scholarly journals Mesospheric turbulent velocity estimation using the Buckland Park MF radar

2001 ◽  
Vol 19 (8) ◽  
pp. 1007-1017 ◽  
Author(s):  
D. A. Holdsworth ◽  
R. A. Vincent ◽  
I. M. Reid
Keyword(s):  
Annual Variation ◽  
Middle Atmosphere ◽  
Velocity Estimation ◽  
Turbulent Velocity ◽  
Radio Science ◽  
Meteorology And Atmospheric Dynamics ◽  
Zonal Velocity ◽  
Instruments And Techniques ◽  
Full Correlation Analysis ◽  
Mf Radar

Abstract. This paper investigates turbulent velocity estimation using the full correlation analysis (FCA) of spaced antenna (SA) data, and its application to the routine FCA observations of the Buckland Park MF (BPMF) radar. The effects of transmitter beamwidths are investigated, confirming the suggestions of previous authors that wide transmit beam widths lead to an overestimation of the turbulent velocity. The annual variation of the turbulent velocity is investigated, revealing an increase in turbulent velocity with height, and equinoctal minima and solstice maxima observed below 80 km. Investigations of the turbulent velocities about the March diurnal tide maximum reveals a diurnal variation in phase with the zonal velocity. Harmonic analysis reveals this relationship exists between February and September. Descending power layers are also observed during this period. A number of mechanisms are proposed to describe these observations.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; instruments and techniques) – Radio science (instruments and techniques)

scholarly journals A brief history of the development of wind-profiling or MST radars

2000 ◽  
Vol 18 (7) ◽  
pp. 740-749 ◽  
Author(s):  
T. E. Van Zandt
Keyword(s):  
Gravity Waves ◽  
Weather Forecasting ◽  
Acoustic Sounding ◽  
Practical Applications ◽  
Radio Science ◽  
Meteorology And Atmospheric Dynamics ◽  
Mst Radar ◽  
History Of ◽  
Instruments And Techniques ◽  
Atmospheric Phenomena

Abstract. The history of the development of the wind-profiling or MST radar technique is reviewed from its inception in the late 1960s to the present. Extensions of the technique by the development of boundary-layer radars and the radio-acoustic sounding system (RASS) technique to measure temperature are documented. Applications are described briefly, particularly practical applications to weather forecasting, with data from networks of radars, and scientific applications to the study of rapidly varying atmospheric phenomena such as gravity waves and turbulence.Key words: Meteorology and atmospheric dynamics (instruments and techniques) · Radio science (remote sensing; instruments and techniques)

scholarly journals Periodicities in energy dissipation rates in the auroral mesosphere/lower thermosphere

2003 ◽  
Vol 21 (3) ◽  
pp. 787-796 ◽  
Author(s):  
C. M. Hall ◽  
S. Nozawa ◽  
C. E. Meek ◽  
A. H. Manson ◽  
Y. Luo
Keyword(s):  
Energy Dissipation ◽  
Annual Variation ◽  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Radar Systems ◽  
Dissipation Rates ◽  
Semiannual Variation ◽  
Measuring Signal ◽  
Signal Fading ◽  
Mf Radar

Abstract. It is possible for medium-frequency (MF) radar systems to estimate kinetic energy dissipation rates by measuring signal fading times. Here, we present approximately 5 years of such results from Tromsø (69° N, 19° E) and in particular, investigate the periodicities present at different altitudes in the regime 80 to 100 km. We detect the known annual variation in the mesosphere and the semiannual variation on the lower thermosphere. In addition, other features are observed including terannual and ~ 27-day components in the lower thermosphere.Key words. Meteorology and atmospheric dynamics (climatology; middle atmosphere dynamics; turbulence)

scholarly journals A partial 45 MHz sky temperature map obtained from the observations of five ST radars

