Past and future evolution of the 3D Brewer-Dobson circulation

布鲁尔-多布森环流(BDC)指的是中层大气(10-100公里)的时间平均质量环流。BDC由行星波、天气尺度波和重力波驱动，将臭氧(O_3)、水汽(H_2O)和其他微量气体成分从热带输送到中纬度和极地纬度。纬向平均(2D)BDC在气候变化中的演变及其与平流层臭氧层的相互作用是当前研究的一个重要问题。然而，二维BDC和波浪驱动力的长期变化与使用的模型和观测结果有很大的不同。基于三维BDC公式的研究可能会带来更详细的图像和对BDC在气候变化中的作用的更好的理解，但这些研究非常少。该项目的目的是调查3D BDC的过去和未来的变化以及基于联合地球系统模式MPI-ESM对1960-2005年的时间段的模拟和直到2100年的气候预测(CMIP5)的局地波浪驱动。对于验证和单靠CMIP5模拟无法实现的方面，还将根据高海拔大气环流和化学模式Hammonia(1957-2006年)、再分析(ERA-期中1979-2012年，MERRA，1979-2012年)和最近的卫星数据(Aura/MLS 2004-2012年)的模拟，分析3D BDC。将开发一种算法，从Aura/MLS资料中推导出新的日平均风场数据集，这将为验证3D BDC提供一个合适的工具，特别是在当地风测量非常稀疏的高度(约30-80公里)。基于收支方程的线性解，将分析3D BDC对中层大气O_3、H_2O、温度和涡度的局地长期变化的影响，特别是对超长驻波的影响。控制中大气3DBDC、对流层波活动和风生洋流耦合的过程将根据MPI-ESM的额外模式敏感性模拟进行检查，其中包括对地表温度、对流层和平流层涡流的规定调制，以及从观测得出的中大气吸收体分布。还计划在SPARC(平流层过程及其在气候中的作用)CCM验证项目执行和提供的化学-气候模式(CCM)模拟的基础上，研究3D BDC对平流层臭氧和中层大气H2O局部长期变化的影响。

The Brewer-Dobson circulation (BDC) denotes the time-mean mass circulation of the middle atmosphere (10-100km). The BDC is driven by planetary waves, synoptic-scale waves and gravity waves, and transports ozone (O3), water vapour (H2O) and other trace gas constituents from the tropics to mid- and polar latitudes. The evolution of the zonal mean (2D) BDC in a changing climate and its interaction with the stratospheric ozone layer is an important issue of current research. However, the long-term changes of the 2D BDC and the wave driving strongly differ between the used models and the observations. Examinations based on a formulation of the three-dimensional (3D) BDC might lead to a more detailed picture and an improved understanding of the role of the BDC in a changing climate, but they are very sparse.The aim of the project is to investigate the past and future changes of the 3D BDC and the local wave driving based on the consortia simulations with the Earth-System Model MPI-ESM for the time period 1960-2005 and the climate projections up to the year 2100 (CMIP5). For validation and aspects which cannot be achieved by the CMIP5 simulations alone, the 3D BDC will also be analysed based on simulations with the high-altitude general circulation and chemistry model HAMMONIA (1957-2006), reanalysis (ERA-Interim 1979-2012, MERRA, 1979-2012) and recent satellite data (Aura/MLS 2004-2012). An algorithm will be developed to derive a new data set of daily-mean wind fields from the Aura/MLS data, which will provide a suitable tool for validating the 3D BDC particularly at altitudes where local wind measurements are very sparse (ca. 30-80km). The impact of the 3D BDC on the local long-term changes of O3, H2O, temperature and vorticity in the middle atmosphere, particularly on the ultra-long stationary waves, will be analysed based on linear solutions of the budget equations. The processes controlling the coupling the middle atmospheric 3D BDC, the tropospheric wave activity and wind-driven ocean currents will be examined based on additional model sensitivity simulations with the MPI-ESM including prescribed modulations of surface temperatures, tropospheric and stratospheric eddy fluxes, and middle atmospheric absorber distributions derived from observations. It is also planned to examine the impact of the 3D BDC on the local long-term changes of stratospheric O3 and middle atmospheric H2O based on the chemistry-climate model (CCM) simulations performed and provided by the SPARC (Stratospheric Processes and their Role in Climate) CCM-Validation project.