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The Cloud Profiling Radar (CPR) of the Earth Cloud, Aerosol and Radiation Explorer (EarthCARE) has a new capability to observe the Doppler velocity related to the vertical air motion of the terminal velocity of hydrometeors. The new observation from space will be used to evaluate and improve the model. Before the launch of EarthCARE, we need to develop a methodology for using the CPR data for model evaluations. In this study, we evaluated simulated data by a stretched version of the global non-hydrostatic model over Japan with a ground-based CPR using an instrument design similar to the EarthCARE CPR. We chose two cases with different precipitation events in September 2019 using two cloud microphysics schemes. We introduced the categorization method for evaluating microphysics using Doppler velocity. The results show that the liquid and solid phases of hydrometeors are divided in Doppler velocity, and the model's terminal velocities of rain, snow, and graupel categories can be evaluated with the observation. The results also show that the choice of microphysics scheme has a more significant impact than the dependence on precipitation cases. We discussed the application of the EarthCARE-like simulation results using a satellite simulator. [ABSTRACT FROM AUTHOR]

Dual-polarization radar often detects columnar regions of enhanced differential reflectivity (ZDR) extending vertically above the environmental 0 °C level. Indicative of supercooled liquid drops and wet ice particles lofted by strong updrafts, these ZDR columns are increasingly understood to be of use in predicting extreme rainfall. With the aim of achieving practical application of ZDR column measurements, this paper focuses on the relationship between the height of ZDR columns and rainfall intensity near the ground. All the data on ZDR columns analyzed in this study was collected from weather radar stations in Japan. The height of each column and rainfall rates at low levels were analyzed using an automated algorithm. A regression analysis result reveals peak column height to be positively correlated with maximum rainfall rate near ground level, and that rainfall intensity on the ground is likely to exceed 50 mm h-1 when radar identifies a ZDR column. Furthermore, extreme rainfall with an intensity of 180 mm h-1 or more is likely associated with a column over 3 km tall from the 0 °C level. These findings suggest that surveillance of ZDR columns can contribute to the reliability of very short-range forecasts or nowcasts as well as assist with the issue of early warnings of extreme rainfall and flash floods. [ABSTRACT FROM AUTHOR]

River water-level prediction is crucial for mitigating flood damage caused by torrential rainfall. In this paper, we attempt to predict river water levels using a deep learning model based on radar rainfall data instead of data from upstream hydrological stations. A prediction model incorporating a two-dimensional convolutional neural network (2D-CNN) and long short-term memory (LSTM) is constructed to exploit geographical and temporal features of radar rainfall data, and a transfer learning method using a newly defined flow–distance matrix is presented. The results of our evaluation of the Oyodo River basin in Japan show that the presented transfer learning model using radar rainfall instead of upstream measurements has a good prediction accuracy in the case of torrential rain, with a Nash–Sutcliffe efficiency (NSE) value of 0.86 and a Kling–Gupta efficiency (KGE) of 0.83 for 6-h-ahead forecast for the top-four peak water-level height cases, which is comparable to the conventional model using upstream measurements (NSE = 0.84 and KGE = 0.83). It is also confirmed that the transfer learning model maintains its performance even when the amount of training data for the prediction site is reduced; values of NSE = 0.82 and KGE = 0.82 were achieved when reducing the training torrential-rain-period data from 12 to 3 periods (with 105 periods of data from other rivers for transfer learning). The results demonstrate that radar rainfall data and a few torrential rain measurements at the prediction location potentially enable us to predict river water levels even if hydrological stations have not been installed at the prediction location. [ABSTRACT FROM AUTHOR]

The WPR-LQ-7 is a UHF (1.3575 GHz) wind profiler radar used for routine measurements of the lower troposphere at Shigaraki MU Observatory (34.85 ∘ N, 136.10 ∘ E; Japan) at a vertical resolution of 100 m and a time resolution of 10 min. Following studies carried out with the 46.5 MHz middle and upper atmosphere (MU) radar (Luce et al., 2018), we tested models used to estimate the rate of turbulence kinetic energy (TKE) dissipation ε from the Doppler spectral width in the altitude range ∼ 0.7 to 4.0 km above sea level (a.s.l.). For this purpose, we compared LQ-7-derived ε using processed data available online (http://www.rish.kyoto-u.ac.jp/radar-group/blr/shigaraki/data/ , last access: 24 July 2023) with direct estimates of ε (εU) from DataHawk UAVs. The statistical results reveal the same trends as reported by Luce et al. (2018) with the MU radar, namely (1) the simple formulation based on dimensional analysis εLout=σ3/Lout , with Lout∼70 m, provides the best statistical agreement with εU. (2) The model εN predicting a σ2N law (N is Brunt–Vaïsälä frequency) for stably stratified conditions tends to overestimate for εU≲5×10-4 m 2 s -3 and to underestimate for εU≳5×10-4 m 2 s -3. We also tested a model εS predicting a σ2S law (S is the vertical shear of horizontal wind) supposed to be valid for low Richardson numbers (Ri=N2/S2). From the case study of a turbulent layer produced by a Kelvin–Helmholtz (K–H) instability, we found that εS and εLout are both very consistent with εU , while εN underestimates εU in the core of the turbulent layer where N is minimum. We also applied the Thorpe method from data collected from a nearly simultaneous radiosonde and tested an alternative interpretation of the Thorpe length in terms of the Corrsin length scale defined for weakly stratified turbulence. A statistical analysis showed that εS also provides better statistical agreement with εU and is much less biased than εN. Combining estimates of N and shear from DataHawk and radar data, respectively, a rough estimate of the Richardson number at a vertical resolution of 100 m (Ri100) was obtained. We performed a statistical analysis on the Ri dependence of the models. The main outcome is that εS compares well with εU for low Ri100 (Ri100≲1), while εN fails. εLout varies as εS with Ri100 , so that εLout remains the best (and simplest) model in the absence of information on Ri. Also, σ appears to vary as Ri100-1/2 when Ri100≳0.4 and shows a degree of dependence on S100 (vertical shear at a vertical resolution of 100 m) otherwise. [ABSTRACT FROM AUTHOR]

