Documentation Revision Date: 2022-01-03
Dataset Version: 1
There are 278 data files included in this dataset,186 data files in ICARTT (*.ict) format and 92 files NetCDF (*.nc) format.
Froyd, K.D., D.M. Murphy, G.P. Schill, and C.A. Brock. 2021. ATom: Measurements from Particle Analysis By Laser Mass Spectrometry (PALMS). ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/1733
Table of Contents
- Dataset Overview
- Data Characteristics
- Application and Derivation
- Quality Assessment
- Data Acquisition, Materials, and Methods
- Data Access
This dataset contains single-particle aerosol composition as measured by the Particle Analysis by Laser Mass Spectrometry (PALMS) instrument during the four ATom campaigns from 2016–2018. Single aerosol particles are classified into several particle types, including mixed sulfate/organic nitrate, biomass burning, elemental carbon, mineral/metallic, meteoric material, alkali salt, sea salt, heavy oil combustion, and others. Particle types are reported as raw number fractions and as absolute mass concentrations. PALMS measures aerosol composition for particles from diameter ~100 to 5,000 nm, with most of the particle data in the size range ~150 to 3,000 nm. Also included are absolute aerosol concentrations measured by a modified Laser Aerosol Spectrometer (LAS). Integrated number, surface area, and volume concentrations from LAS are reported over multiple size ranges.
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.
Wofsy, S.C., S. Afshar, H.M. Allen, E.C. Apel, E.C. Asher, B. Barletta, et al. 2021. ATom: Merged Atmospheric Chemistry, Trace Gases, and Aerosols, Version 2. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/1925
- Data from all ATom instruments and all four flight campaigns, including aircraft location and navigation data, merged to several different time bases.
Wofsy, S.C., and ATom Science Team. 2018. ATom: Aircraft Flight Track and Navigational Data. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/1613
- Flightpath (location and altitude) data for each of the four campaigns provided in KML and CSV formats.
Spatial Coverage: Global. Flights circumnavigate the globe, primarily over the oceans
Spatial Resolution: Point measurements
Temporal Coverage: Periodic flights occurred during each campaign
|ATom-1||July 29 - August 23, 2016|
|ATom-2||January 26 - February 21, 2017|
|ATom-3||September 28 - October 28, 2017|
|ATom-4||April 24 - May 21, 2018|
Temporal Resolution: LASaerosol: 10 s; PALMS, PALMS-Chem-Mass, and PALMS-PartType-Mass: 1 s; PALMS-Neg-Particle-Spectra and PALMS-Pos-Particle-Spectra: <1 s
Data File Information
There are 278 data files included in this dataset,186 data files in ICARTT (*.ict) format and 92 files NetCDF (*.nc) format. Files in ICARTT format conform to the ICARTT File Format Standards V1.1 and files in NetCDF format conform to CF Conventions. The file names are named FileType_DC8_YYYYMMDD_R#.ict, where FileType is the type of data (Table 2), YYYYMMDD is the start date (in UTC time) of the flight, and R# is the file version or revision number.
Table 2. File types and descriptions.
|File Type||Number of Files||Format||Description|
|LASaerosol||48||ICARTT||Number, surface, and volume concentrations of dry aerosol particles measured by a commercial TSI model 3340.|
|PALMS||46||ICARTT||Aerosol number fractions of various particle types|
|PALMS-Chem-Mass||46||ICARTT||Aerosol mass concentrations in non-refractory particles|
|PALMS-Neg-Particle-Spectra||46||NetCDF||PALMS negative ion single-particle spectra|
|PALMS-PartType-Mass||46||ICARTT||Aerosol mass concentrations of various particle types|
|PALMS-Pos-Particle-Spectra||46||NetCDF||PALMS negative ion single-particle spectra|
Data File Details
Table 3. Variable names and descriptions for LASaerosol files. "STP" is the standard temperature and pressure.