2001 ◽  
Vol 19 (8) ◽  
pp. 863-871 ◽  
Author(s):  
B. Campistron ◽  
G. Despaux ◽  
M. Lothon ◽  
V. Klaus ◽  
Y. Pointin ◽  
...  
Keyword(s):  
Performance Monitoring ◽  
Beam Width ◽  
Radio Sources ◽  
Radio Science ◽  
Cassiopeia A ◽  
Meteorology And Atmospheric Dynamics ◽  
Cygnus A ◽  
Instruments And Techniques ◽  
Sky Temperature ◽  
Right Ascension

Abstract. A sky temperature map at 45 MHz covering declination between + 30° and + 60°  is presented. The sampling in right ascension is 20 min (~5°) and 2°  in declination in most of the map. The originality of the work was to use cosmic emission measurements from five VHF Stratosphere-Troposphere (ST) radars collected during long periods of routine meteorological surveys. This map, which has an accuracy in temperature of about 600 K, is intended first for radar reflectivity calibration and system performance monitoring. The presence of two strong radio sources, Cassiopeia A and Cygnus A, can also serve as the verification of the beam diagram, beam width, and beam pointing direction of the antenna. Finally, this work is an attempt to show the potentiality of ST radar for astronomical purposes.Key words. Meteorology and atmospheric dynamics (instruments and techniques) – Radio science (radio astronomy)

scholarly journals A comparison between mesospheric wind measurements made near Christchurch (44°S, 173°E) using the high resolution doppler imager (HRDI) and a medium frequency (MF) radar

2000 ◽  
Vol 18 (5) ◽  
pp. 555-565
Author(s):  
D. J. Frame ◽  
B. N. Lawrence ◽  
G. J. Fraser ◽  
M. D. Burrage
Keyword(s):  
High Resolution ◽  
Middle Atmosphere ◽  
Radar Data ◽  
Atmospheric Composition ◽  
Medium Frequency ◽  
Spatial And Temporal Scales ◽  
Doppler Imager ◽  
Composition And Structure ◽  
Instruments And Techniques ◽  
Mf Radar

Abstract. We report on the comparison of winds measured by a medium frequency (MF) radar near Christchurch, New Zealand, and by the high resolution doppler imager (HRDI). Previous comparisons have demonstrated that there can be significant differences in the winds obtained by the two techniques, and our results are no different. However, these data show relatively good agreement in the meridional direction, but large differences in the zonal direction, where the radar is regularly measuring the zonal wind as too easterly. To do the comparison, overpasses from the satellite must be obtained when it is close to the radar site. The radar data are averaged in time around the overpass because we know the radars sample phenomena which have spatial and temporal scales which make them invisible to HRDI. There are a limited number of overpass comparisons which limit our confidence in these results, but a detailed analysis of these data show that the proximity of the overpass is often an important factor in the differences obtained. Other factors examined include the influence of the local time of the overpass, and the amount of radar data averaged around the overpass time.Key words: Atmospheric composition and structure (instruments and techniques) · Meteorology and atmospheric dynamics (middle atmosphere dynamics; instruments and techniques)

scholarly journals <i>Letter to the Editor</i>: Complete maps of the aspect sensitivity of VHF atmospheric radar echoes

1999 ◽  
Vol 17 (8) ◽  
pp. 1116-1119 ◽  
Author(s):  
R. M. Worthington ◽  
R. D. Palmer ◽  
S. Fukao
Keyword(s):  
Power Distribution ◽  
Middle Atmosphere ◽  
Vertical Shear ◽  
Horizontal Wind ◽  
Vhf Radar ◽  
Meteorology And Atmospheric Dynamics ◽  
Mu Radar ◽  
Radar Echoes ◽  
Instruments And Techniques ◽  
Aspect Sensitivity

