Meteor Radar System Research Articles

Mesosphere/Lower Thermosphere 3‐Dimensional Spatially Resolved Winds Observed by Chinese Multistatic Meteor Radar Network Using the Newly Developed VVP Method

AbstractWe present the first continuous observations of three‐dimensional spatially resolved wind fields and atmospheric motions in the mesosphere and lower thermosphere in the mid‐latitudes of the Northern Hemisphere. Our observations were performed during a 19‐month campaign from January 2022 to July 2023 and exploited the composite data from the first multistatic meteor radar system in China and an adjacent monostatic meteor radar. To retrieve the atmospheric kinetic properties, we introduce an improved volume velocity processing method including coordinate transformations and non‐linear constraints to minimize errors. The vertical winds are estimated separately from the iteration of the horizontal divergence to avoid potential biases or contamination from the horizontal winds. The winds and air motions show annual/semiannual variation characteristics within certain altitudes, usually more variable around the equinoxes. The vertical winds are basically within the magnitude of 1 m/s and are upward as expected at the mesopause during the summer, which corresponds to the adiabatic cooling.

A VHF Circularly Polarized Turnstile Antenna with Balun for Meteor Radar

This paper presents a circularly polarized turnstile antenna for a meteor radar system. The antenna employs a pair of turnstile radiators, a 1:2 power divider and a 90° phase shifter. After a series of simulations and optimizations, the maximum circularly polarized gain at 39 MHz is 5.9 dBic with 96° 3 dB beam width. The simulated axial ratio below 3 dB is from −39° to 39° within the band of interest. Then, the proposed antenna is fabricated and applied to a meteor radar system. Two tests are carried out for radiation characteristics demonstration. In the first test, the VSWR of the proposed antenna is below 1.2 at 38.5–39.5 MHz and keeps good agreement with simulation results. However, the meteor azimuth distribution is illogical when the output results are compared with the Australian meteor detection radar (ATRAD) meteor detection. To address the problem, baluns are investigated and introduced for balanced feeding. The 1:1 unbalance–balance transformer has been used to improve the radiation characteristics of the designed antenna. The final test results show that the meteor radar system with the improved antenna achieves better performances in meteor counts and meteor azimuth distribution.

Validation of Multistatic Meteor Radar Analysis Using Modeled Mesospheric Dynamics: An Assessment of the Reliability of Gradients and Vertical Velocities

AbstractA virtual meteor radar system based on the upper‐atmosphere extension of the high‐resolution ICOsahedral Non‐hydrostatic general circulation model is constructed to validate multistatic specular meteor radar (SMR) analyses. The virtual radar system examines the validity of mean winds and gradients estimation techniques used in multistatic SMRs. The study is motivated by unexpected mean values and tide‐like features recently observed in the vertical velocities estimated from multistatic SMRs at different latitudes in the mesosphere and lower thermosphere. The proposed analysis confirms multistatic SMR systems' excellent capability to measure the horizontal mean wind components and gradient terms. It is also found that multistatic SMRs can estimate mean vertical winds if they have an amplitude greater than ±2 m/s. Due to the smoothing inherent to the model results, these results should be treated as lower bounds to the error incurred using real data. Hourly variability in vertical velocity estimates up to ±1–2 m/s in the observed vertical winds are due to contamination by small‐scale horizontal structures in the horizontal winds.

Error analyses of a multistatic meteor radar system to obtain a three-dimensional spatial-resolution distribution

Abstract. In recent years, the concept of multistatic meteor radar systems has attracted the attention of the atmospheric radar community, focusing on the mesosphere and lower thermosphere (MLT) region. Recently, there have been some notable experiments using such multistatic meteor radar systems. Good spatial resolution is vital for meteor radars because nearly all parameter inversion processes rely on the accurate location of the meteor trail specular point. It is timely then for a careful discussion focused on the error distribution of multistatic meteor radar systems. In this study, we discuss the measurement errors that affect the spatial resolution and obtain the spatial-resolution distribution in three-dimensional space for the first time. The spatial-resolution distribution can both help design a multistatic meteor radar system and improve the performance of existing radar systems. Moreover, the spatial-resolution distribution allows the accuracy of retrieved parameters such as the wind field to be determined.

