scholarly journals Mesospheric winds measured by MF radar with Full Correlation Analysis: error properties and impacts on studies of wind variance

2019 ◽  
Author(s):  
Maude Gibbins ◽  
Andrew Kavanagh
Keyword(s):  
Correlation Analysis ◽  
Gravity Waves ◽  
Horizontal Wind ◽  
Wind Fields ◽  
Wind Retrieval ◽  
Zonal Winds ◽  
Analysis Error ◽  
Full Correlation Analysis ◽  
Balloon Measurements

Abstract. The mesosphere is one of the most difficult parts of the atmosphere to sample; too high for balloon measurements and too low for in-situ satellites. Consequently there is a reliance on remote sensing (either from the ground or from space) to diagnose this region. Ground based radars have been used since the second half of the 20th century to probe the dynamics of the mesosphere; Medium Frequency (MF) radars provide estimates of the horizontal wind fields and are still used to analyse tidal structures and planetary waves that modulate the meridional and zonal winds. The variance of the winds has traditionally been linked qualitatively to the occurrence of gravity waves. In this paper the method of wind retrieval (full correlation analysis) employed by MF radars is considered with reference to two systems in Antarctica at different latitude (Halley at 76° S and Rothera at 67° S). It is shown that the width of the velocity distribution and occurrence of ‘outliers’ is related to the measured levels of anisotropy in the received signal pattern. The magnitude of the error distribution, as represented by the wind variance, varies with both insolation levels and geomagnetic activity. Thus it is demonstrated that for these two radars the influence of gravity waves may not be the primary mechanism that controls the overall variance.

scholarly journals Mesospheric winds measured by medium-frequency radar with full correlation analysis: error properties and impacts on studies of wind variance

2020 ◽  
Vol 9 (1) ◽  
pp. 223-238
Author(s):  
Maude Gibbins ◽  
Andrew J. Kavanagh
Keyword(s):  
Correlation Analysis ◽  
Gravity Waves ◽  
Horizontal Wind ◽  
Wind Fields ◽  
Medium Frequency ◽  
Wind Retrieval ◽  
Zonal Winds ◽  
Analysis Error ◽  
Full Correlation Analysis

Abstract. The mesosphere is one of the most difficult parts of the atmosphere to sample; it is too high for balloon measurements and too low for in situ satellites. Consequently, there is a reliance on remote sensing (either from the ground or from space) to diagnose this region. Ground-based radars have been used since the second half of the 20th century to probe the dynamics of the mesosphere; medium-frequency (MF) radars provide estimates of the horizontal wind fields and are still used to analyse tidal structures and planetary waves that modulate the meridional and zonal winds. The variance of the winds has traditionally been linked qualitatively to the occurrence of gravity waves. In this paper, the method of wind retrieval (full correlation analysis) employed by MF radars is considered with reference to two systems in Antarctica at different latitude (Halley at 76∘ S and Rothera at 67∘ S). It is shown that the width of the velocity distribution and occurrence of “outliers” is related to the measured levels of anisotropy in the received signal pattern. The magnitude of the error distribution, as represented by the wind variance, varies with both insolation levels and geomagnetic activity. Thus, it is demonstrated that for these two radars the influence of gravity waves may not be the primary mechanism that controls the overall variance.

scholarly journals Characteristics of Stratospheric Winds over Jiuquan (41.1°N, 100.2°E) Using Rocketsonde Data in 1967–2004

2017 ◽  
Vol 34 (3) ◽  
pp. 657-667 ◽  
Author(s):  
Z. Sheng ◽  
J. W. Li ◽  
Y. Jiang ◽  
S. D. Zhou ◽  
W. L. Shi
Keyword(s):  
Zonal Wind ◽  
Middle Atmosphere ◽  
Correlation Coefficients ◽  
Meridional Wind ◽  
Horizontal Wind ◽  
Cycle Period ◽  
Observation Data ◽  
Wind Fields ◽  
Zonal Winds ◽  
Model Research

AbstractStratospheric winds play a significant role in middle atmosphere dynamics, model research, and carrier rocket experiments. For the first time, 65 sets of rocket sounding experiments conducted at Jiuquan (41.1°N, 100.2°E), China, from 1967 to 2004 are presented to study horizontal wind fields in the stratosphere. At a fixed height, wind speed obeys the lognormal distribution. Seasonal mean winds are westerly in winter and easterly in summer. In spring and autumn, zonal wind directions change from the upper to the lower stratosphere. The monthly zonal mean winds have an annual cycle period with large amplitudes at high altitudes. The correlation coefficients for zonal winds between observations and the Horizontal Wind Model (HWM) with all datasets are 0.7. The MERRA reanalysis is in good agreement with rocketsonde data according to the zonal winds comparison with a coefficient of 0.98. The sudden stratospheric warming is an important contribution to biases in the HWM, because it changes the zonal wind direction in the midlatitudes. Both the model and the reanalysis show dramatic meridional wind differences with the observation data.

