Dynamical Effects of Solar Ultraviolet Variations in the Lower Stratosphere

该项目旨在测试将太阳紫外线变化对平流层上层的直接影响传输到热带和亚热带大气低层的机制，采用观测和机制模拟技术相结合的方法。以前的研究结果表明，热带平流层下层太阳紫外线变化的动力效应可能通过布鲁尔-多布森环流的调制而发生，这些结果将被更详细地研究，以确定太阳引起的热带外波强迫的年代际变化是否存在。利用精确的臭氧剖面数据和Eliassen-Palm行星波通量散度，还将调查波浪强迫和热带上升率的年代际变化的存在。该项目还扩展了现有的研究，表明在冬季高纬度平流层突然变暖的发生和/或时间可能受到平流层上层纬向风的影响。它们又受到太阳紫外线变化对臭氧光化学和辐射加热的直接影响的干扰。具体而言，将寻求证据来确定观测到的热带对流层顶区域27天太阳紫外线变化的热响应是否是由太阳紫外线引起的平流层突然变暖发生的变化引起的。这将使识别响应的偶极子和四极子结构成为可能，这将表明温带变暖和波吸收事件的动力效应。成功地确定这些变化的原因将对气候模式施加重要的新限制，从而可以更准确地估计太阳强迫对气候变化的贡献。该项目将有助于培养一名研究生研究助理。

This project is designed to test mechanisms for transmitting the direct upper stratospheric effects of solar ultraviolet variations to lower levels in the tropical and subtropical atmosphere, using a combination of observational and mechanistic modeling techniques. The results of previous research showing that the dynamical effects of solar ultraviolet variations in the tropical lower stratosphere may occur through a modulation of the Brewer-Dobson circulation will be investigated in greater detail to establish the presence or absence of solar-induced decadal variations in extratropical wave forcing. Using accurate ozone profile data and Eliassen-Palm planetary wave flux divergences, the existence of decadal variations in wave forcing and tropical upwelling rates will also be investigated This project with also extend existing studies showing that the occurrence and/or timing of stratospheric sudden warmings at high winter latitudes can be influenced by upper stratospheric zonal winds, which are in turn perturbed by the direct effects of solar ultraviolet variations on ozone photochemistry and radiative heating. Specifically, evidence will be sought to determine if the observed thermal responses to 27-day solar ultraviolet variations in the tropical tropopause region are caused by solar ultra-violet-induced changes in the occurrence of sudden stratospheric warmings. This should enable identification of dipole and quadrupole structures of the response, which would be indicative of the dynamical effects of extratropical warmings and wave absorption events. Successful identification of the cause(s) of these variations will impose significant new constraints on climate models so that the solar forcing contribution to climate change can be more accurately estimated. The project will facilitate the training of one graduate research assistant.