Supplementary material to "Heterogeneity and Chemical Reactivity of the Remote Troposphere defined by Aircraft Measurements"

The ATom mission was designed to collect a multi-species, detailed chemical climatology that documents the patterns of physical and chemical heterogeneity throughout the remote troposphere. The work here requires a complete set of key species in each air parcel to initialize global 3D chemistry models to be able to calculate the CH4 and O3 reactivities over a 24 hour cycle. The ATom Modeling Data Stream (MDS) provides a semi-continuous set of 10 s air parcels with a full set of values for the key chemical reactants and conditions. We choose 10 s averages for our air parcels as a compromise to include most of the instruments, and because the 10 s merged data is a standard product Some of our core species are measured with gas chromatographs or flask samples with longer integrations times (30-90 sec), but these can be mapped onto the 10 s parcels with loss of the higher frequency variability found in the 10 s measurements. The frequent profiling of the DC-8 gives us both vertical and horizontal scales: the vertical extent of a 10 s parcel is 50 -110 m (55%-95% of all parcels, with <50% having near level flight) and the horizontal extent is typically 1.4 -2.5 km (10%-90% of all parcels). ATom completed its four deployments: ATom-1 starting 20160729 (YYYMMDD), ATom-2 starting 20170126, ATom-3 starting 20170928, and ATom-4 starting 20180424. ATom targets the remote troposphere by sampling over the middle of the Pacific and Atlantic Ocean basins. The DC-8 aircraft performed in situ profiling of the atmosphere from 0.2 km to 12 km along each flight segment as often as possible. Each deployment lasted about 4 weeks and contained 11 to 13 research flights (RF). Figure For convenience, we designate the RF across the 4 deployments as ATom flights (AF) 1 through 48. The MDS data reported here consisit of 149,133 air parcels over 4 deployments with a total of 48 research flights. AF 46 is a short ferry flight from Kangerlussuaq, Greenland to Bangor, Maine with many instruments turned off and no profiling, thus these 1,106 parcels contain only flight data (MDS variables 1:11) and no chemical data. ATom sampling of the troposphere is more uniform than most aircraft missions, but still contains some biases that can be adjusted by weighting each air parcel. Due to the typical profiling sequence (level at cruising attitude for 10 min, descent for 20 min, level flight about 160 m above the sea level for 5 min, and a 20-min climb back to cruising altitude) and to the occasional requirements of weather or air traffic control, the sampling is skewed towards the uppermost troposphere (P < 300 hPa) and, secondly, the marine boundary layer. We designate a weight for each MDS air parcel to achieve a more uniform sampling of the troposphere by mass: data are binned into 100 hPa-wide pressure bins and 10-wide latitude bins, and each point is assigned a weight equal to the inverse of the number of points in the bin times cosine of the latitude. There are very few measurements for pressures <200 hPa and so these points are included in the uppermost 200-300 hPa bin. This ATom-1 analysis has three study domains: Global includes all parcels (32,383) weighted as above; Pacific considers all measurements (11,486) over the Pacific Ocean from 54S to 60N (research flights RF 1,3,4,5,6); and the Atlantic,