scholarly journals Variance of wind estimates using spaced antenna techniques with the MU radar

2004 ◽  
Vol 22 (11) ◽  
pp. 3863-3868
Author(s):  
G. Hassenpflug ◽  
M. Yamamoto ◽  
S. Fukao
Keyword(s):  
Experimental Data ◽  
Correlation Analysis ◽  
Error Propagation ◽  
Cross Correlation ◽  
Anisotropic Scattering ◽  
Standard Theory ◽  
Horizontal Wind ◽  
Mu Radar ◽  
Full Correlation Analysis

Abstract. Variance of horizontal wind estimates in conditions of anisotropic scattering are obtained for the Spaced Antenna (SA) Full Correlation Analysis (FCA) method of Holloway et al. (1997b) and Doviak et al. (1996), but are equally applicable to the Briggs method of FCA. Variance and covariance of cross-correlation magnitudes are theoretically estimated, and the standard theory of error propagation is used to estimate the variance of the wind components for the infinite SNR case. The effect of baseline orientation is investigated, and experimental data from the MU radar in Japan is presented.

scholarly journals Validating precision estimates in horizontal wind measurements from a Doppler lidar

2017 ◽  
Vol 10 (3) ◽  
pp. 1229-1240 ◽  
Author(s):  
Rob K. Newsom ◽  
W. Alan Brewer ◽  
James M. Wilczak ◽  
Daniel E. Wolfe ◽  
Steven P. Oncley ◽  
...  
Keyword(s):  
Wind Speed ◽  
Radial Velocity ◽  
Sonic Anemometer ◽  
Direct Calculation ◽  
Measurement Precision ◽  
Horizontal Wind ◽  
Retrieval Algorithm ◽  
Doppler Lidar ◽  
Wind Fields ◽  
Wind Retrieval

Abstract. Results from a recent field campaign are used to assess the accuracy of wind speed and direction precision estimates produced by a Doppler lidar wind retrieval algorithm. The algorithm, which is based on the traditional velocity-azimuth-display (VAD) technique, estimates the wind speed and direction measurement precision using standard error propagation techniques, assuming the input data (i.e., radial velocities) to be contaminated by random, zero-mean, errors. For this study, the lidar was configured to execute an 8-beam plan-position-indicator (PPI) scan once every 12 min during the 6-week deployment period. Several wind retrieval trials were conducted using different schemes for estimating the precision in the radial velocity measurements. The resulting wind speed and direction precision estimates were compared to differences in wind speed and direction between the VAD algorithm and sonic anemometer measurements taken on a nearby 300 m tower.All trials produced qualitatively similar wind fields with negligible bias but substantially different wind speed and direction precision fields. The most accurate wind speed and direction precisions were obtained when the radial velocity precision was determined by direct calculation of radial velocity standard deviation along each pointing direction and range gate of the PPI scan. By contrast, when the instrumental measurement precision is assumed to be the only contribution to the radial velocity precision, the retrievals resulted in wind speed and direction precisions that were biased far too low and were poor indicators of data quality.

scholarly journals Simulation of Spaced Antenna Wind Retrieval Performance on an X-Band Active Phased Array Weather Radar

2013 ◽  
Vol 30 (7) ◽  
pp. 1447-1459 ◽  
Author(s):  
V. Venkatesh ◽  
S. J. Frasier
Keyword(s):  
Correlation Analysis ◽  
Electric Fields ◽  
Time Domain ◽  
Phased Array ◽  
Weather Radar ◽  
Wind Retrieval ◽  
Fitting Procedure ◽  
X Band ◽  
The Time Domain ◽  
Full Correlation Analysis

