QBO and Pinatubo signals in the mass flux at 100hPa during the period from 1986 to 1995 Original Research Article

The residual mean meridional circulation is calculated by the transformed Eulerian-mean (TEM) momentum and continuity equations for 10 years from December 1985 to November 1995. The tropical upward mass flux at 100 hPa is estimated from the extratropical downward mass fluxes in the southern and northern hemispheres. The multiple regression statistical model is used to obtain quantitatively the signal of the quasi-biennial oscillation (QBO) and the trend. The results show that the tropical upward mass flux is enhanced during QBO easterly phase and reduced during QBO westerly phase. The signal of Mount Pinatubo volcanic eruption in June 1991 is detected. An abrupt increase of the mass flux is shown in the latter half of 1991, and the increase ceases at the end of 1993, about 2.5 years after the eruption.