Temporal-spatial structural switch and evolution characteristics of the residual circulation in the different seasons

Using the European Center for Medium Range Weather Forecasts Interim (ERA-Interim) data, temporal-spatial structural switch and evolution characteristics of the residual circulation derived from the improved transformed Eulerian-mean equation in the different seasons during 1979-2011 were analyzed. The results show that: (1) The center of the residual circulation upwelling in 150 hPa tends to shift toward the north from April to August, and reaches to a souther location from September to February next year during 1979-2011. The change in June-August (JJA) and Septermber-November (SON) are most obvious; it extends 3.069 degree toward the north in JJA and 2.376 degree toward the south in SON, respectively. (2) The residual circulation in the troposphere observably strengthens in the different seasons during 1979-2011, but it weakens in the circulation upwelling area near the tropical and near tropopause. And, (3) both of downward mass flux in the high latitudes of the two hemispheres and upward mass flux in the tropics near 100 hPa almost all weaken in the different seasons during 1979-2011, except for downward mass flux in the Northern Hemisphere during JJA and SON.