Study On The Temperature Decadal Changes In Arctic Winter Stratosphere

Using ERA-Interim reanalysis from the European Centre for Medium Range Weather Forecasts (ECMWF), CCMVal simulations of SPARC CCMVal report,influence of ozone depletion, combined with a 3-D nonlinear mechanistic model MUAM (Middle and Upper Atmosphere Model), this paper analyzes the climatic changes of the stratosphere in the winter of the last two decades (1980-2000) from the perspective of radiation and dynamic. We mainly pay attention to the change of temperature, circulation, stationary planetary wave activity. We discuss the change of greenhouse gas concentration and the change of the boundary condition and their comprehensive effect on the stratospheric climate change. The possible mechanisms are also discussed. The main conclusions are summarized as follows:(1) In this paper, we use ERA-Interim reanalysis data and CCMs model to analyze the changes of winter stratospheric temperature, circulation and planetary wave activity of the last two decades (1980-2000) by using wave activity diagnosis method. It was found that the stratospheric temperature change in the winter of 1980-2000 was mainly due to the change of greenhouse gases concentrations and the change of the lower boundary conditions. In December, the stratospheric ozone in the Northern Hemisphere (NH) decreased significantly, which is known as Ozone depletion. At the same time, the concentration of CO2 increased significantly, and the temperature of the stratosphere decreased due to the intense emission of infrared long-wave radiation by CO2, and the absorption of infrared radiation of Ozone was also reduced. The radiative active gases concentrations and their radiative forcing have significant effects on the NH stratosphere, but the increase of CO2 concentration has a greater impact than others. The asymmetric response of the polar stratosphere to the lower boundary conditions is more obvious, which is mainly related to the difference of the lower boundary conditions in the northern and southern hemisphere and the associated planetary wave activity and wave propagation processes.(2) Using a 3-D nonlinear mechanistic model MU AM, the temperature and circulation in winter during the past two decades (1980-2000) responses to the radiative active gase changes (Ozone depletion and actually increase in CO2) and their radiative forcing and the dynamic forcing from the boundary condition changes are analyzed. Simulation focused on the influence of reducing ozone concentration,CO2 concentration increase and boundary condition changes on stratospheric temperature. The results show that the stratospheric temperature change in December of 1980-2000 is mainly caused by the change of greenhouse gas concentration and the change of boundary conditions. In the Northern Hemisphere, the stratospheric ozone concentration in the northern hemisphere decreased significantly, this is the ozone depletion, while the CO2 concentration increased significantly. The increase of the carbon dioxide concentration will lead to the decrease of the stratospheric temperature. So the absorption of infrared radiation is also reduced, resulting in decreasing in polar stratospheric temperature. The change of active gas concentration of ozone and CO2 and their effect on radiation force have a significant influence on the stratosphere of the Northern Hemisphere. The asymmetric response of the polar stratosphere to the lower boundary condition is more obvious in the north and south hemisphere, which is mainly related to the lower boundary conditions and the associated planetary wave activity and wave propagation process.(3) During the period of 1980-2000, in January-February, if the CO2 concentration or the lower boundary conditions did not change, the increase in the high stratospheric ozone concentration in the Arctic would lead to an increase in temperature. It is found warming trend about 0.5K / decade in the northern hemisphere high latitudes. This has a certain correlation with the global distribution of ozone in the stratosphere. The change of the lower boundary mainly caused the 1K / decade cooling in the middle and upper Arctic stratosphere. Increased carbon dioxide causes a weak cooling of the middle and lower stratosphere, but the cooling trend is greater in the upper stratosphere. Considering the increase of carbon dioxide and the increase of ozone concentration, there is about 0.5K / decade cooling trend in the upper Arctic stratosphere. In the sensitive simulation when there is no feedback between the active gas and the dynamic mechanism, the cooling effect can also be approximated. In a comprehensive trial considering radiation and dynamic mechanisms, the results show a significant cooling trend in Arctic stratosphere.