著者

Tetsuya Takemi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.iii, 2019 (Released:2019-02-01)

参考文献数

1

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The Editorial Committee of Scientific Online Letters on the Atmosphere (SOLA) gives The SOLA Award to outstanding paper(s) published each year. I am pleased to announce that The SOLA Award in 2018 is going to be presented to the paper by Dr. Kosuke Ito et al., entitled with “Analysis and forecast using dropsonde data from the inner-core region of Tropical Cyclone Lan (2017) obtained during the first aircraft missions of T-PARCII” (Ito et al. 2018). Importance of dropsonde observations in the analysis and forecast of tropical cyclones (TCs) is well known, and such observations were operationally performed for the Atlantic hurricane. After the termination of the operational dropsonde observations in late 1980s, Dvorak technique has been used to estimate the intensity of TCs. However, uncertainties of Dvorak technique have been discussed for a long time, and dropsonde observations are essentially important for the precise information on TCs. The authors conducted dropsonde observations from an aircraft for TC Lan (2017) and, by assimilating the observed data, performed forecast experiments of the TC. They demonstrated potentially a positive impact of the dropsonde observations on the analysis and forecast of the TC. This study has demonstrated the importance of the dropsonde observations for TCs and is expected to enhance further studies investigations on the improvement of the analysis and forecast of TCs. Therefore, the Editorial Committee of SOLA highly evaluates the excellence of the paper.

著者

TOCHIMOTO Eigo NIINO Hiroshi

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.2018-043, (Released:2018-04-27)

被引用文献数

7

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This study used the JRA-55 reanalysis dataset to analyze the structure and environment of extratropical cyclones (ECs) that spawned tornadoes (tornadic ECs: TECs) between 1961 and 2011 in Japan. Composite analysis indicated that the differences between the structure and environment of TECs and those of ECs that did not spawn tornadoes (non-tornadic ECs: NTECs) vary with the seasons. In spring (March–May), TECs are associated with stronger upper-level potential vorticity and colder mid-level temperature than NTECs. The colder air at the mid-level contributes to the increase in convective available potential energy (CAPE) of TECs. TECs in winter (December–February: DJF) and those northward of 40°N in autumn (September–November: SON) are accompanied by larger CAPE than are NTECs. The larger CAPE for TECs in DJF is caused by larger moisture and warmer temperature at low levels, and that for TECs northward of 40°N in SON (NSON) is caused by the colder mid-level temperature associated with an upper-level trough. The distribution of the energy helicity index also shows significant differences between TECs and NTECs for DJF and NSON. On the other hand, the distribution of the 0–1 km storm relative environmental helicity (SREH) shows no significant differences between TECs and NTECs in most seasons except DJF. A comparison of TECs between Japan and the United States (US) shows that SREH and CAPE are noticeably larger in the US. It is suggested that these differences occur because TECs in the US (Japan) develop over land (ocean), which exerts more (less) surface friction and diurnal heating.

著者

Deqiang Liu Xubin Zhang Yerong Feng Ning Pan Chuanrong Huang

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.203-209, 2018 (Released:2018-12-26)

参考文献数

39

被引用文献数

1

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Using data from nine ensemble prediction systems (EPSs), we analyze uncertainties in forecasted tropical cyclone TC track (TCT), TC intensity (TCI) and relevant heavy rainfall (TCHR) for Typhoon Soudelor (2015) as it affected the Taiwan Strait and surrounding regions. The largest uncertainties in track predictions occurred when Soudelor traversed Taiwan and when it recurved northeastward after making landfall in mainland China. These large uncertainties seem to be ascribed to the topography of Taiwan and the spread of the perturbed steering flows, respectively. TCI spread was stronger before rather than after the Soudelor made landfall, with regional EPSs having stronger spread than global EPSs. This TCI spread showed high correlation with the evolution of the spread of vertical wind shear at the location of TC center. Large spread in 24-h TCHR during Soudelor's landfall correlated with low-level jets and convergences in most EPSs, and TC track variation had played important role in TCHR uncertainty. At last, the spread–skill relationships among different groups are explored.

