ATom: Alternative Modeled Reactivities, Ozone and Methane, ATom-1 Air Parcels, 2016

This dataset provides five modeled reactivity data streams for ozone (O3) production and loss, methane (CH4) loss, and photolysis rates (J-values) for O3 and nitrogen dioxide (NO2) for 31,429 ATom-1 flight line air parcels based on five alternative ATom-1 Modeling Data Streams (MDS). The ATom-1 MDS is constructed from the 10-second merged ATom-1 observations with interpolation and fill values for a total of 31,429 unique air parcels and contains initialization values for key species plus temperature and water vapor. The five alternative MDSs were created by changing a selected key species or a class of compounds to either an alternative data stream, as for (1) CO and (2) NOx, or by adjusting values for (3) peroxy acetyl nitrate (PAN), (4) organic nitrates, and (5) other alkanes, for measurement uncertainty. The O3 and CH4 reactivities for the five alternative MDSs were modeled by the UCI global 3D atmospheric chemistry model. The modeled alternative reactivities were derived for five different days (24 hrs) in August (08/01, 08/06, 08/11, 08/16, 08/21) to sample different weather and cloud patterns over the month. Average reactivities and J-values of the five daily values and standard deviations are reported for each parcel. The data from each of the five UCI model runs are for 2016. The use of alternative data streams facilitates the evaluation of measurement uncertainties and the importance of key species on calculated reactivities. Results from the alternative data streams can also be used to set detection threshold level (LLOD) for an instrument.

ATom-1 flew transects through the Pacific, Southern, Atlantic, and Arctic Oceans with the NASA DC-8 aircraft in July and August 2016. Each of the 11 flights included sampling from the boundary layer to the top of the aircraft range (around 39,000 ft or 12,000 m). 

There are five data files in NetCDF (.nc) format with this dataset (one file for each modeled alternative reactivity).

This dataset provides five modeled reactivity data streams for ozone (O3) production and loss, methane (CH4) loss, and photolysis rates (J-values) for O3 and nitrogen dioxide (NO2) for 31,429 ATom-1 flight line air parcels based on five “alternative” ATom-1 Modeling Data Streams (MDS). The ATom-1 MDS is constructed from the 10-second merged ATom-1 observations with interpolation and fill values for a total of 31,429 unique air parcels and contains initialization values for key species plus temperature and water vapor. The five alternative MDSs were created by changing a selected key species or a class of compounds to either an alternative data stream, as for (1) CO and (2) NOx, or by adjusting values for (3) peroxy acetyl nitrate (PAN), (4) organic nitrates, and (5) other alkanes, for measurement uncertainty. The O3 and CH4 reactivities for the five alternative MDSs were modeled by the UCI global 3D atmospheric chemistry model. The modeled alternative reactivities were derived for five different days (24 hrs) in August (08/01, 08/06, 08/11, 08/16, 08/21) to sample different weather and cloud patterns over the month. Average reactivities and J-values of the five daily values and standard deviations are reported for each parcel. The data from each of the five UCI model runs are for 2016. The use of alternative data streams facilitates the evaluation of measurement uncertainties and the importance of key species on calculated reactivities. Results from the alternative data streams can also be used to set detection threshold level (LLOD) for an instrument.

ATom-1 flew transects through the Pacific, Southern, Atlantic, and Arctic Oceans with the NASA DC-8 aircraft in July and August 2016. Each of the 11 flights included sampling from the boundary layer to the top of the aircraft range (around 39,000 ft; 12,000 m). 

Project: Atmospheric Tomography Mission (ATom)

The Atmospheric Tomography Mission (ATom) was a NASA Earth Venture Suborbital-2 mission. It studied the impact of human-produced air pollution on greenhouse gases and on chemically reactive gases in the atmosphere. ATom deployed an extensive gas and aerosol payload on the NASA DC-8 aircraft for systematic, global-scale sampling of the atmosphere, profiling continuously from 0.2 to 12 km altitude. Flights occurred in each of four seasons over a 4-year period.

