Overview and update of the SPARC Data Initiative: comparison of stratospheric composition measurements from satellite limb sounders

• Main Authors: M. I. Hegglin, S. Tegtmeier, J. Anderson, A. E. Bourassa, S. Brohede, D. Degenstein, L. Froidevaux, B. Funke, J. Gille, Y. Kasai, E. T. Kyrölä, J. Lumpe, D. Murtagh, J. L. Neu, K. Pérot, E. E. Remsberg, A. Rozanov, M. Toohey, J. Urban, T. von Clarmann, K. A. Walker, H.-J. Wang, C. Arosio, R. Damadeo, R. A. Fuller, G. Lingenfelser, C. McLinden, D. Pendlebury, C. Roth, N. J. Ryan, C. Sioris, L. Smith, K. Weigel
• Format: Article
• Language: English
• Published: Copernicus Publications 2021-05-01
• Series: Earth System Science Data
• Online Access: https://essd.copernicus.org/articles/13/1855/2021/essd-13-1855-2021.pdf

<p>The Stratosphere-troposphere Processes and their Role in Climate (SPARC) Data Initiative (SPARC, 2017) performed the first comprehensive assessment of currently available stratospheric composition measurements obtained from an international suite of space-based limb sounders. The initiative's main objectives were (1) to assess the state of data availability, (2) to compile time series of vertically resolved, zonal monthly mean trace gas and aerosol fields, and (3) to perform a detailed intercomparison of these time series, summarizing useful information and highlighting differences among datasets. The datasets extend over the region from the upper troposphere to the lower mesosphere (300–0.1 <span class="inline-formula">hPa</span>) and are provided on a common latitude–pressure grid.<span id="page1856"/> They cover 26 different atmospheric constituents including the stratospheric trace gases of primary interest, ozone (<span class="inline-formula">O₃</span>) and water vapor (<span class="inline-formula">H₂O</span>), major long-lived trace gases (<span class="inline-formula">SF₆</span>, <span class="inline-formula">N₂O</span>, <span class="inline-formula">HF</span>, <span class="inline-formula">CCl₃F</span>, <span class="inline-formula">CCl₂F₂</span>, <span class="inline-formula">NO_<i>y</i></span>), trace gases with intermediate lifetimes (<span class="inline-formula">HCl</span>, <span class="inline-formula">CH₄</span>, <span class="inline-formula">CO</span>, <span class="inline-formula">HNO₃</span>), and shorter-lived trace gases important to stratospheric chemistry including nitrogen-containing species (<span class="inline-formula">NO</span>, <span class="inline-formula">NO₂</span>, <span class="inline-formula">NO_<i>x</i></span>, <span class="inline-formula">N₂O₅</span>, <span class="inline-formula">HNO₄</span>), halogens (<span class="inline-formula">BrO</span>, <span class="inline-formula">ClO</span>, <span class="inline-formula">ClONO₂</span>, <span class="inline-formula">HOCl</span>), and other minor species (<span class="inline-formula">OH</span>, <span class="inline-formula">HO₂</span>, <span class="inline-formula">CH₂O</span>, <span class="inline-formula">CH₃CN</span>), and aerosol. This overview of the SPARC Data Initiative introduces the updated versions of the SPARC Data Initiative time series for the extended time period 1979–2018 and provides information on the satellite instruments included in the assessment: LIMS, SAGE I/II/III, HALOE, UARS-MLS, POAM II/III, OSIRIS, SMR, MIPAS, GOMOS, SCIAMACHY, ACE-FTS, ACE-MAESTRO, Aura-MLS, HIRDLS, SMILES, and OMPS-LP. It describes the Data Initiative's top-down climatological validation approach to compare stratospheric composition measurements based on zonal monthly mean fields, which provides upper bounds to relative inter-instrument biases and an assessment of how well the instruments are able to capture geophysical features of the stratosphere. An update to previously published evaluations of <span class="inline-formula">O₃</span> and <span class="inline-formula">H₂O</span> monthly mean time series is provided. In addition, example trace gas evaluations of methane (<span class="inline-formula">CH₄</span>), carbon monoxide (<span class="inline-formula">CO</span>), a set of nitrogen species (<span class="inline-formula">NO</span>, <span class="inline-formula">NO₂</span>, and <span class="inline-formula">HNO₃</span>), the reactive nitrogen family (<span class="inline-formula">NO_<i>y</i></span>), and hydroperoxyl (<span class="inline-formula">HO₂</span>) are presented. The results highlight the quality, strengths and weaknesses, and representativeness of the different datasets. As a summary, the current state of our knowledge of stratospheric composition and variability is provided based on the overall consistency between the datasets. As such, the SPARC Data Initiative datasets and evaluations can serve as an atlas or reference of stratospheric composition and variability during the “golden age” of atmospheric limb sounding. The updated SPARC Data Initiative zonal monthly mean time series for each instrument are publicly available and accessible via the Zenodo data archive (Hegglin et al., 2020).</p>