Brewer, Dobson, Circulation And Its Transport Of Stratospheric Trace Gases

The Brewer-Dobson circulation in the Stratosphere is very important to the distribution and transport of the trace gases such as O₃, HC1, CH4, H₂O. And the distribution and variation of the trace gases can affect the atmosphere in the troposphere by coupling function, and then affect the long-term change of the climate. In this paper, residual velocities were calculated by the NCEP II reanalysis data to verify theoretic and simulation results. This paper then discussed the spatial distribution, seasonal change, interannual change, QBO (Quasi-Biennial Oscillation) character, long-term evolutional trend of the Brewer-Dobson circulation, as well as the transportations of the tracer gases. The Brunt-Vaisala Frequency also was also calculated by the NCEP data to analyze the vertical structure of the atmosphere temperature and the static stability, as well as the relationship between the gravity wave frequency and the Brewer-Dobson circulation. More than that, the NCAR interactive chemical, dynamical and radiative two-dimensional model (SOCRATES) was used to simulate the impacts of the planetary wave and the gravity wave on the Brewer-Dobson circulation, and to investigate the "driven force" of the "extratropical wave pump" and its impacts on the transportations of those tracer gases. Some results were obtained as below:At First, through analyzing the monthly averaged NCEP data from 1979 to 2003, the vertical-meridional distribution and seasonal change of the Brewer-Dobson circulation are given in detail. The calculated results show that circulation upward through the tropical tropopause, poleward and then downward. The center of ascending motion swings around the equator with variation of seasons. The upwelling appears in north hemisphere is stronger than that in south hemisphere while the downwelling in winter hemisphere is stronger than that in summer hemisphere. These results are very consistent with former theoretic and simulation results.In addition, the residual circulation has QBO characters. The upwelling in tropical and the horizontal transport toward the pole in the easterly phase of the tropical zonal wind are stronger than their averages. There is a secondary circulation in the stratosphere in tropical, so the Brewer-Dobson circulation gets enhanced. But in the westerly phase of the tropical zonal wind, the upwelling in tropical is weaker than its average, and the Brewer-Dobson circulation gets weakened. Compared the QBO phase of the departure of the upwelling in tropical with the phases of the departures of...