A study on year-to-year variation in Arctic and mid-latitude atmosphere mixing using the distribution of nitrous oxide concentration

为了更好地模拟极区臭氧的破坏，将CCSR/NIES化学输送模式的辐射传输方案从平面平行近似修改为伪球近似。这使得南极臭氧空洞的开始时间比平面平行模式提前了10天。这一改进还导致臭氧空洞发展阶段的臭氧总量减少了20DU。这些变化使模式更接近实际。利用化学输送模式考察了北极极涡内部臭氧破坏对外部臭氧浓度的影响。对1997年北极极涡外臭氧浓度的模式计算表明，2、3月份北极极涡外臭氧浓度的下降仅限于涡旋边界外5-10度的等值纬度带内。利用化学输送模式和概率分布函数(PDF)技术研究了1978-2002年25年间北半球低平流层中高纬度地区一氧化二氮(N2O)的分布。极涡解体初期和晚期的N_2O分布有明显差异。分析表明，在北纬45°N的整个区域，这种差异是由于解体初期极地平流层下沉运动比解体晚期更强烈所致。在极涡内部，这种差异不是由垂直平流引起的，而是由涡旋边界N_2O浓度水平梯度区的水平混合引起的。所有这些结果表明，N_2O浓度场与大气动力学(经向环流和波动活动)有明显的关系，并表明N_2O分布的年际变化与臭氧的年际变化有关。

For better simulations of ozone destruction in the polar regions, a radiation transfer scheme of CCSR/NIES chemical transport model is modified from a plane parallel approximation to a pseudo-spherical approximation. This leads to an improvement of the onset time of Antarctic ozone hole, which become 10 days earlier than that in the plane parallel model. The modification also leads to a 20 DU smaller total ozone amount in the ozone hole development phase. These changes make the model more realistic.An effect of ozone destruction inside the Arctic polar vortex on the ozone concentration outside is examined using the chemical transport model. A model calculation for the year 1997 shows that the decrease in ozone concentration outside the Arctic polar vortex in February and March is limited to the equivalent latitude belt of 5-10 degrees outside the vortex boundary.The distribution of nitrous oxide (N_2O) at mid-and high-latitudes in the northern hemisphere lower stratosphere is investigated for 25 years from 1978 to 2002 using the output of the chemical transport model and Probability Distribution Function (PDF) technique. A distinct difference in the N_2O distribution between in the early polar vortex breakup years and in the late years is found. Analyses show that in a whole region north 45°N the difference is caused by a stronger downward motion in the polar lower stratosphere in the early breakup years than that in the late breakup years. Inside the polar vortex, however, the difference is caused rather by the horizontal mixing across the large horizontal gradient region of N_2O concentration at the vortex boundary than by the vertical advection.All these results show that there is a clear relationship between N_2O concentration field and the dynamics in the atmosphere (meridional circulation and wave activity) and suggest a relationship between a year-to-year variation of N_2O distribution and that of ozone.