Abstract Spaced antenna baseline wind retrievals, in conjunction with traditional Doppler measurements, are a potential means of fine angular resolution weather radar wind vector retrieval. A spaced antenna implementation on an X-band active phased array architecture is investigated via Monte Carlo simulations of the backscattered electric fields at the antenna array. Several retrieval methods are exercised on the data produced by the simulator. Parameters of the X-band spaced-antenna design are then optimized. Benefiting from the parametric fitting procedure inherent in the time domain slope at zero lag and full correlation analysis, the study finds both of these algorithms to be more immune to thermal noise than the spectral retrieval algorithms investigated. With appropriately chosen baselines, these time domain algorithms are shown to perform adequately for 5-dB SNR and above. The study also shows that the Gaussian slope at zero lag (G-SZL) algorithm leads to more robust estimates over a wider range of beamwidths than the Gaussian full correlation analysis (G-FCA) algorithm. The predicted performance of the X-band array is compared to a similar spaced antenna implementation on the S-band National Weather Radar Testbed (NWRT). Since the X-band signal decorrelates more rapidly (relative to S band), the X-band array accumulates more independent samples, thereby obtaining lower retrieval uncertainty. However, the same rapid decorrelation also limits the maximum range of the X-band array, as the pulse rate must be sufficiently high to sample the cross-correlation function. It also limits the range of tolerable turbulence velocity within the resolution cell.

scholarly journals Validating Precision Estimates in Horizontal Wind Measurements from a Doppler Lidar

2016 ◽  
Author(s):  
Rob K. Newsom ◽  
W. Alan Brewer ◽  
James M. Wilczak ◽  
Daniel E. Wolfe ◽  
Steven P. Oncley ◽  
...  
Keyword(s):  
Wind Speed ◽  
Radial Velocity ◽  
Sonic Anemometer ◽  
Direct Calculation ◽  
Horizontal Wind ◽  
Retrieval Algorithm ◽  
Doppler Lidar ◽  
Wind Fields ◽  
Wind Retrieval ◽  
Turbulence Effects

Abstract. Results from a recent field campaign are used to assess the accuracy of wind speed and direction precision estimates produced by a Doppler lidar wind retrieval algorithm. The algorithm, which is based on the traditional velocity-azimuth-display (VAD) technique, estimates the wind speed and direction measurement precision using standard error propagation techniques. For this study, the lidar was configured to execute an 8-beam plan-position-indicator (PPI) scan once every 12 minutes during the 6 week deployment period. Several wind retrieval trials were conducted using different schemes for estimating the uncertainty in the radial velocity measurements. The resulting wind speed and direction precision estimates were compared to differences in wind speed and direction between the VAD algorithm and sonic anemometer measurements taken on a nearby 300-m tower. All trials produced qualitatively similar wind fields with negligible bias, but substantially different wind speed and direction precision fields. The most accurate wind speed and direction precisions were obtained when the radial velocity uncertainty was determined by direct calculation of radial velocity standard deviation along each pointing direction and range gate of the PPI scan. By contrast, setting the radial velocity uncertainty to the radial velocity precision (thereby ignoring turbulence effects) resulted in wind speed and direction precisions that were biased far too low and poor indicators of data quality.

scholarly journals Observations of in-situ generated gravity waves during a stratospheric temperature enhancement (STE) event

2011 ◽  
Vol 11 (22) ◽  
pp. 11913-11917 ◽  
Author(s):  
A. J. Gerrard ◽  
Y. Bhattacharya ◽  
J. P. Thayer
Keyword(s):  
Gravity Waves ◽  
Background Wind ◽  
Wind Fields ◽  
Vertical Wavelength ◽  
Stratospheric Temperature ◽  
Wave Parameters ◽  
Phase Progression ◽  
Temperature Enhancement ◽  
Atmospheric Gravity

Abstract. Evidence for in situ generated atmospheric gravity waves associated with a stratospheric temperature enhancement (STE) are presented. The signatures of two sets of gravity waves are observed by molecular-aerosol lidar in conjunction with the early December 2000 STE event above Sondrestrom, Greenland. The first set of gravity waves shows downward phase progression with a vertical wavelength of ~8 km while the second set shows upward phase progression with a vertical wavelength of ~9 km. With estimates of the background wind fields from synoptic analyses, the various intrinsic gravity wave parameters of these two wave structures are found. The observed wave features compare well to previous numerical modeling predictions.

scholarly journals Retrieving horizontally resolved wind fields using multi-static meteor radar observations

2018 ◽  
Vol 11 (8) ◽  
pp. 4891-4907 ◽  
Author(s):  
Gunter Stober ◽  
Jorge L. Chau ◽  
Juha Vierinen ◽  
Christoph Jacobi ◽  
Sven Wilhelm
Keyword(s):  
Gravity Waves ◽  
Continuous Wave ◽  
Lower Thermosphere ◽  
Retrieval Algorithm ◽  
Meteor Radar ◽  
Wind Fields ◽  
Data Set ◽  
Wind Retrieval ◽  
Radar Network ◽  
Frequency Agile

