A Study of Spatial-Temporal Evolvement of the Global Cross-Tropopause Ozone Mass Flux

Abstract

Using the 44 years (1958-2001) ECMWF (European Centre for Medium-rangeWeather Forecast) data sets and ozone mixing rate at tropopause, the global cross-tropopause ozone mass flux (CTF) has been calculated by Wei formula. The results are as follows: (1) The global CTF presents zonal and meridional wave patterns which have not reached to the tropic tropopause controlling area by crossing tropopause break, prominently from the Mediterranean area, through the Iran Plateau, Tibetan Plateau, south of Japan, to the North Pacific and in Southern Hemisphere. The spatial variation of STE (Stratosphere-Troposphere Exchange) is uniform over oceans and complicated over continents. The upward and downward flux peak values are −4μg·m−2·s−1 and 2.5μg·m−2·s−1 in the Northern Hemisphere, and –2.5 μg·m−2·s−1 and 1.5μg·m−2·s−1 in the Southern Hemisphere. (2) The zonal means of ozone flux vary with the latitudes, and the flux is unsymmetrical in the Northern and Southern Hemispheres for the general effects transfer from stratosphere to troposphere. The ozone flux which has notable seasonal variation presents the geographical distribution changing with seasons, and it is dominated by seasonal variation of atmospheric environment beside by seasonal change of the tropopause. (3) The seasonal and annual variations of pure ozone flux in Southern Hemisphere have two peak values which show the structure of unsymmetrical seasonal wave, which is completely contrary to Northern Hemisphere. Global average CTF exhibits remarkable characteristic of QBO (Quasi-Biennial Oscillation). Interannual change of STT can be divided into four phases, with a balanced phase in the 1960s, an enhanced phase in the 1970s, another balanced phase in the 1980s and a remarkable variation phase in the 1990s. The downward ozone flux maximums appear in 1977, 1990 and 1998, the minimums in 1993 and 1996, respectively.