著者

ITO Rui AOYAGI Toshinori HORI Naoto OH'IZUMI Mitsuo KAWASE Hiroaki DAIRAKU Koji SEINO Naoko SASAKI Hidetaka

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.2018-053, (Released:2018-08-24)

被引用文献数

7

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Accurate simulation of urban snow accumulation/melting processes is important to provide reliable information about climate change in snowy urban areas. The Japan Meteorological Agency operates a square prism urban canopy (SPUC) model within their regional model to simulate urban atmosphere. However, presently, this model takes no account of snow processes. Therefore, in this study, we enhanced the SPUC by introducing a snowpack scheme, and the simulated snow over Japanese urban areas was assessed by comparing the snow depths from the enhanced SPUC and from a simple biosphere (iSiB) model with the observations. Snowpack schemes based on two approaches were implemented. The diagnostic approach (sSPUCdgn) uses empirical factors for snow temperature and melting/freezing amounts and the Penman equation for heat fluxes, whereas the prognostic approach (sSPUCprg) calculates snow temperatures using heat fluxes estimated from bulk equations. Both snowpack schemes enabled the model to accurately reproduce the seasonal variations and peaks in snow depth, but it is necessary to use sSPUCprg if we wish to consider the physical processes in the snow layer. Compared with iSiB, sSPUCprg resulted in a good performance for the seasonal variations in snow depth, and the error fell to 20 %. While iSiB overestimated the snow depth, a cold bias of over 1°C appeared in the daily mean temperature, which can be attributed to excessive decreases in the snow surface temperature. sSPUCprg reduces the bias by a different calculation method for the snow surface temperature and by the inclusion of heated building walls without snow; consequently, the simulated snow depth is improved. sSPUCprg generated a relationship between the seasonal variations in snowfall and snow depth close to the observed relationship, with the correlation coefficient getting large. Therefore, the simulation accuracy of snowfall becomes more crucial for simulating the surface snow processes precisely by the enhanced SPUC.

著者

Akiyoshi WADA Ryo OYAMA

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.96, no.6, pp.489-509, 2018 (Released:2018-11-22)

参考文献数

52

被引用文献数

8

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Typhoon Lionrock (2016) made landfall in the Pacific side of northern Japan. One of the intriguing events was consecutive deep convections (convective bursts, CBs) occurred before making landfall on 31 August. Lionrock paused the decay of the intensity of the storm, although sea surface cooling (SSC) was induced distinctly by Lionrock along the track. To examine the influence of CBs on changes in storm intensity during the decay phase, numerical simulations were conducted with a 3 km mesh coupled atmosphere-wave-ocean model. The coupled model successfully simulated the occurrence of CBs north of the near-surface-convergence area, which was formed by the confluent of the storm's tangential winds with near-surface frictional spiral inflow from the surrounding region where the significant wave height was high. Simultaneously, the relatively fast translation and asymmetric tropical cyclone (TC) structure were maintained. Lower tropospheric horizontal moisture fluxes have enhanced around the convergence area, although SSC resulted in reduction of the air-sea latent heat fluxes within the storm's inner core. Local occurrences of upward moisture fluxes associated with CBs increased the mid-to-upper tropospheric condensational heating on the upstream side. This caused local increase in lower-tropospheric pressure gradient on the upstream side. This was favorable for pausing the decay of the simulated storm intensity even during the decay phase. Sensitivity experiments regarding the execution time of the coupled model showed that the vertical moisture fluxes and number of CBs could increase around the surface frictional convergence area ahead of the storm when the coupled model was not used. This suggests that the storm in mid-latitude could locally increase the maximum surface wind speed under favorable oceanic conditions. The number and distribution of CBs are indeed sensitive to oceanic conditions and are considered to affect the storm-track simulation and maximum surface wind speeds.

著者

YUMIMOTO Keiya TANAKA Taichu Y. YOSHIDA Mayumi KIKUCHI Maki NAGAO Takashi M. MURAKAMI Hiroshi MAKI Takashi

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.2018-035, (Released:2018-04-08)

