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In the field of meteorology, the global radar network is indispensable for detecting weather phenomena and offering early warning services. Nevertheless, radar data frequently exhibit anomalies, including gaps and clutter, arising from atmospheric refraction, equipment malfunctions, and other factors, resulting in diminished data quality. Traditional radar blockage correction methods, such as employing approximate radial information interpolation and supplementing missing data, often fail to effectively exploit potential patterns in massive radar data, for the large volume of data precludes a thorough analysis and understanding of the inherent complex patterns and dependencies through simple interpolation or supplementation techniques. Fortunately, edge computing possesses certain data processing capabilities and cloud center boasts substantial computational power, which together can collaboratively offer timely computation and storage for the correction of radar beam blockage. To this end, an edge-cloud collaborative driven deep learning model named DenMerD is proposed in this paper, which includes dense connection module and merge distribution (MD) unit. Compared to existing models such as RC-FCN, DenseNet, and VGG, this model greatly improves key performance metrics, with 30.7 % improvement in Critical Success Index (CSI), 30.1 % improvement in Probability of Detection (POD), and 3.1 % improvement in False Alarm Rate (FAR). It also performs well in the Structure Similarity Index Measure (SSIM) metrics compared to its counterparts. These findings underscore the efficacy of the design in improving feature propagation and beam blockage accuracy, and also highlights the potential and value of mobile edge computing in processing large-scale meteorological data.

Compared to traditional single-polarization radar, dual-polarization radar has a number of advantages for quantitative precipitation estimation because more information about the drop size distribution and hydrometeor type can be gleaned. In this paper, an improved dual-polarization rainfall methodology is proposed, which is driven by a region-based hydrometeor classification mechanism. The objective of this study is to incorporate the spatial coherence and self-aggregation of dual-polarization observables in hydrometeor classification and to produce robust rainfall estimates for operational applications. The S-band dual-polarization data collected from the NASA Polarimetric (NPOL) radar during the GPM Iowa Flood Studies (IFloodS) ground validation field campaign are used to demonstrate and evaluate the proposed rainfall algorithm. Results show that the improved rainfall method provides better performance than a few single- and dual-polarization algorithms in previous studies. This paper also investigates the impact of radar beam broadening on various rainfall algorithms. It is found that the radar-based rainfall products are less correlated with ground disdrometer measurements as the distance from the radar increases.

Dynamically controlling terahertz (THz) wavefronts in a designable fashion is highly desired in practice. However, available methods working at microwave frequencies do not work well in the THz regime due to lacking suitable tunable elements with submicrometer sizes. Here, instead of locally controlling individual meta-atoms in a THz metasurface, we show that rotating different layers (each exhibiting a particular phase profile) in a cascaded metadevice at different speeds can dynamically change the effective Jones-matrix property of the whole device, thus enabling extraordinary manipulations on the wavefront and polarization characteristics of a THz beam impinging on the device. After illustrating our strategy based on model calculations, we experimentally demonstrate two proof-of-concept metadevices, each consisting of two carefully designed all-silicon transmissive metasurfaces exhibiting different phase profiles. Rotating two metasurfaces inside the fabricated devices at different speeds, we experimentally demonstrate that the first metadevice can efficiently redirect a normally incident THz beam to scan over a wide solid-angle range, while the second one can dynamically manipulate both the wavefront and polarization of a THz beam. Our results pave the way to achieving dynamic control of THz beams, which is useful in many applications, such as THz radar, and bio- and chemical sensing and imaging.

The ablation of micrometeoroids entering Earth's atmosphere leaves behind a hot, dense column of plasma between 80 and 120 km altitude. Sharp density gradients can drive the plasma unstable, leading to turbulence and waves at the same altitude, which are often observed as coherent radar echoes. These echoes persist for 10s of milliseconds up to several minutes and are known as nonspecular trails. The turbulence from these trails is highly aspect sensitive and typically only observed within a few degrees of perpendicular to the magnetic field. In this letter, we present a new approach to measure the magnetic aspect sensitivity of nonspecular meteor trail echoes using the AMISR‐14 radar system. Using multiple beams, we simultaneously observe each trail at several different angles and directly observe aspect angle effects. Using this approach, we find that at 445 MHz, the observed power decays at 4.58 ± 0.46 dB/degree.