First Studies of Mesosphere and Lower Thermosphere Dynamics Using a Multistatic Specular Meteor Radar Network Over Southern Patagonia

AbstractThis paper presents for the first time results on winds, tides, gradients of horizontal winds, and momentum fluxes at mesosphere and lower thermosphere altitudes over southern Patagonia, one of the most dynamically active regions in the world. For this purpose, measurements provided by SIMONe Argentina are investigated. SIMONe Argentina is a novel multistatic specular meteor radar system that implements a Spread‐spectrum Interferometric Multistatic meteor radar Observing Network (SIMONe) approach, and that has been operating since the end of September 2019. Average counts of more than 30,000 meteor detections per day result in tidal estimates with statistical uncertainties of less than 1 m/s. Thanks to the multistatic configuration, horizontal and vertical gradients of the horizontal winds are obtained, as well as vertical winds free from horizontal divergence contamination. The vertical gradients of both zonal and meridional winds exhibit strong tidal signatures. Mean momentum fluxes are estimated after removing the effects of mean winds using a 4‐h, 8‐km window in time and altitude, respectively. Reasonable statistical uncertainties of the momentum fluxes are obtained after applying a 28‐day averaging. Therefore, the momentum flux estimates presented in this paper represent monthly mean values of waves with periods of 4 h or less, vertical wavelengths shorter than 8 km, and horizontal scales less than 400 km.

Multistatic Specular Meteor Radar Network in Peru: System Description and Initial Results

AbstractThe mesosphere and lower thermosphere (MLT) region is dominated globally by dynamics at various scales: planetary waves, tides, gravity waves, and stratified turbulence. The latter two can coexist and be significant at horizontal scales less than 500 km, scales that are difficult to measure. This study presents a recently deployed multistatic specular meteor radar system, SIMONe Peru, which can be used to observe these scales. The radars are positioned at and around the Jicamarca Radio Observatory, which is located at the magnetic equator. Besides presenting preliminary results of typically reported large‐scale features, like the dominant diurnal tide at low latitudes, we show results on selected days of spatially and temporally resolved winds obtained with two methods based on: (a) estimation of mean wind and their gradients (gradient method), and (b) an inverse theory with Tikhonov regularization (regularized wind field inversion method). The gradient method allows improved MLT vertical velocities and, for the first time, low‐latitude wind field parameters such as horizontal divergence and relative vorticity. The regularized wind field inversion method allows the estimation of spatial structure within the observed area and has the potential to outperform the gradient method, in particular when more detections are available or when fine adaptive tuning of the regularization factor is done. SIMONe Peru adds important information at low latitudes to currently scarce MLT continuous observing capabilities. Results contribute to studies of the MLT dynamics at different scales inherently connected to lower atmospheric forcing and E‐region dynamo related ionospheric variability.

Radio meteor physics – a comparison between techniques from 1945 to the mid-1970's

A description of the physics of radar meteors from 1945 to the mid-1970s is presented. Concrete designs of various radars in different countries are presented. Harvard project is the best documented of these early radars, and we will focus on that radar. Application of multi-receiver stations for orbit determination became relatively common, especially with the advent of the IGY in 1957. Canada also built the Springhill Observatory around the time of the IGY, but of special note was the construction of several meteor radars in the USSR. The contribution of Kashcheyev and his scientific group to the development of radar meteor technologies was emphasized. A discussion of some equipment options of Balakleya geophysical complex in different years was held. Problems of meteor radar technologies in solving problems of astronomy and geophysics are noted. Meteor became a mainstay of upper atmospheric research into dynamical processes after 1960's. Such research was undertaken at multiple sites all over the Western global arena as well as in the USSR. In attention is paid to the history of changes in the methods of obtaining, processing and storage of meteor information. Some aspects of the application of innovative technologies in meteor radar systems were discussed, primarily in the study of winds and atmospheric circulation in the meteor zone. The advent of personal computers, plus the somewhat simultaneous development of digitizers in the early 1970's, was a major breakthrough for many areas of scientific research and studies. This work is the first part of a planned review of radar meteor physics and related technologies from 1945 to 2020.

