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Tsukuba, Japan

Mashiko W.,Meteorological Research Institute | Inoue H.Y.,Meteorological Research Institute | Hayashi S.,Meteorological Research Institute | Kusunoki K.,Meteorological Research Institute | And 10 more authors.
Scientific Online Letters on the Atmosphere | Year: 2012

Two adjacent shear lines accompanied by wind gusts exceeding 20 m s-1 passed over the Shonai region on the Japan Sea coast during a moderate cold-air outbreak on 12 December 2010. The structure of the shear lines were examined using simulation results and observational data including high-frequency upper-air soundings. Simulation results revealed that cold-airmass outflow from the Eurasian Continent had a split-flow pattern due to the blocking effect of the Changbai Mountains. One is from the south side of the mountains (SCF), and the other is from the north side (NCF). NCF also has two streams: a shallow southward-meandering flow on the south and a slightly deeper straight flow on the north. A shallow shear line was formed between SCF and the shallow southward-meandering flow of NCF. The deeper straight flow of NCF sharply formed another shear line on the north at around 1-km height with SCF. This result implies that the shear lines accompanied by wind gusts on the Japan Sea coast during a coldair outbreak have various structures and that the horizontal wind shear a little above the surface could cause surface wind gusts. © 2012, the Meteorological Society of Japan.

Nishihashi M.,Alpha denshi Co. | Shimose K.-I.,Alpha denshi Co. | Kusunoki K.,Meteorological Research Institute | Hayashi S.,Meteorological Research Institute | And 5 more authors.
Journal of Atmospheric and Oceanic Technology | Year: 2013

A three-dimensional (3D) winter lightning mapping system employing very high frequency (VHF) broadband signals was developed for continuous remote observation in winter. VHF broadband pulses radiated by leader progression are received with three discone antennas arranged in a triangle (20-30 m) and recorded on a high-speed digital oscilloscope (1.25-GHz sampling) with GPS digital timing data. The two-dimensional (2D) mapping for azimuth and elevation of the VHF radiation sources was conducted by computing the arrival time differences of three pulses using a cross-correlation technique. From azimuth and elevation data from two sites extracted within a given time frame, 3D lightning mapping was performed using the triangulation scheme. An observation network for winter lightning was constructed within a comprehensive meteorological observation network in the Shonai area, which is located on the coast of the Japan Sea. This report includes the preliminary 2D and 3D mapping of winter lightning observed on 3 December 2010. The horizontal and vertical distributions of VHF radiation sources were consistent with the radar echo observed with X-band Doppler radar. These results indicate that the system can detect winter lightning discharges and perform 2D and 3D lightning mapping in detail. © 2013 American Meteorological Society.

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