Isoprene is the dominant non-methane organic compound emitted to the atmosphere1-3. It drives ozone and aerosol production, modulates atmospheric oxidation and interacts with the global nitrogen cycle4-8. Isoprene emissions are highly uncertain1,9, as is the nonlinear chemistry coupling isoprene and the hydroxyl radical, OH-its primary sink10-13. Here we present global isoprene measurements taken from space using the Cross-track Infrared Sounder. Together with observations of formaldehyde, an isoprene oxidation product, these measurements provide constraints on isoprene emissions and atmospheric oxidation. We find that the isoprene-formaldehyde relationships measured from space are broadly consistent with the current understanding of isoprene-OH chemistry, with no indication of missing OH recycling at low nitrogen oxide concentrations. We analyse these datasets over four global isoprene hotspots in relation to model predictions, and present a quantification of isoprene emissions based directly on satellite measurements of isoprene itself. A major discrepancy emerges over Amazonia, where current underestimates of natural nitrogen oxide emissions bias modelled OH and hence isoprene. Over southern Africa, we find that a prominent isoprene hotspot is missing from bottom-up predictions. A multi-year analysis sheds light on interannual isoprene variability, and suggests the influence of the El Niño/Southern Oscillation.

中文翻译：

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卫星异戊二烯检索限制排放和大气氧化


异戊二烯是排放到大气中的主要非甲烷有机化合物1-3。它驱动臭氧和气溶胶的产生，调节大气氧化并与全球氮循环相互作用4-8。异戊二烯排放量具有高度不确定性1,9，异戊二烯和羟基自由基（OH-其主要汇）的非线性化学耦合也是如此10-13。在这里，我们展示了使用跨轨红外探测器从太空获取的全球异戊二烯测量结果。结合对异戊二烯氧化产物甲醛的观察，这些测量结果提供了对异戊二烯排放和大气氧化的限制。我们发现，从太空测量的异戊二烯-甲醛关系与当前对异戊二烯-OH化学的理解大致一致，没有迹象表明在低氮氧化物浓度下缺少OH循环。我们根据模型预测分析了四个全球异戊二烯热点的这些数据集，并直接根据异戊二烯本身的卫星测量结果对异戊二烯排放进行了量化。亚马逊流域出现了重大差异，目前对自然氮氧化物排放量的低估偏向于模拟 OH 以及异戊二烯。在南部非洲，我们发现自下而上的预测中缺少一个突出的异戊二烯热点。多年分析揭示了异戊二烯的年际变化，并表明了厄尔尼诺/南方涛动的影响。