Changes between Version 1 and Version 2 of 2013WP/INGV-Basic-Reliability-tests


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Timestamp:
2013-11-12T16:33:19+01:00 (7 years ago)
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poddo
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  • 2013WP/INGV-Basic-Reliability-tests

    v1 v2  
    2525 
    2626Introducing a bathymetric gradient produces the amplification of the numerical noise in case of implicit vertical physics for the active tracers. For the second experiment, the bathymetry have been designed as in Mellor et al (1998) or Ezer et al (2002). This is the "classical" Sea Mountain case designed to study the hydrostatic pressure gradient errors in sigma coordinate. We have used the same geometry (Figure-1) but with close lateral boundaries, no surface forcing and initial condition characterized by no motion and homogeneous density field. In order to evaluate NEMO behavior we compared NEMO results with results from an equivalent implementation of the Princeton Ocean Model (POM, Blumberg and Mellor 1987). Where Possible the difference between the two codes have been minimized, setting the NEMO configuration as much as possible similar to POM (Annex-1). In this experiment NEMO code seems to have less numerical noise than POM. Figure-2. 
     27 
    2728[[Image(Fig_bathy_seamount.png)]] 
     29 
     30Figure.1 Seamountain Bathymetry 
     31 
    2832[[Image(sea_mountain_res.png)]] 
    2933 
    30 === Case 3 (Realistic Geometry) === [[BR]] 
     34Figure.2 Top-left panel: SSH from NEMO simulation after 14 days. Top-right panel: SSH from POM simulation after 14 days. Middle-left panel: SSH from NEMO simulation after 7 days. Middle-right panel: SSH from POM simulation after 7 days. Bottom panel: time series of potential temperature (initialized at 15) for NEMO (blu line) and POM (red line) 
     35 
     36=== Case 3 (Realistic Geometry) === 
    3137 
    3238The third experiment is done using a realistic bathymetry for the Northern Adriatic Sea; T and S are still homogeneous. The bathymetry is shown in figure-3. With realistic bathymetry, even if NEMO better preserve T and S (Temperature bottom panel Fig.3), there is a strange pattern in the SSH field that oscillate in time. There are large and small scale noise. A 2-point numerical noise is evident as the SSH field appears as purple (the combination of red and blu in adiacent grid boxes). A large scale propagation of the induced numerical noise is also evident as a wave propagating from the deeper west part toward the centre of the basin. Different tests have been done using the same bathymetric file but varying the number of vertical levels (from 31 to 89, letting the model to decide the distribution). Also in this case the namelist setup is as similar as possible to POM. 
     39 
    3340[[Image(Fig_bathy_adri.png)]] 
     41 
     42FIgure.3 Adriatic Bathymetry. 
     43 
    3444[[Image(adri_res.png)]] 
     45 
     46Figure.4 Top-left panel: SSH from NEMO simulation after 14 days.  Top-right panel: SSH from POM simulation after 14 days. Middle-left  panel: SSH from NEMO simulation after 7 days. Middle-right panel: SSH  from POM simulation after 7 days. Bottom-left  panel: SSH from NEMO simulation after 1 hr. Bottom-right panel: SSH  from POM simulation after 1 hr. 
    3547 
    3648'''References:''' [[BR]] 
     
    4254Mellor, G. L., L-Y. Oey, T. Ezer, 1998: Sigma Coordinate Pressure Gradient Errors and the Seamount Problem. J. Atmos. Oceanic Technol., 15, 1122-1131. 
    4355 
    44 '''Annex-1''' 
    45 Differences with standard GYRE namelist 
     56'''Annex-1''' Differences with standard GYRE namelist 
    4657 
    4758{{{ 
     
    6879rn_ahm_0_lap     = 100.   !  horizontal laplacian eddy viscosity   [m2/s] 
    6980}}} 
    70