scholarly journals Interhemispheric comparison of mesosphere/lower thermosphere winds from GAIA, WACCM-X and ICON-UA simulations and meteor radar observations at mid- and polar latitudes

2021 ◽  
Author(s):  
Gunter Stober ◽  
Ales Kuchar ◽  
Dimitry Pokhotelov ◽  
Huixin Liu ◽  
Hanli Liu ◽  
...  
Keyword(s):  
Climate Model ◽  
Middle Atmosphere ◽  
Spatial Scales ◽  
Lower Thermosphere ◽  
Winter Season ◽  
Meteor Radar ◽  
Radar Observations ◽  
Meridional Winds ◽  
Free Running ◽  
Seasonal Characteristic

<p>There is a growing scientific interest to investigate the forcing from the middle atmosphere dynamics on the thermosphere and ionosphere. This forcing is driven by atmospheric waves at various temporal and spatial scales. In this study, we cross-compare the nudged models Ground-to-topside model of Atmosphere and Ionosphere for Aeronomy (GAIA) and Whole Atmosphere Community Climate Model Extended</p><p>Version (Specified dynamics) ( WACCM-X(SD)), a free-running version of Upper Atmosphere ICOsahedral Non-hydrostatic (ICON-UA) with six meteor radars located at conjugate polar and mid-latitudes. Mean winds, diurnal and semidiurnal tidal amplitudes and phases were obtained from the radar observations at the mesosphere and lower thermosphere (MLT) and compared to the GAIA, WACCM-X(SD), and ICON-UA data for similar locations applying a harmonized diagnostic.</p><p>Our results indicate that GAIA zonal and meridional winds show a good agreement to the meteor radars during the winter season on both hemispheres, whereas WACCM-X(SD) and ICON-UA seem to reproduce better the summer zonal wind reversal. However, the mean winds also exhibit some deviation in the seasonal characteristic concerning the meteor radar measurements, which are attributed to the gravity wave parameterizations implemented in the models. All three models tend to reflect the seasonality of diurnal tidal amplitudes, but show some dissimilarities in tidal phases. We also found systematic interhemispheric differences in the seasonal characteristic of semidiurnal amplitudes and phases. The free-running ICON-UA apparently shows most of these interhemispheric differences, whereas WACCM-X(SD) and GAIA trend to have better agreement of the semidiurnal tidal variability in the northern hemisphere.</p>

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

2021 ◽  
Author(s):  
Gunter Stober ◽  
Ales Kuchar ◽  
Dimitry Pokhotelov ◽  
Huixin Liu ◽  
Han-Li Liu ◽  
...  
Keyword(s):  
General Circulation ◽  
Climate Models ◽  
Climate Model ◽  
Lower Thermosphere ◽  
Winter Season ◽  
General Circulation Models ◽  
Meteor Radar ◽  
Radar Observations ◽  
Seasonal Characteristics

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).

scholarly journals Interhemispheric differences of mesosphere–lower thermosphere winds and tides investigated from three whole-atmosphere models and meteor radar observations

2021 ◽  
Vol 21 (18) ◽  
pp. 13855-13902
Author(s):  
Gunter Stober ◽  
Ales Kuchar ◽  
Dimitry Pokhotelov ◽  
Huixin Liu ◽  
Han-Li Liu ◽  
...  
Keyword(s):  
General Circulation ◽  
Climate Models ◽  
Climate Model ◽  
Lower Thermosphere ◽  
Winter Season ◽  
General Circulation Models ◽  
Meteor Radar ◽  
Radar Observations ◽  
Seasonal Characteristics

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 timescales 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 the Ground-to-Topside Model of Atmosphere and Ionosphere for Aeronomy (GAIA), the Whole Atmosphere Community Climate Model Extension (Specified Dynamics) (WACCM-X(SD)), and the 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 are also some differences in the mean wind climatologies of the models and the observations. Our results indicate that GAIA shows reasonable agreement with the meteor radar observations during the winter season, whereas WACCM-X(SD) shows 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).

scholarly journals MF radar observations of mean winds and tides over Poker Flat, Alaska (65.1° N, 147.5° W)