|Start_LAS||Seconds||Start time in seconds since 0000 UTC|
|End_LAS||Seconds||End time in seconds since 0000 UTC|
|N_LAS||std cm-3||Integrated number concentration, approx.0.1 to 4.8 um dry diameter|
|S_LAS||std um2 cm-3||Integrated surface area concentration, approx.0.1 to 4.8 um dry diameter|
|V_LAS||std um3 cm-3||Integrated volume concentration, approx. 0.1 to 4.8 um dry diameter|
|Nacc_LAS||std cm-3||Integrated number concentration, approx. 0.1 to 0.9 um dry diameter|
|Sacc_LAS||std um2 cm-3||Integrated surface area concentration, approx. 0.1 to 0.9 um dry diameter|
|Vacc_LAS||std um3 cm-3||Integrated volume concentration, approx. 0.1 to 0.9 um dry diameter|
|Ncoarse_LAS||std cm-3||Integrated number concentration, approx. 0.9 to 4.8 um dry diameter|
|Scoarse_LAS||std um2 cm-3||Integrated surface area concentration, approx. 0.9 to 4.8 um dry diameter|
|Vcoarse_LAS||std um3 cm-3||Integrated volume concentration, approx. 0.9 to 4.8 um dry diameter|
Table 4. Variable names and descriptions for PALMS files.
|PALMSstartTime||Seconds||Start time in seconds since 0000 UTC|
|SulfOrgNitFrac_PALMS||Number fraction||Mixed sulfate-organic-nitrate particles|
|BioBurnFrac_PALMS||Number fraction||Biomass burning particles|
|SootFrac_PALMS||Number fraction||Elemental carbon particles|
|MineralFrac_PALMS||Number fraction||Mineral/metallic particles|
|MeteoricFrac_PALMS||Number fraction||Particles with meteoric material|
|AlkaliSaltFrac_PALMS||Number fraction||Alkali salt particles|
|SeaSaltFrac_PALMS||Number fraction||Sea salt particles|
|OilCombFrac_PALMS||Number fraction||Particles from heavy oil combustion|
|UnclassFrac_PALMS||Number fraction||Unclassified particles|
|OrgSulfMF_PALMS||Mass fraction||Organic-to-sulfate mass fraction|
|IEPOXmf_PALMS||Mass fraction||Fraction of submicron aerosol mass attributed to IEPOX sulfate|
|GASmf_PALMS||Mass fraction||Fraction of submicron aerosol mass attributed to glycolic acid sulfate|
|SulfNeut_PALMS||Molar Ratio||Degree of sulfate neutralization as NH4+:SO42-|
|Npos_PALMS||Count||Number of particles positive ion spectra used|
|NNeg_PALMS||Count||Number of negative ion spectra used|
|NAcid_PALMS||Count||Number of spectra used for SulfNeut data product|
Table 5. Variable names and descriptions for PALMS-Chem-Mass files.
|StartTimeChem_PALMS||Seconds||Start time in seconds since 0000 UTC|
|OrgMass_PALMS||ug stdm-3||Mass concentration of organic material in non-refractory particles|
|SulfateMass_PALMS||ug stdm-3||Mass concentration of sulfate in non-refractory particles|
|BromineMass_PALMS||ug stdm-3||Mass concentration of bromine in non-refractory particles|
|IodineMass_PALMS||ug stdm-3||Mass concentration of iodine in non-refractory particles|
|IEPOXsulfMass_PALMS||ug stdm-3||Mass concentration of IEPOX sulfate ester in non-refractory particles|
|GASMass_PALMS||ug stdm-3||Mass concentration of glycolic acid sulfate in non-refractory particles|
Table 6. Variable names and descriptions for PALMS-Neg-Particle-Spectra and PALMS-Pos-Particle-Spectra files.
