the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
18 Mar 2021
18 Mar 2021
Interhemispheric differences of mesosphere/lower thermosphere winds and tides investigated from three whole atmosphere models and meteor radar observations
- 1Institute of Applied Physics & Oeschger Center for Climate Change Research, Microwave Physics, University of Bern, Switzerland
- 2Institute for Meteorology, Universität Leipzig, Leipzig, Germany
- 3Institute for Solar-Terrestrial Physics, German Aerospace Center (DLR), Neustrelitz, Germany
- 4Department of Earth and Planetary Science, Kyushu University, Japan
- 5High Altitude Observatory, National Center for Atmospheric Research, Boulder, CO, USA
- 6Max Planck Institute for Meteorology, Hamburg, Germany
- 7Fraunhofer Institute for Computer Graphics Research IGD, Rostock, Germany
- 8Dept. of Physics and Astronomy, University of Western Ontario, London, Ontario, Canada N6A 3K7
- 9Western Institute for Earth and Space Exploration, University of Western Ontario, London, Ontario, N6A 5B7, Canada
- 10ITM Physics Laboratory, Mail Code 675, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
- 11Australian Antarctic Division, Kingston, Tasmania, Australia
- 12Sodankyla Geophysical Observatory, University of Oulu, Finland
- 13University of Leicester, Leicester, UK
- 14Swedish Institute of Space Physics, Kiruna, Sweden
- 1Institute of Applied Physics & Oeschger Center for Climate Change Research, Microwave Physics, University of Bern, Switzerland
- 2Institute for Meteorology, Universität Leipzig, Leipzig, Germany
- 3Institute for Solar-Terrestrial Physics, German Aerospace Center (DLR), Neustrelitz, Germany
- 4Department of Earth and Planetary Science, Kyushu University, Japan
- 5High Altitude Observatory, National Center for Atmospheric Research, Boulder, CO, USA
- 6Max Planck Institute for Meteorology, Hamburg, Germany
- 7Fraunhofer Institute for Computer Graphics Research IGD, Rostock, Germany
- 8Dept. of Physics and Astronomy, University of Western Ontario, London, Ontario, Canada N6A 3K7
- 9Western Institute for Earth and Space Exploration, University of Western Ontario, London, Ontario, N6A 5B7, Canada
- 10ITM Physics Laboratory, Mail Code 675, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
- 11Australian Antarctic Division, Kingston, Tasmania, Australia
- 12Sodankyla Geophysical Observatory, University of Oulu, Finland
- 13University of Leicester, Leicester, UK
- 14Swedish Institute of Space Physics, Kiruna, Sweden
Abstract. Long-term and continuous observations of mesospheric/lower thermospheric winds are rare, but they are important to investigate climatological changes at these altitudes on time scales of several years, covering a solar cycle and longer. Such long time series are a natural heritage of the mesosphere/lower thermosphere climate, and they are valuable to compare climate models or long term runs of general circulation models (GCMs). Here we present a climatological comparison of wind observations from six meteor radars at two conjugate latitudes to validate the corresponding mean winds and atmospheric diurnal and semidiurnal tides from three GCMs, namely Ground-to-Topside Model of Atmosphere and Ionosphere for Aeronomy (GAIA), Whole Atmosphere Community Climate Model Extension (Specified Dynamics) (WACCM-X(SD)) and Upper Atmosphere ICOsahedral Non-hydrostatic (UA-ICON) model. Our results indicate that there are interhemispheric differences in the seasonal characteristics of the diurnal and semidiurnal tide. There also are some differences in the mean wind climatologies of the models and the observations. Our results indicate that GAIA shows a reasonable agreement with the meteor radar observations during the winter season, whereas WACCM-X(SD) shows a better agreement with the radars for the hemispheric zonal summer wind reversal, which is more consistent with the meteor radar observations. The free running UA-ICON tends to show similar winds and tides compared to WACCM-X(SD).
Gunter Stober et al.
Status: open (until 13 May 2021)
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RC1: 'Comment on acp-2021-142', Anonymous Referee #1, 19 Apr 2021
reply
This study compares model simulations with metero radar (MR) observations. it presents the first systematic investigation of interhemispheric differences of mean winds and atmospheric tides at conjugate latitudes from observations and comprehensive models applying a unified diagnostic. It is a much needed study. While I appreciate the heroic effort of the authors, I am troubled by the lack of similarity between the model simulations described here and the MR observations. Previous studies - as properly discussed in this manuscript - revealed a much closer match between MR data and NAVGEM-HA. I am troubled by how badly the models are doing here.
The authors discuss the different behavior of the gravity wave drag parameterization in these models, arguing that the mean circulation is different to partialy explain the differences, i believe. I don't disagree in general, however such discrepancies seems to point to a fundamental flaw in these models: the lack of observations at MLT altitudes. Isn't that the take-home-message of this study?
Moreover, some of the models use atmospheric specifications (like MERRA): what is the time cadence of these atmospheric specifications? Typically these data are provided 6-hourly, which would not resolve semdiurnal variability, and in such case the comparison is between observations and the model's own climatology. In the same spirit, what it the nudging time scale? A long time scale would prevent the model to be tightly associated with the atmospheric analysis.
Specific comments:
Page 3, bottom: Why McCormack et al. (2015). That's a QBO paper. I think you want to use McCormack et al. (2017) as in the rest of the manuscript.
Figure 3 and similar figures. The authors really need to add contours: the color palette has a very large dynamic range and for the reader it is impossible to discern contours, especially when the largerst values are at the edges of the panels and the vast majority of the figure is a bland uniform color. Also, I think would it help explaining the figures (and for us the readers, understanding it) if one hemisphere (say the SH) is rotate by 6 months, so that the same season is always in the middle.
Page 10, middle. Why is it expected that conjugate latitudes see almost the same behavior?
Gunter Stober et al.
Gunter Stober et al.
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