2002 ◽  
Vol 20 (5) ◽  
pp. 679-690 ◽  
Author(s):  
P. Kishore ◽  
S. P. Namboothiri ◽  
K. Igarashi ◽  
Y. Murayama ◽  
B. J. Watkins
Keyword(s):  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Winter Season ◽  
Wave Model ◽  
Global Scale ◽  
Meridional Winds ◽  
Wind Measurements ◽  
The Mean ◽  
Tidal Characteristics ◽  
Mf Radar

Abstract. MF radar wind measurements in the mesosphere and lower thermosphere over Poker Flat, Alaska (65.1° N, 147.5° W) are used to study the features of mean winds and solar tides. Continuous observation with the newly installed radar is in progress and in the present study we have analyzed a database of the first 27 months (October 1998–December 2000) of observation. The observed mean wind climatology has been compared with previous measurements and the latest empirical model values (HWM93 model). Similarly, the tidal characteristics are described and compared with the Global Scale Wave Model (GSWM00). The mean wind characteristics observed are fairly consistent with previous wind measurements by the Poker Flat MST radar. The main feature of the zonal circulation is the annual variation with summer westward flow and winter eastward flow. The annual mean zonal wind has a west-ward motion at altitudes below 90 km. The annual mean meridional circulation has mainly southward motion at 70–100 km. There is very good agreement between the radar zonal winds and the HWM93 model winds. Comparison of the meridional winds shows some discrepancy. Analysis of two years of data indicated that the year-to-year consistency is preserved in the mean circulation in the mesosphere. Tidal characteristics observed are also consistent with previous measurements. Semidiurnal tides have the largest amplitudes in summer while the weakest amplitude is observed during the winter months. The vertical wavelength is longer during the summer season compared to the winter season. Comparison with the GSWM00 produces mixed results. There is reasonable agreement between the observed and modeled phases. Diurnal tide amplitudes are comparable in magnitude with that of the semidiurnal tide. Seasonal variation is less evident in the amplitudes. Comparison of the observed tidal parameters with the GSWM00 reveals some agreement and discrepancies.Key words. Meteorology and atmospheric dynamics (climatology; middle atmosphere dynamics; waves and tides)

scholarly journals The diurnal and semidiurnal tides over Ascension Island (8° S, 14° W) and their interaction with the stratospheric QBO: studies with meteor radar, eCMAM and WACCM

2013 ◽  
Vol 13 (2) ◽  
pp. 4785-4837 ◽  
Author(s):  
R. N. Davis ◽  
J. Du ◽  
A. K. Smith ◽  
W. E. Ward ◽  
N. J. Mitchell
Keyword(s):  
Seasonal Variation ◽  
Climate Model ◽  
Middle Atmosphere ◽  
Atmospheric Tides ◽  
Meteor Radar ◽  
Vertical Wavelength ◽  
Atlantic Region ◽  
Meridional Component ◽  
Ascension Island ◽  
Good For

Abstract. Horizontal winds in the mesosphere have been measured over Ascension Island (8° S, 14° W) in the tropical mid-Atlantic region throughout the years 2002–2011. The observations were made by a VHF meteor radar. The results reveal the presence of atmospheric tides of large amplitude. The results are analysed to characterise the seasonal and interannual variability of the diurnal and semidiurnal tides. Monthly-mean diurnal tidal amplitudes are found to reach values as large as 48 m s−1 in the meridional component and 41 m s−1 in the zonal. A semiannual seasonal variation is found in diurnal-tidal amplitudes with amplitude maxima at the equinoxes and amplitude minima at the solstices. Diurnal tidal meridional vertical wavelengths are generally in the range 24–30 km. The diurnal zonal vertical wavelengths are similar to the meridional, except for the winter months when the zonal vertical wavelengths are much longer, occasionally exceeding 100 km. Semidiurnal amplitudes are observed to be significantly smaller than diurnal amplitudes. Semidiurnal vertical wavelengths range from 20 to more than 100 km. Our observations of tidal amplitudes and phases are compared with the predictions of the extended Canadian Middle Atmosphere Model (eCMAM) and the Whole Atmosphere Community Climate Model (WACCM). Both eCMAM and WACCM reproduce the trend for greater diurnal amplitudes in the meridional component than the zonal. However, in winter eCMAM tends to over-estimate meridional amplitudes, while WACCM under-estimates zonal and meridional amplitudes. Semidiurnal amplitude predictions are generally good for both models. Vertical wavelength predictions are also generally good for both models, however eCMAM predicts shorter zonal vertical wavelengths than observed for the diurnal tide in winter, while WACCM predicts longer zonal semidiurnal vertical wavelengths than observed for most months. It is found that larger-than-average diurnal and semidiurnal tidal amplitudes occur when the stratospheric QBO at 10 hPa is eastwards, and smaller-than-average amplitudes occur when it is westwards. However, the precise mechanism for this modulation of tidal amplitudes by the stratospheric QBO remains unclear.