被引用文献数

21

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The Japan Meteorological Agency (JMA) launched a next-generation geostationary meteorological satellite (GMS), Himawari-8, on October 7, 2014 and began its operation on July 7, 2015. The Advanced Himawari Imager (AHI) onboard Himawari-8 has 16 observational bands that enable the retrieval of full-disk maps of aerosol optical properties (AOPs), including aerosol optical thickness (AOT) and the Ångström exponent (AE) with unprecedented spatial and temporal resolution. In this study, we combined an aerosol transport model with the Himawari-8 AOT using the data assimilation method, and performed aerosol assimilation and forecasting experiments on smoke from an intensive wildfire that occurred over Siberia between May 15 and 18, 2016. To effectively utilize the high observational frequency of Himawari-8, we assimilated 1-h merged AOTs generated through the combination of six AOT snapshots taken over 10-min intervals, three times per day. The heavy smoke originating from the wildfire was transported eastward behind a low-pressure trough, and covered northern Japan from May 19 to 20. The southern part of the smoke plume then traveled westward, in a clockwise flow associated with high pressure. The forecast without assimilation reproduced the transport of the smoke to northern Japan; however, it underestimated AOT and the extinction coefficient compared with observed values, mainly due to errors in the emission inventory. Data assimilation with the Himawari-8 AOT compensated for the underestimation and successfully forecasted the unique C-shaped distribution of the smoke. In particular, the assimilation of the Himawari-8 AOT during May 18 greatly improved the forecast of the southern part of the smoke flow. Our results indicate that the inheritance of assimilation cycles and the assimilation of more recent observations led to better forecasting in this case of a continental smoke outflow.

著者

Keiichi ISHIOKA

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.96, no.2, pp.241-249, 2018 (Released:2018-03-27)

参考文献数

18

被引用文献数

10

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A new recurrence formula to calculate the associated Legendre functions is proposed for efficient computation of the spherical harmonic transform. This new recurrence formula makes the best use of the fused multiply–add (FMA) operations implemented in modern computers. The computational speeds in calculating the spherical harmonic transform are compared between a numerical code in which the new recurrence formula is implemented and another code using the traditional recurrence formula. This comparison shows that implementation of the new recurrence formula contributes to a faster transform. Furthermore, a scheme to maintain the accuracy of the transform, even when the truncation wavenumber is huge, is also explained.

著者

Tetsuya Takemi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.ii-iii, 2018 (Released:2018-01-25)

参考文献数

2

---

The Editorial Committee of Scientific Online Letters on the Atmosphere (SOLA) gives The SOLA Award to outstanding paper(s) published each year. I am pleased to announce that The SOLA Award in 2017 is going to be presented to the paper by Dr. Hiroaki Miura, entitled with “Coupling the hexagonal B1-grid and B2-grid to avoid computational mode problem of the hexagonal ZM-grid” (Miura 2017), and to the paper by Dr. Daisuke Goto et al., entitled with “Vertical profiles and temporal variations of greenhouse gases in the stratosphere over Syowa Station, Antarctica” (Goto et al. 2017).

出版者

Meteorological Society of Japan

雑誌

Journal of the Meteorological Society of Japan. Ser. II (ISSN:21869057)

巻号頁・発行日

pp.2018-004, (Released:2017-11-24)

被引用文献数

20

著者

Qoosaku Moteki Atsuyoshi Manda

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.9, pp.19-22, 2013 (Released:2013-03-01)

参考文献数

19

被引用文献数

9 16

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We propose a new scenario for the seasonal migration of the Baiu frontal zone over the East China Sea in which this migration is affected by variations in the sea surface temperature (SST). Using atmospheric and oceanic objective analysis datasets, a relationship was determined between the seasonal migration of the Baiu frontal zone and the decaying process of the cold high over the East China Sea. Before the middle of June, the cold high, cooled by the low SST, is present over the continental shelf, and the position of the Baiu frontal zone corresponds to that of the Kuroshio Front. After the middle of June, the cold high decays and is shifted northward in association with the warming SST over the shelf. As a result, the Baiu frontal zone migrates northward and ends in the middle of July due to the dissipation of the cold high.

著者

TSENG Wang-Ling HONG Chi-Cherng LEE Ming-Ying HSU Huang-Hsiung CHANG Chi-Chun

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.2020-071, (Released:2020-10-07)

