Comparative study between ground-based observations and NAVGEM-HA reanalysis data in the MLT region

Abstract

<p><strong>Abstract.</strong> Atmospheric waves are a key driving mechanism for the circulation in the Earth's atmosphere. Such waves covervarious spatial and temporal scales, e.g., planetary waves with periods of several days, atmospheric tides with periods of aninteger fraction of a day and gravity waves with periods ranging from minutes to several hours. In particular, atmospheric tidesgain large amplitudes at the Mesosphere/lower Thermosphere (MLT) region. Recently the day-to-day tidal variability as driverof the thermosphere-ionosphere system become an emerging topic. Here we study the intermittent behavior of atmospheric tides by using meteor radars at altitudes of 75–110 km accompanied with lidar measurements. The observations are comparedto meteorological analyses from NAVGEM-HA to infer how well the tidal variability on a daily to a seasonal basis is capturedin the model. Therefore, a new diagnostic approach, a so-called adaptive spectral filter, is used to decompose the time seriesinto a mean wind (zonal and meridional component) and temperature containing the planetary wave activity, atmospheric tides(diurnal, semi-diurnal and terdiurnal) as well as the gravity wave activity. By combining the local data with global reanalysis fields, we extract the relative contribution of the migrating and non-migrating tides for the available data using a global versionof the adaptive spectral filter. Our results indicate that the SW2 tide, which is the dominant mode at mid- and high latitudes at theMLT, shows a large seasonal variability in amplitude and phase. The comparison of NAVGEM-HA results and the meteor radarobservations demonstrate that the reanalysis data reproduce rather consistent the mean seasonal behavior as well as the day-to-day variability. This is especially obvious during sudden stratospheric warmings, where the SW2 tide shows a significant phase shift and amplitude modulation. These findings show the benefit of combining global high altitude data assimilation productswith ground-based observations of the MLT region to better understand the tidal variability in the atmosphere.</p>

Migrating tide climatologies measured by a high-latitude array of SuperDARN HF-radars

“…For comparison with ground-based instruments, vertical profiles of NAVGEM-HA analyzed winds and temperatures are converted from the model vertical grid in geopotential altitude to a geometric altitude grid. To date, NAVGEM-HA winds and tides have been shown to be in good agreement with ground-based meteor radar observations (McCormack et al, 2017;Eckermann et al, 2018;Laskar et al, 2019;Stober et al, 2019) and with independent satellite-based wind observations as reported in Dhadly et al (2018). In the present study we employ NAVGEM-HA analyzed winds at 82.5 km altitude, staying below altitudes where sponge layer effects may impact the tides, to validate the method of extracting migrating tidal signatures from the SD meteor wind data.…”

Coupling From the Middle Atmosphere to the Exobase: Dynamical Disturbance Effects on Light Chemical Species

“…Therefore, we cannot completely rule out aliasing from the lunar semidiurnal tide into modeled SW2 amplitudes and phases that were calculated using a Fourier decomposition of hourly TIME-GCM output. However, we suspect that the contribution from aliasing by the lunar semidiurnal tide into our calculated SW2 amplitudes and phases to be fairly small (see Stober et al, 2019). Nonetheless, we can assess to what extent the predominant semidiurnal wave forcing or SW2, differs between the three cases we have simulated (2012-2013 with and without GW and 2013-2014).…”

“…Data from the Sodankylä meteor radar (SGO) used herein are available at https://www.sgo.fi/pub/JGR_SSW_2013https://www.sgo.fi/pub(cd to JGR_SSW_2013/HWD_201301 or JGR_SSW_2013/HWD_201401). Access to data from the CMOR and Collm meteor radars is discussed in Stober et al (2019). SABER atomic hydrogen data are available at http://saber.gats-inc.com/data.php then by clicking on the ftp://saber.gats-inc.com/Version2_0/Level2A/ link.…”

Interhemispheric differences of mesosphere/lower thermosphere winds and tides investigated from three whole atmosphere models and meteor radar observations

“…A detailed summary of each system can be found in Table 2.1. The systems are well-known and have proven to provide reliable and continuous measurements for cross-validation (McCormack et al, 2017;Stober et al, 2019) or long-term change studies (Iimura et al, 2011;Jacobi et al, 2015;Wilhelm et al, 2019;Pancheva et al, 2020). In Figure 2.1, we present an overview of where each system is located.…”

“…We applied a harmonized data processing to generate homogeneous wind time series for all sites. The wind retrieval is described in more detail in (Stober et al, 2018) and was validated against meteorological analysis NAVGEM-HA (Navy Global Environment Model -High Altitude) (McCormack et al, 2015;Stober et al, 2019). NAVGEM-HA meteorological analysis utilizes a sophisticated 4DVAR data assimilation scheme, which assimilates observations including mesospheric data from MLS and SABER (Kuhl et al, 2013;McCormack et al, 2015;Eckermann et al, 2018).…”