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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]

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]

Research goal: the search for "extrasolar" sources of meteor substance in the Earth atmosphere using positions of meteor radiants in the Galactic coordinate system; comparison of the distributions of meteor substance in the Galactic coordinate system from the radar database of MARS (Meteor Radar Automated System in Kharkiv) and from the SonotaCo's TV catalogue. Hyperbolic meteors can be associated with the "extrasolar" space. In such case, properties of their "extrasolar" motion may manifest both in the orbital parameters of Earth meteors and in their Galactic coordinates. Extensive observations can give the answer to such hypothesis. Two large databases of meteoroid orbital elements exist: MARS radar database, obtained in 1972–1978 in Ukraine (Kashcheyev and Tkachuk, 1980), and SonotaCo's TV catalogue obtained in 2007–2013 in Japan (SonotaCo, 2009). Differences were found in the distributions in these two databases, as well as between different samples taken from them. Baseline differences between these two sets of observational data in magnitude, observational techniques and other parameters demonstrate the selection effect in the distribution of meteoric substance. Based on a visual analysis, we conclude that we cannot rule out the possibility of the concentration of the radiants of MARS hyperbolas relative to apexes of the Sun motion in Equatorial/Galactic coordinate systems. The coordinates of the apexes of Sun's motion are determined: for the point with respect to the nearest stars in Hercules constellation as (270,30)/(56,23) degrees; and for the point with respect to the Galactic center in Cygnus as (318,48)/(0,90) degrees. Image 1 • Distributions of meteor radiants in the Galactic coordinate system have been studied. • The m ain attention was paid to the hyperbolic and highly eccentric orbits meteoroids. • We compare the meteor data of the video network (Japan) and the one radar (Ukraine). • Differences between the distributions of meteors SonotaCo and MARS were identified. • Search for possible directions of inflow of interstellar substances was carried out. [ABSTRACT FROM AUTHOR]

Abstract: Classification of ocean data maps is important for analysis of ocean data. Here, we compare self-organizing map (SOM) analysis with cluster methods such as the Ward method and K-means method. The HF (high-frequency) radar surface current data east of Okinawa Island, Japan were used for the comparison. There are two typical current patterns in the observation area: a strong southward current and a clockwise eddy-like current pattern. The classification results by the Ward method was similar to that by the SOM analysis. SOM analysis was insensitive to the cut-off empirical orthogonal function (EOF) mode number for reducing the data dimensions and noise, while the K-means method was the most sensitive to the EOF mode number. [Copyright &y& Elsevier]

Abstract: Mesosphere summer echoes (MSE) were observed during 2000–2001 and in 2009 with a 46.5-MHz VHF radar at Wakkanai, Japan (45.4°N). MSE at VHF (VHF-MSE) are active at 80–90km altitudes in the daytime mainly during June–July. Echo layer thickness ranges from a few to about 5km, and layer altitude and echo intensity are often modulated by short-period atmospheric gravity waves while the layer descends gradually at 0.2–0.8m/s with time, maybe due to tides. Detailed analyses of three VHF-MSE events show that meridional winds at the MSE altitudes over Wakkanai observed with a collocated 1.96-MHz MF radar are equatorward, indicating that cold ice particles and/or irregularities are advected southward from higher latitudes. It is found that VHF-MSE are often accompanied by simultaneous MSE at MF (MF-MSE) from a common volume, suggesting that plasma turbulence and/or short-scale electron density structures are responsible for the generation of VHF- and MF-MSE. [Copyright &y& Elsevier]

Abstract: Horizontal wind data over Indonesia obtained by global reanalyses were compared with wind-profiling radar (WPR) observations in Indonesia at Kototabang (100.32°E, 0.20°S), Pontianak (109.37°E, 0.00°S), Manado (124.92°E, 1.55°N), and Biak (136.10°E, 1.18°S). The global-reanalysis data were 850- and 700-hPa horizontal winds for 2007 and 2008. These data were obtained from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis (R1), the NCEP-Department of Energy (DOE) Atmospheric Model Intercomparison Project (AMIP-II) Reanalysis (R2), the Japan Meteorological Agency Climate Data Assimilation System (JCDAS), the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis-interim (ERA-Interim). All the four reanalyses showed good agreement with the WPR zonal and meridional wind data (correlation coefficient >0.7 in most cases). Of the four reanalyses, ERA-Interim had the highest correlation coefficient with the WPR winds in both zonal (correlation coefficient 0.89) and meridional (0.77) components. It can be explained that ERA-Interim used four-dimensional variational analysis (4D-var) for data assimilation, whereas the other reanalyses used three-dimensional variational analysis (3D-var). The zonal winds of the four reanalyses had smaller (78–87%) amplitudes than did the WPR winds. Further comparison of the zonal winds between the global reanalyses and operational radiosondes indicated that global-reanalysis zonal winds with smaller amplitudes are common in and around Indonesia. [Copyright &y& Elsevier]

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]

Abstract: Volume imaging radar often shows echo patterns on horizontal scale , moving across the radar. The echoes could be from convection, and moving at near the background wind velocity; other explanations are clouds or regions of turbulence. This paper studies the motion of echoes, with a two-dimensional correlation method widely used for cloud motion winds and tracking weather radar echoes, but not applied before to wind profiling radar. Data are from the MU (middle and upper atmosphere) radar, Japan. Several factors causing an underreading of echo speed are removed; however, remaining data still show echoes moving a few slower than the background wind, with similar direction. This could be explained by convection, consistent also with some increased vertical-beam spectral width showing turbulence. Motion of convective echoes slower than the background wind could bias other radar wind measurements. [Copyright &y& Elsevier]

Abstract: Ground-penetrating radar (GPR) profiles of Holocene beach deposits were documented from the Kujukuri strand plain, Pacific coast of Japan, to examine a marker of past sea level recognized in these profiles. The Kujukuri strand plain has been uplifted over the last 6000 years, with a total relative sea-level fall of about 5 m suggested by seaward lowering of the lithologic boundary between the foreshore and upper shoreface facies. A GPR survey was performed on a modern aeolian dune and beach ridges of the strand plain using a PulseEkko100 system with 100-MHz antennae. The profiles obtained contain five vertically stacked radar units (R1–R5) with characteristic reflections. Ground truthing using sediment cores and the morphology of the modern beach suggest that these radar units correspond to aeolian dune (R1), small-scale swale (R2), backshore and foreshore (R3), upper shoreface (R4), and lower shoreface (R5) deposits, in descending order. The backshore and foreshore radar unit shows a sequence of continuous reflections dipping seaward at an angle consistent with the modern beach, whereas the underlying upper shoreface radar unit represents complicated and less-continuous reflections. The boundary between these two units is a downlap surface of the foreshore reflections, and is thought to have formed at about 1 m below the mean sea level at the time of deposition. The lateral tracing of the boundary in radar profiles across the strand plain indicates a total fall in relative sea level of 5 m, which is consistent with the drill core results. Radar profiles of the foreshore and upper shoreface deposits in the Kujukuri strand plain thus provide a past sea-level indicator that is available without drilling sediment cores. [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]

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]

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]