The Daily Wave 1 on the Southern Hemispherein Winter (Invited Presentation)

Zonal Harmonic wave 1 is the dominant spatial component in the mean and daily circulation on the Southern Hemisphere. In the troposphere the wave has one peak in the latitudes 50S--60S and another near 30S, both reaching the largest amplitude in winter. The ridge of the subantarctic peak is near 120W, and the ridge of the lower-latitude peak is near 30E, and they are thus 150 degrees out-of-phase. The two peaks of wave 1 are visible on most days, and their amplitudes and share of the total spatial variance wax and wane simultaneously --- implying the existence of a travelling wave 1 of nearly opposite phase in the two latitude zones.

On days when the amplitudes of both peaks are large, the mid-latitude westerlies are strong in the Atlantic-Indian Ocean Sector and weak in the Pacific, and the wind maximum spirals in toward Antarctica. When the peaks are both weak there is less of a meridional component to the flow. This description summarizes results gained from data of the Internatinal Geophysical Year, 1957--1958.

We examine the day-to-day behavior of wave 1 and the wind in the middle troposphere by means of the NCEP/NCAR re-analyses; and at the surface by means of satellite-observed winds over the oceans from ERS-1,2, from the NASA Scatterometer (NSCAT), and from the newly launched SeaWINDS instrument aboard QSCAT.