Major Changes in Circulation Features over the South Pacific During FGGE, 10–27 January 1979

Abstract

An analysis of the large-scale atmospheric circulation patterns over the South Pacific during part of FGGE SOP-1, 10–27 January 1979, is presented. Results, which are derived from Level III-b analyses produced at ECMWF, are composited for three time periods, based on changing characteristics of the South Pacific Convergence Zone (SPCZ): 0000 GMT 10 January–1200 GMT 18 January, when the SPCZ was a quasistationary persistent feature of the circulation; 0000 GMT 19 January–0000 GMT 24 January, when the SPCZ propagated westward and began to weaken; and 1200 GMT 24 January–1200 GMT 27 January, when it disappeared. The major findings include 1) the buildup of high pressure in the eastern Pacific coincident with the westward movement of the SPCZ, followed by a rapid buildup of high pressure over the central Pacific and demise of the SPCZ; 2) a trend from middle and upper tropospheric wavelike patterns in wind, temperature and height to more zonally-oriented patterns when the SPCZ disappears; and 3) strong cross-equatorial flow from the SPCZ into the Northern Hemisphere during the first period and strong poleward flow from the SPCZ into middle latitudes during the first two periods.