被引用文献数

4

---

In July and August (JA) 2018, the monsoon trough in the western North Pacific (WNP) was unusually strong, the anticyclonic ridge was anomalously northward-shifted, and enhanced and northward-shifted tropical cyclone activity was observed. Studies have examined the effects of sea surface temperature (SST) anomalies on the North Atlantic (NA), the Indian Ocean (IO), and the tropical North Pacific. However, a synthetic view of SST forcings has yet to be identified. Based on a series of numerical experiments, this study demonstrated that the SST anomaly in the tropical WNP was the key forcing that formed the structure of the observed anomalous phenomena in the monsoon trough. Moreover, the combined effect of the SST anomaly in both the tropical and extratropical WNP resulted in enhanced circulation anomalies in the WNP. The NA SST anomaly also enhanced the monsoon trough in the presence of WNP SST anomaly. By contrast, the individual SST anomaly in the NA, IO, the extratropical WNP, and the subtropical eastern North Pacific could not force the enhanced monsoon trough. We proposed that the local effect of both the tropical and extratropical WNP SST anomaly as the major driver and the remote effect of NA SST anomaly as a minor contributor jointly induced the anomalous circulation and climate extremes in the WNP during JA 2018.

著者

Kei SAKAMOTO Masaaki TAKAHASHI

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.83, no.5, pp.817-834, 2005 (Released:2005-11-19)

参考文献数

16

被引用文献数

23 23

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Near the tropopause over the North Pacific in summer an isolated low pressure system (Upper Cold Low, UCL) is often generated by the deepening and cutting off of a trough in the mid-latitude westerlies. The tracks and structures of these UCLs have been investigated in previous studies, but understanding of the cut off and weakening processes remains poor. In this paper, the tracks of UCLs generated in the 1999 summer are analyzed using ECMWF data. The physical processes occurring in one ofthese systems are investigated in detail using the ECMWF data, and the meso-scale model MM5. We focus particularly on cut off and weakening processes, and on the structure of the vertical velocity in the UCL.The summer of 1999 was hot over Japan, and part of the Tibetan high pressure, around 200 hPa, was shifted northward. This allowed some UCLs to approach Japan in July and August. A UCL on August 19th is selected for detailed analysis, and was generated in the following process. Positive vorticity in a westerly wave at 200 hPa was extended by a northeast wind in the upper layer only. The positive vorticity was cut off by non-liner effects and upper level divergence, associated with convective clouds, generating the isolated UCL. The structure of the cyclonic circulation and the warm and cold cores were similar to those in previous studies. The structure of the vertical motion of the moving UCL was explained by dry dynamics and there was upward motion on the front side of the UCL, in the direction of movement. Upper level clouds in the UCL strengtJhened this upward motion. Convective clouds were seen in the system. The latent heat of these convective clouds played an important role in weakening the cold core of the UCL.

著者

釜江 陽一 植田 宏昭 井上 知栄 三寺 史夫

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.101, no.2, pp.125-137, 2023 (Released:2023-03-07)

参考文献数

31

被引用文献数

1

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冬季オホーツク海における海氷分布は、極東域および北太平洋域の大気と強く相互作用する。先行研究は、オホーツク海海氷面積の年々変動は広域の大気循環と対応することを指摘している。一方で、オホーツク海における海氷面積の数日から1週間程度の時間スケールでの急激な変動に対応する大気現象については明らかにされていない。本研究では、日ごとの高解像度海洋再解析データを用いることで、オホーツク海海氷密接度の急激な減少イベントをもたらす大気循環について調査した。1993年から2019年にかけて、海氷急減イベントを合計21事例抽出した。急減イベントに共通した大気循環の特徴として、オホーツク海南部における発達した温帯低気圧とベーリング海北部における高気圧偏差、およびその間の強い地表の南東風が確認された。海氷の季節的な張り出しを左右する気候学的な西風とは逆向きである強い南東風は、オホーツク海海氷密接度の急減をもたらす。オホーツク海北部と中部で起こる海氷の急減は、海氷の移流と東風に伴う海氷融解によって起こる。東へと移動する温帯低気圧は、海氷密接度の急減と北太平洋北部の海面気圧の低下をもたらし、結果としてオホーツク海海氷密接度の変動とアリューシャン低気圧の強度の変動の間には時間差が存在する。

著者

倉持 将也 植田 宏昭

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.101, no.1, pp.21-37, 2023 (Released:2023-02-07)

