Two-Month Oscillation of Geopotential Height and Wind in the Tropic Pacific and Large-Scale Tropospheric Response to Anomalous Tropical Sea-Surface Temperatures during the Winters of 1962-66.

摘要

Spectral analysis of 1962-1963 daily rawinsonde data for Canton Island (3 S, 172 W) has revealed significant peaks in the geopotential height and zonal wind spectrum. A period of 57 days is observed for the geopotential oscillation and 50 days for that of the zonal wind. Both oscillations are confined to the lower and upper levels of the troposphere with the middle level (300-500 mb) acting as a 'buffer zone' (i.e. no significant peaks found in the middle level). Variations in sea-surface temperature from long-term means were found to have a pronounced effect on the amplitudes of the two month oscillation. Anomalously warm sea-surface temperatures intensify amplitudes of zonal and meridional winds along with the temperature wave. They will, however, reduce the geopotential height amplitude. Subsequent co-spectrum analysis of u and v components yields a strong negative peak at a period of two-months, indicating southward momentum transport. Conversely, an anomalously cool sea-surface will reduce the zonal wind amplitude variations and eliminate the two-month cycle in the meridional wind and temperature wave. The two-month geopotential oscillation is a basic feature of all years analyzed 1962-1967), having a maximum amplitude in '62-'63.