Dynamical response of the stratosphere to the solar forcing

卫星测量的太阳总辐照度（TSI）显示，TSI的变化仅为0.1%左右，太小，无法产生任何有意义的气候影响。太阳光谱的紫外线部分变化较大（3-8%），可能引起平流层环流的变化。然而，这种涉及高度非线性响应的过程很难仅通过观测或通过特定的大气环流模式研究来识别。因此，本研究是作为国际合作研究“SPARC的一般流通模式现实比较项目”的一部分进行的。特别地，与柏林自由大学的模式以及观测数据进行了比较，以阐明在冬季平流层顶区域产生的太阳影响如何向下穿透到地球表面的过程。平流层的太阳加热与臭氧的产生和破坏密切相关，因此了解化学物质的变化也很重要。为了研究太阳对臭氧的影响，我们利用观测到的太阳光谱变化和风场进行了化学气候模式研究。本研究的结果表明，太阳辐照度和臭氧浓度变化在平流层顶区域产生的太阳影响通过两个过程向下传递到对流层：1)冬季半球高纬度地区波平均流相互作用的变化和ii)上述波平均流相互作用引起的平均经向环流（或布鲁尔-多布森环流）的变化。从这两个过程解释了太阳对北大西洋涛动和印度季风活动的影响机制。

Total solar irradiance (TSI) measurements by satellites revealed that the variation in the TSI is only about 0.1%, which is too small to produce any meaningful climatic effects. The ultra-violet part of the solar spectrum shows larger (3-8%) variation and may possible to produce a change in stratospheric circulation. However, such processes involving highly non-linear responses are difficult to identify sole from the observation or by a particular general circulation model studies.Accordingly, the present study is conducted as a part of an international cooperative study "General Circulation Model Reality Intercomparison Project for SPARC (GRIPS)". In particular, comparison with the Free University of Berlin model as well as observational data, was conducted to elucidate the processes how the solar influence produced in the winter stratopause region can penetrate down to the Earth's surface.The solar heating in the stratosphere is closely related with the production and destruction of the ozone, so that it is also important to understand the variation of chemical species. To investigate the solar effect on ozone, we conducted a chemical climate model study by imposing the observed solar spectrum variation and wind field.The results of the present study demonstrate that the solar influence created in the stratopause region by change in solar irradiance and ozone concentration comes down to the troposphere by two processes through i) change in the wave mean-flow interaction in higher latitudes of the winter hemisphere and ii) change in mean meridional (or Brewer-Dobson) circulation induced by the abovementioned wave mean-flow interactions.From these two processes the mechanism of the solar influence on the North Atlantic Oscillation and the Indian Monsoon activity is explained.