Changes in sea surface salinity (SSS) caused by the discharge of freshwater plumes from rivers affect the marine environment in estuaries; therefore, monitoring SSS is essential for understanding the changes in physical phenomena within coastal ecosystems induced by river plume discharge. Previous studies showed that salinity could be estimated using a very-high-frequency radar; however, this method was only validated over a short period and few qualitative evaluations were performed. Therefore, to verify quantitative assessments of SSS estimates for practical use, we estimated SSS using the Doppler spectrum of a 24.5-MHz phased-array high-frequency (HF) radar installed in Ise Bay, Japan, and data of approximately 1 year were used for verification. The radar-estimated SSS map was consistent with the velocity field and salinity distribution reported in previous studies. The root mean square error (RMSE) of the SSS estimate for 1-h radar data compared with in situ observations was 4.42 psu when the effect of wind on the received power was removed and 5.04 psu when it was not. For the daily (25-h) average, the RMSE when the effect of wind was considered was 3.32 psu. These results were considered sufficiently applicable in closed coastal areas such as Ise Bay, where the SSS decreases rapidly by 10 psu or more due to river flooding. The results revealed that the HF radar, which can continuously measure sea surface velocity and SSS with a high spatiotemporal resolution, can be a useful tool for providing a deeper understanding of the physical and environmental phenomena that are greatly affected by river water discharge. [ABSTRACT FROM AUTHOR]

We present an automated radar data analysis algorithm developed to calculate probability distributions of meteor- and meteoroid parameters for head echoes detected with the Middle and Upper atmosphere (MU) radar in Shigaraki, Japan. The algorithm utilizes direct Monte Carlo simulations of uncertainties, with Bayesian Markov-chain Monte Carlo estimation of meteor model parameters and N -body propagation of distributions to perform orbit determination. The implementation has been validated using raw data simulations and a comparison with previous analysis methods. The concepts are applicable on a wide range of possible head echo measurements with other radar systems. The generated probability distributions provide quantitative reliability, which enables improved statistical studies and investigating the origins of detected meteoroids. The methodology section is highly detailed in order for the methods to be reproducible and provide a solid reference foundation for future studies. One such study is presented in a companion paper called 'High-altitude meteors detected by the interferometric MU radar'. [ABSTRACT FROM AUTHOR]

Tornadoes are one of the most severe meteorological phenomena on the earth and their high winds cause serious damage to society. It is well known that vortices (mesocyclone or misocyclone, depending on their scale) in convective clouds contribute to tornadogenesis. High temporal resolution radar observations are necessary to elucidate the mechanism of tornadogenesis because convective clouds change drastically over time. This study focused on waterspouts that occurred on 15 May 2017 near Okinawa, Japan. Using Phased Array Weather Radar (PAWR) data, which provide three-dimensional data with high temporal resolution (every 30 s), radar reflectivity factors and Doppler velocity data were used to detect the three-dimensional structure of vortices. Using PAWR data, vorticities and diameters of these misocyclones were detected every 30 s and their potential vorticities, which are only possible because of the three-dimensional observation by PAWR, were calculated to understand the vortex generation and advection. The structures of two misocyclones (MC1 and MC2) were detected from Doppler velocity patterns. Combined with the radar reflectivity analysis, MC2 can be divided into two misocyclones (MC2a and MC2b). Potential vorticity of MC1 increased with time, probably because an outflow from the strong echo enhanced the lower horizontal shear. Potential vorticities in MC2a and MC2b were conserved in each period, with MC2b being nearly twice as large as MC2a. [ABSTRACT FROM AUTHOR]