|AeroDiam||Microns||The aerodynamic diameter of the particle derived from the time between the timing and trigger scatter signals|
|Altitude||Meters||Altitude of aircraft|
|AreasNoID||Fraction of ions||The areas of all peaks for which no mass number was assigned|
|AreasNonInt||Fraction of ions||The areas of all peaks with half-mass or other non-integer peak identification|
|DateTime||Seconds||Start time in seconds since 0000 UTC|
|ExcimerND||Fraction of ions||The value of a neutral density filter in the excimer beam|
|FlagBioBurn||Numeric||Shows if a particle was identified by automated criteria as a biomass burning particle|
|FlagKRich||Numeric||Shows if a particle was identified by automated criteria as an alkali-rich particle|
|FlagMinMet||Numeric||Shows if a particle was identified by automated criteria as a mineral or metal particle|
|FlagSeaSalt||Numeric||Shows if a particle was identified by automated criteria as a sea salt particle|
|FlagSoot||Numeric||Shows if a particle was identified by automated criteria as a soot particle|
|FlagSulfOrg||Numeric||Shows if a particle was identified by automated criteria as a sulfate-organic-nitrate mixture|
|FlightTDay||Numeric||UTC time of measurement in seconds since 0000 UTC|
|JouleMtr||Relative||The time the particle was sampled in seconds since Jan 1, 1904|
|MassScaleA||us||A constant in an equation to convert ion arrival time to mass: time = A + B*sqrt(mass)|
|MassScaleB||us (Da-1)/2||A constant in an equation to convert ion arrival time to mass: time = A + B*sqrt(mass)
Da = aerodynamic diameter
|MScaleFitVariance||Da2||The variance when the positions of the peaks are fit to the mass scale equation using integer values for the peak positions|
|NumPks||1||Number of non-zero peaks in each mass spectrum|
|spectra||Fraction of ions||Two-dimensional array giving the area of every mass peak for every particle mass spectrum|
|TimingScatHt||Degree||The size of the optical pulse when the particle scattered light as it went through the first 405 nm laser beam|
|TotalMCPBackground||Electrons||There is a very small ion background in PALMS in the positive ion mode, mostly at m/z=12. This is the value that was subtracted to obtain TotalMCPSignal|
|TotalMCPSignal||Electrons||The total signal from the microchannel plate (MCP) integrated over all peaks in the mass spectrum|
|TrigScatHt||Relative||The size of the optical pulse when the particle scattered light|
Table 7. Variable names and descriptions for PALMS-PartType-Mass.
|StartTime_PALMS||Seconds||Start time in seconds since 0000 UTC|
|SulfOrgNitMass_PALMS||ug stdm-3||mass concentration of mixed sulfate-organic-nitrate particles for 0.1-4.8 um dry diameter|
|BioBurnMass_PALMS||ug stdm-3||mass concentration of biomass burning particles for 0.1-4.8 um dry diameter|
|SootMass_PALMS||ug stdm-3||mass concentration of elemental carbon particles for 0.1-4.8 um dry diameter|
|MineralMass_PALMS||ug stdm-3||mass concentration of mineral/metallic particles for 0.1-4.8 um dry diameter|
|MeteoricMass_PALMS||ug stdm-3||mass concentration of particles with meteoric material for 0.1-4.8 um dry diameter|
|AlkaliSaltMass_PALMS||ug stdm-3||mass concentration of alkali salt particles for 0.1-4.8 um dry diameter|
|SeaSaltMass_PALMS||ug stdm-3||mass concentration of sea salt particles for 0.1-4.8 um dry diameter|
|OilCombMass_PALMS||ug stdm-3||mass concentration of particles from fuel oil combustion for 0.1-4.8 um dry diameter|
|UnclassMass_PALMS||ug stdm-3||mass concentration of unclassified particles for 0.1-4.8 um dry diameter|
|NposMass_PALMS||Count||number of positive ion particle spectra|
Application and Derivation
ATom builds the scientific foundation for mitigation of short-lived climate forcers, in particular, methane (CH4), tropospheric ozone (O3), and Black Carbon aerosols (BC).
