Global atmospheric chemistry – which air matters

Abstract

Abstract. An approach for analysis and modeling of global atmospheric chemistry is developed for application to measurements that provide a tropospheric climatology of those heterogeneously distributed, reactive species that control the loss of methane and the production and loss of ozone. We identify key species (e.g., O 3 , NO x , HNO 3 , HNO 4 , C 2 H 3 NO 5 , H 2 O, HOOH, CH 3 OOH, HCHO, CO, CH 4 , C 2 H 6 , acetaldehyde, acetone) and presume that they can be measured simultaneously in air parcels on the scale of a few km horizontally and a few tenths of a km vertically. As a first step, six global models have prepared such climatologies sampled at the modeled resolution for August with emphasis on the vast central Pacific Ocean basin. Objectives of this paper are to identify and characterize differences in model-generated reactivities as well as species covariances that could readily be discriminated with an unbiased climatology. A primary tool is comparison of multidimensional probability densities of key species weighted by the mass of such parcels or frequency of occurrence as well as by the reactivity of the parcels with respect to methane and ozone. The reactivity-weighted probabilities tell us which parcels matter in this case, and this method shows skill in differentiating among the models' chemistry. Testing 100 km scale models with 2 km measurements using these tools also addresses a core question about model resolution and whether fine-scale atmospheric structures matter to the overall ozone and methane budget. A new method enabling these six global chemistry-climate models to ingest an externally sourced climatology and then compute air parcel reactivity is demonstrated. Such an objective climatology containing these key species is anticipated from the NASA Atmospheric Tomography (ATom) aircraft mission (2015-2020), executing profiles over the Pacific and Atlantic Ocean basins. This modeling study addresses a core part of the design of ATom.

Description and evaluation of the UKCA stratosphere–troposphere chemistry scheme (StratTrop vn 1.0) implemented in UKESM1

“…This is a region where the majority of methane oxidation takes place and may explain the slightly low modelled methane lifetime. With the recent development of aircraft OH datasets appropriate for global model evaluation (Prather et al, 2017) we intend to extend this analysis further and interrogate the model with these data to confirm if the bias is indeed large compared with direct observations.…”

“…The lightning NO x emissions scheme in UKCA StratTrop is based on the cloud-top parameterisation proposed by Price and Rind (1992). Based on satellite data and storm measurements, the lightning flash density is parameterised as…”

Global atmospheric CO<sub>2</sub> inverse models converging on neutral tropical land exchange, but disagreeing on fossil fuel and atmospheric growth rate

“…Current appraisals of the global atmospheric carbon budget are informed by surface fluxes computed by inverse transport models (e.g., Newsam and Enting, 1988;Tans et al, 1990;Rayner et al, 1999;Gurney et al, 2002Gurney et al, , 2003Gurney et al, , 2004Peylin et al, 2013). Net carbon flux to the atmosphere is derived from temporal and spatial CO 2 gradients given by atmospheric observations and prior estimates of component fluxes and their uncertainties.…”

The IAGOS NO<sub><i>x</i></sub> instrument – design, operation and first results from deployment aboard passenger aircraft

“…Parameterization of natural NO x emissions by lightning still has large uncertainty in global chemical transport models (e.g., Gressent et al, 2016). Brunner et al (2005) and Prather et al (2017) concluded that a better description of emissions, chemistry and sinks of NO x (and other key species) is needed to improve chemistry in the UTLS region in global chemistry models.…”