Abstract
Abstract. In this study we compared temperatures and horizontal winds of meteorological analyses in the Antarctic lower stratosphere, a region of the atmosphere that is of major interest regarding chemistry and dynamics of the polar vortex. The study covers the European Centre for Medium-Range Weather Forecasts (ECMWF) operational analysis, the ERA-Interim reanalysis, the Modern-Era Retrospective analysis for Research and Applications version 1 and 2 (MERRA and MERRA-2), and the National Centers for Environmental Prediction and National Center for Atmospheric Research (NCEP/NCAR) reanalysis. The comparison was performed with respect to long-duration observations from 19 superpressure balloon flights during the Concordiasi field campaign in September 2010 to January 2011. Most of the balloon measurements were conducted at altitudes of 17–18.5 km and latitudes of 60–85° S. We found that large-scale state temperatures of the analyses have a mean precision of 0.5–1.4 K and a warm bias of 0.4–2.1 K with respect to the balloon data. Zonal and meridional winds have a mean precision of 0.9–2.3 m s−1 and a bias below ±0.5 m s−1. Standard deviations related to small-scale fluctuations due to gravity waves are reproduced at levels of 15–60 % for temperature and 30–60 % for the horizontal winds. Considering the fact that the balloon observations have been assimilated into all analyses, except for NCEP/NCAR, notable differences found here indicate that other observations, the forecast models, and the data assimilation procedures have a significant impact on the analyses as well. We also used the balloon observations to evaluate trajectory calculations with our new Lagrangian transport model Massive-Parallel Trajectory Calculations (MPTRAC), where vertical motions of simulated trajectories were nudged to pressure measurements of the balloons. We found relative horizontal transport deviations of 4–12 % and error growth rates of 60–170 km day−1 for 15-day trajectories. Dispersion simulations revealed some difficulties with the representation of subgrid-scale wind fluctuations in MPTRAC, as the spread of air parcels simulated with different analyses was not consistent. However, although case studies suggest that the accuracy of trajectory calculations is influenced by meteorological complexity, diffusion generally does not contribute significantly to transport deviations in our analysis. Overall, evaluation results are satisfactory and compare well to earlier studies using superpressure balloon observations.
Highlights
The seasonal formation and decay of the Southern Hemisphere polar vortex is likely the most prominent feature of the extratropical stratospheric circulation (e.g., Schoeberl and Hartmann, 1991; Newman and Schoeberl, 2003; Waugh and Polvani, 2010)
The Concordiasi balloon observations have been assimilated into the European Centre for MediumRange Weather Forecasts (ECMWF) data sets, MERRA, and MERRA2, but they were not considered for the NCEP/NCAR reanalysis
Note that the largest biases and standard deviations were typically found for the NCEP/NCAR data set, which may be attributed to the fact that this data set is independent, whereas the Concordiasi balloon observations have been assimilated into the other analyses
Summary
The seasonal formation and decay of the Southern Hemisphere polar vortex is likely the most prominent feature of the extratropical stratospheric circulation (e.g., Schoeberl and Hartmann, 1991; Newman and Schoeberl, 2003; Waugh and Polvani, 2010). Hoffmann et al.: Intercomparison of meteorological analyses in the Antarctic lower stratosphere plays a critical role in polar ozone depletion and the annual formation of the Antarctic ozone hole (Solomon, 1999, and references therein) These topics have motivated various observational and modeling studies in recent years to better understand the structure and dynamics of the polar vortex as well as implications on polar ozone loss in the stratosphere. The results of the intercomparison of the temperature and wind data of the meteorological analyses may be of interest for studies using chemistry-transport models to assess polar ozone loss in the stratosphere (e.g., Chipperfield, 1999; Grooß et al, 2002, 2005; Wohltmann et al, 2013).
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