ATom Science Questions
- What are chemical processes that control the short-lived climate forcing agents CH4, O3, and BC in the atmosphere? How is the chemical reactivity of the atmosphere on a global scale affected by anthropogenic emissions? How can we improve the chemistry-climate modeling of these processes?
- Over large, remote regions, what are the distributions of BC and other aerosols important as short-lived climate forcers? What are the sources of new particles? How rapidly do aerosols grow to CCN-active sizes? How well are these processes represented in models?
- What type of variability and spatial gradients occurs over remote ocean regions for greenhouse gases (GHGs) and ozone-depleting substances (ODSs)? How do the variations among air parcels help identify anthropogenic influences on photochemical reactivity, validate satellite data for these gases, and refine knowledge of sources and sinks?
ATom delivers unique data and analysis to address the Science Mission Directorate objectives of acquiring “datasets that identify and characterize important phenomena in the changing Earth system” and “measurements that address weaknesses in current Earth system models leading to improvement in modeling capabilities.” ATom will provide unprecedented challenges to the CCMs used as policy tools for climate change assessments, with comprehensive data on atmospheric chemical reactivity at global scales, and will work closely with modeling teams to translate ATom data to better, more reliable CCMs. ATom provides extraordinary validation data for remote sensing.
Quality assessment procedures differ by data file type. Quality flags are provided within the data files for many of the measured parameters.
Data Acquisition, Materials, and Methods
ATom makes global-scale measurements of the chemistry of the atmosphere using the NASA DC-8 aircraft. Flights span the Pacific and Atlantic Oceans, nearly pole-to-pole, in continuous profiling mode, covering remote regions that receive long-range inputs of pollution from expanding industrial economies. The payload has proven instruments for in situ measurements of reactive and long-lived gases, diagnostic chemical tracers, and aerosol size, number, and composition, plus spectrally resolved solar radiation and meteorological parameters.
Combining distributions of aerosols and reactive gases with long-lived GHGs and ODSs enables disentangling of the processes that regulate atmospheric chemistry: emissions, transport, cloud processes, and chemical transformations. ATom analyzes measurements using customized modeling tools to derive daily averaged chemical rates for key atmospheric processes and to critically evaluate CCMs. ATom also differentiates between hypotheses for the formation and growth of aerosols over the remote oceans.
Particle Analysis by Laser Mass Spectrometry
The NOAA Particle Analysis by Laser Mass Spectrometry (PALMS) instrument measures single-particle aerosol composition using UV laser ablation to generate ions that are analyzed with a time-of-flight mass spectrometer. The PALMS size range is approximately 150 nm to >3000 nm and encompasses most of the accumulation and coarse mode aerosol volume. Individual aerosol particles are classified into compositional classes. The size-dependent composition data are combined with aerosol counting instruments from Aerosol Microphysical Properties (AMP), the Langley Aerosol Research Group Experiment (LARGE), and other groups to generate quantitative, composition-resolved aerosol concentrations. Background tropospheric concentrations of climate-relevant aerosol including mineral dust, sea salt, and biomass burning particles are the primary foci for the ATom campaigns. PALMS also provides a variety of compositional tracers to identify aerosol sources, probe mixing state, track particle aging, and investigate convective transport and cloud processing. Additional information can be found in Froyd et al. (2019) and on the ESPO PALMS Instrument page.
These data are available through the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).
Contact for Data Center Access Information:
- E-mail: email@example.com
- Telephone: +1 (865) 241-3952
Froyd, K.D., D.M. Murphy, C.A. Brock, P. Campuzano-Jost, J.E. Dibb, J.-L. Jimenez, A. Kupc, A.M. Middlebrook, G.P. Schill, K.L Thornhill, C.J. Williamson, J.C. Wilson, and L.D. Ziemba. 2019. A new method to quantify mineral dust and other aerosol species from aircraft platforms using single-particle mass spectrometry. Atmospheric Measurement Techniques 12:6209-6239. https://doi.org/10.5194/amt-12-6209-2019