Shallow convective systems occasionally cause heavy precipitation through active warm-rain processes, although the mechanism is not well understood. In this study, a shallow line-shaped precipitation (SLSP) system, which produced heavy rainfall in the Kanto Region, Japan, was investigated using Ka-band and X-band radars, in addition to a numerical weather prediction model. The SLSP system exhibited features similar to squall lines (SLs), such as rapid movement perpendicular to the line, but the echo-top height remained below the 0 °C level, despite the rainfall intensity reaching approximately 78 mm h−1. Therefore, the SLSP system was considered to be dominated by a shallow convective system that contained cloud droplets, raindrops and drizzle rather than a deep convective system that included ice particles. The Ka-band radar observed a low-level cloud deck spreading to the front side of the convective system, and low-level cloud subsequently entered the SLSP system. In addition, large amounts of water vapor were transported by a super typhoon came from the southwest of the Kanto Region. Cloud water supplied from the cloud deck and that condensed from the water vapor supplied by the typhoon were considered to play an important role in the heavy precipitation associated with the SLSP system through the accretion of raindrops. This study provides insights into the microphysical structure of SLSP systems as well as the precipitation processes. • A shallow line-shaped precipitation system was observed by cloud radar. • Abundant water vapor and low-level stratocumulus clouds were transported by typhoon. • Active accretion process was responsible for driving production of heavy rainfall. [ABSTRACT FROM AUTHOR]

The relationships between the radar reflectivity factor for horizontal polarization (Zh) at the X-band and the liquid-equivalent snowfall rate (R) are presented for six hydrometeor classes of solid precipitation. These relationships were derived by comparing the values of Zh, R, and the hydrometeor class obtained by performing simultaneous observations in Niigata Prefecture, Japan. The relationships were assumed to be of the form Zh = B R1.67, where B denotes an experimentally determined coefficient. The values of R and the hydrometeor class were determined using a high-resolution precipitation gauge and an optical disdrometer, respectively, set up inside a windshield net. The average Zh value was determined for an analysis area of approximately 100 km2, located upwind of the ground-observation site. The prevailing hydrometeor class, its representative size, and the fall speed, along with the average Zh, R, and B values, were determined for 48 cases considered over three winters. The average B value for the "heavily rimed snow aggregate" was smaller than that for the "rimed snow aggregate". The largest B value was derived for a case of aggregates of unrimed dendritic particles (unrimed-D class). The case involving aggregates of unrimed low-temperature-type crystals (unrimed-C class) showed the smallest B value. For graupel cases, the average B value was roughly twice that of the rimed and heavily rimed snow aggregate classes and much smaller than that of the unrimed-D class. Snow aggregates demonstrated a stronger or weaker backscattering than graupel depending on the riming degree and types of constituent ice crystals in the X-band. [ABSTRACT FROM AUTHOR]

The seasonal features of the eastward jet through the Tsugaru Strait was investigated using surface velocity data between 2014 and 2019 obtained from high‐frequency radar located in the eastern part of the strait, as well as data obtained from repeated shipboard observations from 2009 to 2019. The potential‐vorticity‐front‐model was used, and the volume transport of low potential vorticity (PV) water and the intensity of the PV gap at the front in the eastern part of the strait were estimated from these data. The influence of these parameters on the seasonal flow pattern of the Tsugaru Warm Current out to the Pacific Ocean (the summer/autumn "gyre mode" or winter/spring "coastal mode") was examined. The distribution of the parameters was consistent with the theoretical understanding, showing that in addition to the volume transport, an increase in the local PV gap can also contribute to the development of the gyre. Plain Language Summary: The Tsugaru Warm Current forms part of the coastal flow around Japan and shows remarkable seasonal changes in its flow pattern, which are similar to the Kuroshio meandering. The current flows along the coast from winter to spring, but demonstrates large anticyclonic meandering in the offshore direction, known as "gyre mode," from summer to autumn. The cause of this change in the flow pattern has been thought to be the seasonal change in volume transport. In this study, we used high‐resolution temporal and spatial data obtained from a high‐frequency radar system, as well as shipboard hydrographic data collected over a period of 10 years, combined with a theory based on the relationship between coastal waves and offshore jets with fronts to identify another important factor that affects the seasonal flow pattern of the current, namely, "potential vorticity." This study is important because it helps our knowledge of the behavior of fluids flowing out of channels and straits as well as that in relation to the connection between local phenomena and larger phenomena. Key Points: Observational verification of the seasonal flow pattern theory of the Tsugaru Warm Current based on velocity data from high‐frequency radarImportance of potential vorticity gap at the front recognized as well as the volume transport of the current on the flow pattern changeIntegration and improvement of our understanding about the behavior of fluids flowing out from channels and straits [ABSTRACT FROM AUTHOR]