Novel specular meteor radar systems using coherent MIMO techniques to study the mesosphere and lower thermosphere

Abstract. Typical specular meteor radars (SMRs) use one transmitting antenna and at least a five-antenna interferometric configuration on reception to study the mesosphere and lower thermosphere (MLT) region. The interferometric configuration allows the measurement of the angle-of-arrival (AOA) of the detected meteor echoes, which in turn is needed to derive atmospheric parameters (e.g., mean winds, momentum fluxes, temperatures, and neutral densities). Recently, we have shown that coherent MIMO configurations in atmospheric radars, i.e., multiple input (transmitters) and multiple output (receivers), with proper diversity in transmission can be used to enhance interferometric atmospheric and ionospheric observations. In this study we present novel SMR systems using multiple transmitters in interferometric configuration, each of them employing orthogonal pseudorandom coded transmitted sequences. After proper decoding, the angle of departure (AOD) of the detected meteor echoes with respect to the transmitter site are obtained at each receiving antenna. We present successful bistatic implementations of (1) five transmitters and one receiver using coded continuous wave (CW) (MISO-CW), and (2) five transmitters and five receivers using coded CW (MIMO-CW). The latter system allows simultaneous independent observations of the specular meteor trails with respect to the transmitter (AOD) and with respect to the receiver (AOA). The quality of the obtained results is evaluated in terms of the resulting mean winds, the number of detections and the daily diffusion trail vs. altitude behavior. We show that the proposed configurations are good alternatives to explore the MLT region. When combined with multi-static approaches, they can increase the number of meteor detections, thereby improving the quality of atmospheric estimates and allowing the measurement of new atmospheric parameters (e.g., horizontal divergence, vorticity), The use of multiple collocated transmitters for interferometric AOD determination makes building a multi-static radar network easier logistically, as only one receiver per receiving site antenna is sufficient.

Mesosphere/lower thermosphere wind regime parameters using a newly installed SKiYMET meteor radar at Kazan (56°N, 49°E)

New meteor radar (MR) horizontal wind data obtained during 2015–2018 at Kazan (56°N, 49°E) are presented. The measurements were carried out with a state-of-the-art SKiYMET meteor radar. Monthly mean vertical profiles of zonal and meridional components of the prevailing wind speeds, also amplitudes and phases of the components of diurnal (DT) and semidiurnal tide (SDT) winds are displayed as contour plots for a mean calendar year over the four recent years and compared with distributions of these parameters provided by the previous multiyear (1986–2002) meteor radar (MR) measurements at Kazan and by the recent HWM07 empirical model. The analysis shows that the SKiYMET zonal and meridional prevailing wind speeds are generally in good agreement, sharing the same seasonal features, with the earlier MR seasonal winds. Comparisons with the HWM07 model are not favourable: eastward solstitial cells as modelled are significantly larger, >30 m/s compared to 15–20 m/s. Also, reversal lines are too variable with height, and the positions of modelled cells (positive and negative) are unlike those of either MRs at Kazan or other MLT radars. Both MR systems provide the large SDT amplitudes, approximately 30 m/s and vertical wavelengths, approximately 55 km, for both components at middle latitudes in winter. They also show the well known strong SDT September feature (heights 85–100 km, the vertical wavelength ∼55–60 km), and the weak summer SDT for 80–91 km. HWM07 shows unrealistic amplitudes and phases above 90 km by height and month: minimal amplitudes in equinoxes and no September feature.The weak DT of middle to high latitudes provide similar amplitude and phase structures from both MRs, 1986–2002 and 2015–2017: largest amplitudes (10–12 or 8–10 m/s) for the evanescent meridional tide in summer, peaking in late July; weakest (0–2, 2–4 m/s) at 80 to 92–96 km, when the tide is vertically propagating (January, February, November, December) with a vertical wavelength near 40 km. Again, HWM07 differs in amplitude and phase structures: showing peak amplitudes in equinoxes: April, 15 m/s at 88 km; October, 21 m/s at 89 km.Coupling of the MR wind parameters with the ERA5 wind parameters is studied for a case in 2016. It is shown that the prevailing winds and DT amplitudes and phases of both datasets can be simply linked together, but that the ERA5 SDT amplitudes are significantly underestimated at the top model levels of the ERA5 reanalysis project.

