Test of improved boundaries configuration for the Tagus Estuary Pre-operational Model (OM) Ângela Canas Maretec SANEST

Objective What was known: Studies show needed improvement of boundary conditions: large, surface, rivers, bathymetry (e.g. R. Fernandes, 2005) Version 4 of MOHID allows advanced advection Assess effect in 3D Level 2 results of all possible improvements of boundaries and advection now possible Continental Portuguese Coast Level 1 Level 2 New bathymetry MM5 HDF5 forcing Advection TVD - Superbee Sorraia hourly flow Relaxation to Levitus monthly profile climatology (T, S) Common in literature

Changes: Level 1: Portuguese Coast, resolution 2  4km, TVD - Superbee, BIHARMONIC_COEF : 1e9, HDF5 MM5 forcing (best resolution) Level 2: 3D (33 layers), BAROCLINIC_METHOD : 3, BAROCLINIC_POLIDEGREE : 1, TVD - Superbee, relax. to 1 T/S Levitus profile in all boundary, HDF5 MM5 forcing (best resolution) Methodology Simulation 1 (S1) Current configuration but Version 4 Simulation 2 (S2) Improved configuration (Version 4) To support internal tide ConvertToHDF5  action Patch HDF5 Files Background: Level 1: S. Vicente  Leixões, 2D, resolution 2 km, barotrophic, upwind, BIHARMONIC_COEF : 1e8, time serie MM5 forcing, tide,  t = 60s Level 2: 3D (11 layers), resolution 0.3  2km, baroclinic, BAROCLINIC_METHOD : 1, upwind, 36 psu relax. b.c., hydro Flather radiation b.c., time serie MM5 forcing,  t = 15s, Tagus – Sorraia – Trancão river flows, GOTM

Methodology Initialization: Slowstart, wind smooth period (1 day) Level 2: water level = 2.08m, baroclinic ramp 1 inertial period (S2) Temperature: constant 16ºC (S1), Levitus (S2) Salinity: estuary boxes, sea constant 36 psu (S1) or Levitus (S2) Density: constant g/m3 (S1), variable in depth for pressure (S2) Assessment (01/02/2005  01/03/2005) : Predicted tide gauge water level (TidePrev) SST (MODIS) CTD (SANEST) 15/01/2005, 0h  01/03/2005, 0h S1 S2 After 08/02/2005, 6h: b.c. for T/S = null gradient for dephts < 100m  bigger concurrence with MODIS SST

Results: hydrodynamic Velocity modulus (m/s) S1 Velocity modulus (m/s) S2 Surface values Internal tide: Associated with vertical oscilations of isotherms due to interaction between tide and continental shelf slope Not visible in the water level (change only a few cm) Maximum velocity points in Nazare canyon according with known internal tide (H. Coelho, C. Garcia)

Results: hydrodynamic Greater improvement inside estuary Still, better results outside estuary higher resolution better bathymetry

Results: hydrodynamic Significant phase differences do not occur Mean level generally smaller in model Study of the effect of pressure in water level (to be released) evidences que existence of a systematic error in mean level used for tide forcing (2.08m)  causes degradation of RMSE Water level in channel areas still poorly represented Improve grid resolution

Results: SST Improvements: more realistic spatial variability acceptable results in the Outfall in upwelling events

Results: SST Remaining problems: off-coast poor results systematic general cooling null gradient b. c. not adequate boundaries too close to interest area excessive internal tide causes too much mixture (low sensitivity to meteo) systematic cooling

Results: vertical stratification, temperature and salinity Overestimation of T and underestimation of S greatly reduced Measurement date: 01/02/05 Guia Outfall near location G08 Depths: 2.55m, 7.5m, 15m and 27.5m

Results: vertical stratification, temperature and salinity Stratification still poorly captured Error in salinity and temperature non concurrent Poor vertical discretization ? CTD and field data should be found and analysed for off-coast (Coriolis) and inside estuary

Results: kinetic and potential energy Higher initial energy  effect of internal tide Decrease of potential energy  water too hot induces sinking Still observed in Simulation 2 Different tide print on potential energy  ?

Conclusions New configuration provides improved results for: Water level: especially inside the Tagus estuary  effect of new bathymetry; Temperature/salinity: especially in the Guia Outfall area  effect of improved stratification; Unsolved problems: Water level in channels near river locations; SST away from coast.

Conclusions Detected incorrections: Time serie for atmospheric forcing of current configuration not represent surface values (average of first MM5 layer): Explains in part disparities found by R. Fernandes (2005)

Conclusions Detected incorrections: Tide component files for Montijo, Seixal and Alcochete with incorrect time reference (less 1h) Tide appears first in model