Upper‐tropospheric clouds in the outflow layer of typhoons can affect the track of typhoons (tropical cyclones) through radiation effects. In this study, the microstructure of the outflow‐layer clouds of several typhoons was examined. Cloud radar observations of three typhoons around Japan revealed numerous protuberances in echoes along the base of the upper‐level clouds, which are referred to as mammatus‐like echoes. The horizontal and vertical scales of these mammatus‐like echoes were 0.5–3.0 and 0.3–1.5 km, respectively. Vertical observations revealed downward (upward) Doppler velocities in (between) the hanging echo regions. Upward and downward velocity maxima were estimated at 3 m s−1 around the mammatus‐like echoes. Neutral stratification developed in the dry layer beneath the cloud base in which the mammatus‐like echoes formed. These mammatus‐like structures may promote mixing along the cloud base that contributes to dissipation of the outflow‐layer clouds. Plain Language Summary: Heating and cooling due to radiative effects associated with upper‐level clouds spreading from a typhoon have been reported to have an impact on the actual track of the typhoon. Therefore, it is important to clarify the processes of formation and dissipation of the upper‐level clouds of typhoons. However, observations of such clouds, which are formed from relatively small ice particles, are scarce and the process of their dissipation is not well understood. In this study, we used cloud radar, which can detect clouds formed of small ice particles, to observe the upper‐level clouds of three typhoons that approached Japan. At the base of the upper‐level clouds, we found many protuberance structures with 0.5–3.0 km width and 0.3–1.5 km depth. These protuberance structures were accompanied by relatively large vertical motions of approximately 3 m s−1. The temperature and water vapor distributions near the base of the upper‐level clouds of the studied typhoons were conducive to these vertical motions. The small‐scale protuberance structures might promote dissipation of upper‐level clouds along their base. Key Points: Protuberances observed by cloud radar along the base of outflow‐layer clouds of typhoons are termed mammatus‐like echo structuresThe mammatus‐like echo structures are associated with vertical motions with velocity of several meters per secondMammatus‐like echoes occur in a layer with high potential for turbulence caused by sublimation of ice particles falling into a drier layer [ABSTRACT FROM AUTHOR]

Specific attenuation and equivalent radar reflectivity in a melting layer were measured using a dual Ka-band radar system. The system consists of two identically designed Ka-radars. When the two radars are arranged to face each other and a precipitation system comes between the two radars, they observe the system from opposite directions. The radar echoes suffer from rain attenuation, which appears symmetrically in both radar echo profiles. By differentiating measured radar reflectivity with range, the specific attenuation (k) can be estimated. After obtaining the specific attenuation, the equivalent radar reflectivity (Ze) is estimated. Melting layer observations were conducted on a slope of Mt. Zao, Japan. In the melting layer, the specific attenuation and the equivalent radar reflectivity vary considerably along the radio path. The relationship between k and Ze showed interesting characteristics that appear in a loop-shape on a k-Ze diagram. A simple theoretical study using the Rayleigh and Mie scattering theories for melting snow spheres showed that the basic loop-shape is because of the change in permittivity of precipitation particles during melting. The loop-shape is greatly expanded by the change of the particle size. The Mie effect, which is significant for large precipitation particles, slightly modifies the loop-shape by reducing backscattering cross sections. The results also explain the shelf-like profile instead of the peak-like for Ze. [ABSTRACT FROM AUTHOR]

The Tropical Rainfall Measuring Mission (TRMM) satellite was launched in 1997, and the observations continued for more than 17 years. The features of TRMM observation were as follows: (a) it followed a non-sun synchronized orbit that enabled the diurnal variation of precipitation to be investigated; (b) it carried a precipitation radar and microwave and infrared radiometers, along with two instruments of opportunity in the form of a lighting sensor and a radiation budget sensor; and (c) it worked as a standard reference for precipitation measurements for other spaceborne microwave radiometers, which enabled global rain maps to be developed. For science, TRMM provided precise and accurate rain distributions over tropical and subtropical regions. The rainfall results are primarily essential for the study of precipitation climatologies, whereas the three-dimensional images of precipitation systems enabled the study of the global characteristics of precipitation systems. Technologically, the spaceborne rain radar onboard TRMM demonstrated the effectiveness of radars in space, whereas the combination with other rain observation instruments showed its effectiveness as a calibration source. Multi-satellite rain maps in which TRMM was the reference standard have been developed, and they became prototypes of the multi-satellite Earth observation systems. On the basis of the great success of TRMM, the Global Precipitation Measurement (GPM) was designed to expand TRMM's coverage to higher latitudes. The core satellite of GPM is equipped with a dual-frequency precipitation radar (DPR) and a microwave radiometer. DPR comprises a Kuband radar (KuPR) and a Ka-band radar (KaPR) and can discriminate solid from liquid precipitation. The period of the precipitation measurement with spaceborne radars extended to more than 23 years, which may make it possible to detect the change of precipitation climatology related to change in the global environment. Although TRMM's and GPM's accomplishments are very broad, this paper attempts to highlight Japan's contributions to the science of these missions. [ABSTRACT FROM AUTHOR]

In this study, the polarimetric variables of clear-air echoes (CAEs), that appeared on May 21, 2016 in the Tokyo metropolitan area, Japan, were investigated using the Ka-band (8.6-mm-wavelength) polarimetric cloud radar capable of detecting non-precipitating clouds. The objective was to establish the potential for distinguishing CAEs and hydrometeor echoes in the initial stage of cloud formation using a Ka-band polarimetric cloud radar. On the day being studied, CAEs showed evident diurnal variation. There were no CAEs before sunrise. The equivalent radar reflectivity (Ze) increased with time after sunrise, and horizontally widespread echoes (max. value > -15 dBZ) occurred within the radar observation range in the early afternoon. After sunset and into the early part of the night, Ze decreased rapidly. Range-height indicator observations showed that CAEs were restricted to heights of < 1.5 km. The differential reflectivity (ZDR) values of the CAEs were largely positive (1.8 dB) with a large standard deviation at 18:00 local time, i.e., considerably larger than those of cloud/weak precipitation echoes (0.4 dB) observed simultaneously. In comparison with cloud/precipitation echoes, the copolar correlation coefficient (ρhv) of the CAEs was smaller (< 0.9), whereas the variability of the total differential phase (?DP) in the range direction was larger. The upper limit of Ze and the distributions of ZDR and ρ hv were inconsistent with the characteristics of the Bragg scattering observed by the S-band (10-cm-wavelength) radar in previous studies. However, the larger ZDR, smaller ρ hv, and larger variability of ?DP in the range direction, associated with the horizontally widespread echoes, were consistent with the characteristics of insect echoes. The depolarization ratio defined using ZDR and ρhv could be effective in distinguishing this type of CAE and hydrometeor echoes observed by Ka-band polarimetric cloud radar. The polarimetric variables obtained by Ka-band polarimetric cloud radar are useful in distinguishing between CAEs and hydrometeor echoes. [ABSTRACT FROM AUTHOR]