Observations of gravity wave forcing of the mesopause region during the January 2013 major Sudden Stratospheric Warming

AbstractStudies of vertical and interhemispheric coupling during Sudden Stratospheric Warmings (SSWs) suggest that gravity wave (GW) momentum flux divergence plays a key role in forcing the middle atmosphere, although observational validation of GW forcing is limited. We present a whole atmosphere view of zonal winds from the surface to 100 km during the January 2013 major SSW, together with observed GW momentum fluxes in the mesopause region derived from uninterrupted high‐resolution meteor radar observations from an All‐Sky Interferometric Meteor Radar system located at Trondheim, Norway (63.4°N, 10.5°E). Observations show GW momentum flux divergence 6 days prior to the SSW onset, producing an eastward forcing with peak values of ∼+145 ± 60ms−1d−1. As the SSW evolves, GW forcing turns westward, reaching a minimum of ∼−240 ± 70ms−1d−1∼+18 days after the SSW onset. These results are discussed in light of previous studies and simulations using the Whole Atmosphere Community Climate Model with Specified Dynamics.

Simulation of the parameters of the meteor radar system in order to optimize its operation

Since 1966 the Meteor Automated Radar System (MARS) has been operating at the Balakleya scientific testing ground of the Kharkov National University of Radio Electronics, which had provided with the unique scientific data on meteors and the earth's atmosphere.For a long time of operation the equipment has undergone considerable moral and physical obsolescence. The need to continue the meteoric research on the one hand, and the inability to do so on the available equipment on the other hand, requires the modernization of the complex with regard of the new objectives and new opportunities.Simple switch to the new element base without taking into account the changing of the working conditions and new research objectives is not reasonable. It is necessary to revise a number of parameters of the available equipment. A large number of factors can be found by means of modeling of the improved complex. However, the simulation can not be carried out without a major component - the model of the meteor-trail reflections. Therefore, the primary problem is to develop a model that would include the ground-based research equipment parameters and the model of the processes occurring in the meteor zone as well.The article proposes the structure of this model, presents the analytical concepts for some modeling stages and their graphic interpretation. The above model is implemented as a computer program. The above model is implemented as a computer program. It differs by the change of the signal amplitude in the meteor trail formation process; the ability to model meteor propagation to the "ultra-short" routs - between the main and offset points; as well as to determine the trail coordinates, which is necessary for further determination of the meteor radiant.

Short‐term variation of the s = 1 nonmigrating semidiurnal tide during the 2002 stratospheric sudden warming

In this study, the NCAR Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model (TIME‐GCM) is used to examine short‐term changes in the global structure of the migrating and s = 1 nonmigrating semidiurnal tides in a model run approximating the 2002 Southern Hemisphere stratospheric sudden warming. The TIME‐GCM is found to resolve an s = 1 nonmigrating semidiurnal tide with latitudinal structure similar to that of prior studies and with global structure in the MLT region strongly correlated with Southern Hemisphere planetary wave 1 (PW1) wave events, prior to equinox. Comparison with a control run with no planetary wave activity, Eliassen‐Palm flux, and correlation analysis of the s = 1 semidiurnal tide structure suggest that the wave propagates from the source region in the winter hemisphere stratosphere into both the summer and winter lower thermospheres. The amplitudes of the migrating semidiurnal tide in the Southern Hemisphere are anticorrelated with the nonmigrating tide, suggesting significant energy loss due to nonmigrating tidal generation, a result not previously seen. The amplitude of the s = 1 nonmigrating semidiurnal tide from TIME‐GCM is also compared with data from the South Pole meteor radar system. While the observations show bursts of nonmigrating tidal activity correlated to PW1 activity of comparable amplitudes to the model results, these events do not always appear at the same times as those in the model. This suggests that while the processes generating the nonmigrating tide in TIME‐GCM are realistic, the TIME‐GCM run itself displays differences in time evolution compared to the observations during this time.

