BCC_GCM2.1模式对平流层环流变化特征的数值模拟及其模式评估

Validation of BCC_AGCM2.1 model in simulating variations of the stratospheric circulations

使用国家气候中心大气环流模式BCC_AGCM2.1的30年模拟试验资料,对平流层纬向环流场、高空急流、极涡及爆发性增温过程进行了数值模拟研究,并使用欧洲中期天气预报中心(ECMWF)和美国国家环境预报中心(NCEP)的再分析资料对模式输出结果进行了对比、分析。结果表明:(1)在观测海温、二氧化碳、气溶胶等外强迫地驱动下,BCC模式能够很好地再现出与再分析资料一致的平流层纬向平均风场、温度场的分布特征和季节变化过程;模拟得到的温度廓线和高空急流与再分析资料的主要差别出现在南、北半球冬季的中高纬度地区;模拟得到的平流层温度普遍偏低,主要的差异位于对流层顶区域和平流层高层。(2)模拟的对流层上层的副热带急流位置偏南、强度也偏弱,而平流层中的绕极极夜急流则位置偏北、强度更大。这样的急流分布特征使模拟的行星波向赤道的波导更强,向极的波导偏弱;同时由于模式中本身可以形成的行星波就比再分析资料弱,因此导致模拟结果中北半球冬季的平流层极涡更加稳定、极区温度更低。(3)BCC模式对于平流层极涡的季节变化特征模拟得较好,但对强极涡扰动过程,即北半球冬季的平流层爆发性增温(SSW)事件则模拟效果不佳,不论是增温事件出现的频率,还是增温的时间、强度,模拟结果和再分析资料都还存在一定偏差,需要在今后的工作中逐步改善。

The Beijing Climate Center atmospheric general circulation model version 2.1 （BCC_AGCM2.1,or simply BCC）de-veloped by National Climate Center （NCC）is applied to investigate the stratospheric zonal circulation,upper level jet,polar vortex and stratospheric sudden warming （SSW）events.The comparative analyses of the simulative results with the ECMWF and NCEP reanalysis data show that the BCC_AGCM2.1 simulations forced by the observed sea-surface temperature,CO2 and aerosol can reproduce the observational characteristics in the distributions and seasonal cycles of the stratospheric zonal mean wind and temperature.The main differences between the reanalysis data and the simulated temperature profiles and upper level jets appear in the middle and high latitudes of the southern and northern hemisphere winter.The simulated stratospheric tem-perature is generally colder than that of observational results,and the obvious biases exist in the tropopause regions and the stratospheric upper levels.On the other hand,in the simulation results,the upper tropospheric subtropical jet locates a little southward with weaker intensity,while the stratospheric polar night j et is closer to the polar areas and stronger than the rean-alysis data.These distribution features of westerly jets lead to a stronger equatorial waveguide of planetary waves in the model, and the intensity of simulated planetary wave is weaker than that in reanalysis data.Therefore,the polar vortex in the model is much more stable and has lower temperature in the polar regions in northern hemisphere winter.In addition,the model is also able to reproduce the seasonal cycle of polar vortex,but with a bad simulation about the stratospheric sudden warming events happened in northern hemisphere winter.There are some differences between the simulation results and the reanalysis data a-bout the SSW processes,including the frequency of warming occurrence,the triggered time and warming intensity.These re-sults demonstrate that there is still a lot of work to do to improve the simulation ability of our BCC model.