Stratosphere-to-troposphere Ozone Flux and Surface Ultraviolet Radiation during Cold Climates and Impact on Tropospheric Oxidants

更好地了解平流层对截然不同的气候的反应，包括末次冰盛期(LGM)的寒冷气候，将在评估21世纪平流层对人类活动引起的气候变化的反应时拓宽视角并提供洞察。通过该项目获得的各种气候状态下平流层臭氧、平流层到对流层臭氧通量和到达对流层低层的紫外线辐射的空间分布将提供给对流层化学模型界。研究成果将通过科学出版物向更广泛的大气和气候研究界传播。该提案将支持一名博士生和一名博士后，并为研究生和博士后提供大气动力学和化学方面的跨学科培训。研究小组致力于公共宣传，包括为K-12年级制作教育视频和其他宣传材料；就这项研究进行公开讲座。布鲁尔-多布森环流(BDC)是连接热带和冬半球极地的平流层经向环流。BDC通过将臭氧消耗气体从热带对流层输送到平流层，然后从平流层输送到中高纬度的对流层，将对流层和平流层连接在一起，影响了甲烷等痕量气体的寿命。通过将平流层臭氧从产生臭氧的热带地区输送到两极，BDC还决定了臭氧层丰度的空间分布，这是紫外线辐射穿透低对流层的主要控制因素，在推动大气化学方面发挥了重要作用。由于辐射和化学成分(例如，CO2、H2O、CH4、N2O、氟氯化碳)、地表边界条件(较冷的海面温度、较大的纬度温度梯度和大冰盖)以及对流层环流的不同浓度，在末次冰盖的寒冷气候期间，温度和布鲁尔-多布森环流可能与今天有很大的不同。最近使用冰芯观测的工作表明，与温暖气候相比，寒冷气候下的对流层臭氧浓度更高，这表明平流层-对流层臭氧输送的潜在重要性。然而，关于寒冷气候期间的BGC和臭氧的研究很少，到目前为止还没有对这一时期平流层到对流层的臭氧通量和地面紫外线辐射进行量化的研究。在最近冰芯观测结果的推动下，这一研究项目将通过调查BDC和平流层臭氧并量化平流层到对流层的臭氧通量和紫外线辐射及其在末次盛冰期寒冷气候期间对对流层化学的影响来填补这一知识空白。他们的研究人员将应用具有交互平流层化学的全大气社区气候模式的最新版本，以及冰河时代化学和代理对流层化学-气候模式来解释寒冷气候下对流层臭氧的高浓度。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Improved understanding of the stratospheric response to very different climate including the cold climate of the Last Glacial Maximum (LGM) will broaden the perspective and provide insight when assessing the stratospheric response to anthropogenically-induced climate changes in the 21st century. The spatial distributions of stratospheric ozone, stratosphere-to-troposphere ozone flux, and ultraviolet radiation reaching to the lower troposphere under various climate states obtained from the project will become available to the tropospheric chemistry modeling community. The research results will be disseminated to the broader atmospheric and climate research community through scientific publications. The proposal will support a Ph.D. student and a postdoc and provide interdisciplinary training in atmospheric dynamics and chemistry to the graduate student and postdoc. The research team is committed to public outreach, including developing educational videos and other outreach materials for grades K-12; giving public lectures on the research.The Brewer-Dobson circulation (BDC) is the stratospheric meridional circulation that links the tropics and pole in the winter hemisphere. The BDC couples the troposphere and the stratosphere through the transporting of ozone-depleting gases from tropical troposphere to the stratosphere and then from the stratosphere to the troposphere in the mid- and high-latitudes, influencing the lifetime of trace gases such as methane. By transporting stratospheric ozone from the tropics where it is produced to the poles, the BDC also determines the spatial distribution of the ozone column abundance that is the primary control on ultraviolet radiation penetration into the lower troposphere, playing an important role for driving atmospheric chemistry. During the cold climate of the LGM, both temperature and Brewer-Dobson circulation could be very different from the present day, because of different concentrations of radiative and chemical constituents (e.g., CO2, H2O, CH4, N2O, CFC), surface boundary conditions (colder sea surface temperatures, larger latitudinal temperature gradients and large ice sheets) and tropospheric circulations. Recent work using ice core observations shows higher tropospheric ozone concentrations in cold climates relative to warm climates, indicative of the potential importance of stratosphere-troposphere ozone transport. However, there are very few studies on the BGC and ozone during the cold climate and there is no study so far quantifying the stratosphere-to-troposphere ozone flux and surface ultraviolet radiation during that time. Motivated by the recent findings from ice core observations, this research project will fill this knowledge gap by investigating the BDC and stratospheric ozone and quantifying the stratosphere-to-troposphere ozone flux and ultraviolet radiation and their impact on the tropospheric chemistry during the cold climate of the LGM. They researchers will apply the most recent version of the Whole Atmosphere Community Climate Model with interactive stratospheric chemistry, and the ice age chemistry and proxy tropospheric chemistry-climate model to explain the high concentration of tropospheric ozone in cold climates.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.