Abstract. Recently, the MMARIA (Multi-static, Multi-frequency Agile Radar for Investigations of the Atmosphere) concept of a multi-static VHF meteor radar network to derive horizontally resolved wind fields in the mesosphere–lower thermosphere was introduced. Here we present preliminary results of the MMARIA network above Eastern Germany using two transmitters located at Juliusruh and Collm, and five receiving links: two monostatic and three multi-static. The observations are complemented during a one-week campaign, with a couple of addition continuous-wave coded transmitters, making a total of seven multi-static links. In order to access the kinematic properties of non-homogenous wind fields, we developed a wind retrieval algorithm that applies regularization to determine the non-linear wind field in the altitude range of 82–98 km. The potential of such observations and the new retrieval to investigate gravity waves with horizontal scales between 50–200 km is presented and discussed. In particular, it is demonstrated that horizonal wavelength spectra of gravity waves can be obtained from the new data set.

scholarly journals Modeling study of mesospheric planetary waves: genesis and characteristics

2004 ◽  
Vol 22 (6) ◽  
pp. 1885-1902 ◽  
Author(s):  
H. G. Mayr ◽  
J. G. Mengel ◽  
E. R. Talaat ◽  
H. S. Porter ◽  
K. L. Chan
Keyword(s):  
Heat Source ◽  
Gravity Waves ◽  
Zonal Flow ◽  
Planetary Waves ◽  
Wave Number ◽  
Horizontal Wind ◽  
Small Scale ◽  
Wind Fields ◽  
Zonal Jets ◽  
Nonmigrating Tides

Abstract. The Numerical Spectral Model (NSM) extends from the ground into the thermosphere and incorporates Hines' Doppler Spread Parameterization for small-scale gravity waves (GWs). In the present version of the model we account for a tropospheric heat source in the zonal mean (m=0), which reproduces qualitatively the observed zonal jets near the tropopause and the accompanying reversal in the latitudinal temperature variations. In the study presented here, we discuss the planetary waves (PWs) that are solely generated internally, i.e. without the explicit excitation sources related to tropospheric convection or topography. Our analysis shows that PWs are not produced when the zonally averaged heat source into the atmosphere is artificially suppressed, and that the PWs are generally weaker when the tropospheric source is not applied. Instabilities associated with the zonal mean temperature, pressure and wind fields, which still need to be explored, are exciting PWs that have amplitudes in the mesosphere comparable to those observed. Three classes of PWs are generated in the NSM. (1) Rossby type PWs, which slowly propagate westward relative to the mean zonal flow, are carried by the winds so that they appear (from the ground) to propagate, respectively, eastward and westward in the winter and summer hemispheres below 80km. Depending on the zonal wave number and magnitudes of the zonal winds, and under the influence of the equatorial oscillations, these PWs typically have periods between 2 and 20 days. Their horizontal wind amplitudes can exceed 40 m/s in the lower mesosphere. (2) Rossby-gravity waves, which propagate westward at low latitudes and have periods around 2 days for zonal wave numbers m=2 to 4. (3) Eastward propagating equatorial Kelvin waves, which are generated in the upper mesosphere with periods between 1 and 3 days depending on m. A survey of the PWs reveals that the largest wind amplitudes tend to occur below 80km in the winter hemisphere; but above that altitude the amplitudes are larger in the summer hemisphere where the winds can approach 50m/s. This pattern in the seasonal variations also appears in the baroclinity of the zonal mean (m=0). The nonmigrating tides in the mesosphere are significantly larger for the model with the tropospheric heat source, in which PWs are apparently generated by the instabilities that arise around the tropopause.

scholarly journals A Comparison of Meteor Radar Observation over China Region with Horizontal Wind Model (HWM14)

Atmosphere ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 98
Author(s):  
Qiong Tang ◽  
Yufeng Zhou ◽  
Zhitao Du ◽  
Chen Zhou ◽  
Jiandong Qiao ◽  
...  
Keyword(s):  
Model Prediction ◽  
Meridional Wind ◽  
Radar Observation ◽  
Horizontal Wind ◽  
Meteor Radar ◽  
Wind Fields ◽  
Wind Model ◽  
Zonal Winds ◽  
Radar Measurements ◽  
China Region

This paper compares the wind fields measured by the meteor radar at Mohe, Beijing, Wuhan, and Sanya stations and horizontal wind model (HWM14) predictions. HWM14 appears to successfully reproduce the height-time distribution of the monthly mean zonal winds, although large discrepancies occur in wind speed between the model and measurement, especially in the summer and winter months. For meridional wind, the consistency between model prediction and radar observation is worse than that of zonal wind. The consistency between radar measurements and model prediction at Sanya station is worse than other sites located at higher latitudes. Harmonic analysis reveals large discrepancies in diurnal, semidiurnal, and terdiurnal tides extracted from meteor radar observations and HWM14 predictions.

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