NSF-RUI: Stratospheric Warming and Its Relationship to Surface Climate

The proposed project examines the coupled (or two-way) interaction between the circulation of the stratosphere and that of the troposphere, in association with the “sudden stratospheric warming” phenomenon. Characterized by wintertime, episodic warming of the polar stratospheric region, sudden stratospheric warming is an integral component of the dominant mode of winter climate variability called the Northern Hemisphere Annular Mode (NAM). This climate mode describes the North-South vacillation of storm location, the distribution of surface temperature, and the fluctuation in strength of the stratospheric polar vortex.

Using lead-lag composite technique based on an objectively defined warming index, the proposed study will detail the propagation of atmospheric waves from the troposphere into the stratosphere and the development of anomalous (i.e. departure from climatology) circulation during a typical sudden warming event. By diagnosing heat and momentum fluxes on the meridional cross-sections and planar surfaces, wave forcings on the underlying flow will be assessed to help determine the degree of influence that stratospheric circulation exerts on surface flows. The central mechanism of coupled stratospheric-tropospheric interaction and precursory events leading up to sudden warming will be examined in association with the NAM.

Traditionally, stratospheric influence on the surface climate is usually assumed to be minimal and thus ignored. However, better understanding of the coupled stratospheric-tropospheric interaction can potentially improve intermediate range forecasting. Significant downward influence on the troposphere by stratospheric circulation means that possible clues for predicting surface flow evolution can be obtained by observations of the stratosphere. In addition, as this coupled mecha- nism is fundamental to the Northern Hemisphere climate variation, the knowledge of how it functions will help assess the effects of anthropological influences on our climate and its evolution.

Overall, the proposed study fully involves undergraduate students at Coastal Carolina University (CCU) as an effort to integrate research into the school’s science education and strengthen the institution’s new Applied Physics program. In addition to increasing interests in Atmospheric Sciences, CCU’s Applied Physics research-education program in a primarily undergraduate insti- tution will be unique in South Carolina and the greater Southeastern Region.