参考文献数

56

被引用文献数

1

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熱帯インド洋-西部太平洋域の対流活動に関連して、2020/21年冬季の前半と後半の間で東アジアの気温偏差は負から正へと転じた。平年より気温が低かった2020/21年冬季の前半では、対流圏上層のチベット高原南東部と日本上空にそれぞれ高気圧性と低気圧性の循環偏差対が発現していた。この波列パターンは、東インド洋から南シナ海上で強化された熱帯積雲対流に励起されたロスビー波の伝播を示し、本研究で新たに東南アジア-日本(Southeast Asia–Japan: SAJ)パターンと呼称する。一方、2020/21年冬季の後半では、活発な対流活動域は東方のフィリピン海へ移動し、上層高気圧偏差もまた日本の南へと位置を変えた。このような循環偏差は西太平洋(western Pacific: WP)的なパターンとして認識でき、東アジアの高温偏差をもたらした。SAJパターンに関連するチベット高原南東部の高気圧性循環偏差と南シナ海の対流強化の関係は、パターンが顕著に発現した月を抽出した合成解析でも統計的に有意であることが確認された。一方、WP的なパターンの半分の場合では、フィリピン海での対流の活発化を伴っていた。これらの異なる2つの循環偏差は、線形傾圧モデルに南シナ海とフィリピン海に熱源を与えることでそれぞれ再現された。さらに渦度収支解析から、チベット高原南東への気候学的な上層風の収束が SAJパターンの空間的な位相固定性において重要であることが示唆された。

著者

ISHIJIMA Kentaro TSUBOI Kazuhiro MATSUEDA Hidekazu TANAKA Taichu Yasumichi MAKI Takashi NAKAMURA Takashi NIWA Yosuke HIRAO Shigekazu

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.2022-017, (Released:2021-12-10)

被引用文献数

2

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Temporal variations of atmospheric radon-222 (222Rn) observed at four Japan Meteorological Agency stations in Japan by the Meteorological Research Institute were analyzed using an on-line Global Spectral Atmosphere Model–Transport Model (GSAM-TM). Monthly and diurnal variations, and a series of synoptic high-222Rn events were extracted from 5-12 years of 222Rn observations during 2007-2019. Observed seasonal patterns of winter maxima and summer minima, driven mainly by monsoons, were well reproduced by the GSAM-TM based on existing 222Rn emission inventories, but their absolute values were generally underestimated, indicating that our understanding of 222Rn emission processes in East Asia is lacking. The high-resolution model (∼ 60 km mesh) demonstrated that observed consecutive high-222Rn peaks at several-hour timescales were caused by two 222Rn streams from different regions and were not well resolved by the low-resolution model (∼ 200 km mesh). GSAM-TM simulations indicate that such cold-front-driven events are sometimes accompanied by complicated three-dimensional atmospheric structures such as stratospheric intrusion over the front, significantly affecting distributions of atmospheric components. A new calculation approach using hourly 222Rn values normalized to daily means was used to analyze the diurnal 222Rn cycle, allowing diurnal cycles in winter to be extracted from 222Rn data that are highly variable due to sporadic continental 222Rn outflows, which tend to obscure the diurnal variations. Normalized diurnal cycles of 222Rn in winter are consistent between observations and model simulations, and seem to be driven mainly by diurnal variations of planetary-boundary-layer height (PBLH). These results indicate that 222Rn in the near-surface atmosphere, transported from remote source regions, could vary diurnally by up to 10 % of the daily mean owing mainly to local PBLH variations, even without significant local 222Rn emissions.

著者

石川 高見

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.4, no.6, pp.137-146, 1926-09-04 (Released:2009-02-05)

被引用文献数

2 4

著者

村松 照男

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.64, no.6, pp.913-921, 1986 (Released:2007-10-19)

参考文献数

17

被引用文献数

33 37

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明瞭な多角形眼が台風8019のPPIエコー上で観測された。直径30kmの眼は4角形から6角形までその形を変え,台風眼中心に対して半時計回りに回転していた。回転周期は5-6角形で41-43分,4角形で47-50分と回転速度が速い(周期が短い)ほど多角形の角数が増加した。多角形眼は形状を変えながら約15時間観測され,5角形が最も頻度が高く,111分という長寿命であった。逆に,4角形は不安定で寿命は12分前後で,頻度も最もひくく,3角形や7角形は観測されなかった。多角化は眼の壁雲の最も内側の数km幅の狭い領域で起こっていた。眼の中の小エコーセルの追跡の結果,小エコーセル(眼の中の気塊)は等角速度運動をしており,多角形に変形した部分はそれよりやや速い速度で回転していた。多角形眼の現象は水平シヤーの大きい,眼の中の下降流と眼の壁雲の上昇流領域の境界で起こり,境界面の不安定を示唆する多角形の各辺の波打ち現象がしばしば見られた。この現象は発達した台風(ハリケーン)で明瞭な二重眼構造をもつ,中心気圧940mb前後,眼径が30-50kmの場合で多く見られた。

