Multinest highresolution model of submesoscale circulation features in
Multi-nest high-resolution model of submesoscale circulation features in the Gulf of Taranto F. Trotta, N. Pinardi, E. Fenu, A. Grandi EGU General Assembly 27/04/2017 - Session CL 5. 08/AS 1. 3/OS 4. 10 Downscaling: methods and applications
NESTED-GRID OCEAN CIRCULATION MODELLING SYSTEM Parent Domain Dl, Dj, Dz NEST 1 Dl, Dj, Dz C NEST 2 La te ra l. B Dl, Dj, Dz ON E– WA Y–N Ø SURF provides a numerical ES TE plataform for short-time forecast DM at high spatial and temporal resolution. OD EL LIN Ø It is based on NEMO code: 3 D Finite Difference GA Hydrodynamic (FDH) model which solve the primitive PP RO equations on an Arakawa C-grid with free surface. AC H C NEST 3 l. B ra te La Ø It can be easily and quickly deployed in any region of a large-scale Ocean Forecasting System via nesting procedure(one-way nesting approach) C La te ra l. B Dl, Dj, Dz Ø The plataform include multiple nesting capability. Ø For each nesting, the coarse-grid (parent) model provides initial and lateral boundary condition to the fine-grid (child) model. Ø We can increase the model resolution in a sub-domain and resolve a wider range of scale, not only the mesoscale flow field (10 -100 km) but also the submesoscale flow field (100 m-10 km)
CASE STUDY: THE GULF OF TARANTO LS 1 CS 01 Oct 02 Oct 03 Oct 04 Oct 05 Oct 06 Oct 07 Oct LS 2 08 Oct 09 Oct 10 Oct 11 Oct 12 Oct GULF OF TARANTO t Oceanographic cruise (MREA 14) in Taranto Gulf was carried out in October 2014 on Galatea (Italian Navy Hydrographic Institute) Mar Grande Costal Scale A multi-scale CTD data collection (from 1 to 11 October 2014) Large Scale Ø Large Scale: LS 1 &LS 2 with resolution 16 km Ø Coastal Scale: CS with resolution 5 km Ø Mar Grande : MG with resolution of 1 km
MODEL SET-UP LS 1 CS 01 Oct 02 Oct 03 Oct 04 Oct 05 Oct 06 Oct 07 Oct NEST 1 NEST 2 t 08 Oct 09 Oct 10 Oct 11 Oct 12 Oct Spin-up NEST 3 Spin-up MFS 6 km NEST 1 2 km TIME SPATIAL GRID NEST 3 227 m INITIAL CONITION MFS-field (T, S, u, v and SSH) with LS 1 -CTD data assimilated Surface BC (MFS Bulk formulae using ECMWF data ) Lateral close BC (No-slip condition) Lateral open BC (Flather and Flow Relaxation scheme) Bottom BC (Non linear friction) Start Date n. Day Time Step MFS - NEST 1 NEST 2 PHYSICS NEST 3 200 s 2014/10/05 (00: 00) 8 150 s 2014/10/06 (00: 00) 7 72 s 2014/10/07 (00: 00) 6 36 s 821 x 253 1/16 6114 m 94 x 79 1/48 2038 m 230 x 160 1/144 680 m 220 X 200 1/432 227 m Horizzontal Grid (spherical coordinate system) N° of points Grid resolution Vertical Grid (z-coord with partial step) NEST 2 680 m BOUNDARY CONITION LS 2 N° of levels Grid res 1° layer Maximu Depth 72 2. 8 m 2000 m 120 2. 8 m 2000 m Viscosity coeff Diffusivity coeff -1 e+09 -6 e+08 -1. 2 e+07 -7. 4 e+06 -152416 -91449 -1881 -1129 1. 2 e-05 1. 2 e-06 10 Horizontal Subgrid-scale physics (bilaplacian operator) Vert Subgrid-scale physics (PP mixing parametrization) Viscosity coeff Diffusivity coeff EVD Max coeff 1. 2 e-05 1. 2 e-06 10 SPECIFIC NUMERIC FORMUL. Moment Adevection (EEN scheme) Tracer Adevection (MUSCL scheme) Bottom BC (Non linear friction)
SUBMESOSCALE STRUCUTREs MFS 6000 m NEST 1 2038 m MFS VS Horiz. section of Temp + Current at 10 m (October 10 2014 24: 00) 1 NEST 01 02 NEST 1 2038 m NEST 2 680 m 1 NEST VS 2 NEST 2 680 m NEST 3 2 NEST VS 3 NEST 227 m 03 04 05 06 07 08 09 10 11 12 Ø Large scale anticyclonic rim current with intesified jets and additional features emerged in the higher resolution nests. Ø A submesoscale cyclonic vortex with diameter of 4 km was found. To generate this eddy a 200 m resolution was required Ø This eddy was confirmed by observational data collected in the study area. Pinardi et all. 2016
