著者

独立行政法人国立文化財機構奈良文化財研究所埋蔵文化財センター 山崎 健 やまざき たけし Yamazaki Takeshi 上中 央子 うえなか ひさこ Uenaka Hisako 林 竜馬 はやし りょうま Hayashi Ryoma 佐々木 尚子 ささき なおこ Sasaki Naoko 辻本 裕也 つじもと ゆうや Tsujimoto Yuuya

出版者

独立行政法人国立文化財機構奈良文化財研究所埋蔵文化財センター

雑誌

埋蔵文化財ニュース (ISSN:03893731)

巻号頁・発行日

no.184, pp.1-27, 2021-03-30

著者

SUZUKI Kento IWASAKI Toshiki YAMAZAKI Takeshi

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2021-002, (Released:2020-10-21)

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Local fronts formed near the coast of the Kanto Plain mainly in a cold season, so-called “coastal fronts”, tend to be forecast on the inland side of their actual positions by the operational mesoscale Numerical Weather Prediction (NWP with a horizontal grid spacing of 5 km) model at Japan Meteorological Agency (JMA). In this study, we confirm a systematic NWP error through statistical validations of coastal fronts that occurred with southerly onshore winds during 2015-2018. Using a nonhydrostatic numerical model (JMA-NHM), we explore the relevant physical mechanisms through sensitivity experiments involving different horizontal resolution, envelope orography, and physics parameterization schemes for three cases with typical errors. The operational NWP model is shown to have a systematic error, with local fronts being consistently shifted to the inland side of their actual positions when the forecast period exceeds 5 hours, regardless of precipitation. The sensitivity experiments suggest that the systematic error associated with coastal fronts may be primarily caused by an underestimation of the mountain barrier surrounding the Kanto Plain in the model. The northwestward distance error of coastal fronts, averaged over the three illustrative cases, can be reduced by 27 % and 37 % by increasing the horizontal resolution from 5 km to 2 km and 1 km, respectively, and can be almost entirely eliminated by using the envelope orography. Moreover, the evaporative cooling of precipitation shifts coastal fronts to the seaward. Most coastal fronts are thought to take the form of cold air trapped on the southeastern slope of the mountains surrounding the Kanto Plain, where the elevation angle of the frontal surface is roughly controlled dynamically. The local front shifts to the seaward when the ridgelines of the mountains become higher, and shifts to the seaward through the reduction of the elevation angle when the trapped air becomes colder.

著者

KAWASE Hiroaki SASAI Takahiro YAMAZAKI Takeshi ITO Rui DAIRAKU Koji SUGIMOTO Shiori SASAKI Hidetaka MURATA Akihiko NOSAKA Masaya

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2018-022, (Released:2018-01-30)

被引用文献数

27

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Geographical distributions of heavy snowfall, especially in the Pacific Ocean side of Japan, have not been elucidated due to low occurrence frequency of heavy snowfall and limited number of snow observation points. This study investigates the characteristics of synoptic conditions for heavy daily snowfall from western to northeastern Japan in the present climate, analyzing high-resolution regional climate ensemble experiments with 5-km grid spacing. The Japanese 55-year Reanalysis (JRA-55) and the 10-ensemble members of the database for Policy Decision making for Future climate change (d4PDF) historical experiments are applied to the lateral boundary conditions of the regional climate model. Dynamical downscaling using d4PDF (d4PDF-DS) enables us to evaluate much heavier snowfall events than those simulated by dynamical downscaling using JRA-55 (JRA55-DS). Over the Sea of Japan side, heavy snowfall occurs due to cold air outbreaks, while over the Pacific Ocean side, heavy snowfall is brought by extratropical cyclones passing along the Pacific Ocean coast. A comparison between JRA55-DS and d4PDF-DS indicates that heavier snowfall can occur due to more developed extratropical cyclones and enhanced cold air damming in the Tokyo metropolitan area. The geographical distributions of extremely heavy snowfall are different between two typical synoptic conditions, i.e., cold air outbreaks and extratropical cyclones. The difference is much clearer in the extremely heavy snowfall events than in all snowfall events. Heavy daily snowfall occurs in January and February on the Pacific Ocean side, in December and January on the Sea of Japan side, and in November and March in high mountainous areas. Saturated water vapor pressure is largest around 0 ℃ under the snowing conditions. Synoptic conditions from late fall to winter are closely related to preferable conditions for heavy snowfall over the mountainous areas where the surface air temperature is much less than 0 ℃ in the heavy snowfall events.

