AIRS/Aqua Observations of non-LTE Emissions
Introduction
This data repository provides access to observations of carbon dioxide non-LTE emissions provided by the Atmospheric Infrared Sounder (AIRS) aboard NASA's Aqua satellite. Aqua was launched in May 2002 into a nearly polar, low earth orbit (705 km altitude, 100 min orbit period, 14.4 orbits per day). AIRS is an infrared nadir sounder with across-track scanning capabilities. Each across-track scan covers 1780 km ground distance and consists of 90 footprints. Two adjacent scans are separated by 18 km along-track distance. The footprint size varies between 14 x 14 km2 at nadir and 21 x 42 km2 at the scan extremes. AIRS measurements cover three wavelength bands in the 3.74-15.4 μm spectral range.
Information on carbon dioxide non-LTE emissions is derived from AIRS radiance measurements in the 4.3 and 15 μm CO2 fundamental bands. These bands typically get optically thick in the middle stratosphere at about 30-40 km of altitude. In order to extract the non-LTE signals, a physical retrieval scheme is applied to retrieve stratospheric temperature profiles from the AIRS 15 μm radiance measurements. As these measurements are not affected by non-LTE conditions, the retrieval can be conducted using a radiative transfer model suitable for LTE conditions. In the second step, the radiative transfer model and the retrieved temperature profile are used to simulate the 4.3 μm radiance measurements AIRS would make under LTE conditions. The non-LTE index is defined as the difference between the real AIRS 4.3 μm measurements, including the non-LTE effects, and the simulated 4.3 μm measurements for LTE conditions.
Browse images
The browse images provided on this web site show polar maps of the AIRS non-LTE index. Data are shown separately for nighttime observations for both hemispheres. In the browse images we restricted the range of the non-LTE index to make also weak events visible. Note that the non-LTE index is reported in units of Kelvin as it refers to a brightness temperature difference. The browse images also show geomagnetic field lines for reference.
Data access
The AIRS non-LTE index data sets provided on this web site have been created using AIRS/Aqua L1B Infrared (IR) geolocated and calibrated radiances V005 as distributed by the NASA Goddard Earth Sciences Data and Information Services Center (GES DISC). Please see the GES DISC website for further information on the AIRS/Aqua operational data products. Note that this data repository provides access to non-operational research data products, which are dedicated to the research on atmospheric chemistry and dynamics.
Legal notes
The data sets and browse images provided on this web site are licensed under a Creative Commons Attribution 4.0 International License. You are free to share the material in any medium or format and adapt it for any purpose, even commercially. You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use. You may not apply legal terms or technological measures that legally restrict others from doing anything the license permits. The licensor cannot revoke these freedoms as long as you follow the license terms. The data are distributed in the hope that it will be useful, but without any warranty. Please follow the link to see the terms and conditions of the license:
References
This data repository can be cited as:
Hoffmann, Lars, "AIRS/Aqua Observations of non-LTE Emissions", https://doi.org/10.26165/JUELICH-DATA/PHL4EE, 2023.
Citation, if the data are used in publications:
Bossert, K., Hoffmann, L., Mlynczak, M., & Hunt, L., Observations of 4.26 um CO2 auroral emissions from AIRS nadir sounder measurements, Geophysical Research Letters, 50, e2023GL103856, https://doi.org/10.1029/2023GL103856, 2023.
Contact
We encourage any scientist interested in this data set to contact us for discussion on how you would like to use the data. This might help to reduce the risk of mistaken applications and helps us to track the distribution and areas of applications of the data set.
Please do not hesitate to contact us if you have any further questions:
Dr. Lars Hoffmann
Forschungszentrum Jülich
Jülich Supercomputing Centre
52425 Jülich
Germany
e-mail: l.hoffmann@fz-juelich.de