scholarly journals Meteor radar observations of mesopause region long-period temperature oscillations

2016 ◽  
Vol 14 ◽  
pp. 169-174
Author(s):  
Ch. Jacobi ◽  
N. Samtleben ◽  
G. Stober
Keyword(s):  
Time Scales ◽  
Lower Thermosphere ◽  
Planetary Waves ◽  
Meteor Radar ◽  
Mesopause Region ◽  
Radar Observations ◽  
Long Period ◽  
Temperature Oscillations ◽  
Wind Measurements

Abstract. Meteor radar observations of mesosphere/lower thermosphere (MLT) daily temperatures have been performed at Collm, Germany since August 2004. The data have been analyzed with respect to long-period oscillations at time scales of 2–30 days. The results reveal that oscillations with periods of up to 6 days are more frequently observed during summer, while those with longer periods have larger amplitudes during winter. The oscillations may be considered as the signature of planetary waves. The results are compared with analyses from radar wind measurements. Moreover, the temperature oscillations show considerable year-to-year variability. In particular, amplitudes of the quasi 5-day oscillation have increased during the last decade, and the quasi 10-day oscillations are larger if the equatorial stratospheric winds are eastward.

Resolving spatial dynamics at polar latitudes using the GROMOS-C radiometer on Svalbard and the Nordic meteor radar cluster

2020 ◽  
Author(s):  
Gunter Stober ◽  
Franziska Schranz ◽  
Chris Hall ◽  
Alexander Kozlovsky ◽  
Mark Lester ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Temporal Resolution ◽  
Lower Thermosphere ◽  
Winter Season ◽  
Spatial Characteristic ◽  
Small Scale ◽  
Meteor Radar ◽  
Atmospheric Waves ◽  
Spatio Temporal ◽  
Remote Sensing Techniques

<p>The middle polar atmosphere dynamics is driven by atmospheric waves from the planetary scale to small scale perturbation due to gravity waves. The different atmospheric waves are characterized by their temporal and spatial variability posing challenges to ground-based remote sensing techniques to disentangle and resolve the spatio-temporal ambiguity. Here we present two ground-based remote sensing techniques to resolving spatio-temporal variability at the polar middle atmosphere.</p><p>Since 2017 the GROMOS-C radiometer measures ozone and winds at NyÅlesund (78.9°N, 11.9°E) on Svalbard. The radiometer employs four beams in the cardinal directions at 22.5° elevation angle to retrieve ozone profiles and winds at altitudes between 30-75 km. the temporal resolution of the ozone retrievals is 30 minutes. Further, we obtain daily mean winds. Due to the high polar latitude the spatial separation between the beams at stratospheric altitudes covers several degrees in longitude to infer spatial gradients in the ozone densities and their perturbation due to planetary waves.</p><p>Another recently established ground-based remote sensing approach to retrieve the spatial characteristic at the mesosphere and lower thermosphere (MLT) is provided by the Nordic meteor radar cluster consisting of the meteor radars at Tromsø, Alta, Esrange, Sodankylä and on Svalbard. Since October 2019 horizontally resolved winds are obtained using a 3DVAR approach with a temporal resolution of 30 minutes and a vertical resolution of 2 km. Here we present preliminary results to infer horizontal wavelength spectra, the tidal variability as well as gravity activity of the winter season 2019/20.</p><p>Both datasets are of high value for data assimilation into weather forecast and reanalysis models or for cross-comparisons and validation of meteorological analysis systems (e.g. NAVGEM-HA).</p>

scholarly journals Mean winds in the MLT, the SQBO and MSAO over Ascension Island (8° S, 14° W)

