In this paper, the response of the atmospheric 3-5 year cycle to Northern Pacific SST is discussed, The results are as follows: 1. From the simultaneous temporal correlations between the Equatorial Eastern Pacific SST, the westerly dirft area's SST and the Northern Pacific SST at all gridpoints, we find that there are three correlative regions in the Northern Pacific SST field, they are the westerly drift area, the Equatorial Eastern Pacific and the Alaska Bay, and their structures are very similar to the PNA pattern in the atmosphere The difference PTI between the Equatorial Eastern Pacific SST anomaly and the westerly drift area's SST anomaly can indicate the change of the PNA pattern of the Northern Pacific SST anomaly. It can represent SST change of 65% areas over the Northern Pacific and can keep watch on El Nino and un-El Nino. 2. Simultaneous temporal correlative field between PTI and filtered 500hPa (there is 3-5 year cycle only) of the Northern Hemisphere presents clear PNA structure. The responses of the filtered 500hPa to El Nino and to un-El Nino prodace +PNA and-PNA wavetrains respectively. 3. According to the different positions of the sea-surface temperature rise (drop), El Nino (un-El Nino)can be divided into two classes; east-pattern and middle-pattern. The responses of the filtered 500hPa to the east-pattern and to the middle-pattern will produce PNA and EAA wavetrain respectively. This indicates that the responses of the atmosphere to the stationary heat sources in diffrent areas will produce wavetrains in diffrent track.
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