Related Publication:

Flynn, C.M.,  M.J. Prather, S.A. Strode, S.D. Steenrod, L. Emmons, F. Lacey, A.M. Fiore, G. Correa, L.T. Murray, G. Wolfe, M. Kim, J. Crounse, G. Diskin, J. DiGangi, B.C. Daube, R. Commane, K. McKain, T.B. Ryerson, C.Thompson, T.F. Hanisco, D. Blake, N. Blake, E. Apel, R. Hornbrook, J. Elkins, E. Hintsa, F. Moore, and S. Wofsy. Chemical Reactivity in the Remote Troposphere: Patterns and Heterogeneity based on ATom measurements (2019, in process).

Related Datasets:

Flynn, C.M.,  M.J. Prather, S.A. Strode, S.D. Steenrod, L. Emmons, F. Lacey, A.M. Fiore, G. Correa, L.T. Murray, G. Wolfe, M. Kim, J. Crounse, G. Diskin, J. DiGangi, B.C. Daube, R. Commane, K. McKain, T.B. Ryerson, C. Thompson, T.F. Hanisco, D. Blake, N. Blake, E. Apel, R. Hornbrook, J. Elkins, E. Hintsa, F. Moore, and S. Wofsy. ATom: ATom: Modeled Reactivities for Ozone and Methane for ATom-1 Air Parcels, 1997-2016. ORNL DAAC, Oak Ridge, Tennessee, USA https://doi.org/10.3334/ORNLDAAC/1688

Wofsy, et al. 2018. ATom: Merged Atmospheric Chemistry, Trace Gases, and Aerosols. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/1581

Prather, M.J., C.M. Flynn, A. Fiore, G. Correa, S.A. Strode, S.D. Steenrod, L.T. Murray, and J.-F. Lamarque. 2018. ATom: Simulated Data Stream for Modeling ATom-like Measurements. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/1597

Acknowledgements:

This study was funded with NASA grant numbers NNX15AJ23G and NNX15AG57A.

Spatial Coverage: ATom-1 flights over the remote Pacific, Southern, Atlantic, and Arctic Oceans

Spatial Resolution:  Each air parcel is ~2.5 km horizontal by 160 m vertical

Temporal Coverage: 2016-08-01 to 2016-08-21

Temporal Resolution: Air parcels collected at ~8 to 12 second intervals

Study Area (coordinates in decimal degrees).

Site	Northern Extent	Southern Extent	Western Extent	Eastern Extent
ATom-1 flights	80.00	-65.33	178.99	-180.00

 

Data File Information

There are five data files with this dataset in NetCDF (.nc) format. The files provide the O3 production and loss, CH4 loss, and O3 and NO2 photolysis rates for each of the 31,429 air parcels for year 2016 from the UCI CTM model. The data variables are the same for all files (refer to Table 2). Spatial reference is the standard WGS84 (EPSG = 4326).

These netCDF files are formatted as Climate and Forecast (CF) compliant with featureType = "trajectory". For more information on trajectory files see: http://cfconventions.org/cf-conventions/cf-conventions.html#_single_trajectory. You can use the Panoply Data Viewer (https://www.giss.nasa.gov/tools/panoply/) to open, plot, and export the data.

 

Table 1. File names and descriptions

File name	Description
UCI_AltPAN_ReactivityDatastream_ATom-1.nc	Provides modeled reactivities using the peroxy acetyl nitrate alternative data stream
UCI_AltOrgNitrates_ReactivityDatastream_ATom-1.nc	Provides modeled reactivities using the organic nitrates alternative data stream
UCI_AltNOX_ReactivityDatastream_ATom-1.nc	Provides modeled reactivities using the nitrogen oxide alternative data stream
UCI_AltCO_ReactivityDatastream_ATom-1.nc	Provides modeled reactivities using the carbon monoxide alternative data stream
UCI_AltAlkane_ReactivityDatastream_ATom-1.nc	Provides modeled reactivities using the alkanes alternative data stream

 