Initial results from SKiYMET meteor radar at Thumba (8.5°N, 77°E): 1. Comparison of wind measurements with MF spaced antenna radar system

In the present communication, initial results from the allSKy interferometric METeor (SKiYMET) radar installed at Thumba (8.5°N, 77°E) are presented. The meteor radar system provides hourly zonal and meridional winds in the mesosphere lower thermosphere (MLT) region. The meteor radar measured zonal and meridional winds are compared with nearby MF radar at Tirunalveli (8.7°N, 77.8°E). The present study provided an opportunity to compare the winds measured by the two different techniques, namely, interferometry and spaced antenna drift methods. Simultaneous wind measurements for a total number of 273 days during September 2004 to May 2005 are compared. The comparison showed a very good agreement between these two techniques in the height region 82–90 km and poor agreement above this height region. In general, the zonal winds compare very well as compared to the meridional winds. The observed discrepancies in the wind comparison above 90 km are discussed in the light of existing limitations of both the radars. The detailed analysis revealed the consistency of the measured winds by both the techniques. However, the discrepancies are observed at higher altitudes and are attributed to the contamination of MF radar neutral wind measurements with Equatorial Electro Jet (EEJ) induced inospheric drifts rather than the limitations of the spaced antenna technique. The comparison of diurnal variation of zonal winds above 90 km measured by both the radars is in reasonably good agreement in the absence of EEJ (during local nighttime). It is also been noted that the difference in the zonal wind measurements by both the radars is directly related to the strength of EEJ, which is a noteworthy result from the present study.

Initial results from SKiYMET meteor radar at Thumba (8.5°N, 77°E): 2. Gravity wave observations in the MLT region

In the present communication, allSKy interferometric METeor (SKiYMET) radar observations of gravity wave activity in the mesosphere lower thermosphere (MLT) region over Thumba (8.5°N, 77°E) are presented. The present meteor radar system provides hourly zonal and meridional winds in the MLT region, which can be readily used for studying the tides, planetary waves, gravity waves of periods 2–6 hours, and other long period oscillations in this region. However, these hourly winds are not sufficient for studying short period gravity waves having periods less than an hour, which demand high temporal resolution measurements. Even though the winds are estimated on an hourly basis, information such as zenith angle, azimuth angle, and radial velocity of each detected meteor are archived. Using these details of the meteor, an algorithm is developed to obtain the 15‐min temporal resolution wind data. The output of the algorithm is compared with hourly wind data, and it showed a good agreement during the high meteor shower periods. Most of the times high meteor counts are observed during late night and early morning hours (local) over this latitude. Continuous wind measurements during the high meteor shower periods are used for studying the gravity wave activity in the MLT region. As the wave activity is intermittent and nonstationary, wavelet analysis has been used for delineating the wave features. The results showed the upward propagating intermittent gravity waves with periods 1–2 and 4–5 hours. The new aspect of the present communication is the usage of meteor radar for gravity wave studies for the first time over this latitude and studying their seasonal variability.

An intercomparison of meteor radar measurements at the South Pole using two different processing systems

A new meteor radar system was installed at the Amundsen–Scott station South Pole in 2001 to further the understanding of the dynamics of the Antarctic region. The antenna array consists of four yagis pointed along the 0°, 90°, 180°, and 270° meridians and five folded crossed dipoles arranged in a cross configuration and operating as an interferometer to provide position measurements for the detected radio meteors. The four yagis are time division multiplexed and used for both transmitting and receiving while the five folded crossed dipoles are only used for reception. The current arrangement of data acquisition (DAQ) systems at the South Pole allows the collection of meteors in a configuration similar to the previous meteor radar system that operated at the South Pole in the mid 1990s while also using an interferometer to accurately determine the meteor positions in the sky, which enables the determination of the vertical structure of the observed waves. This has been accomplished through the use of two DAQ and post-processing systems: COBRA (Colorado Obninsk radar) connected to the yagis and MEDAC (meteor echo detection and collection) connected to the folded crossed dipoles. With two separate DAQ systems operating in parallel we have the ability to directly compare the results and understand the inherent variability in the derived scientific results based on different system architectures and processing assumptions. The impact of operating a system without an interferometer on the amplitudes and phases of the observed wave components is considered. We find that the lack of altitude resolution of the COBRA DAQ system leads to an underestimation of the amplitude of the s = 1 component of the semidiurnal tide of ∼20% during the summer months.

