Changes between Initial Version and Version 1 of ticket/0851

Timestamp:

2011-07-20T19:55:06+02:00 (13 years ago)

Author:

poddo

Comment:

--

ticket/0851

@@ +1 @@
+[[PageOutline]]
+Last edited [[Timestamp]]
+
+[[BR]]
+
+'''Author''' : Paolo Oddo 
+
+'''ticket''' : #851
+
+'''Branch''' : [http://forge.ipsl.jussieu.fr/nemo/browser/branches/2011/dev_r2802_INGV4_zdfRic dev_r2802_INGV4_zdfRic ] 
+----
+
+=== Description ===
+In the current version of the Richardson number vertical turbolence scheme eddy viscosities and diffusivities are estimated based on the local gradient Richardson number Ri, using a scheme similar to that of Pacanowski and Philander (1981).
+
+
+Where Ri(x, y, z, t) is ≥0, 
+
+
+Av=Abv+ (v0) / (1+αRi)**nn_ri
+
+and
+
+Kv=Kbv + (v0) / (1+ αRi)**(nn_ric+1).
+
+
+In this shear vertical mixing scheme, the adjustable parameters are:
+ the background coefficients, Abv and Kbv;
+
+ the shear eddy viscosity at Ri=0 denoted by v0
+
+ the exponent (nn_ric=2)
+
+ the alpha parameter (5).
+
+
+
+This simple scheme has been largely used in numerical models (it is simple and robust) however it does not have any parameterization of the mixing layer.
+
+The basic idea is to introduce near the surface, a mixing-layer model to transfer and dissipate the atmospheric forcings (̌wind-stress and buoyancy flux).
+
+Following the scheme used in HOPS (Harvard Ocean Prediction System) and described in PFJ Lermusiaux (2001) we first evaluate the local depth of turbulent wind-mixing or “Ekman depth” hee(̌x, y, t).
+
+
+This depth is assumed proportional to the “depth of frictional influence” that is limited by rotation:
+
+
+hee=Ek u* / f0          (Rossby and Montgomery, 1935; Cushman-Roisin, 1994).
+
+In this similarity height relationship, the turbulent friction velocity:
+
+
+u*(x,y)=SQRT(||τ|| / ρ0)
+
+
+is computed from the wind stress vector τ and reference density ρ0.
+
+
+The coefficient Ek is an empirical factor (tunable)  and f0 is the Coriolis parameter.
+
+
+The final he is further constrained by adjustable bounds hemin≤ he ≤ hemax.
+
+
+Once hee is computed, the vertical eddy coefficients within hee are set to the empirical values Ae and Ke. This vertical mixing-layer model is one of the common results of more complex models (̌e.g. Mofjeld and Lavelle, 1984; Garwood et al., 1985; Stigebrandt, 1985; Large et al., 1994).
+
+
+----
+=== Testing ===
+Testing could consider (where appropriate) other configurations in addition to NVTK].
+
+||NVTK Tested||!'''YES/NO!'''||
+||Other model configurations||!'''YES/NO!'''||
+||Processor configurations tested||[ Enter processor configs tested here ]||
+||If adding new functionality please confirm that the [[BR]]New code doesn't change results when it is switched off [[BR]]and !''works!'' when switched on||!'''YES/NO/NA!'''||
+
+(Answering UNSURE is likely to generate further questions from reviewers.)
+
+'Please add further summary details here'
+
+ * Processor configurations tested
+ * etc----
+
+=== Bit Comparability ===
+||Does this change preserve answers in your tested standard configurations (to the last bit) ?||!'''YES/NO !'''||
+||Does this change bit compare across various processor configurations. (1xM, Nx1 and MxN are recommended)||!'''YES/NO!'''||
+||Is this change expected to preserve answers in all possible model configurations?||!'''YES/NO!'''||
+||Is this change expected to preserve all diagnostics? [[BR]]!,,!''Preserving answers in model runs does not necessarily imply preserved diagnostics. !''||!'''YES/NO!'''||
+
+If you answered !'''NO!''' to any of the above, please provide further details:
+
+ * Which routine(s) are causing the difference?
+ * Why the changes are not protected by a logical switch or new section-version
+ * What is needed to achieve regression with the previous model release (e.g. a regression branch, hand-edits etc). If this is not possible, explain why not.
+ * What do you expect to see occur in the test harness jobs?
+ * Which diagnostics have you altered and why have they changed?Please add details here........
+
+----
+=== System Changes ===
+||Does your change alter namelists?||!'''YES !'''||
+||Does your change require a change in compiler options?||!'''YES/NO !'''||
+
+additional parameters must be included in the corresponding namelist.
+
+
+----
+=== Resources ===
+!''Please !''summarize!'' any changes in runtime or memory use caused by this change......!''
+
+----
+=== IPR issues ===
+||Has the code been wholly (100%) produced by NEMO developers staff working exclusively on NEMO?||!'''YES/ NO !'''||
+
+If No:
+
+ * Identify the collaboration agreement details
+ * Ensure the code routine header is in accordance with the agreement, (Copyright/Redistribution etc).Add further details here if required..........