Global Atmospheric Chemistry – Which Air Matters

Abstract

<p><strong>Abstract.</strong> 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<sub>3</sub>, NO<sub>x</sub>, HNO<sub>3</sub>, HNO<sub>4</sub>, C<sub>2</sub>H<sub>3</sub>NO<sub>5</sub>, H<sub>2</sub>O, HOOH, CH<sub>3</sub>OOH, HCHO, CO, CH<sub>4</sub>, C<sub>2</sub>H<sub>6</sub>, 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 vertically. Six global models have prepared such climatologies (at model resolution) for August with emphasis on the vast central Pacific and Atlantic Ocean basins. We show clear 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 multi-dimensional probability densities of key species weighted by 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. 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 observed climatology is anticipated from the NASA Atmospheric Tomography (ATom) aircraft mission (2015–2020), measuring the key species, executing profiles over the Pacific and Atlantic Ocean basins. This work is a core part of the design of ATom.</p>

How Atmospheric Chemistry and Transport Drive Surface Variability of N2O and CFC‐11

“…The CTMs are similar in resolution (1°–3° horizontal) with 40–70 atmospheric layers. GMI uses Modern‐Era Retrospective analysis for Research and Applications‐2 (MERRA‐2) wind fields and full stratosphere‐troposphere chemistry (Strahan et al., 2016); LMDz5 uses the European Center for Medium‐Range Weather Forecasts Re‐Analysis‐Interim (ECMWF ERA‐Interim) meteorology with prescribed fields for O( 1 D) and photolysis rates from a previous run (Remaud et al., 2018); and UCI uses ECMWF Integrated Forecast System (IFS) pieced forecasts with a linearized stratospheric chemistry including O 3 , N 2 O, and CH 4 (Hsu & Prather, 2010; Prather et al., 2017).…”

Global-scale distribution of ozone in the remote troposphere from the ATom and HIPPO airborne field missions

“…Together, ATom and HIPPO provide recent and comprehensive information about the altitudinal, latitudinal, and seasonal composition of the remote troposphere over the Pacific, and ATom also provides this information over the Atlantic. In addition, ATom and HIPPO sampling strategies were designed to deliver an objective climatology of key species to enable the modeling of the air parcel reactivity of the remote troposphere (Prather et al, 2017).…”

A round Earth for climate models

“…This latter model was run for January 2015, taking hourly steps and using meteorological data from the ECMWF IFS forecasts at T159L60 resolution (about 1.1° × 1.1° resolution with 60 layers; for details, see ref. 31). Ozone profiles are taken from a satellite climatology included in Cloud-J and Solar-J.…”

“…Calculations shown here of the Earth’s solar radiation budget use the new Solar-J version 7.6c and meteorological data for January 2015 from the ECMWF OpenIFS system (cycle 38R1) (30, 31). We use 3-h averages for temperature, pressure, water vapor, ice-/liquid-water clouds on a 1.1° × 1.1° × 60-layer flat grid.…”