ATom: L2 Measurements from CU High-Resolution Aerosol Mass Spectrometer (HR-AMS)

This dataset provides the atmospheric concentrations of separated ions from inorganic and organic species measured by the High-Resolution Aerosol Mass Spectrometer (HR-AMS) collected during flights of the NASA ATom Mission. Data are available from all four ATom Campaigns. The HR-AMS detects non-refractory submicron aerosol composition by impaction on a vaporizer at 600 degrees C, followed by electron ionization and time-of-flight mass spectral analysis. The measurements include chemically speciated submicron non-refractory particulate mass at a one second and 60 second resolution, and the size distribution of chemically speciated submicron non-refractory particulate mass at 60 second resolution.

This is Version 1.1 of this dataset. Version 1.1 contains the initial release of data from the ATom-4 campaign. No other data files from ATom-1, ATom-2, or ATom-3 have been updated. For more details see Section 8. Dataset Revisions.

This dataset includes 133 data files in ICARTT (.ict) format.

This dataset provides the atmospheric concentrations of separated ions from inorganic and organic species measured by the High-Resolution Aerosol Mass Spectrometer (HR-AMS) collected during flights of the NASA ATom Mission.  Data are available from all four ATom Campaigns. The HR-AMS detects non-refractory submicron aerosol composition by impaction on a vaporizer at 600 degrees C, followed by electron ionization and time-of-flight mass spectral analysis. The measurements include chemically speciated submicron non-refractory particulate mass at a one second and 60 second resolution, and the size distribution of chemically speciated submicron non-refractory particulate mass at 60 second resolution.

This is Version 1.1 of this dataset. Version 1.1 contains the initial release of data from the ATom-4 campaign. No other data files from ATom-1, ATom-2, or ATom-3 have been updated. For more details see Section 8. Dataset Revisions.

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 Data:

ATom: Merged Atmospheric Chemistry, Trace Gases, and Aerosols. Data from all ATom instruments and all four flight campaigns, including aircraft location and navigation data, merged to several different time bases: https://doi.org/10.3334/ORNLDAAC/1581

ATom Flight Track and Navigational Data. Flight path (location and altitude) data for each of the four campaigns provided in KML and csv format: https://doi.org/10.3334/ORNLDAAC/1613

Spatial Coverage: Global. Flights circumnavigate the globe, primarily over the oceans

Spatial Resolution: Point measurements

Temporal Coverage: Periodic flights occurred during each campaign

Table 2. Flight campaign schedule. Note: AMS and AMS-60s files are available for all four ATom campaigns and AMSSD files are available for ATom 1, 3, and 4 campaigns.

Deployment	Date Range
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: AMS files: 1 second, AMSSD and AMS-60s files: 60 seconds.

Data File Information

File names are structured as AMS _DC8_YYYYMMDD_R#.nc, AMS-60s _DC8_YYYYMMDD_R#.nc, or AMSSD _DC8_YYYYMMDD_R#.nc where YYYYMMDD is the start date (in UTC time) of the flight and R# is the file version or revision number. 

• AMS files contain chemically speciated submicron non-refractory aerosol masses at one-second resolution,
• AMS-60s files contain chemically speciated submicron non-refractory aerosol masses at 60-second resolution, and
• AMSSD files contain chemically speciated submicron non-refractory aerosol masses at 60-second resolution.

Missing data values are listed as -9999. Variables descriptions are contained in data dictionary companion files (see Companion Files below)

Companion Files

There are three companion files associated with this dataset, containing a data dictionary for each type of data file. The naming convention for these companion files is DATATYPE_Data_Dictonary.csv, where DATATYPE is AMS, AMS-60s, or AMSSD.

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

Tier 1

• 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 chemistry-climate modeling of these processes?

Tier 2

• 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 occur 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?

Significance

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.

Accuracy estimate (2 SD): Inorganics +/-34%, Organics +/-38%, dominated by uncertainty in particle collection efficiency due to particle bounce, and absolute and relative ionization efficiency. Precision error (1 SD) for each species is provided as a variable.

Project Overview

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.

High-Resolution (Time-of-Flight) Aerosol Mass Spectrometer (HR-AMS):

Instrument	Full Name	Contact Person	Type	Measurements
HR-AMS	CU Aircraft High-Resolution Aerosol Mass Spectrometer	Jose-Luis Jimenez	spectrometer (in situ)	aerosol mass

The High-Resolution (Time-of-Flight) Aerosol Mass Spectrometer (HR-AMS) detects non-refractory submicron aerosol composition by impaction on a vaporizer at 600°C, followed by electron ionization and time-of-flight mass spectral analysis. Size-resolved composition can be quantified by measuring the arrival times of the aerosol at the vaporizer. For more information, see DeCarlo et al. (2006) and the AMS FAQ page.

DeCarlo, P.F., J.R.Kimmel, A. Trimborn, M.J. Northway, J.T. Jayne, A.C. Aiken, M. Gonin, K. Fuhrer, T. Horvath, K.S. Docherty,& D.R. Worsnop. 2006. Field-deployable, high-resolution, time-of-flight aerosol mass spectrometer. Analytical chemistry, 78(24), pp.8281-8289, https://doi.org/10.1021/ac061249n.