77
Table 6. Difference between the modelled - in run III - water mass properties and the
Levitus (1982) climatological values. The quantity 6V'denotes the average over the surface of
the World Ocean of the modelled variable, i.e., potential temperature (in 0c) or salinity (in
PSU), and the corresponding value in the Levitus (1982) climatology; 6V'nns represent the root
mean square difference. All statistical quantities are evaluated at the 20 model levels, the depths
of which are given in meters.
level
depth
tlT
tlT rms
tlS
tlS rrns
1
5
-0.003
0.7
0.0003
0.1
2
16
-0.4
1.1
0.002
0.2
3
29
-0.5
1.5
0.002
0.3
4
45
-0.3
1.6
-0.02
0.4
5
65
0.1
1.7
-0.03
0.4
6
90
0.5
1.9
-0.05
0.4
7
122
0.9
2.1
-0.06
0.4
8
163
1.0
2.1
-0.05
0.3
9
219
1.6
2.4
-0.02
0.3
10
299
2.0
2.7
0.03
0.3
11
415
2.6
3.1
0.1
0.3
12
589
2.9
3.4
0.1
0.3
13
850
3.0
3.3
0.07
0.3
14
1225
2.5
2.7
-0.04
0.2
15
1718
1.6
1.7
-0.2
0.2
16
2307
0.9
1.1
-0.2
0.3
17
2963
0.6
0.7
-0.3
0.3
18
3661
0.3
0.6
-0.3
0.3
19
4385
0.1
0.5
-0.4
0.4
20
5126
0.07
0.4
-0.3
0.4
An important variable for global climate is the poleward heat transport, p. The latter is
calculated from the model results as
0 x
p
f I hx v T dx dz,
(69)
-h x -
where the interval [x _, x.J spans the whole terrestrial sphere along a curve where y is constant.
In the Northern Hemisphere, this quantity is larger in III than in II (Fig. 18). In both
hemispheres, the poleward heat transport is somewhat smaller than the estimates derived from
observations (e.g. Hastenrath, 1982; Hsiung, 1985). This deficiency is common to many
OGCMs (e.g. Semtner and Chervin, 1992; Maier-Reimer et ai., 1993). However, other recent
numerical experiments have achieved quite realistic heat transports in the Southern Hemisphere
(England, 1993; Hirst and Cai, 1994), as well as in the Northern Hemisphere (Hirst and Cai,
1994).