In this letter, the jamming resource allocation problem of distributed jammers cooperatively jamming netted radar system is investigated. A well‐constructed jamming resource allocation model considering jamming beams, jamming power and other influencing factors is established. Random keys are used in this letter to improve the coding mode of genetic algorithm. Simulation results show that in the case of limited jamming resources, the model and algorithm proposed can achieve effective jamming allocation schemes facing a netted radar with any number of radar nodes.

Terrain-scattered interference (TSI), that is, jammer signals reflected on the earth's surface, is a significant problem to military airborne radar. In auxiliary beam TSI suppression, the TSI in the main radar beam is estimated by a single or several auxiliary beams and is subtracted from the main beam channel. The signal to subtract is the auxiliary beam signals fed through an estimate of the ‘reflection system’, which describes scattering on the surface. The authors first present results on the structure of this TSI suppression, on the estimation of the reflection system and on the quality of the estimate. Then the authors derive theoretical expressions for the signal-to-interference plus noise ratio (SINR) and the remaining TSI power for a single auxiliary beam. Since the SINR is directly connected to the radar performance, it can be seen what factors affect the performance and how. It was noted that when the estimated reflection system is missing one or more delays of the true system, the TSI filter cannot suppress the TSI signal completely. This phenomenon, which is called ‘TSI leakage’, has a very large impact on the performance. The SINR cannot be kept constant. Instead, an ‘SINR improvement’ can be defined.

A THz radar, with its wide bandwidth, is capable of high‐resolution imaging down to the centimeter scale. In this study, a THz radar is applied to detect hydrometeors generated in a spray chamber. The observed backscattering signals show fluctuations at centimeter scales, indicating various hydrometeor distribution patterns along the radar beam. A co‐located High‐Speed Imaging (HSI) sensor is used to measure the Drop Size Distributions (DSD) in the spray chamber. The radar sampling beam is well aligned with the HSI probes, allowing an objective comparison between the remote sensing and in situ observations. In this study, the observed radar power is compared with the power estimated from the HSI measurements. Results show great consistency, with power difference smaller than 0.5 dB. This study demonstrates the feasibility and great potential of using a THz radar for ultra‐high‐resolution observations of clouds in a laboratory facility, and in the real atmosphere. Plain Language Summary An improved understanding of how precipitation forms in clouds calls for new observational instruments and novel measurement strategies. Radars operating at ultra‐high frequency (a.k.a. THz radars) are known for their unprecedented resolution down to centimeter scale. Here, for the first time, we applied a THz radar to detect hydrometeors generated in a spray chamber. An additional in situ probe is utilized within the chamber to validate the THz radar observations. The radar beam is directed through the same volume that is sampled by the in situ probe, thus enabling an objective comparison between the in situ and remote sensing measurements. Different hydrometeor distributions are generated in the chamber, each being jointly observed by the radar and the in situ probes. Results show that the THz radar measurements agree well with the radar power calculated from the in situ observations. This unique experiment indicates promising scenarios of applying THz radar to cloud and precipitation studies in a laboratory facility and in the real atmosphere. Key Points A novel experiment is conducted by applying a THz radar to detect hydrometeors generated in a spray chamber Good agreement between in situ and radar observations demonstrates the unique capability of THz radar for cloud and precipitation studies Implications of applying THz radar to design novel observational strategies for solving fundamental gaps in cloud physics are demonstrated

This paper introduces an advanced beamforming methodology for time-modulated arrays by leveraging harmonic coordination. The proposed approach assigns complex beams to designated angular ranges and synthesizes distinct harmonic beams to achieve sophisticated beamforming. Furthermore, this study introduces two innovative structural models, namely the parallel and cascade structures, to amplify the degree of freedom for harmonics in the frequency domain. Through rigorous derivations and comprehensive simulations, the efficacy of the proposed methodology is demonstrated. The results reveal that the harmonic coordination approach outperforms conventional methods in synthesizing optimal beam patterns, thereby enhancing the efficacy of different detection states in automotive radar systems.

