# AIRS/Aqua observations of stratospheric gravity waves of the January 2022 Hunga Tonga-Hunga Ha'apai volcanic eruption ## Overview This data repository provides access to infrared satellite observations of stratospheric gravity waves obtained by the Atmospheric Infrared Sounder (AIRS) instrument following the Hunga Tonga-Hunga Ha'apai volcanic eruption on 14-15 January 2022. We provide a 4.3 and 15 micron brightness temperature data product showing gravity wave signals for three height ranges of the stratosphere (20-25 km, 30-40 km, and 40-45 km). As a second data product, we provide high-resolution 3-D stratospheric temperature retrievals conducted with a radiative transfer model and an optimal estimation retrieval scheme. ## Data sets Two gravity wave data products from AIRS/Aqua are provided: a) Brightness temperature data product This data product contains brightness temperature perturbations showing stratospheric gravity signals derived from three AIRS channel sets covering the 4.3 and 15 micron carbon dioxide wavebands. The 4.3 micron data set is most sensitive to stratospheric temperatures at about 30-40 km of altitude. The 15 micron "low" data set is most sensitive to 20-25 km. The 15 micron "high" data set is most sensitive to 40-45 km. Being a cross-track sounder, AIRS observations provide high horizontal resolution, but vertical resolution is limited. The vertical resolution, represented by the FWHM of the temperature kernel functions, is about 15 km for the 15 micron channels and 25 km for the 4.3 micron channels. The 4.3 micron channel set has better noise characteristics than the 15 micron channel sets. For more detailed information, please see the references. References: Hoffmann, L., X. Xue, and M. J. Alexander, A global view of stratospheric gravity wave hotspots located with Atmospheric Infrared Sounder observations, J. Geophys. Res. Atmos., 118, 416-434, doi:10.1029/2012JD018658, 2013. Hoffmann, L., Alexander, M. J., Clerbaux, C., Grimsdell, A. W., Meyer, C. I., Roessler, T., and Tournier, B.: Intercomparison of stratospheric gravity wave observations with AIRS and IASI, Atmos. Meas. Tech., 7, 4517-4537, https://doi.org/10.5194/amt-7-4517-2014, 2014. b) High-resolution stratospheric temperature retrieval We retrieved 3-D stratospheric temperature distributions from AIRS by applying a fast forward model and an optimal estimation retrieval scheme. The range of the retrieval is limited to the stratosphere. It does not require cloud-clearing as for the troposphere. Independent retrievals are carried out at the full horizontal sampling capacity of the AIRS instrument. Horizontal resolution is enhanced by a factor 3 x 3 in the along- and across-track direction compared to operational Level-2 data. The total retrieval error of the temperature data is 1.6 to 3.0 K in the altitude range from 20 to 60 km. Retrieval noise is 1.4 to 2.1 K in the same range. The vertical resolution of the retrieval varies between 7 to 15 km from 20 to 60 km of altitude. Reference: Hoffmann, L., and Alexander, M. J., Retrieval of stratospheric temperatures from Atmospheric Infrared Sounder radiance measurements for gravity wave studies, J. Geophys. Res., 114, D07105, doi:10.1029/2008JD011241, 2009. ## Further information Further information and access to large parts of the AIRS gravity wave observations is available at: https://datapub.fz-juelich.de/slcs/airs/gravity_waves/ AIRS/Aqua observations of sulfur dioxide and volcanic ash are available at: https://datapub.fz-juelich.de/slcs/airs/volcanoes/ ## Data access and legal notes The gravity wave data sets have been created using AIRS/Aqua Level-1 and Level-2 data distributed by the NASA Goddard Earth Sciences Data and Information Services Center (GES DISC). Please see the GES DISC website (https://disc.gsfc.nasa.gov/) for further information on the AIRS/Aqua operational data products. The data sets are provided under a Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/). 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 note that the AIRS/Aqua operational data products as well as the gravity wave data products provided here are subject to potential future changes. We added md5 checksums to verify the integrity of the data files and to identify changes of the data. This documentation will be updated in case of changes of the data. To support our work, please reference the papers listed above in your scientific publications. Next to our scientific publications describing the data, the AIRS data sets for the Hunga Tonga eruption themselves can be cited via the following DOI: Hoffmann, Lars, "AIRS/Aqua observations of stratospheric gravity waves of the January 2022 Hunga Tonga-Hunga Ha'apai volcanic eruption", https://doi.org/10.26165/JUELICH-DATA/DWABVZ, Juelich DATA, V1, 2022. ## Contact We are happy to collaborate on scientific studies applying the AIRS/Aqua gravity wave products. For further information and questions, please contact: Lars Hoffmann Forschungszentrum Juelich Juelich Supercomputing Centre 52428 Juelich, Germany e-mail: l.hoffmann@fz-juelich.de