Documentation Revision Date: 2020-04-14
Dataset Version: 1
This dataset includes 82 files in comma-delimited text (ICARTT) format, with two data files (CH4-CO-N2O and CO2) per flight.
Commane, R., J.W. Budney, Y. Gonzalez ramos, M. Sargent, S.C. Wofsy, and B.C. Daube. 2020. ATom: Measurements from the Quantum Cascade Laser System (QCLS). ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/1747
Table of Contents
- Dataset Overview
- Data Characteristics
- Application and Derivation
- Quality Assessment
- Data Acquisition, Materials, and Methods
- Data Access
This dataset provides atmospheric concentrations of CO2, CH4, CO, and N2O measured by the Harvard Quantum Cascade Laser System (QCLS) instruments during airborne campaigns conducted by NASA's Atmospheric Tomography (ATom) mission. The QCLS (DUAL and CO2) instrument package contains two separate optical assemblies and calibration systems, and a common data system and power supply. The QCLS DUAL instrument simultaneously measures CO, CH4, and N2O concentrations in-situ using two thermo-electrically cooled pulsed-quantum cascade lasers light sources, a multiple pass absorption cell, and two liquid nitrogen-cooled solid-state detectors. The QCLS CO2 instrument measures CO2 concentrations in-situ using a thermoelectrically cooled pulsed-quantum cascade laser light source, gas cells, and liquid nitrogen cooled solid-state detectors. The CO2 mixing ratio of air flowing through the sample gas cell is determined by measuring absorption from a single infrared transition line at 4.32 microns relative to a reference gas of known concentration. The ATom mission 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 4 seasons from 2016 to 2018.
Project: Atmospheric Tomography Mission
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.
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 1. Flight campaign schedule
|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: 1 second
Data File Information
This dataset includes 82 files in comma-delimited text (ICARTT) format, with two files (CH4-CO-N2O and CO2) per flight date for all four ATom flight campaigns. Data files conform to the ICARTT File Format Standards V1.1.
File names are structured as QCLS-X_DC8_YYYYMMDD_R#.ict
X is CH4-CO-N2O or CO2,
YYYYMMDD is the start date (in UTC time) of the flight, and
R# is the file version or revision number.
Missing data are indicated by -99999
Table 2. Variables in the data files QCLS-CH4-CO-N2O_DC8_YYYYMMDD_R#.ict
|START_UTC||seconds||seconds since midnight UTC|
|CH4_QCLS||ppb||methane dry air molar mixing ratio|
|N2O_QCLS||ppb||nitrous oxide dry air molar mixing ratio|
|CO_QCLS||ppb||carbon monoxide dry air molar mixing ratio|
Table 3. Variables in the data files QCLS-CO2_DC8_YYYYMMDD_R#.ict
|START_UTC||seconds||seconds since midnight UTC|
|CO2_QCLS||ppm||carbon dioxide dry air molar mixing ratio|
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 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 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?
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 & Precision
Listed below are accuracy and precision as provided in the ICARTT header files in accordance with ICARTT File Format Standards.
- CH4: 1.0 & 0.5 ppb
- CO: 3.5 & 0.15 ppb
- N2O: 0.2 & 0.1 ppb
- CO2: 0.1 & 0.02 ppm
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 Chemistry-Climate Models (CCMs). ATom also differentiates between hypotheses for the formation and growth of aerosols over the remote oceans.
Quantum Cascade Laser System
|Instrument||Full Name||Contact Person||Type||Measurements||Data Variables|
|QCLS||Quantum Cascade Laser System||Bruce Daube||laser absorption||trace gasses||CO2, CO, CH4, N2O|
The Harvard QCLS (DUAL and CO2) instrument package contains two separate optical assemblies and calibration systems, and a common data system and power supply. The Harvard QCL DUAL instrument simultaneously measures CO, CH4, and N2O concentrations in-situ using two thermoelectrically cooled pulsed-quantum cascade lasers (QCL) light sources, a multiple pass absorption cell, and two liquid nitrogen-cooled solid-state detectors. In-flight calibrations for QCLS had two different schemes:
For Atom 1 and 2, it was zeroes every 15 mins and calibrations every 30 mins.
For Atom 3 and 4, it was zeroes and calibrations every 30 mins.
For CO2 a reference gas was used every 15 mins with low and high span calibrations every 30 mins.
The Harvard QCL CO2 instrument measures CO2 concentrations in situ using a thermoelectrically cooled pulsed-quantum cascade laser (QCL) light source, gas cells, and liquid nitrogen cooled solid-state detectors. The CO2 mixing ratio of air flowing through the sample gas cell is determined by measuring absorption from a single infrared transition line at 4.32 microns relative to a reference gas of known concentration. In-flight calibrations are performed by replacing the air sample with reference gas every 10 minutes, and with a low-span and a high-span gas every 20 minutes.
These data are available through the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).
Contact for Data Center Access Information:
- E-mail: firstname.lastname@example.org
- Telephone: +1 (865) 241-3952