The first X-band dual polarized phased array weather radar (DP-PAWR), which simultaneously transmits pulses of horizontal and vertical polarized radiation, was developed and installed at Saitama University, Japan, in December 2017. The DP-PAWR uses mechanical and electronic scanning at azimuth and elevation angles, respectively. It provides polarimetric precipitation measurements via 3-D volume scanning with an update rate between 10 and 60 s, for a range of up to 80 km. Here, we describe the initial DP-PAWR observation results. To evaluate the DP-PAWR observation accuracy, we compared the observational data with radar variables derived from Parsivel disdrometer data. In comparison with the disdrometer, the relative observation accuracy for the DP-PAWR radar reflectively factor had a standard deviation of 1.1 dB and mean value of 0.4 dB. We also conducted detailed observations of a developing thunderstorm using a specific differential phase (Kdp) column, focusing on the Kdp core during the storm. The Kdp core movements provided useful information about the convection flow during the storm. [ABSTRACT FROM AUTHOR]

In this study, we propose a new methodology for analysis of the initial stage of localized convective precipitation. The developed algorithm was used to create three-dimensional constant-altitude plan-position-indicator (3D CAPPI) data, which are high-spatiotemporal-resolution volumetric data, using two X-band polarimetric radars that are located in the Kanto region of Japan. Advection vectors are estimated by applying the normalized cross-correlation method to observed successive precipitation echoes on the polar coordinate system at each antenna tilt angle. The estimated advection vectors are expressed by a linear regression model that depends on time and tilt angle. In addition, 3D CAPPI data utilize the mosaic method to obtain further precipitation information from radar observations. The algorithm produces the detailed 3D structure of rapidly developing convective cells and provides quantitative information on convective precipitation, such as the echo top height, maximum reflectivity, and appearance time and height of each cell. The 3D CAPPI mosaic also clearly shows the back-building process at the initial stage of convective precipitation. • Data from two X-band polarimetric radars were used to develop the proposed algorithm. • The algorithm produces the detailed 3D structure and quantitative information on convective cells. • The mosaic clearly showed the back-building process at the initial stage of convective precipitation. [ABSTRACT FROM AUTHOR]

This paper presents the major specifications and characteristics of the Ku-band high-speed scanning Doppler radar for volcano observation (KuRAD) introduced to Kagoshima University in March 2017 as well as the results of a test observation at Sakurajima. KuRAD is a Doppler radar for research with a wavelength of approximately 2 cm and uses a 45 cm diameter Luneberg lens antenna as a transmitting and receiving antenna to observe the development of a volcanic eruption column immediately following eruption at a maximum rotation speed of 40 rpm. The maximum transmitter power is 9.6 W and the maximum observational range is 20 km. Observed data includes radar reflectivity factor, Doppler velocity, and Doppler spectrum width. Another feature of KuRAD is an obtained radio station license for observation of a total of seven active volcanos in Kyushu. To assess the basic performance of KuRAD, we carried out test observations of volcanic eruptions at Sakurajima, Kagoshima Prefecture, Japan and collected a total of 87 eruptions (20 of which are explosive eruptions and 7 of which had 3,000 m or higher eruptive smoke from vents). From the eruption data of Showa vent on May 2, 2017, it was confirmed that KuRAD could monitor the three-dimensional internal structure of a volcanic eruption column immediately following eruption. Eruption data from Minamidake of Sakurajima on March 5, 2018, showed that KuRAD successfully observed the eruptive smoke reaching a height of 4,000 m, although the eruptive smoke was covered with clouds and could not be detected by optical instruments of the Japan Meteorological Agency. [ABSTRACT FROM AUTHOR]