 Table 2. Variables in the data files for the alternative data streams

Parameter	Units	Description
ATom_parcel		Parcel number in ascending order for each air parcel
time	seconds	Defined as "seconds since 2016-01-01 00:00:00.0 UTC. The interval between parcel observations is 8 or 12 seconds.
longitude	degrees	Degrees east
latitude	degrees	Degrees north
pressure	Pa	Air pressure
alt_rate_of_production_mole_fraction_of_ozone_in_air_due_to_chemical_production	mole fraction/day	Rate of production (mole fraction) of ozone in air due to chemical production
alt_rate_of_production_stddev_mole_fraction_of_ozone_in_air_due_to_chemical_production	mole fraction/day	Standard deviation of the 24-hr average rate of production of ozone in air due to chemical production, in mole fraction/day
alt_rate_of_loss_mole_fraction_of_ozone_in_air_due_to_chemical_loss	mole fraction/day	24-hr average rate of loss of ozone in air due to chemical loss, in mole fraction/day
alt_rate_of_loss_stddev_mole_fraction_of_ozone_in_air_due_to_chemical_loss	mole fraction/day	Standard deviation of the 24-hr average rate of loss of ozone in air due to chemical loss, in mole fraction/day
alt_rate_of_loss_mole_fraction_of_methane_in_air_due_to_chemical_loss	mole fraction/day	Rate of loss of methane in air due to chemical loss, in mole fraction/day
alt_rate_of_loss_stddev_mole_fraction_of_methane_in_air_due_to_chemical_loss	mole fraction/day	Standard deviation of the rate of loss of methane in air due to chemical loss, in mole fraction/day
alt_photolysis_rate_of_ozone_to_1D_oxygen_atom	1/s/day	24-hr average photolysis rate of ozone to O(1D), in 1/s/day
photolysis_rate_stddev_of_ozone_to_1D_oxygen_atom	1/s/day	Standard deviation of the 24-hr average photolysis rate of ozone to O(1D), in 1/s/day
alt_photolysis_rate_of_nitrogen_dioxide	1/s/day	24-hr average photolysis rate of NO2, in 1/s/day for the CO alternative stream (the Picarro measurements stream)
alt_photolysis_rate_stddev_of_nitrogen_dioxide	1/s/day	Standard deviation of the 24-hr average photolysis rate of NO2, in 1/s/day

The ATom data will be used to improve the representation of chemically reactive gases and short-lived climate forcers in global models of atmospheric chemistry and climate. The profiles of the reactive gases will also provide critical information for validation of satellite data, particularly in remote areas where in situ data is lacking (Wofsy et al., 2018). This work represents a significant, new accomplishment in that we are able to constrain full, 3D models to measurements for the purpose of calculating tropospheric reactivity (Flynn et al., 2019, in process).

Standard deviations over the five August days are included, as a proxy for variability due to cloud synoptic variability. These five alternative reactivity data streams are themselves uncertainty streams, so analyzing them against the recommended stream run through the UCI is the main uncertainty/sensitivity analysis.

ATom-1 Flights

ATom-1 flew transects through the Pacific, Southern, Atlantic, and Arctic Oceans with the NASA DC-8 aircraft in July and August 2016. Each of the 11 flights included sampling from the boundary layer to the top of the aircraft range (around 39,000 ft or 12,000 m). Details of the ATom mission and data sets can be found on the NASA mission web site (https://espo.nasa.gov/atom/content/ATom) and at the final archive at the Oak Ridge National Laboratory Distributed Active Archive Center (ORNL DAAC).

ATom-1 Modeling Data Stream (MDS)

A modeling data stream (MDS) based on the 10-second merged observations (Wofsy et al., 2018) with interpolation and fill values was constructed containing 31,429 air parcel records of latitude, longitude, pressure, temperature, and chemical composition from the 11 research flights. Landing and takeoff data are stripped.  Each record is effectively an air parcel of approximate size 2.5 km horizontal by 160 m vertical.  Due to the typical profiling sequence (level at cruise for 10 min, descent for 20 min, level flight at 500 ft over the ocean for 5 min, and a 20-min climb back to cruise 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. The MDS provides a global, continuous, dense, 10-second data stream for the purpose of initializing 3D models and calculating the tropospheric reactivities (P-O3, L-O3, and L-CH4) for each MDS air parcel. ATom-1 MDS Source Data:  For additional information on the MDS data, refer to: https://espoarchive.nasa.gov/archive/browse/atom/DC8/MDS

