Recent changes of the general circulation in the stratosphere, and its relation to the tropospheric general circulation

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Recent changes of the general circulation in the stratosphere and the troposphere are investigated by satellite data analyses and numerical simulation. Zonal-mean differences of the temperature and zonal wind for March between 1990s and 1980s are firstly examined on the basis of stratospheric analyses of the UK Meteorological Office. We can see a cooling of order 10K in the North polar lower stratosphere and a warming of order 10K in the North polar upper stratosphere. The corresponding intensification of the polar night jet of order 15 m/s is also seen in high latitudes. These tendencies are considered to be due to the ozone depletion in 1990s.In order to investigate effects of ozone depletion on the general circulation, numerical simulation by using a general circulation model is performed. In Arctic ozone depletion experiment, a cooling in the North polar lower stratosphere and a warming in the North polar upper stratosphere are obtained. The cooling brings about the intensification of the polar night jet. These changes are consistent with observations. The cooling is caused by the decrease of solar UV heating due to the ozone depletion, while the warming is caused by adiabatic heating due to the enhancement of downward motion. In subsequent studies, further experiments are required to exclude the contamination of stratospheric sudden warming s occurring in the experiments.