2013 ◽  
Vol 13 (18) ◽  
pp. 9515-9523 ◽  
Author(s):  
K. A. Day ◽  
N. J. Mitchell
Keyword(s):  
Gravity Waves ◽  
Lower Thermosphere ◽  
Strong Support ◽  
Phase Relationship ◽  
Second Phase ◽  
Meteor Radar ◽  
Quasi Biennial Oscillation ◽  
Zonal Winds ◽  
Ascension Island ◽  
Meridional Winds

Abstract. Mean winds in the mesosphere and lower thermosphere (MLT) over Ascension Island (8° S, 14° W) have been measured at heights of approximately 80–100 km by a meteor radar. The results presented in this study are from the interval October 2001 to December 2011. In all years, the monthly-mean meridional winds display a clear annual oscillation. Typically, these winds are found to be southward during April–October, when they reach velocities of up to about −23 m s−1, and northward throughout the rest of the year, when they reach velocities up to about 16 m s−1. The monthly-mean zonal winds are generally westward throughout most of the year and reach velocities of up to about −46 m s−1. However, eastward winds are observed in May–August and again in December at the lower heights observed. These eastward winds reach a maximum at heights of about 86 km with velocities of up to about 36 m s−1, but decay quickly at heights above and below that level. The mesospheric semi-annual oscillation (MSAO) is clearly apparent in the observed monthly-mean zonal winds. The winds in first westward phase of the MSAO are observed to be much stronger than in the second phase. The westward phase of the MSAO is found to maximise at heights of about 84 km with typical first-phase wind velocities reaching about −35 m s−1. These meteor-radar observations have been compared to the HWM-07 empirical model. The observed meridional winds are found to be generally more southward than those of the model during May–August, when at the lower heights observed the model suggests there will be only weakly southward, or even northward, winds. The zonal monthly-mean winds are in generally good agreement, although in the model they are somewhat less westward than those observed. Throughout the observations there were eight occasions in which the first westward phase of the MSAO was observed. Strikingly, in 2002 there was an event in which the westward winds during the first phase of the MSAO were much stronger than normal and reached velocities of about −75 m s−1. This event is explained in terms of a previously proposed mechanism in which the relative phasing of the stratospheric quasi-biennial oscillation (SQBO) and the MSAO allows an unusually large flux of gravity waves of large westward phase speed to reach the mesosphere. It is the dissipation of these gravity waves that then drives the MLT winds to the large westward velocities observed. It is demonstrated that the necessary SQBO–MSAO phase relationship did indeed exist during 2002, but not during the other years observed here. This demonstration provides strong support for the suggestion that extreme zonal-wind events during the MSAO result from the modulation of gravity-wave fluxes.

scholarly journals Global empirical wind model for the upper mesosphere/lower thermosphere. I. Prevailing wind

2000 ◽  
Vol 18 (3) ◽  
pp. 300-315 ◽  
Author(s):  
Y. I. Portnyagin ◽  
T. V. Solovjova
Keyword(s):  
General Circulation ◽  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Systematic Bias ◽  
Prevailing Wind ◽  
Wind Model ◽  
Zonal Winds ◽  
Meridional Winds ◽  
Contour Plots ◽  
Thermospheric Dynamics

Abstract. An updated empirical climatic zonally averaged prevailing wind model for the upper mesosphere/lower thermosphere (70-110 km), extending from 80°N to 80°S is presented. The model is constructed from the fitting of monthly mean winds from meteor radar and MF radar measurements at more than 40 stations, well distributed over the globe. The height-latitude contour plots of monthly mean zonal and meridional winds for all months of the year, and of annual mean wind, amplitudes and phases of annual and semiannual harmonics of wind variations are analyzed to reveal the main features of the seasonal variation of the global wind structures in the Northern and Southern Hemispheres. Some results of comparison between the ground-based wind models and the space-based models are presented. It is shown that, with the exception of annual mean systematic bias between the zonal winds provided by the ground-based and space-based models, a good agreement between the models is observed. The possible origin of this bias is discussed.Key words: Meteorology and Atmospheric dynamics (general circulation; middle atmosphere dynamics; thermospheric dynamics)

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