Xz. Jin et al., Fundamental framework and experiments of the third generation of IAP/LASG world ocean general circulation model, ADV ATMOS S, 16(2), 1999, pp. 197-215
A new generation of the IAP / LASG world ocean general circulation model is
designed and presented based on the previous 20-layer model, with enhanced
spatial resolutions and improved parameterizations. The model uses a trian
gular-truncated spectral horizontal grid system with its zonal wave number
of 63 (T63) to match its atmospheric counterpart of a T63 spectral atmosphe
re general circulation model in a planned coupled ocean-atmosphere system.
There are 30 layers in vertical direction, of which 20 layers are located a
bove 1000 m for better depicting the permanent thermocline. As previous oce
an models developed in IAP / LASG, a free surface (rather than "rigid-lid"
approximation) is included in this model. Compared with the 20-layer model,
some more detailed physical parameterizations are considered, including th
e along / cross isopycnal mixing scheme adapted from the Gent-MacWilliams s
cheme.
The model is spun up from a motionless state. Initial conditions for temper
ature and salinity are taken from the three-dimensional distributions of Le
vitus' annual mean observation. A preliminary analysis of the first 1000-ye
ar integration of a control experiment shows some encouraging improvements
compared with the twenty-layer model, particularly in the simulations of pe
rmanent thermocline, thermohaline circulation, meridional heat transport, e
tc. resulted mainly from using the isopycnal mixing scheme. However, the us
e of isopycnal mixing scheme does not significantly improve the simulated e
quatorial thermocline. A series of numerical experiments show that the most
important contribution to the improvement of equatorial thermocline and th
e associated equatorial under current comes from reducing horizontal viscos
ity in the equatorial regions. It is found that reducing the horizontal vis
cosity in the equatorial Atlantic Ocean may slightly weaken the overturning
rate of North Atlantic Deep Water.