scholarly journals The 16-day planetary waves: multi-MF radar observations from the arctic to equator and comparisons with the HRDI measurements and the GSWM modelling results

2002 ◽  
Vol 20 (5) ◽  
pp. 691-709 ◽  
Author(s):  
Y. Luo ◽  
A. H. Manson ◽  
C. E. Meek ◽  
C. K. Meyer ◽  
M. D. Burrage ◽  
...  
Keyword(s):  
Middle Atmosphere ◽  
Wave Model ◽  
Global Scale ◽  
The Arctic ◽  
Planetary Scale ◽  
Christmas Island ◽  
Wind Measurements ◽  
Strong Amplitude ◽  
Waves And Tides ◽  
Thermospheric Dynamics

Abstract. The mesospheric and lower thermospheric (MLT) winds (60–100 km) obtained by multiple MF radars, located from the arctic to equator at Tromsø (70° N, 19° E), Saskatoon (52° N, 107° W), London (43° N, 81° W), Hawaii (21° N, 157° W) and Christmas Island (2° N, 157° W), respectively, are used to study the planetary-scale 16-day waves. Based on the simultaneous observations (1993/1994), the variabilities of the wave amplitudes, periods and phases are derived. At mid- and high-latitude locations the 16-day waves are usually pervasive in the winter-centred seasons (October through March), with the amplitude gradually decreasing with height. From the subtropical location to the equator, the summer wave activities become strong at some particular altitude where the inter-hemisphere wave ducts possibly allow for the leakage of the wave from the other hemispheric winter. The observational results are in good agreement with the theoretical conclusion that, for slowly westward-traveling waves, such as the 16-day wave, vertical propagation is permitted only in an eastward background flow of moderate speed which is present in the winter hemisphere. The wave period also varies with height and time in a range of about 12–24 days. The wave latitudinal differences and the vertical structures are compared with the Global Scale Wave Model (GSWM) for the winter situation. Although their amplitude variations and profiles have a similar tendency, the discrepancies are considerable. For example, the maximum zonal amplitude occurs around 40° N for radar but 30° N for the model. The phase differences between sites due to the latitudinal effect are basically consistent with the model prediction of equatorward phase-propagation. The global 16-day waves at 95 km from the HRDI wind measurements during 1992 through 1995 are also displayed. Again, the wave is a winter dominant phenomenon with strong amplitude around the 40–60° latitude-band on both hemispheres.Key words. Meteorology and atmospheric dynamics – waves and tides – middle atmosphere dynamics – thermospheric dynamics

scholarly journals The summertime 12-h wind oscillation with zonal wavenumber <i>s</i> = 1 in the lower thermosphere over the South Pole

1998 ◽  
Vol 16 (7) ◽  
pp. 828-837 ◽  
Author(s):  
Y. I. Portnyagin ◽  
J. M. Forbes ◽  
N. A. Makarov ◽  
E. G. Merzlyakov ◽  
S. Palo
Keyword(s):  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Thermal Excitation ◽  
South Pole ◽  
Planetary Scale ◽  
Zonal Wavenumber ◽  
Wind Measurements ◽  
Waves And Tides ◽  
Thermospheric Dynamics

Abstract. Meteor radar measurements of winds near 95 km in four azimuth directions from the geographic South Pole are analyzed to reveal characteristics of the 12-h oscillation with zonal wavenumber one (s=1). The wind measurements are confined to the periods from 19 January 1995 through 26 January 1996 and from 21 November 1996 through 27 January 1997. The 12-h s=1 oscillation is found to be a predominantly summertime phenomenon, and is replaced in winter by a spectrum of oscillations with periods between 6 and 11.5 h. Both summers are characterized by minimum amplitudes (5–10 ms–1) during early January and maxima (15–20 ms–1) in November and late January. For 10-day means of the 12-h oscillation, smooth evolutions of phase of order 4–6 h occur during the course of the summer. In addition, there is considerable day-to-day variability (±5–10 ms–1 in amplitude) with distinct periods (i.e., ~5 days and ~8 days) which suggests modulation by planetary-scale disturbances. A comparison of climatological data from Scott Base, Molodezhnaya, and Mawson stations suggests that the 12-h oscillation near 78°S is s=1, but that at 68°S there is probably a mixture between s=1 and other zonal wavenumber oscillations (most probably s=2). The mechanism responsible for the existence of the 12-h s=1 oscillation has not yet been identified. Possible origins discussed herein include in situ excitation, nonlinear interaction between the migrating semidiurnal tide and a stationary s=1 feature, and thermal excitation in the troposphere.Key words. Meteorology and atmospheric dynamics · Middle atmosphere dynamics · Thermospheric dynamics · Waves and tides

scholarly journals Seasonal variations of the semi-diurnal and diurnal tides in the MLT: multi-year MF radar observations from 2–70° N, modelled tides (GSWM, CMAM)