著者

OHARA Ryota IWASAKI Toshiki YAMAZAKI Takeshi

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2021-065, (Released:2021-07-02)

被引用文献数

1

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This paper presents a study of impacts of evaporative cooling from raindrops on precipitation over western Japan associated with the Baiu front during a heavy rainfall event from 5 to 8 July 2018. First, we conducted analyses on dynamic and thermodynamic features of the stationary Baiu front using the Japanese 55-year Reanalysis (JRA-55). During this period, great amounts of water vapor were transported continuously to the stationary Baiu front, supporting the record-breaking rainfall. The 299 K isentropic surface was identified as a frontal surface. Along the isentropic surface, warm moist air adiabatically ascended, became saturated at around an altitude of 500 m, and initiated active precipitation systems. We found that the diabatic cooling near the tip of the frontal surface played an important role in keeping the position of the frontal surface without its northward retreat. Next, numerical sensitivity experiments were conducted to examine impacts of evaporative cooling and the topography on the heavy rainfall formation by using a cloud-resolving non-hydrostatic numerical model (The Japan Meteorological Agency Non-hydrostatic Model: JMA-NHM) with a horizontal resolution of 3 km. A heavy precipitation area extending from the Chugoku region to central Kinki was simulated regardless of whether the terrain was flattened or not. The precipitation was formed mainly by updrafts above a frontal surface at a potential temperature of 300 K. This precipitation area shifted northward by more than 100 km when the raindrop evaporation was turned off. The raindrop evaporation suppressed the northward retreat of the frontal surface by maintaining cold airmass amounts below the frontal surface.

著者

独立行政法人国立文化財機構奈良文化財研究所埋蔵文化財センター 高妻 洋成 こうづま ようせい Kouzuma Yousei 金田 明大 かねだ あきひろ Kaneda Akihiro 松田 和貴 まつだ かずたか Matsuda Kazutaka 箱崎 和久 はこざき かずひさ Hakozaki Kazuhisa 星野 安治 ほしの やすはる Hoshino Yasuharu 村田 泰輔 むらた たいすけ Murata Taisuke 山崎 健 やまざき たけし Yamazaki Takeshi 柳田 明進 やなぎだ あきのぶ Yanagida Akinobu 馬場 基 ばば はじめ Baba Hajime 脇谷 草一郎 わきや そういちろう Wakiya Souichirou 田村 朋美 たむら ともみ Tamura Tomomi

出版者

独立行政法人国立文化財機構奈良文化財研究所埋蔵文化財センター

雑誌

埋蔵文化財ニュース (ISSN:03893731)

巻号頁・発行日

no.176, pp.1-22, 2019-03-28

著者

Yamazaki Takeshi Ishikawa Ken-ichi Kuramashi Yoshinobu Ukawa Akira

出版者

American Physical Society

雑誌

Physical review D (ISSN:15507998)

巻号頁・発行日

vol.86, no.7, pp.074514, 2012-10

被引用文献数

92

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We calculate the binding energies for multinucleon bound states with the nuclear mass number less than or equal to 4 in 2+1 flavor QCD at the lattice spacing of a=0.09  fm employing a relatively heavy quark mass corresponding to mπ=0.51  GeV. To distinguish a bound state from attractive scattering states, we investigate the volume dependence of the energy shift between the ground state and the state of free nucleons by changing the spatial extent of the lattice from 2.9 to 5.8 fm. We conclude that 4He, 3He, deuteron and dineutron are bound at mπ=0.51  GeV. We compare their binding energies with those in our quenched studies and also with several previous investigations.