Abstract. Using the MU radar at Shigaraki, Japan (34.85°N, 136.10°E), we measure the power distribution pattern of VHF radar echoes from the mid-troposphere. The large number of radar beam-pointing directions (320) allows the mapping of echo power from 0° to 40° from zenith, and also the dependence on azimuth, which has not been achieved before at VHF wavelengths. The results show how vertical shear of the horizontal wind is associated with a definite skewing of the VHF echo power distribution, for beam angles as far as 30° or more from zenith, so that aspect sensitivity cannot be assumed negligible at any beam-pointing angle that most existing VHF radars are able to use. Consequently, the use of VHF echo power to calculate intensity of atmospheric turbulence, which assumes only isotropic backscatter at large beam zenith angles, will sometimes not be valid.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; turbulence; instruments and techniques)

scholarly journals An improvement of wind velocity estimation from radar Doppler spectra in the upper mesosphere

2001 ◽  
Vol 19 (8) ◽  
pp. 837-843 ◽  
Author(s):  
S. Takeda ◽  
T. Nakamura ◽  
T. Tsuda
Keyword(s):  
Parameter Estimation ◽  
Middle Atmosphere ◽  
Gaussian Function ◽  
Estimation Method ◽  
Velocity Estimation ◽  
Least Square ◽  
Satellite Mission ◽  
Radio Science ◽  
Doppler Imager ◽  
Mu Radar

Abstract. We have developed a new parameter estimation method for Doppler wind spectra in the mesosphere observed with an MST radar such as the MU radar in the DBS (Doppler Beam Swinging) mode. Off-line incoherent integration of the Doppler spectra is carried out with a new algorithm excluding contamination by strong meteor echoes. At the same time, initial values on a least square fitting of the Gaussian function are derived using a larger number of integration of the spectra for a longer time and for multiple heights. As a result, a significant improvement has been achieved with the probability of a successful fitting and parameter estimation above 80 km. The top height for the wind estimation has been improved to around 95 km. A comparison between the MU radar and the High Resolution Doppler Imager (HRDI) on the UARS satellite is shown and the capability of the new method for a validation of a future satellite mission is suggested.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics) – Radio science (remote sensing; signal processing)

scholarly journals Spectral characteristics of spring arctic mesosphere dynamics

1998 ◽  
Vol 16 (12) ◽  
pp. 1607-1618 ◽  
Author(s):  
C. M. Hall ◽  
A. H. Manson ◽  
C. E. Meek
Keyword(s):  
Energy Dissipation ◽  
Middle Atmosphere ◽  
Spectral Characteristics ◽  
Turbulent Energy ◽  
Energy Dissipation Rate ◽  
Spectral Signature ◽  
Upper Limits ◽  
Waves And Tides ◽  
Signal Fading ◽  
Mf Radar

Abstract. The spring of 1997 has represented a stable period of operation for the joint University of Tromsø / University of Saskatchewan MF radar, being between refurbishment and upgrades. We examine the horizontal winds from the February to June inclusive and also include estimates of energy dissipation rates derived from signal fading times and presented as upper limits on the turbulent energy dissipation rate, ε. Here we address the periodicity in the dynamics of the upper mesosphere for time scales from hours to one month. Thus, we are able to examine the changes in the spectral signature of the mesospheric dynamics during the transition from winter to summer states.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; turbulence; waves and tides).

scholarly journals NLC and the background atmosphere above ALOMAR

2011 ◽  
Vol 11 (12) ◽  
pp. 5701-5717 ◽  
Author(s):  
J. Fiedler ◽  
G. Baumgarten ◽  
U. Berger ◽  
P. Hoffmann ◽  
N. Kaifler ◽  
...  
Keyword(s):  
Diurnal Cycle ◽  
Middle Atmosphere ◽  
Thermal State ◽  
Atmospheric Tides ◽  
Data Set ◽  
Ice Particles ◽  
Cloud Water Content ◽  
Radar Measurements ◽  
Mf Radar

