Figure 10b shows layer velocity after 20 years integration of cyclo-stationary ocean forced with monthly varying wind stresses, monthly varying turbulent kinetic energy of wind, and acnnual averaged atmospheric heat and salt fuxes. Figure 10c shows layer velocity after 20 years integration of cyclo-stationary ocean with monthly varying atmospheric heat fluxes and annual averaged wind stress, and annual averaged turbulent kinetic energy of wind.
The seasonal cycle of meridional flow is predominantly wind driven from the mixed layer to the 13th layer in the Indonesain seas. From the mixed layer to the second layer, wind drives annual cycle (Figure 10b) while the buoyancy drives semi-annual cycle (Figure 10c). It is interesting to note that the semi-annual cycle represents the solar insolation signal in the tropical region. In Figure 10c, the buoyancy driven flow in the mixed layer and the second layer shows oposite phase, indicating that the thermal expansion due to solar insolation penetrate down to the second layer situated at about 175 m in the Indonesian seas. Below 175m, the flow driven by wind stress shows weak annual cycle while buoyancy flux drives almost constant flow with amplitude comparable to the wind driven flow. The 12the layer flow driven by monthly varying wind stress and monthly varying turbulent kietic energy (Figure 10b) shows almost the same seasonal variation as that of 130 year integrated cyclo-stationary flow(Figure 10a), while buoyancy driven flow in the 12th layer in Figure 10c shows almost constant northward flow without vanishing seasoanl cycle. It is suggested that the monthly varying wind stress and turbulent kinetic energy were used to maintain the flow from the mixed layer to the 12th layer due to strong stresses between these layers, while the downward buoyancy flux penetrates from the mixed layer to the second layer situated at about 175 m and extinguishes below.
Figure 11 shows standard deviation of sea surafce level indicating small scale activities in the northern hemisphere and southern Indian ocean. Figure 12 shows the standard deviation of sea level when the cyclo-stationary ocean is forced by monthly varying wind stress, monthly varying turbulent kinetic energy and constant buoyancy flux. Figure 13 shows the standrad deviation of sea level when the cyclo-stationary ocean is forced by monthly varying buoyncy flux, constant wind and constant turbulant kinetic energy. Figure 14 is the ratio between Figure 11 and Figure 12. It is seen that the tropical ocean level variation is more sensitive to wind stress whie the mid-latitude sea level is more sensitive to buoyancy flux. The wind stress-sensitive area. with value larger than three is located in the area between 40 S and 60 S in the southern hemispheric Indian and Atlantic Oceans and in the area from 20 S to 10 S in the Pacific, Indian and Atlantic Oceans, and small spots in the Kuroshio and Gulf stream region. The heat flux-sensitive area with value smaller than unity is located most of the mid latitudes in both northern and southern hemispheres and north Atlantic ocean where deep water is formed by sinking of high salinity water.