Statistical characterization of the meteor trail distribution at the South Pole as seen by a VHF interferometric meteor radar

A VHF meteor radar system was installed at the geographical South Pole in 2001. The purpose of this system is to measure the horizontal wind field in the mesosphere–lower thermosphere (MLT) region and to understand the large‐scale dynamics of the Antarctic polar region. The radar operated for a few months in 2001 and with minor interruptions since that time. In this paper we will describe the meteor radar system, the data detection and collection process, and the postprocessing software that was developed to extract information from the meteor echoes collected with the interferometer that is part of the radar system. Finally, the main features of the meteor distribution will be presented and discussed. Our results show that the meteor activity peaks during the Antarctic summer. Furthermore, it occurs mostly in a small region around the ecliptic plane roughly ∼20° wide in terms of elevation angle spread.

Propagation of short-period gravity waves at high-latitudes during the MaCWAVE winter campaign

Abstract. As part of the MaCWAVE (Mountain and Convective Waves Ascending Vertically) winter campaign an all-sky monochromatic CCD imager has been used to investigate the properties of short-period mesospheric gravity waves at high northern latitudes. Sequential measurements of several nightglow emissions were made from Esrange, Sweden, during a limited period from 27–31 January 2003. Coincident wind measurements over the altitude range (~80–100 km) using two meteor radar systems located at Esrange and Andenes have been used to perform a novel investigation of the intrinsic properties of five distinct wave events observed during this period. Additional lidar and MSIS model temperature data have been used to investigate their nature (i.e. freely propagating or ducted). Four of these extensive wave events were found to be freely propagating with potential source regions to the north of Scandinavia. No evidence was found for strong orographic forcing by short-period waves in the airglow emission layers. The fifth event was most unusual exhibiting an extensive, but much smaller and variable wavelength pattern that appeared to be embedded in the background wind field. Coincident wind measurements indicated the presence of a strong shear suggesting this event was probably due to a large-scale Kelvin-Helmholtz instability.

Diurnal and seasonal variability of the meteoric flux at the South Pole measured with radars

A meteor radar system was installed at the South Pole in 2001 to measure the horizontal wind field in the MLT region. It uses four 6‐element yagi antennas pointing in orthogonal directions for transmission. For reception two independent systems are used: the same yagi antennas used for transmission (COBRA data acquisition system) and an interferometric array of five crossed‐dipole antennas (MEDAC data acquisition system). In this paper we present and discuss VHF radio meteor observations from the South Pole. Preliminary results showing the diurnal and seasonal variability of the meteor flux indicate that most of the activity occurs during the Antarctic summer around a very concentrated region of the sky in elevation and azimuth. These results agree well with meteor observations performed at Arctic latitudes. Speculations on the radiant distribution and possible meteor sources are presented.

Buckland Park all‐sky interferometric meteor radar

A VHF all‐sky interferometric meteor radar system has been developed and installed at Buckland Park, South Australia. The radar is portable, allows a wide range of operating parameters, and can also be operated as a boundary layer radar. The analysis techniques have been developed using extensive simulations in an attempt to improve on standard techniques used by previous investigators. The results suggest that although pulse repetition frequencies (PRFs) around 2 kHz allow meteor velocity and deceleration estimation, PRFs around 500 Hz maximize count rate and improve the quality of meteor echo height estimates for this radar. Typical results are presented, indicating the radar obtains annual count rate variation of between 9000 and 14,000 height resolvable underdense meteors per day.

Interferometric meteor radar phase calibration using meteor echoes

A technique for the phase calibration of interferometric meteor radar systems is presented. This technique uses phase differences of meteor echoes measured between spaced receiving antennas. The technique can be applied to data collected during routine observations, effectively allowing self phase calibration without the need for additional hardware or scheduled down time for off‐line phase calibration measurements. The technique can also be used to correct data collected using erroneous phase calibration estimates. Simulations of typical range and angle of arrival distributions are used to illustrate the technique and verify its performance. The results reveal that the phase offsets can be estimated to within 2° using realistic simulation parameters. The technique is also applied to data collected using the Buckland Park meteor radar, with the standard deviation of the daily phase offsets estimated over a four month period found to be less than 3°.