changes to the kpp vertical mixing parameterization g. danabasoglu and w. g. large shallowness of...
TRANSCRIPT
Changes to the KPP Vertical Mixing
ParameterizationG. Danabasoglu and W. G.
Large•Shallowness of summer-time
boundary/mixed layer depths
•Presence of some grid-point noise in boundary /mixed layer depths, particularly in the Tropics•General review of physics and numerics
ENERGY INPUT AND DISSIPATION NOT CONSIDERED
TEST BED
x1 POP forced with QSCAT, NCEP, ISCCP, and MSU / Xie-Arkin data sets for July 1999 – December 2001
The initial conditions are for July 1, 1999, obtained from a 42-year forcing cycle experiment.The results shown are from the last years of 2.5-year experiments.
Short-wave heat flux has a diurnal cycle.
For simplicity, the internal wave mixing is the only interior mixing allowed.
BOUNDARY LAYER DEPTH
= HBLT
= 0.3
This value of the critical bulk Richardson number is based on some sensitivity studies where comparisons with observed ocean responses during the Ocean Storm Experiment were made. The vertical grid resolution was 1 m.
Large et al. (1994)
CRITICAL BULK RICHARDSON NUMBER
Large et al. (1994) suggests that the critical bulk Ri should somewhat increase as the vertical resolution degrades.
Obtained by matching 1-m vertical resolution results
= 1.8
This value is chosen to satisfy the empirical rule of pure convection, i.e. the ratio of entrainment flux to surface buoyancy flux should be 0.2.Large et al. (1994)
Obtained by satisfying the above rule
No dependence on resolution
BOUNDARY LAYER DEPTH
CONTROL Ri and Cv MODS
Jan
July
TURBULENT VELOCITY SCALES
Figure 2 of Large et al. (1994)
QUADRATIC INTERPOLATION
BOUNDARY LAYER DEPTH
CONTROL Quadratic Interpolation MODS
Jan
July
SUMMARY OF CHANGES• Diurnal cycle in short-wave heat flux
• Critical bulk Ri as a function of the vertical resolution
• Cv as a function of N
• Turbulent velocity scale limit in stable regions
• Quadratic interpolation for HBLT
• Use 4-pt maximum instead of 4-pt average for resolved shear
• Consider interior convection after HBLT is determined• Correct the Ekman and Monin-Obukhov depth limit computations
• Modify usage of N in turbulent shear computation
BOUNDARY LAYER DEPTH
CONTROL All Physics MODS
Jan
July
SUMMARY OF CHANGES• Diurnal cycle in short-wave heat flux
• Critical bulk Ri as a function of the vertical resolution
• Cv as a function of N
• Turbulent velocity scale limit in stable regions
• Quadratic interpolation for HBLT
• Use 4-pt maximum instead of 4-pt average for resolved shear
• Consider interior convection after HBLT is determined• Correct the Ekman and Monin-Obukhov depth limit computations
• Modify usage of N in turbulent shear computation
• Use OLDTIME level data in KPP to eliminate temporal noise• Use a Gaussian filter to smooth HBLT
BOUNDARY LAYER DEPTH
CONTROL All Physics + Numerical MODS
Jan
July
MIXED LAYER DEPTH
CONTROL All Physics + Numerical MODS
Jan
July
EQUATORIAL TEMPERATURE
CONTROL All MODSJan
July
LEVITUS
EQUATORIAL TEMPERATURE
CONTROL All MODSLEVITUS
PMEL