EVOLUTION OF SUBMESOSCALE STRUCTUREs Horizontal section of Temperature + Current at 10 m (October 10 2014 from 00: 00 to 24: 00) 01 Oct 02 Oct 03 Oct 04 Oct 05 Oct 06 Oct 07 Oct 10– 00: 00 Oct 10– 06: 00 Oct 10– 18: 00 Oct 10– 24: 00 08 Oct 09 Oct 10 Oct 11 Oct 12 Oct t Oct 10– 12: 00 Ø Formation of a meander. Ø Eddy formation process accours in severa hours over a space scale of few ten km
EVOLUTION OF SUBMESOSCALE STRUCTUREs Horizontal section of Relative Vorticity at 10 m (October 10 2014 from 00: 00 to 24: 00) 01 Oct 02 Oct 03 Oct 04 Oct 05 Oct 06 Oct 07 Oct 10– 00: 00 Oct 10– 06: 00 Oct 10– 18: 00 Oct 10– 24: 00 08 Oct 09 Oct 10 Oct 11 Oct 12 Oct t Oct 10– 12: 00 Ø Formation of a meander. Ø Eddy formation process accours in severa hours over a space scale of few ten km
SURFACE MIXED-LAYER Zonal section of Vertical Velocity Field (October 10 2014 from 00: 00 to 24: 00) 01 Oct 02 Oct 03 Oct 04 Oct 05 Oct 06 Oct 07 Oct 08 Oct 09 Oct 10 Oct 11 Oct 12 Oct t Oct 10– 00: 00 Ø Increasing resolution was accompanied by an increase of vertical velocity (from few m/day (NEST 1) up to 100 m/day (NEST 3) near the surface.
SURFACE MIXED-LAYER Zonal section of Vertical Velocity Field (October 10 2014 from 00: 00 to 24: 00) 01 Oct 02 Oct 03 Oct 04 Oct 05 Oct 06 Oct 07 Oct 08 Oct 09 Oct 10 Oct 11 Oct 12 Oct t Oct 10– 06: 00 Ø Increasing resolution was accompanied by an increase of vertical velocity (from few m/day (NEST 1) up to 100 m/day (NEST 3) near the surface.
SURFACE MIXED-LAYER Zonal section of Vertical Velocity Field (October 10 2014 from 00: 00 to 24: 00) 01 Oct 02 Oct 03 Oct 04 Oct 05 Oct 06 Oct 07 Oct 08 Oct 09 Oct 10 Oct 11 Oct 12 Oct t Oct 10– 12: 00 Ø Increasing resolution was accompanied by an increase of vertical velocity (from few m/day (NEST 1) up to 100 m/day (NEST 3) near the surface.
SURFACE MIXED-LAYER Zonal section of Vertical Velocity Field (October 10 2014 from 00: 00 to 24: 00) 01 Oct 02 Oct 03 Oct 04 Oct 05 Oct 06 Oct 07 Oct 08 Oct 09 Oct 10 Oct 11 Oct 12 Oct t Oct 10– 18: 00 Ø Increasing resolution was accompanied by an increase of vertical velocity (from few m/day (NEST 1) up to 100 m/day (NEST 3) near the surface. Ø Starting with a weakly stratified ML, we observed, in higher resolution nests, a faster restratification (increase in the restratification rate)
CONCLUSIONs • We implemented a triple-nested model using the new relocatable ocean platform “SURF” from the coarser resolution (6000 m) MFS model to the NEST 1 (2000 m), NEST 2 (700 m) and NEST 3 (200 m) models in order to explicitly resolve the submesoscale in the Gulf of Taranto. § The flow field showed large-scale anticyclonic rim current with intensified jets and additional small-scale features emerging in higher resolution nests. § A submesoscale cyclonic vortex with diameter of 4 km was found in the northwest region of the central anticyclonic gyre. To generate submesoscale eddies, it was found that ∼ 200 m resolution was required. § This eddy was confirmed by observational data collected in the study area. § Increasing resolution was accompanied by an increase in the vertical velocity field in the upper ocean (up to 100 m/day). § As horizontal resolution increased, we obseved an increase in the restratification rate in the Mixed Layer.
END
- Slides: 13