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

改进的理解平流层应对不同气候包括最后的寒冷气候冰川最大高强)将扩大视角,提供评估平流层时应对anthropogenically-induced气候变化在21世纪。该项目获得的不同气候状态下平流层臭氧、平流层-对流层臭氧通量和到达对流层下层的紫外线辐射的空间分布将提供给对流层化学模拟界。研究结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的跨学科培训。研究小组致力于公共宣传，包括为K-12年级开发教育视频和其他宣传材料；就这项研究发表公开演讲。布鲁尔-多布森环流（BDC）是连接冬季半球热带和极地的平流层经向环流。在中高纬地区，BDC通过将消耗臭氧气体从热带对流层输送到平流层，再从平流层输送到对流层，将对流层和平流层耦合在一起，从而影响了甲烷等微量气体的寿命。通过将产生臭氧的热带地区的平流层臭氧输送到两极，BDC还决定了臭氧柱丰度的空间分布，臭氧柱丰度是紫外线辐射穿透到对流层下层的主要控制因素，在驱动大气化学方面起着重要作用。在LGM的寒冷气候期间，由于不同浓度的辐射和化学成分（如CO2、H2O、CH4、N2O、CFC）、表面边界条件（更低的海面温度、更大的纬向温度梯度和更大的冰盖）和对流层环流，温度和布鲁尔-多布森环流可能与现在有很大的不同。最近利用冰芯观测的工作表明，相对于温暖气候，寒冷气候下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，迄今为止还没有量化该时期平流层-对流层臭氧通量和地表紫外线辐射的研究。在冰芯观测成果的推动下，本研究项目将通过研究BDC和平流层臭氧，量化平流层-对流层臭氧通量和紫外线辐射及其对LGM寒冷气候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最新版本的全大气群落气候模型，其中包括相互作用的平流层化学，冰河时代化学和代用的对流层化学-气候模型来解释寒冷气候下对流层臭氧浓度高的原因。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.