Fig. 1. Distribution of the centroid of cold patch formed between 2003-2008. Red stars denote the distribution of cold patch in summer (June to October) and green stars show that in winter. (Cheng et al., 2009)
Fig. 2. Schematic of the whole domain under consideration
30 July 2008
Typhoon Fung-Wong (28 July) just pass.
16 May 2008
7 November 2009
2 May 2009
Fig. 3. The SST image around the vicinity region. The dark red encircled lines indicate Cold-Dome Favorite Region (CDFR). The fronts identify the boundary of warm water carried by Kuroshio and the cold water remained on continental shelf or the cold-dome.
Fig. 4. Time-longitude plot of filtered SST north of Taiwan. Half degree span on latitude (25.4°N-25.9°N) was chosen to verify the variation. Of 2008 the dashed lines denote typhoons from left to right is Kalmaegi, Fung-Wong, Sinlaku and Jangmi, respectively. Of 2009 the dashed line denotes typhoon Morakot.
Fig. 5. The Argo data, marked as red solid circles, since 3 August 2001 to 6 September 2009 in the study region, only 2047 data are available. Argo data gathered on Kuroshio main stream totally 21 profiles in from May to October, stand for summer pattern (b), and 12 profiles in from November to April, stand for winter pattern (c).
Fig. 6. Argo float, WMOID 2900797, for (a) the trajectory; (b) MW_IR SST and a marker denotes the Argo data on 16 December 2008. The rests are subsurface comparisons of (c) temperature, (d) salinity, and (e) T-S profiles of the four measures.
Fig. 7. Argo float, WMOID 2900819, for (a) trajectory of the float; (b) MW_IR SST and the a marker denotes the Argo data on 17 July 2008. The rest figures are subsurface comparisons of (c) temperature, (d) salinity, and (e) T-S profiles of the four measures. Typhoon Kalmaegi passed this region on 17-18 July 2008. The path of Typhoon Kalmaegi are marked as hollow circles in (a).
Z = 54 m
Z = 6 m
Fig. 8. The SST results and current velocities at different depth on day 157, Year 37 of the model results. Note that a cold region was formed off northeast Taiwan just as the observations of satellite SST results.
Z = 75 m
Z = 98 m
Fig. 9. The possible trajectories from Kuroshio Tropical Water (KTW). The sources were located over the model year and recorded the position until tracers flow out of the domain or rest on bathymetry.
North Mien-Hua CanyonNumerical results (3/3) ─ Trajectory
Fig. 10. A trajectory shows the route of Kuroshio Tropical Water. The background flow field are model results at z = 198 m on day 122.
Boundary mixingMechanism Analysis (2/11)
Fig. 11. Wind-driven Ekman upwelling determined by monthly Hellerman and Rosenstein wind stress and model’s vertical eddy viscosity.
Garrett et al.
Inverse currents introduced little dowelling transport.
Garrett et al. (1993), JFM.
Fig. 12. Meridional current velocity distribution (Tang et al., 2000).Mechanism Analysis (5/11) ─ Boundary layer effects
Diffusion, little H. Advection
Fig. 13. Zonal temperature profile at 25.6°NMechanism Analysis (6/11)
Fig. 14. Isothermal plan at 21℃ calculated by model output.
Fig. 15. Contour of Uplift height.
Topographical upwelling, eddy introduced dynamic uplift and other minor effects.
Fig. 16. Comparison of uplift height introduced by different mechanism.
(a) Realistic bathymetry
(b) Deepened Case
(c) Shallowed Case
Fig. 17. Flow field and temperature at 50 m deep of numerical experiments.
(a) Zonal Temperature (℃) profile
(b) Eddy diffusivities (cm2/s)
Fig. 18. Instantaneous zonal profiles of temperature and eddy diffusivities at 25.6°N. The vertical temperature gradient near surface coupled with the high surface eddy diffusivities suggested energetic vertical hear transfer in surface cold-dome.