美国圣路易斯华盛顿大学 Chakrabarty, Rajan K. 和 Mishra, Rohan 的团队在研究褐碳为主的野火烟雾对短波的吸收中取得新进展。2023年8月7日出版的《自然—地球科学》发表了这项成果。

研究小组介绍了美国西部野火烟流中总体尺度和粒子尺度短波吸收的测量工作。研究发现一种褐碳贡献了短可见光吸收的四分之三的量和长可见光吸收的二分之一的量。这中强吸收性的有机气溶胶物质不溶于水，能抵抗白天的光漂白，并随着夜间的大气处理而增加其吸收率。研究结果表明，气候模型中的褐碳的参数化，需要被修订以改进烟雾气溶胶辐射作用力和相关变暖的估算。

据悉，野火向大气中排放大量的黑碳和吸光有机碳，即所谓的褐碳。这些粒子通过吸收入射的短波辐射来扰乱地球的辐射收支。人们普遍认为，由于阳光驱动的光化学漂白，褐碳在被排放到大气中后，会失去其吸收率。因此，与相对不活泼的黑碳相比，褐碳在气候模型中表现不佳，且对大气变暖的影响仍然变化很大。鉴于未来几十年野火预计会增加，量化这些辐射的影响变得越来越重要。

附：英文原文

Title: Shortwave absorption by wildfire smoke dominated by dark brown carbon

Author: Chakrabarty, Rajan K., Shetty, Nishit J., Thind, Arashdeep S., Beeler, Payton, Sumlin, Benjamin J., Zhang, Chenchong, Liu, Pai, Idrobo, Juan C., Adachi, Kouji, Wagner, Nicholas L., Schwarz, Joshua P., Ahern, Adam, Sedlacek, Arthur J., Lambe, Andrew, Daube, Conner, Lyu, Ming, Liu, Chao, Herndon, Scott, Onasch, Timothy B., Mishra, Rohan

Issue&Volume: 2023-08-07

Abstract: Wildfires emit large amounts of black carbon and light-absorbing organic carbon, known as brown carbon, into the atmosphere. These particles perturb Earth’s radiation budget through absorption of incoming shortwave radiation. It is generally thought that brown carbon loses its absorptivity after emission in the atmosphere due to sunlight-driven photochemical bleaching. Consequently, the atmospheric warming effect exerted by brown carbon remains highly variable and poorly represented in climate models compared with that of the relatively nonreactive black carbon. Given that wildfires are predicted to increase globally in the coming decades, it is increasingly important to quantify these radiative impacts. Here we present measurements of ensemble-scale and particle-scale shortwave absorption in smoke plumes from wildfires in the western United States. We find that a type of dark brown carbon contributes three-quarters of the short visible light absorption and half of the long visible light absorption. This strongly absorbing organic aerosol species is water insoluble, resists daytime photobleaching and increases in absorptivity with night-time atmospheric processing. Our findings suggest that parameterizations of brown carbon in climate models need to be revised to improve the estimation of smoke aerosol radiative forcing and associated warming.

DOI: 10.1038/s41561-023-01237-9

Source: https://www.nature.com/articles/s41561-023-01237-9