著者

NAKAMURA Shingo KUSAKA Hiroyuki SATO Ryogo SATO Takuto

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.2022-030, (Released:2022-04-08)

被引用文献数

4

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This study assesses heatstroke risk in the near future (2031-2050) under RCP8.5 scenario. The developed model is based on a generalized linear model with the number of ambulance transport due to heatstroke (hereafter the patients with heatstroke) as the explained variable and the daily maximum temperature or Wet-Bulb Globe Temperature (WBGT) as the explanatory variable. With the model based on the daily maximum temperature, we performed the projection of the patients with heatstroke in case of considering only climate change (Case 1), climate change and population dynamics (Case 2), and climate change, population dynamics, and long-term heat acclimatization (Case 3). In Case 2, the number of patients with heatstroke in the near future will be 2.3 times higher than that in the baseline period (1981-2000) on average nationwide. The number of future patients with heatstroke in Case 2 is about 10 % larger than that in Case 1 on average nationwide despite of population decline. This is due to the increase in the number of elderly people from the baseline period to the near future. However, there were 21 prefectures where the number of patients in Case 2 is smaller compared to Case 1. Comparing the results from Cases 1 and 3 reveals that the number of patients with heatstroke could be reduced by about 60 % nationwide by acquiring heat tolerance and changing lifestyles. Notably, given the lifestyle changes represented by the widespread use of air conditioners, the number of patients with heatstroke in the near future was lower than that of the baseline period in some areas. In other words, lifestyle changes can be an important adaptation to the risk of heatstroke emergency. All of the above results were also confirmed in the prediction model with WBGT as the explanatory variable.

著者

ISLAM Md. Rezuanul SATOH Masaki TAKAGI Hiroshi

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.2022-024, (Released:2022-02-03)

被引用文献数

6

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This study investigated tidal records and landfall tropical cyclone (TC) best tracks from 1980 to 2019 to determine changes in storm surge heights in coastal regions of Central Japan, including Tokyo. The results indicate that annual mean storm surge heights have increased in the last 20 years (2000-2019) compared to those in 1980-1999, and that these changes are noteworthy, particularly in Tokyo Bay. TC wind intensity and size during landfall time frame have become stronger and larger, respectively, corresponding to increasing storm surge magnitudes from 1980 to 2019. The increased occurrence frequency of TCs with more northeastward tracks is another factor that may have contributed to the increased surge hazards around Tokyo. Additionally, a positive correlation between surge heights and a hazard index supports these statistical findings. Japan central coast will likely experience increasing numbers of extreme storm surge events in the future, if, the current increasing tendency continues.

著者

Yasutaka Hirockawa Teruyuki Kato Kentaro Araki Wataru Mashiko

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16, pp.265-270, 2020 (Released:2020-12-24)

参考文献数

25

被引用文献数

16 37

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An extreme rainfall event brought precipitation amounts exceeding 1000 mm in Kyushu district, southwestern Japan, in early July 2020. Especially, an elongated and stagnated mesoscale convective system formed around the Kuma River in central Kyushu district produced localized heavy rainfall with precipitation amounts larger than 600 mm in 13 hours. Characteristics of this extreme rainfall event were investigated using distributions of radar/raingauge-analyzed precipitation amounts (RAP) and statistically compared with those during the warm seasons (April–November) in 2009-2019. The results are shown as follows; (1) nine heavy rainfall areas of linear-stationary type (LS-HRAs) were extracted, (2) spatial and temporal scales of two LS-HRAs among them respectively exceeded 270 km and 10 hours, (3) the maximum RAP exceeding 100 mm in LS-HRAs were comparable to those in previous extreme rainfall events, (4) large accumulated three-hour precipitation amounts exceeding 200 mm were more frequently observed than those in the previous events, and (5) the accumulated five-day precipitation amount integrated around Kyushu Island was the largest since 2009. This study also showed that the large area-integrated precipitation amount was produced mainly from widespread precipitation systems associated with the Baiu front, while the nine LS-HRAs significantly contributed localized heavy rainfall.