著者

Ken-ichi Shimose Shingo Shimizu Takeshi Maesaka Ryohei Kato Kaori Kieda Koyuru Iwanami

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.12, pp.215-219, 2016 (Released:2016-08-05)

参考文献数

28

被引用文献数

4

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This study investigated the impact of observation operators on low-level wind speed analysis. An evaluation of wind speeds retrieved by variational multiple-Doppler analyses using radial velocities (Vr) based on the formats of both a Plan Position Indicator (PPI) (hereafter, PPI-VAR) and a Constant Altitude Plan Position Indicator (CAPPI) (hereafter, CAPPI-VAR) was performed for comparison with wind speeds observed by a wind profiler during the warm season of three consecutive years. The statistical analysis showed that PPI-VAR was more accurate than CAPPI-VAR at 500 m above ground level (AGL). The error of CAPPI-VAR at 500 m AGL was caused by a representative error of CAPPI-formatted Vr derived from a certain radar whose beam height was far from the analysis level, and this error became more obvious the greater the vertical difference in wind speed across the analysis level. CAPPI-VAR uses CAPPI-formatted Vr from each radar equally; thus, the representative error might cause performance degradation of CAPPI-VAR at 500 m AGL. Conversely, PPI-VAR uses PPI-formatted Vr from each radar with appropriate weighting based on the beam height distance from the analysis level. PPI-VAR showed better results at 500 m AGL because the observation grid points were dense around 500 m AGL.

著者

Ryohei MISUMI Namiko SAKURAI Takeshi MAESAKA Shin-ichi SUZUKI Shingo SHIMIZU Koyuru IWANAMI

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.51-66, 2018 (Released:2018-02-19)

参考文献数

26

被引用文献数

4

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Convective storms are frequently initiated over mountains under weak synoptic forcing conditions. However, the initiation process of such convective storms is not well understood due to a lack of observations, especially the transition process from non-precipitating cumuli to precipitating convective clouds. To investigate the initiation process, we conducted observations around the mountains in the Kanto region, Japan on 18 August 2011 using a 35 GHz (Ka-band) Doppler radar and a pair of digital cameras. The evolution of convective clouds was classified into three stages: convective clouds visible but not detected by the Ka-band radar (stage 0), convective clouds detectable by the Ka-band radar with reflectivity below 15 dBZ (stage 1), and convective clouds accompanied by descending echoes corresponding to precipitation (stage 2). During the transition process from stage 1 to stage 2, weak radar echoes rose to the higher level and reflectivity rapidly increased. This phenomenon suggests that drizzle particles produced in a preexisting convective cloud were lifted by a newly developed updraft, and raindrops were formed rapidly by coalescence of the drizzle particles and cloud droplets. This hypothetical process explains the precipitation echo formation in the lower layer frequently observed in the mountainous area in the Kanto region.

著者

Ryohei Kato Ken-ichi Shimose Shingo Shimizu

出版者

Fuji Technology Press Ltd.

雑誌

Journal of Disaster Research (ISSN:18812473)

巻号頁・発行日

vol.13, no.5, pp.846-859, 2018-10-01 (Released:2018-10-01)

参考文献数

36

被引用文献数

25

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Torrential rainfall associated with linear precipitation systems occurred in Northern Kyushu, Japan, during July 5–6, 2017, causing severe damage in Fukuoka and Oita Prefectures. According to our statistical survey using ground rain gauges, the torrential rainfall was among the heaviest in recorded history for 6- and 12-h accumulated rainfall, and was unusual because heavy rain continued locally for nine hours. The predictability of precipitation associated with linear precipitation systems for this event was investigated using a cloud-resolving numerical weather prediction model with a horizontal grid interval of 1 km. The development of multiple linear precipitation systems was predicted in experiments whose initial calculation time was from several hours to immediately before the torrential rain (9:00, 10:00, 11:00, and 12:00 Japan Standard Time on July 5), although there were some displacement errors in the predicted linear precipitation systems. However, the stationary linear precipitation systems were not properly predicted. The predictions showed that the linear precipitation systems formed one after another and moved eastwards. In the relatively accurate prediction whose initial time was 12:00 on July 5, immediately before the torrential rainfall began, the forecast accuracy was evaluated using the 6-h accumulated precipitation (P6h) from 12:00 to 18:00 on July 5, the period of the heaviest rainfall. The average of the P6h in an area 100 km×40 km around the torrential rainfall area was nearly the same for the analysis and the prediction, indicating that the total precipitation amount around the torrential rainfall area was predictable. The result of evaluating the quantitative prediction accuracy using the Fractions Skill Score (FSS) indicated that a difference in location of 25 km (50 km) or greater should be allowed for in the models to produce useful predictions (those defined as having an FSS ≥0.5) for the accumulated rainfall of P6h ≥50 mm (150 mm). The quantitative prediction accuracy examined in this study can be basic information to investigate the usage of predicted precipitation data.

著者

Shin-ichi SUZUKI Takeshi MAESAKA Koyuru IWANAMI Shingo SHIMIZU Kaori KIEDA

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.25-33, 2018 (Released:2018-02-19)

参考文献数

20

被引用文献数

4

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X-band dual-polarization (multi-parameter) radars were used to observe a supercell storm that generated an F3 tornado in Ibaraki Prefecture, Japan on 6 May 2012. The observed data collected for this storm clearly exhibited the typical polarimetric features of a supercell storm, such as the ZDR (differential reflectivity) arc, ZDR column, and the KDP (specific differential phase) column, as well as their time evolution. The ZDR arc emerged at 10 to 15 min before the tornadogenesis. The ZDR column appeared approximately 1 h before the formation of the ZDR arc and was intermittent until tornadogenesis. As the ZDR arc appeared, the column became tall and stable and lasted until the dissipation of the tornado. These ZDR signatures of the supercell storm persisted for approximately half an hour.

著者

Namiko Sakurai Koyuru Iwanami Shingo Shimizu Yasushi Uji Shin-ichi Suzuki Takeshi Maesaka Ken-ichi Shimose Paul R. Krehbiel William Rison Daniel Rodeheffer

出版者

Fuji Technology Press Ltd.

雑誌

Journal of Disaster Research (ISSN:18812473)

巻号頁・発行日

vol.16, no.4, pp.778-785, 2021-06-01 (Released:2021-06-01)

参考文献数

26

被引用文献数

3

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The National Research Institute for Earth Science and Disaster Resilience deployed a lightning mapping array (LMA) in the Tokyo metropolitan area in March 2017. Called the “Tokyo LMA,” it obtains detailed three-dimensional observations of the total lightning activity (cloud-to-ground and intracloud flashes) in storms. The network initially consisted of 8 receiving stations, expanded to 12 stations in March 2018. Real-time total lightning images were first opened on the webpage in Japan. Real-time observations from the Tokyo LMA will be used in nowcasting lightning hazards and mitigating lightning disasters. Archived data will be used to develop lightning prediction techniques and a lightning climatology for the Tokyo metropolitan area.