2002 ◽  
Vol 20 (5) ◽  
pp. 661-677 ◽  
Author(s):  
A. H. Manson ◽  
C. Meek ◽  
M. Hagan ◽  
J. Koshyk ◽  
S. Franke ◽  
...  
Keyword(s):  
General Circulation ◽  
Middle Atmosphere ◽  
Circulation Model ◽  
Wave Model ◽  
Global Scale ◽  
Diurnal Tide ◽  
Data Set ◽  
Height Range ◽  
Christmas Island ◽  
Tidal Data

Abstract. In an earlier paper (Manson et al., 1999a) tidal data (1990–1997) from six Medium Frequency Radars (MFR) were compared with the Global Scale Wave Model (GSWM, original 1995 version). The radars are located between the equator and high northern latitudes: Christmas Island (2° N), Hawaii (22° N), Urbana (40° N), London (43° N), Saskatoon (52° N) and Tromsø (70° N). Common harmonic analysis was applied, to ensure consistency of amplitudes and phases in the 75–95 km height range. For the diurnal tide, seasonal agreements between observations and model were excellent while for the semi-diurnal tide the seasonal transitions between clear solstitial states were less well captured by the model. Here the data set is increased by the addition of two locations in the Pacific-North American sector: Yamagawa 31° N, and Wakkanai 45° N. The GSWM model has undergone two additional developments (1998, 2000) to include an improved gravity wave (GW) stress parameterization, background winds from UARS systems and monthly tidal forcing for better characterization of seasonal change. The other model, the Canadian Middle Atmosphere Model (CMAM) which is a General Circulation Model, provides internally generated forcing (due to ozone and water vapour) for the tides. The two GSWM versions show distinct differences, with the 2000 version being either closer to, or further away from, the observations than the original 1995 version. CMAM provides results dependent upon the GW parameterization scheme inserted, but one of the schemes provides very useful tides, especially for the semi-diurnal component.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; waves and tides)

scholarly journals Diurnal and semidiurnal tide in the upper middle atmosphere during the first year of simultaneous MF radar observations in northern and southern Japan (45°N and 31°N)

1999 ◽  
Vol 17 (3) ◽  
pp. 405-414 ◽  
Author(s):  
K. Hocke ◽  
K. Igarashi
Keyword(s):  
Middle Atmosphere ◽  
Wave Model ◽  
Global Scale ◽  
Diurnal Tide ◽  
First Year ◽  
Semidiurnal Tide ◽  
Tidal Amplitude ◽  
Latitudinal Dependence ◽  
Waves And Tides ◽  
Mf Radar

Abstract. The climatology of mean wind, diurnal and semidiurnal tide during the first year (1996-1997) of simultaneous wind observations at Wakkanai (45.4°N, 141.7°E) and Yamagawa (31.2°N, 130.6°E) is presented. The locations of the radars allow us to describe the latitudinal dependence of the tides. Tidal amplitude and phase profiles are compared with those of the global scale wave model (GSWM). While the observed amplitude profiles of the diurnal tide agree well with the GSWM values, the observed phase profiles often indicate longer vertical wavelengths than the GSWM phase profiles. In contrast to the GSWM simulation, the observations show a strong bimodal structure of the diurnal tide, with the phase advancing about 6 hours from summer to winter.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; waves and tides)

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 Latitudinal wave coupling of the stratosphere and mesosphere during the major stratospheric warming in 2003/2004

2008 ◽  
Vol 26 (3) ◽  
pp. 467-483 ◽  
Author(s):  
D. Pancheva ◽  
P. Mukhtarov ◽  
N. J. Mitchell ◽  
B. Andonov ◽  
E. Merzlyakov ◽  
...  
Keyword(s):  
Inverse Relationship ◽  
Indirect Evidence ◽  
Global Scale ◽  
The Arctic ◽  
Neutral Wind ◽  
Stratospheric Warming ◽  
Low Latitude ◽  
Dynamical Regimes ◽  
Wind Measurements ◽  
Dynamical Coupling

