CAREER: Toward Improved Parameterizations of Brown Carbon in Wildland-Fire Emissions

这个CAREER项目将促进对野火排放的棕色碳（BrC）的光吸收特性的理解。BrC的光吸收特性变化超过3个数量级，这对在气候模式中表示BrC提出了重大挑战。将开发一个光学分布框架，通过考虑BrC光吸收特性的变化及其在大气中光化学老化过程中的演变，增强BrC在气候计算中的代表性。这项研究可以为提高对BrC在地球气候系统中的作用的认识做出重大贡献。作为本研究的一部分，将进行的任务如下：(1)模拟美国林务局设施的野火；(2) BrC光吸收特性（光分布）的检索；(3)参数化开发；(4)化学输运和辐射传输模型。将进行模拟野火和规定火灾的生物质燃烧实验，并研究诸如燃料类型、燃烧技术和水分含量等关键变量对排放剖面的影响。将在新建的美国森林服务中心森林扰动科学燃烧设施中进行三次密集的测量活动。BC和BrC发射因子及其光学分布将从这些实验中得到，并参数化为燃烧条件的代表——火焰辐射功率（FRP）的函数。该框架的新颖之处在于利用BrC物理化学和光学性质之间的相关性来检索光学分布。通过这些研究制定的参数化将把测量活动的结果与遥感观测结合起来。然后，这些参数化将在WRF-Chem（一个耦合的化学输送和气候模式）中实现。研究生和本科生都将通过这一努力接受培训。该项目还包括一个独特的跨学科教育组成部分，包括开发一门课程，将佐治亚大学工程专业的学生与参加区域规划课程的城市设计专业的学生联系起来。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。

This CAREER project will advance the understanding of the light-absorption properties of brown carbon (BrC) emitted from wildfires. The light-absorption properties of BrC vary over 3 orders of magnitude, posing major challenges to representing BrC in climate models. An optical distributions framework will be developed to enhance the representation of BrC in climate calculations by accounting for the variability in BrC light-absorption properties and their evolution upon photochemical aging in the atmosphere. This research could make a major contribution to improving the understanding of the role of BrC in earth's climate system.The tasks to be conducted as part of this research are as follows: (1) Simulating wildland fires at the U.S. Forest Service facility; (2) Retrieval of BrC light-absorption properties (optical distributions); (3) Parameterization development; and (4) Chemical transport and radiative-transfer modeling. Biomass combustion experiments will be conducted that simulate wildfires and prescribed fires, and the effects of critical variables such as fuel type, firing techniques, and moisture content on emission profiles will be investigated. Three intensive measurement campaigns will be conducted at the newly built U.S. Forest Service Center for Forest Disturbance Science combustion facility. The BC and BrC emission factors, and their optical distributions, will be derived from these experiments and parameterized as a function of fire radiative power (FRP), a proxy of combustion conditions. The novelty of the framework lies in the utilization of correlations between BrC physicochemical and optical properties to retrieve optical distributions. The parameterizations developed through these studies will combine findings from the measurement campaigns with remote-sensing observations. The parameterizations then will be implemented in WRF-Chem, a coupled chemical-transport and climate model.Both graduate and undergraduate students will receive training through this effort. The project also includes a unique cross-disciplinary education component that involves developing a course that would link University of Georgia engineering students with urban design students taking a regional planning course.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.