Therefore, the EKE of TIWs and related TIW activity were much lower south of the equator. To depict the longitudinal propagation features of a TIW, Bt and Bc, a longitude-time plot was drawn of climatological Bt and Bc, as well as the moving variance of temperature and meridional current, which was used in Figure 4. All values in Figure 5 were averaged between 0��C5��N and a depth of 0�C50m. As EPZ-5676 mll shown in Figure 5, TIW activity associated with both temperature and meridional current grew first at the eastern edge of the eastern Pacific around May and spread to the west slowly over time [10]. The maximum activity occurred around 130��W and in August. Consistent features were found in Bt and Bc as seen in Figures 5(c) and 5(d), respectively, and their contributions were almost equal over this region.

Figure 5Longitude-time plot of the climatological cycle of the 30-day moving variance of filtered temperature (a) and meridional current (b), and barotropic (c) and baroclinic (d) conversion rates averaged between 0 and 5��N over the upper 50m. …To illustrate the detailed seasonal features of Bt and Bc, the zonal averages during the June to September (JJAS) and March to April (MA) seasons were computed, that is, the maximum and minimum TIW activity, respectively. In JJAS (Figure 6(a)), a strong positive conversion was observed near a depth of 80m between the equator and 3��N, and near the surface between 2�� and 6��N. On the other hand, in MA (Figure 6(c)), the maximum but small magnitude of Bt was observed only at a depth of 40m near the surface between 2�� and 6��N.

Just north of the equator, negative conversion occurred during MA, while a positive conversion occurred during JJAS. Spatial distributions of Bc (Figures 6(b) and 6(d)) were similar between the two seasons, but their magnitudes were different. A strong positive conversion appeared just north of the equator, and a weak positive conversion appeared just south of the equator. Figure 6Vertical distributions of zonal mean barotropic ((a), (c)) and baroclinic ((b), (d)) conversions averaged from June Drug_discovery to September (a) and (b) and from March to April (c) and (d). Units are W/m3. Positive values are shaded. The seasonal variations of Bt and Bc are related to the seasonality of mean fields. Figure 7 shows the zonal-averaged zonal currents for JJAS and MA. Between the two seasons, EUC and NECC did not change much, although NECC was somewhat weaker in MA. However, there was a significant change in SEC. The westward SEC had its maximum value during JJAS at 1��-2��N, and its influence reached below 100m, which produced a large shear between EUC and SEC, inducing a high Bt.