Fu Dejian, Millet Dylan B, Wells Kelley C, Payne Vivienne H, Yu Shanshan, Guenther Alex, Eldering Annmarie
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, 91109, USA.
University of Minnesota, St. Paul, MN, 55108, USA.
Nat Commun. 2019 Aug 23;10(1):3811. doi: 10.1038/s41467-019-11835-0.
Isoprene is the atmosphere's most important non-methane organic compound, with key impacts on atmospheric oxidation, ozone, and organic aerosols. In-situ isoprene measurements are sparse, and satellite-based constraints have employed an indirect approach using its oxidation product formaldehyde, which is affected by non-isoprene sources plus uncertainty and spatial smearing in the isoprene-formaldehyde relationship. Direct global isoprene measurements are therefore needed to better understand its sources, sinks, and atmospheric impacts. Here we show that the isoprene spectral signatures are detectable from space using the satellite-borne Cross-track Infrared Sounder (CrIS), develop a full-physics retrieval methodology for quantifying isoprene abundances from these spectral features, and apply the algorithm to CrIS measurements over Amazonia. The results are consistent with model output and in-situ data, and establish the feasibility of direct global space-based isoprene measurements. Finally, we demonstrate the potential for combining space-based measurements of isoprene and formaldehyde to constrain atmospheric oxidation over isoprene source regions.
异戊二烯是大气中最重要的非甲烷有机化合物，对大气氧化、臭氧和有机气溶胶有关键影响。现场异戊二烯测量数据稀少，基于卫星的限制采用了一种间接方法，利用其氧化产物甲醛，但甲醛受非异戊二烯源影响，且异戊二烯与甲醛关系存在不确定性和空间模糊性。因此，需要直接进行全球异戊二烯测量，以更好地了解其来源、汇和大气影响。在此，我们表明利用卫星搭载的交叉轨道红外探测器（CrIS）可从太空探测到异戊二烯的光谱特征，开发了一种全物理反演方法，用于从这些光谱特征量化异戊二烯丰度，并将该算法应用于亚马逊地区的CrIS测量。结果与模型输出和现场数据一致，确立了直接进行全球天基异戊二烯测量的可行性。最后，我们展示了结合异戊二烯和甲醛的天基测量来限制异戊二烯源区大气氧化的潜力。