Abstract. The coupling of the dynamical regimes in the high- and low-latitude stratosphere and mesosphere during the major SSW in the Arctic winter of 2003/2004 has been studied. The UKMO zonal wind data were used to explore the latitudinal coupling in the stratosphere, while the coupling in the mesosphere was investigated by neutral wind measurements from eleven radars situated at high, high-middle and tropical latitudes. It was found that the inverse relationship between the variability of the zonal mean flows at high- and low-latitude stratosphere related to the SSW is produced by global-scale zonally symmetric waves. Their origin and other main features have been investigated in detail. Similar latitudinal dynamical coupling has been found for the mesosphere as well. Indirect evidence for the presence of zonally symmetric waves in the mesosphere has been found.

scholarly journals Combined wind measurements by two different lidar instruments in the Arctic middle atmosphere

2012 ◽  
Vol 5 (3) ◽  
pp. 4123-4156 ◽  
Author(s):  
J. Hildebrand ◽  
G. Baumgarten ◽  
J. Fiedler ◽  
U.-P. Hoppe ◽  
B. Kaifler ◽  
...  
Keyword(s):  
Middle Atmosphere ◽  
The Arctic ◽  
Horizontal Wind ◽  
Small Scale ◽  
Wind Component ◽  
Lower Altitude ◽  
Wind Speeds ◽  
Lidar Measurements ◽  
Wind Measurements ◽  
Good Agreement

Abstract. During a joint campaign in January 2009 the Rayleigh/Mie/Raman (RMR) lidar and the sodium lidar at the ALOMAR Observatory (69° N, 16° E) in Northern Norway were operated simultaneously for more than 40 h, collecting data for wind measurements in the middle atmosphere from 30 up to 110 km altitude. At the upper (lower) altitude range where the RMR (sodium) lidar can operate, both lidars probe the same sounding volume, allowing to compare the derived wind speeds. We present the first simultaneous common volume wind measurements in the middle atmosphere using two different lidar instruments. The comparison of winds derived by RMR and sodium lidar is excellent for long integration times of 10 h as well as shorter ones of 1 h. Combination of data from both lidars allows identifying wavy structures between 30 and 110 km altitude, whose amplitudes increase with height. We have also performed lidar measurements of the same wind component using two independent branches of the RMR lidar and found a good agreement of the results but also identified inhomogeneities in the horizontal wind at about 55 km altitude of up to 20 ms−1. Such small scale inhomogeneities in the horizontal wind field are an essential challenge when comparing data from different instruments.

scholarly journals Zonal-Mean Dynamics of Extended Recoveries from Stratospheric Sudden Warmings

2013 ◽  
Vol 70 (2) ◽  
pp. 688-707 ◽  
Author(s):  
Peter Hitchcock ◽  
Theodore G. Shepherd
Keyword(s):  
Middle Atmosphere ◽  
Polar Vortex ◽  
The Arctic ◽  
Quasi Biennial Oscillation ◽  
Planetary Scale ◽  
Stratospheric Sudden Warmings ◽  
Quasigeostrophic Model ◽  
Mean Circulation ◽  
Jet Oscillation ◽  
Biennial Oscillation

Abstract The recovery of the Arctic polar vortex following stratospheric sudden warmings is found to take upward of 3 months in a particular subset of cases, termed here polar-night jet oscillation (PJO) events. The anomalous zonal-mean circulation above the pole during this recovery is characterized by a persistently warm lower stratosphere, and above this a cold midstratosphere and anomalously high stratopause, which descends as the event unfolds. Composites of these events in the Canadian Middle Atmosphere Model show the persistence of the lower-stratospheric anomaly is a result of strongly suppressed wave driving and weak radiative cooling at these heights. The upper-stratospheric and lower-mesospheric anomalies are driven immediately following the warming by anomalous planetary-scale eddies, following which, anomalous parameterized nonorographic and orographic gravity waves play an important role. These details are found to be robust for PJO events (as opposed to sudden warmings in general) in that many details of individual PJO events match the composite mean. A zonal-mean quasigeostrophic model on the sphere is shown to reproduce the response to the thermal and mechanical forcings produced during a PJO event. The former is well approximated by Newtonian cooling. The response can thus be considered as a transient approach to the steady-state, downward control limit. In this context, the time scale of the lower-stratospheric anomaly is determined by the transient, radiative response to the extended absence of wave driving. The extent to which the dynamics of the wave-driven descent of the stratopause can be considered analogous to the descending phases of the quasi-biennial oscillation (QBO) is also discussed.

scholarly journals Planetary wave activity in the lower ionosphere during CRISTA I campaign in autumn 1994 (October−November)