Background: A consensus exists that the first author and corresponding author make the most contribution to the publication of an article. The Y-index has been proposed to assess the scientific achievements of authors, institutions, and countries/regions (AIC/R for short) based on the number of first-author publications (FPs) and corresponding-author publications (RPs). Nonetheless, the Y-index is defined in terms of count and radian (represented by j and h) instead of using the relative radius and angle degree to simplify understanding. In the literature, a method for drawing radar diagrams online with the Y-index is also lacking. This study was conducted to enhance the Y-index with an additional relative radius denoted by k and the angle degree represented by h* (named Yk-index), include easy-to-use features (e.g., copying and pasting) for the delivery of the online Radar-Yk, and identify which one of AIC/R contributed the most to a scientific journal., Methods: From the Web of Science (WoS) database, we downloaded 9498 abstracts of articles published in the journal of Medicine (Baltimore) in 2020 and 2021. Three visual representations were used, including a Sankey diagram, a choropleth map, and a radar diagram, to identify the characteristics of contributions by AIC/R to Medicine (Baltimore) using the Yk-index (j, k, h*). A demonstration of Rada-Yk with easy-to-use features was given using the copy-and-paste technique., Results: We found that Qiu Chen (China), Sichuan University (China), China, and South Korea (based on regions, e.g., provinces/metropolitan areas in China) were the most productive AIC/R, with their Yk equal to 27,715, 12415.1, and 2045, respectively; a total of 85.6% of the published articles in Medicine (Baltimore) came from the 3 countries (China, South Korea, and Japan); and this method of drawing the Radar-Yk online was provided and successfully demonstrated., Conclusion: A breakthrough was achieved by developing the online Radar-Yk to show the most contributions to Medicine (Baltimore). Visualization of Radar-Yk could be replicated for future academic research and applications on other topics in future bibliographical studies., Competing Interests: The authors have no funding and conflicts of interest to disclose., (Copyright © 2022 the Author(s). Published by Wolters Kluwer Health, Inc.)

Quantitative real-time observations of a tsunami have been limited to deep-water, pressure-sensor observations of changes in the sea surface elevation and observations of sea level fluctuations at the coast, which are essentially point measurements. Constrained by these data, models have been used for predictions and warning of the arrival of a tsunami, but to date no system exists for local detection of an actual incoming wave with a significant warning capability. Networks of coastal high frequency (HF)-radars are now routinely observing surface currents in many countries. We report here on an empirical method for the detection of the initial arrival of a tsunami, and demonstrate its use with results from data measured by fourteen HF radar sites in Japan and USA following the magnitude 9.0 earthquake off Sendai, Japan, on 11 March 2011. The distance offshore at which the tsunami can be detected, and hence the warning time provided, depends on the bathymetry: the wider the shallow continental shelf, the greater this time. We compare arrival times at the radars with those measured by neighboring tide gauges. Arrival times measured by the radars preceded those at neighboring tide gauges by an average of 19 min (Japan) and 15 min (USA) The initial water-height increase due to the tsunami as measured by the tide gauges was moderate, ranging from 0.3 to 2 m. Thus it appears possible to detect even moderate tsunamis using this method. Larger tsunamis could obviously be detected further from the coast. We find that tsunami arrival within the radar coverage area can be announced 8 min (i.e., twice the radar spectral time resolution) after its first appearance. This can provide advance warning of the tsunami approach to the coastline locations. [ABSTRACT FROM AUTHOR]

A cloud-resolving nonhydrostatic four-dimensional variational data assimilation system (NHM-4DVAR) was modified to directly assimilate radar reflectivity and applied to a data assimilation experiment using actual observations of a heavy rainfall event. Modifications included development of an adjoint model of the warm rain process, extension of control variables, and development of an observation operator for radar reflectivity. The responses of the modified NHM-4DVAR were confirmed by single-observation assimilation experiments for an isolated deep convection, using pseudo-observations of rainwater at the initial and end times of the data assimilation window. The results showed that the intensity of convection could be adjusted by assimilating appropriate observations of rainwater near the convection and that undesirable convection could be suppressed by assimilating small or no reflectivity. An assimilation experiment using actual observations of a local heavy rainfall in the Tokyo, Japan, metropolitan area was conducted with a horizontal resolution of 2 km. Precipitable water vapor derived from global positioning system data was assimilated at 5-min intervals within 30-min assimilation windows, and surface and wind profiler data were assimilated at 10-min intervals. Doppler radial wind and radar-reflectivity data below the elevation angle of 5.4°° were assimilated at 1-min intervals. The 4DVAR assimilation reproduced a line-shaped rainband with a shape and intensity consistent with the observation. Assimilation of radar-reflectivity data intensified the rainband and suppressed false convection. The simulated rainband lasted for 1 h in the extended forecast and then gradually decayed. Sustaining the low-level convergence produced by northerly winds in the western part of the rainband was key to prolonging the predictability of the convective system. [ABSTRACT FROM AUTHOR]

