- 著者
- Nobuyasu Shiga Kohta Kido Satoshi Yasuda Bhola Panta Yuko Hanado Seiji Kawamura Hiroshi Hanado Kenichi Takizawa Masugi Inoue
- 出版者
- (社)電子情報通信学会
- 雑誌
- IEICE Communications Express (ISSN:21870136)
- 巻号頁・発行日
- vol.6, no.2, pp.77-82, 2017 (Released:2017-02-01)
- 参考文献数
- 2
- 被引用文献数
- 12
Wireless two-way interferometry (Wi-Wi) is the simplified version of “carrier phase based two-way satellite time and frequency transfer,” wherein a wireless communication technology is used instead of a satellite communication technology. We used the carrier phase of a 2.4 GHz ZigBee module to measure the variation of two rubidium clocks at remote sites. Since clocks in the ZigBee module are much less precise than rubidium clocks, the carrier phase of the ZigBee signal cannot be used to compare two rubidium clocks in a simple manner. Using a technique to cancel the clock error of transmitters, we demonstrated picosecond-level precision measurement of the time variation of clocks between two remote systems. This synchronization technique at picosecond-level precision opens the door to low-cost wireless positioning at millimeter accuracy.
- 著者
- Ginaldi Ari Nugroho Kosei Yamaguchi Eiichi Nakakita Masayuki K. Yamamoto Seiji Kawamura
- 出版者
- Meteorological Society of Japan
- 雑誌
- SOLA (ISSN:13496476)
- 巻号頁・発行日
- vol.17, pp.63-68, 2021 (Released:2021-04-13)
- 参考文献数
- 17
High-resolution boundary layer radar (BLR) and wavelet are utilized to observe microscale downdraft-updraft combinations. High-resolution BLR can observe thermal activity that pushed the stable layer. During this thermal, a combination of downdraft-updraft was also observed. A detailed observation of this combination was conducted in this study. Using a 1-dimensional continuous wavelet transform with Paul wavelet, we could quantify this downdraft-updraft combination based on the height and period. Using this quantification and wavelet variance in different weather conditions, we showed the essential period from 0 to 0.25 min, 2 to 4 min, and 4 to 8 min of this microscale downdraft-updraft combination.
- 著者
- Hironori IWAI Shoken ISHII Seiji KAWAMURA Eiichi SATO Kenichi KUSUNOKI
- 出版者
- Meteorological Society of Japan
- 雑誌
- 気象集誌. 第2輯 (ISSN:00261165)
- 巻号頁・発行日
- vol.96A, pp.3-23, 2018 (Released:2018-02-19)
- 参考文献数
- 61
- 被引用文献数
- 4
During the Tokyo Metropolitan Area Convection Study for Extreme Weather Resilient Cities (TOMACS), many isolated convective storms developed in the southern Kanto Plain on August 17, 2012. The aim of this study was to clarify the dynamics leading to the convection initiation of one of them using different remote sensing instruments. Before the convection initiation, a southeasterly flow transported water vapor inland from Tokyo Bay and the well-mixed and a cumulus-cloud-topped convective boundary layer developed. A convergence line in the form of a sea breeze front (SBF) also moved inland from Tokyo Bay. A near-surface air parcel was lifted to its lifting condensation level (LCL) by an updraft in a convergence zone with a 3 km horizontal scale, which formed the west edge of the convergence line. The saturated air parcel at the LCL was then lifted to its level of free convection (LFC) by the updrafts associated with thermals below the cumulus cloud base. A Ku-band radar detected the first echo of hydrometeors about 6 minutes after the air parcel reached its LFC, then the convective cell developed rapidly. When an SBF arriving from Sagami Bay passed under the cell, the updraft over the nose of the SBF triggered a new precipitation cell, but no intensification of the preexisting cell was observed.