What does the global mean OH concentration tell us?

作者：M. G. Lawrence, Patrick Jöckel, R. von Kuhlmann · 发表于：Atmospheric chemistry and physics · 年份：2001 · DOI：10.5194/acp-1-37-2001 · 被引用次数：252 · 研究领域：Atmospheric chemistry and aerosols、Atmospheric and Environmental Gas Dynamics、Atmospheric Ozone and Climate

Abstract. The global mean OH concentration ([OH]GM) has been used as an indicator of the atmospheric oxidizing efficiency and its changes over time. It is also used for evaluating the performance of atmospheric chemistry models by comparing with other models or with observationally-based reference [OH]GM levels. We contend that the treatment of this quantity in the recent literature renders it problematic for either of these purposes. Several different methods have historically been used to compute [OH]GM: weighting by atmospheric mass or volume, or by the reaction with CH4 or CH3CCl3. In addition, these have been applied over different domains to represent the troposphere. While it is clear that this can lead to inconsistent [OH]GM values, to date there has been no careful assessment of the differences expected when [OH]GM is computed using various weightings and domains. Here these differences are considered using four different 3D OH distributions, along with the weightings mentioned above applied over various atmospheric domains. We find that the [OH]GM values computed based on a given distribution but using different domains for the troposphere can result in differences of 10% or more, while different weightings can lead to differences of up to 30%, comparable to the uncertainty which is commonly stated for [OH]GM or its trend. Thus, at present comparing [OH]GM values from different studies does not provide clearly interpretable information about whether the OH amounts a...