Abstract: Rain attenuation correction is very important to obtain accurate radar reflectivity (Z H) and differential reflectivity (Z DR), particularly with the X-band wavelength radar. In the case of a dual-polarized radar, Z H and Z DR can easily be corrected by differential phase (Φ DP) measurements. In the self-consistent method with constraints proposed by Bringi et al. [Bringi, V.N., Keenan, T.D., and Chandrasekar, V., 2001. Correcting C-band radar reflectivity and differential reflectivity data for rain attenuation: a self-consistent method with constraints. IEEE Trans. Geosci. Remote Sens. 39, 1906–1915.], the relationship A H = αK DP b (where A H is the specific attenuation and K DP is the specific differential phase) is shown to be almost linear and the coefficient α is determined by employing a minimization process for each beam of the radar. However, α can be varied along the path length (r 0 ~ r) in the same precipitation system since α depends on the temperature and raindrop size distribution (DSD). The correction algorithm is modified to obtain the optimum α distribution for the relationship A H = α K DP b, and it is applied to the multiparameter X-band-wavelength (MP-X) radar operated by the National Research Institute for Earth Science and Disaster Prevention (NIED) in Japan. The optimum α is distributed over a wide range from 0.16 to 0.76 dB deg− 1 with a 1.5 km resolution. The reconstructed Φ DP by using the optimum α shows a good agreement with the measured Φ DP during the validation. Moreover, the corrected relationships between K DP–Z H, A H–Z H, Z DR–Z H, and Z DP–Z H are also similar to the theoretical values predicted by scattering simulations [Park, S.-G., Bringi, V.N., Chandrasekar, V., Maki, M., and Iwanami, K., 2005a. Correction of radar reflectivity and differential reflectivity for rain attenuation at X-band. Part I: theoretical and empirical basis. J. Atmos. Ocean. Technol. 22, 1621–1632.]. The proposed new algorithm in this study could be used and effectively adapted to estimate rainfall amounts with more accuracy. [Copyright &y& Elsevier]

This Polar Science special issue, "SuperDARN/Studies of Geospace Dynamics - Today and Future," originated from an international SuperDARN (Super Dual Auroral Radar Network) annual workshop held in Japan in June 2019, and is focused on studies of geospace dynamics particularly related to SuperDARN. Its purpose is to overview recent wide and active research, new scientific results and future perspectives mainly through, but not limited to, the scientific papers presented at the workshop. This special issue is an opportunity to commemorate a quarter century since the establishment of SuperDARN in 1995 and to contribute to the further development of geospace sciences and relevant technology. Thirteen valuable papers have been published covering a wide variety of scientific and technical topics. [ABSTRACT FROM AUTHOR]

In Japan, older adults account for the highest proportion of the population of any country in the world. When large-scale earthquake disasters strike, large numbers of casualties are known to particularly occur among seniors. Many are physically or mentally vulnerable and require assistance during the different phases of disaster response, including rescue, evacuation, and living in an evacuation center. However, the growing number of older adults has made it difficult, after a disaster, to quickly gather information on their locations and assess their needs. The authors are developing a proposal to enable vulnerable people to signal their location and needs in the aftermath of a disaster to response teams by deploying radar reflectors that can be detected in synthetic aperture radar (SAR) satellite imagery. The purpose of this study was to develop a radar reflector kit that seniors could easily assemble in order to make this proposal feasible in practice. Three versions of the reflector were tested for detectability, and a sample of older adults was asked to assemble the kits and provide feedback regarding problems they encountered and regarding their interest in using the reflectors in the event of a large-scale disaster. [ABSTRACT FROM AUTHOR]

To conduct accurate lightning prediction and nowcasting, it is important to clarify the relationship between electrification and microphysical properties in clouds. Using the dual-polarization Doppler radar with the hydrometeor classification algorithm and lightning observation, radar-derived microphysical properties related to lightning flash rate were investigated in terms of 10 isolated thunderstorm cases over the Kanto Plain, Japan, with 351 radar volume scans conducted every 5 min during the summer period. In this study, the ice-related particles within the 35 dBZ volume (V35IC) showed the highest correlation coefficient (r = 0.75) and the lowest normalized root mean square error (NRMSE = 8.3%) in relation to cloud-to-ground lightning (CG), and also best to intra-cloud lightning (IC, r = 0.69, NRMSE = 8.1%). The correlation between V35IC and CG flash rate was better than that of the mixed-phase (between 0 °C and − 40 °C) 35 dBZ volume (r = 0.64), without considering the microphysical particles. The second-best radar-derived microphysical property was the ice mass consisting of the radar grids of all the ice-related particles (r = 0.72). These results suggest that an effective lightning indicator in terms of a radar-derived property is the ice-related particle volume, in addition to the traditionally used graupel and hail. The ice-related particle volume in the colder region of the thunderstorm (air temperature lower than −10 °C) showed a higher correlation with CG and IC than that in the warmer region, especially in terms of IC. These results are consistent with the non-inductive charging theory that has been well accepted in previous studies. Following time-lag correlation analysis from 0 to −30 min every 5 min before thunderstorm initiation, it was found that the ice-related index of V35IC demonstrated the slowest decrease (r = 0.75–0.65 in 30 min) in the correlation coefficient with time lapse and may be suitable as a lightning nowcast indicator. • The relationship between lightning flash rate and ice-related volume derived from the dual-polarization radar is investigated. • The ice-related volume with greater than 35 dBZ (V35IC) showed the highest correlation in relation to CG and IC lightning. • Using a time-lag correlation from 0 to 30 min before lightning initiation, V35IC showed the slowest decrease with time-lapse. [ABSTRACT FROM AUTHOR]

