美国加州大学Michael J. Prather团队报道了利用紫外水吸收重设对流层OH和CH4寿命。相关研究成果发表在2024年7月12日出版的《科学》。

甲基氯仿是一种被禁止的臭氧消耗物质，其衰变为对流层羟基自由基（OH）的平均丰度提供了一个明确的观测指标。几乎所有当前的全球化学模型都计算出约15%的OH过量，因此甲烷损失过快。甲烷是一种短暂的气候因子，对实现全球变暖目标至关重要，这一错误影响了人们对气候变化的模型预测。

对紫外线区域（290至350纳米）水蒸气吸收的新观测表明，近地表热带大气中的关键光解速率降低了8%至12%，阳光减少。将这一新机制纳入化学传输模型中，OH和甲烷的损失仅减少了4%，但结合其他提出的机制，如对流层卤素化学（7%），该研究可能能够解决这一难题。

附：英文原文

Title: Resetting tropospheric OH and CH4 lifetime with ultraviolet H2O absorption

Author: Michael J. Prather, Lei Zhu

Issue&Volume: 2024-07-12

Abstract: The decay of methyl chloroform, a banned ozone-depleting substance, has provided a clear observational metric of mean tropospheric hydroxyl radical (OH) abundance. Almost all current global chemistry models calculate about 15% too much OH and thus too rapid methane loss. Methane is a short-lived climate forcer, critical to achieving global warming targets, and this error affects our model projections of climate change. New observations of water vapor absorption in the ultraviolet region (290 to 350 nanometers) imply reductions in sunlight with key photolysis rates decreasing by 8 to 12% in the near-surface tropical atmosphere. Incorporation of this new mechanism in a chemistry-transport model reduces OH and methane loss by only 4%, but combined with other proposed mechanisms, such as tropospheric halogen chemistry (7%), we may be able to resolve this conundrum.

DOI: adn0415

Source: https://www.science.org/doi/10.1126/science.adn0415