Heterogeneity and chemical reactivity of the remote troposphere defined by aircraft measurements – corrected

[摘要] The NASA Atmospheric Tomography (ATom) mission built aphotochemical climatology of air parcels based on in situ measurements withthe NASA DC-8 aircraft along objectively planned profiling transects throughthe middle of the Pacific and Atlantic oceans. In this paper we present andanalyze a data set of 10 s (2 km) merged and gap-filled observations of thekey reactive species driving the chemical budgets of O 3 and CH 4 (O 3 , CH 4 , CO, H 2 O, HCHO, H 2 O 2 , CH 3 OOH,C 2 H 6 , higher alkanes, alkenes, aromatics, NO x , HNO 3 ,HNO 4 , peroxyacetyl nitrate, and other organic nitrates), consisting of146 494 distinct air parcels from ATom deployments 1 through 4. Six modelscalculated the O 3 and CH 4 photochemical tendencies from thismodeling data stream for ATom 1. We find that 80 %–90 % of thetotal reactivity lies in the top 50 % of the parcels and 25 %–35 % in the top 10 %, supporting previous model-only studies thattropospheric chemistry is driven by a fraction of all the air. Surprisingly,the probability densities of species and reactivities averaged on a modelscale (100 km) differ only slightly from the 2 km ATom 10 s data, indicatingthat much of the heterogeneity in tropospheric chemistry can be capturedwith current global chemistry models. Comparing the ATom reactivities overthe tropical oceans with climatological statistics from six global chemistrymodels, we find generally good agreement with the reactivity rates forO 3 and CH 4 . Models distinctly underestimate O 3 productionbelow 2 km relative to the mid-troposphere, and this can be traced to lowerNO x levels than observed. Attaching photochemical reactivities tomeasurements of chemical species allows for a richer, yet moreconstrained-to-what-matters, set of metrics for model evaluation. This paperpresents a corrected version of the paper published under the same authorsand title (sans “corrected”) as https://doi.org/10.5194/acp-21-13729-2021 .

[学科分类] 医学（综合）