Investigating the Sensitivity of Modeled Reactivities with Alternative Data Streams

As described in (Flynn et al., 2019, in process), the focus of their study was the core set of species that control the primary reactivity of the remote troposphere, specifically the chemical tendencies of O₃ and CH₄. The key species are O₃, H₂O, NO_x, CO, HNO₃, HNO₄, H₂O₂, methyl hydroperoxide (CH₃OOH), HCHO, CH₄, peroxy acetyl nitrate (PAN), methyl nitrate (MeONO₂), higher organic nitrates, isoprene, acetone, acetaldehyde, ethane and higher alkanes, alkenes, alkynes, and the aromatic species benzene, toluene, and xylene. 

Alternative data streams allow the sensitivity of the modeled reactivities to measurement uncertainties or detection levels among the core set of species to be identified. For example, results from the alternative data can be used to set a detection threshold level (LLOD) for an instrument, i.e., from the point of view of reactivities, there is or is not a reason to improve the instrument to reduce the LLOD.

MDS -- Alternative Data Streams

To evaluate the uncertainties and importance of key species on calculated reactivities, five MDS alternative data streams were derived, one with each of the following key species modified in some manner: carbon monoxide, nitrogen oxides, organic nitrates, PAN, and other alkanes.

Alternative data streams

For CO, the continuous Picarro 10-sec averages was used as the alternative stream;

For NOx, the measured values were used instead of the PSS calculation. 

For H₂O₂, CH₃OOH, HNO₃, HNO₄, acetone, and acetaldehyde the alternative data were calculated by adding twice the standard deviation over the ATom-1 record (in absolute abundance) to the primary MDS value.

For PAN, this approach was also necessary, because the ATom-1 measurements had large variability in regions where PAN was expected to be nearly constant. The standard deviation of PAN was 121 ppt, and this value was added to all PAN values to create its alternative stream within the MDS. The PAN uncertainty was greatly reduced with the addition of a new instrument for ATom-2, -3, and -4. 

For the organic species measured by WAS and TOGA (except for acetone and acetaldehyde), four times the species LLOD value was used as the minimum value. Using the alternative stream the LLOD level was tested for the hydrocarbons and organic nitrates to determine if the LLOD was below the threshold of importance in terms of the reactivities. The LLOD is 3 ppt for most species and hence the alternative streams test whether 12 ppt is large enough to affect the reactivities.

ATom-1 Alternative Reactivity Data Stream (RDS)

Each of the five alternative MDS were run through UCI model beginning with five different days in August (08/01, 08/06, 08/11, 08/16, 08/21) to sample different weather and cloud patterns. Average reactivities and J-values of the five daily values and standard deviations are reported for each parcel. The data from each of the five UCI models runs are for the representative year 2016.

Calculating Chemical Reactivities

The MDS is designed to provide the information about the location, physical state, and chemical composition necessary to initialize a grid cell in the global chemistry models and integrate the photochemistry for 24 hours. For details on calculating reactivities and photolysis rates (J-values) see Flynn et al., 2019 (in process).

Flynn, C.M.,  M.J. Prather, S.A. Strode, S.D. Steenrod, L. Emmons, F. Lacey, A.M. Fiore, G. Correa, L.T. Murray, G. Wolfe, M. Kim, J. Crounse, G. Diskin, J. DiGangi, B.C. Daube, R. Commane, K. McKain, T.B. Ryerson, C.Thompson, T.F. Hanisco, D. Blake, N. Blake, E. Apel, R. Hornbrook, J. Elkins, E. Hintsa, F. Moore, and S. Wofsy. Chemical Reactivity in the Remote Troposphere: Patterns and Heterogeneity based on ATom measurements (2019, in process).

Wofsy, et al. 2018. ATom: Merged Atmospheric Chemistry, Trace Gases, and Aerosols. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/1581