Through applying a 4‐MHz linear frequency modulation waveform, which has high range resolution and signal intensity, we successfully detected for the first time the ionospheric 150‐km echo enhancement at 430–450 MHz of the Ultra‐High‐Frequency (UHF) band using the newly built Sanya Incoherent Scatter Radar (SYISR). The obtained low signal enhancement (less than 0.5 dB) explains why previous UHF experiments did not detect them. We also found that our measured fine structure shows a much wider forbidden region than previous results and covers a much larger altitudinal and local time region. In comparison with recent upper‐hybrid instability theory and simulation, our results confirmed the predicted higher altitude occurrence, wider gaps between enhancements, the turn corner feature around sunrise, and perhaps the weak enhancement, which provide an independent evaluation of the newly proposed mechanism in UHF band. Future UHF experiments could further improve the physical understanding of 150‐km echo phenomenon. Plain Language Summary In the altitude range of 130–170 km above the Earth's surface, the electrons ionized by the solar radiation effecting on the neutrals can generate enhanced radar echo with specific layered structures if the radar beam points perpendicular to or slightly off perpendicular to the geomagnetic field. Up to date, this phenomenon was only detected by lower frequency radars (30–60 MHz). Its physical mechanism has been a puzzle over several decades. Recently, due primarily to the advancement of numerical simulation technology and the improvement of computing power, this puzzle was resolved well by the newly proposed across scales energy transformation physical mechanism in several recent publications. However, these simulations also concluded that it is hard to be detected by higher frequency radars. In this paper, using our newly built Sanya Incoherent Scatter Radar, we applied a novel experimental setup to gain very high range resolution and signal intensity. We finally successfully detected this phenomenon in 430–450 MHz. By comparing our results with previous measurements and theoretical simulation, we can enhance current physical understanding from the perspective of observations. Key Points Successful first detection of daytime 150‐km echoes in the Ultra‐High‐Frequency band with Sanya Incoherent Scatter Radar We detected wider forbidden region and larger altitudinal and local time coverage than previous results Narrow layering features not following the zenith angle point to field‐aligned irregularitie echoes

Monitoring the generation and movement of equatorial plasma bubbles (EPBs) in a large longitude region is crucial important for better understanding their day‐to‐day variability. Using the newly developed Low lAtitude long Range Ionospheric raDar (LARID) at Dongfang (19.2°N, 108.8°E, dip lat. 13.8°N), China, an extremely long‐range experiment for observing EPB irregularities in a range of ±9,600 km to the radar site was first carried out. The results show that EPB irregularities with ranges up to 7,000 and 9,500 km were observed by the east and west beams of LARID, respectively. By incorporating simultaneous observations from GNSS receiver and ionosonde networks, it is demonstrated that the EPBs generated from post‐sunset to sunrise over a very wide longitude of ∼140°, from Pacific to Africa could be observed by LARID. The results, for the first time, demonstrate the possibility for tracing global EPBs in real time using a few low latitude over‐the‐horizon radars. Plain Language Summary Equatorial plasma bubble (EPB), which can cause severe ionospheric scintillation, is an important space weather phenomenon. The occurrence of EPBs exhibits complex longitude variation characteristics. Due to the fact that most of the equatorial and low latitude region is covered by ocean, it is challenging to monitor the generation and movement of global EPBs. Recently, an over‐the‐horizon (OTH) radar at low latitude, that is, the LARID, has been built for observing EPB irregularities. However, it is not clear that how far an OTH radar at low latitude can observe irregularities. This would be very important in the design of a low latitude OTH radar network for tracing global EPB irregularities. To address this issue, an extremely long‐range experiment covering a wide longitude of about 180° was performed for the first time with LARID. The successful observation of EPB irregularities from Pacific to Africa sectors demonstrates the possibility of monitoring the complex longitudinal variations of EPBs by an OTH radar, even during geomagnetic storms. The results provide meaningful insight for building a low latitude OTH radar network in future, that consists of three to four OTH radars could have the capability to obtain global EPBs in real time. Key Points First extremely long‐range experiment for observing equatorial plasma bubbles over a large longitude was conducted Equatorial plasma bubbles with ranges as far as 9,500 km were successfully observed by an over‐the‐horizon radar The results demonstrate the capability for tracing global equatorial plasma bubbles using a few low latitude over‐the‐horizon radars