Ground-based remote sensing equipment have the potential to be used for the nowcasting of the tephra hazard from volcanic eruptions. To do so raw data from the equipment first need to be accurately transformed to tephra-related physical quantities. In order to establish these relations for Sakurajima volcano, Japan, we propose a methodology based on high-resolution simulations. An eruption that occurred at Sakurajima on 16 July 2018 is used as the basis of a pilot study. The westwards dispersal of the tephra cloud was ideal for the observation network that has been installed near the volcano. In total, the plume and subsequent tephra cloud were recorded by 2 XMP radars, 1 lidar and 3 optical disdrometers, providing insight on all phases of the eruption, from plume generation to tephra transport away from the volcano. The Weather Research and Forecasting (WRF) and FALL3D models were used to reconstruct the transport and deposition patterns. Simulated airborne tephra concentration and accumulated load were linked, respectively, to lidar backscatter intensity and radar reflectivity. Overall, results highlight the possibility of using such a high-resolution modelling-based methodology as a reliable complementary strategy to common approaches for retrieving tephra-related quantities from remote sensing data. [ABSTRACT FROM AUTHOR]

Neutral air temperatures at 90 km altitude over Svalbard (78°N, 16°E) for the period 2002 to 2019 inclusive have been estimated from observations by the Nippon/Norway Svalbard Meteor Radar (NSMR). The data are presented per se and we shall not attempt to identify contributions from extra-terrestrial or anthropogenic driving. On the other hand, comparison with the corresponding period of solar UV flux notably fails to exhibit similarities. Moreover, there is indeed evidence of systematic temporal changes, possibly with a breakpoint around 2012. Selecting winter and summer months and years before and after 2012 and fitting trend-lines, we see strong evidence for cooling during summer. An apparent winter cooling prior to 2012 lacks statistical significance. A suggestion of reversal to winter warming after 2012 is also very uncertain. The summer cooling is found to be 9.9 ± 2.9 K decade−1 between 2002 and 2012, and 4.3 ± 1.2 K decade−1 between 2002 and 2019. Importantly, there is a suggestion (although lacking statistical significance) that summer cooling alleviated after 2012, and even reversed in winter. [ABSTRACT FROM AUTHOR]

VHF band stratosphere/troposphere (ST) radars around the globe are seldom operated in range-imaging mode. As such, the typical range resolution of their backscatter images is about 150 m. The only exception is the Kyoto University's Middle and Upper Atmosphere (MU) radar in Shigaraki, Japan. Range imaging using frequency diversity was implemented there in 2005 and has often been used since then. During the Shigaraki UAV Radar Experiment (ShUREX) campaigns in the spring/summers of 2015, 2016, and 2017, the MU radar was operated in range-imaging mode to provide a range resolution of typically 20 m, for good signal to noise (SNR) ratios. The resulting Capon backscatter images revealed a variety of atmospheric structures in the moist troposphere in great detail. They were also quite useful in deploying in situ sensors on board unmanned aerial vehicles (UAVs) to probe such structures in near real time guided by the images. The goal of this paper is to present and discuss some such structures of interest to atmospheric dynamics collectively, to provide an overarching view. They include Kelvin-Helmholtz (KH) billows generated by shear instability, mid-level cloud-base turbulence (MCT) layers generated by convective instability in a moist troposphere, convective boundary layer (CBL), and sheet and layer (S&L) structures in a stably stratified atmospheric column. Videos of radar images collected during the 2015 and 2016 campaigns are included as Additional file 1 to demonstrate the fascinating, ever-changing evolution of atmospheric structures over the MU radar. [ABSTRACT FROM AUTHOR]

Improving the accuracy of flood forecasting is critical in reducing the damage that can occur during flood disasters. In Japan, the flood prediction system is in operation in the first class rivers – relatively large and important rivers. However, small rivers, especially urban rivers, are so difficult to predict the river stage because of the quick rainfall-runoff responses. Such rivers are regarded as difficult to deliver the real time information on flood risk.Recently in Japan, X-band radar rainfall data can be used in real-time prediction for operation. X-band radar is highly resolution in both spatially and temporally. Furthermore, deep learning model has been applied to the river stage prediction and confirmed to have a good accuracy. By applying the X-band radar data to the deep learning model, river-stage prediction could be possible to the urban small rivers.In this study, we developed the deep learning river stage prediction model using the x-band radar rainfall data. We applied the model to the small urban rivers in Tokyo and confirmed the good prediction result. [ABSTRACT FROM AUTHOR]

High-power-large-aperture (HPLA) VHF radars at the lower frequency band around 50 MHz have been employed to observe the atmosphere for several decades, which can collect not only the echoes from clear-air turbulence in the neutral atmosphere and plasma irregularities in the ionosphere, but also the returns from aircrafts, meteors, precipitation, and so on. In this study, we examined the meteor echoes collected by the middle and upper (MU) atmosphere radar, operated by Research Institute for Sustainable Humanosphere, Kyoto University, Japan. Twenty receivers and five frequencies (46.25, 46.375, 46.5, 46.625, 46.75 MHz) were utilized in observation. With multi-channel echoes, angular and range distributions of the meteor heads and long-duration trails in the radar volume have been resolved by using adaptive constrained methods such as the Capon method and its modified version, the so-called norm-constrained Capon method. Some results will be shown. For example, fragmentation of the meteoroid can be disclosed from the range imaging of the long-duration trail echoes, angular imaging can make an identification of multiple echo centers that could be associated with meteoric fragmentation. [ABSTRACT FROM AUTHOR]