Abstract. Noctilucent clouds (NLC) have been measured by the Rayleigh/Mie/Raman-lidar at the ALOMAR research facility in Northern Norway (69° N, 16° E). From 1997 to 2010 NLC were detected during more than 1850 h on 440 different days. Colocated MF-radar measurements and calculations with the Leibniz-Institute Middle Atmosphere (LIMA-) model are used to characterize the background atmosphere. Temperatures as well as horizontal winds at 83 km altitude show distinct differences during NLC observations compared to when NLC are absent. The seasonally averaged temperature is lower and the winds are stronger westward when NLC are detected. The wind separation is a robust feature as it shows up in measurements as well as in model results and it is consistent with the current understanding that lower temperatures support the existence of ice particles. For the whole 14-year data set there is no statistically significant relation between NLC occurrence and solar Lyman-α radiation. On the other hand NLC occurrence and temperatures at 83 km show a significant anti-correlation, which suggests that the thermal state plays a major role for the existence of ice particles and dominates the pure Lyman-α influence on water vapor during certain years. We find the seasonal mean NLC altitudes to be correlated to both Lyman-α radiation and temperature. NLC above ALOMAR are strongly influenced by atmospheric tides. The cloud water content varies by a factor of 2.8 over the diurnal cycle. Diurnal and semidiurnal amplitudes and phases show some pronounced year-to-year variations. In general, amplitudes as well as phases vary in a different manner. Amplitudes change by a factor of more than 3 and phases vary by up to 7 h. Such variability could impact long-term NLC observations which do not cover the full diurnal cycle.

scholarly journals Classification of hemispheric monthly mean stratospheric potential vorticity fields

2003 ◽  
Vol 21 (3) ◽  
pp. 805-817 ◽  
Author(s):  
R. Huth ◽  
P. O. Canziani
Keyword(s):  
Potential Vorticity ◽  
General Circulation ◽  
Middle Atmosphere ◽  
Principal Component ◽  
Volcanic Eruptions ◽  
Atmospheric Processes ◽  
Meteorology And Atmospheric Dynamics ◽  
Stratospheric Dynamics ◽  
Northern And Southern Hemispheres

Abstract. Monthly mean NCEP reanalysis potential vorticity fields at the 650 K isentropic level over the Northern and Southern Hemispheres between 1979 and 1997 were studied using multivariate analysis tools. Principal component analysis in the T-mode was applied to demonstrate the validity of such statistical techniques for the study of stratospheric dynamics and climatology. The method, complementarily applied to both the raw and anomaly fields, was useful in determining and classifying the characteristics of winter and summer PV fields on both hemispheres, in particular, the well-known differences in the behaviour and persistence of the polar vortices. It was possible to identify such features as sudden warming events in the Northern Hemisphere and final warming dates in both hemispheres. The stratospheric impact of other atmospheric processes, such as volcanic eruptions, also identified though the results, must be viewed at this stage as tentative. An interesting change in behaviour around 1990 was detected over both hemispheres.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; general circulation; climatology)

scholarly journals Local wavelet correlation: applicationto timing analysis of multi-satellite CLUSTER data

2004 ◽  
Vol 22 (12) ◽  
pp. 4185-4196 ◽  
Author(s):  
J. Soucek ◽  
T. Dudok de Wit ◽  
M. Dunlop ◽  
P. Décréau
Keyword(s):  
Large Scale ◽  
Timing Analysis ◽  
Stationary Time Series ◽  
Time Lags ◽  
Radio Science ◽  
Large Scale Structures ◽  
Cluster Data ◽  
Instruments And Techniques ◽  
Scale Structures ◽  
Multiple Spacecraft

Abstract. Multi-spacecraft space observations, such as those of CLUSTER, can be used to infer information about local plasma structures by exploiting the timing differences between subsequent encounters of these structures by individual satellites. We introduce a novel wavelet-based technique, the Local Wavelet Correlation (LWC), which allows one to match the corresponding signatures of large-scale structures in the data from multiple spacecraft and determine the relative time shifts between the crossings. The LWC is especially suitable for analysis of strongly non-stationary time series, where it enables one to estimate the time lags in a more robust and systematic way than ordinary cross-correlation techniques. The technique, together with its properties and some examples of its application to timing analysis of bow shock and magnetopause crossing observed by CLUSTER, are presented. We also compare the performance and reliability of the technique with classical discontinuity analysis methods. Key words. Radio science (signal processing) – Space plasma physics (discontinuities; instruments and techniques)

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