Troposphere-Stratosphere Coupling Processes

最具挑战性的全球环境问题之一是化学污染可能在下个世纪造成平流层臭氧层严重耗损的威胁。由于复杂的化学、辐射和动力过程共同决定了臭氧的全球收支，因此在开发用于预测臭氧层演变的综合模式之前，必须了解许多物理机制。平流层臭氧的收支受平流层内的全球输送和各种微量化学物质在对流层和平流层之间的转移的强烈影响。从而了解对流层的机制和全球分布。平流层耦合对于了解平流层的全球环流及其对臭氧层的影响至关重要。积雨云对流风暴对对流层有贡献。平流层耦合是通过产生垂直传播的波浪运动，将动量从对流层转移到平流层，以及通过单个云塔的对流超调将化学痕量成分转移到平流层，随后是湍流混合。Holton教授和Durran教授将借助一个数值模型来研究这些过程，该模型旨在模拟热带积雨云系统的动力学、微物理和辐射特性。最近实地试验的观察结果将用于帮助确定初始条件，并验证模型结果。Holton教授和Durran教授还将评估由积雨云对流形成的高空卷云砧状云在通过辐射不稳定和由此产生的冰粒生长和沉降使平流层脱水中的可能作用。

Among the most challenging global environmental problems is the threat that chemical pollution may cause significant depletion of the stratospheric ozone layer during the next century. Because of the complex chemical, radiative, and dynamical processes that together determine the global budget of ozone, many physical mechanisms must be understood before a comprehensive model can be developed for prediction of the evolution of the ozone layer. The budget of stratospheric ozone is strongly influenced by global transport within the stratosphere and by transfer of various trace chemicals between the troposphere and stratosphere. Thus an understanding of the mechanisms and global distribution of troposphere.stratosphere coupling is essential for an understanding of the global circulation of the stratosphere, and its influence on the ozone layer. Cumulonimbus convective storms can contribute to troposphere.stratosphere coupling through production of vertically propagating wave motions that transfer momentum from the troposphere to the stratosphere, and through transfer of chemical trace constituents into the stratosphere by convective overshooting of individual cloud turrets, followed by turbulent mixing. Professors Holton and Durran will study these processes with the aid of a numerical model designed to simulate the dynamical, microphysical, and radiative properties of cumulonimbus cloud systems in the tropics. Observations from recent field experiments will be used to help specify initial conditions, and to validate the model results. Professors Holton and Durran will also evaluate the possible role of high altitude cirrus anvil clouds formed by cumulonimbus convection in dehydrating the stratosphere through radiative destabilization and resultant ice particle growth and fallout.