1998 ◽  
Vol 16 (8) ◽  
pp. 1014-1023 ◽  
Author(s):  
D. Pancheva ◽  
J. Laštovička
Keyword(s):  
Planetary Wave ◽  
Middle Atmosphere ◽  
Lower Ionosphere ◽  
Wave Activity ◽  
Atmospheric Dynamics ◽  
Planetary Scale ◽  
Meteorology And Atmospheric Dynamics ◽  
Wave Numbers ◽  
Dominant Period ◽  
Waves And Tides

Abstract. On the basis of MEM spectrum analysis, the main planetary scale fluctuations formed in the lower ionosphere are studied over a period of 3–25 days during the CRISTA campaign (October-November 1994). Three dominant period bands are found: 3–5, 6–8 and 15–23 (mainly 16–18) days. For 7–8 and 16–18 day fluctuations, propagation was eastward with wave numbers K = 3 and K = 1, respectively. The magnitude of planetary wave activity in the mid-latitudes of the Northern Hemisphere during the CRISTA campaign seems to be fairly consistent with the expected undisturbed normal/climatological state of the atmosphere at altitudes of 80–100 km.Key words. Ionosphere (ionosphere-atmosphere interactions) · Meteorology and atmospheric dynamics (middle atmosphere dynamics; waves and tides)

scholarly journals Mesopause dynamics from the scandinavian triangle of radars within the PSMOS-DATAR Project

2004 ◽  
Vol 22 (2) ◽  
pp. 367-386 ◽  
Author(s):  
A. H. Manson ◽  
C. E. Meek ◽  
C. M. Hall ◽  
S. Nozawa ◽  
N. J. Mitchell ◽  
...  
Keyword(s):  
Large Scale ◽  
Middle Atmosphere ◽  
The Arctic ◽  
Small Scale ◽  
Wind Variability ◽  
Middle Latitudes ◽  
Radar Systems ◽  
Waves And Tides ◽  
Year 2000 ◽  
Mf Radar

Abstract. The "Scandinavian Triangle" is a unique trio of radars within the DATAR Project (Dynamics and Temperatures from the Arctic MLT (60–97km) region): Andenes MF radar (69°N, 16°E); Tromsø MF radar (70°N, 19°E) and Esrange "Meteor" radar (68°N, 21°E). The radar-spacings range from 125-270km, making it unique for studies of wind variability associated with small-scale waves, comparisons of large-scale waves measured over small spacings, and for comparisons of winds from different radar systems. As such it complements results from arrays having spacings of 25km and 500km that have been located near Saskatoon. Correlation analysis is used to demonstrate a speed bias (MF smaller than the Meteor) between the radar types, which varies with season and altitude. Annual climatologies for the year 2000 of mean winds, solar tides, planetary and gravity waves are presented, and show indications of significant spatial variability across the Triangle and of differences in wave characteristics from middle latitudes. Key words: Meteorology and atmospheric dynamics (middle atmosphere dynamics; waves and tides: instrument and techniques)

scholarly journals The 16-day planetary wave in the mesosphere and lower thermosphere

1999 ◽  
Vol 17 (11) ◽  
pp. 1447-1456 ◽  
Author(s):  
N. J. Mitchell ◽  
H. R. Middleton ◽  
A. G. Beard ◽  
P. J. S. Williams ◽  
H. G. Muller
Keyword(s):  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Late Summer ◽  
Wave Activity ◽  
Motion Field ◽  
Mesopause Region ◽  
Waves And Tides ◽  
Mesosphere And Lower Thermosphere ◽  
Thermospheric Dynamics ◽  
The Uk

Abstract. A meteor radar located at Sheffield in the UK has been used to measure wind oscillations with periods in the range 10–28 days in the mesosphere/lower-thermosphere region at 53.5°N, 3.9°W from January 1990 to August 1994. The data reveal a motion field in which wave activity occurs over a range of frequencies and in episodes generally lasting for less than two months. A seasonal cycle is apparent in which the largest observed amplitudes are as high as 14 ms–1 and are observed from January to mid-April. A minimum in activity occurs in late June to early July. A second, smaller, maximum follows in late summer/autumn where amplitudes reach up to 7–10 ms–1. Considerable interannual variability is apparent but wave activity is observed in the summers of all the years examined, albeit at very small amplitudes near mid summer. This behaviour suggests that the equatorial winds in the mesopause region do not completely prevent inter-hemispheric ducting of the wave from the winter hemisphere, or that it is generated in situ.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; thermospheric dynamics; waves and tides)

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