著者

Tetsuya Takemi Takashi Unuma

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15A, pp.60-65, 2019 (Released:2019-09-19)

参考文献数

32

被引用文献数

25

---

This study documented the environmental properties of precipitation systems that produced the July 2018 Heavy Rainfall event in Japan. The gridded analysis data were used to diagnose the potential for the development of convective systems in terms of thermodynamic environmental indices. Precipitable water vapor was extremely larger than that seen in the climatology of warm-season quasi-stationary convective clusters (QSCCs). Such an extreme moisture content was realized by very humid conditions at the middle-levels. In contrast, temperature lapse rate in a convectively unstable layer was not so significant in comparison to the QSCC climatology. Among the environmental indices, K Index was shown to describe the potential for the rainfall development. Based on the analysis, the roles of moisture content and profile on the convection development were discussed. It was suggested that the middle-level high humidity contributes to the occurrence of the present heavy rainfall by minimizing negative effects of environmental mixing and by decreasing vertical displacements to reach levels of free convection. In regions where heavy rainfall occurred, an automated algorithm detected the development of QSCCs, which were mostly categorized as a linear type.

著者

Tetsuya Takemi Toshiya Yoshida Shota Yamasaki Kentaro Hase

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.22-27, 2019 (Released:2019-02-06)

参考文献数

27

被引用文献数

25

---

An intense tropical cyclone, Typhoon Jebi (2018), landed the central part of Japan and caused severe damages. Quantitative assessment of strong winds in urban districts under typhoon conditions is important to understand the underlying risks. As a preliminary study, we investigate the influences of densely built urban environments on the occurrence of wind gusts in an urban district of Osaka City during Typhoon Jebi by merging mesoscale meteorological and building-resolving large-eddy simulations (LES). With the successful reproduction of the track and intensity of the typhoon in meteorological simulations, the simulated winds at the boundary-layer top of the LES model are used to quantitatively estimate the wind gusts in the urban district. The maximum wind gust in the analysis area of Osaka was estimated as 60-70 m s−1, which is comparable to the wind speed at the height of about 300 m.

著者

Toshiya Yoshida Tetsuya Takemi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.174-178, 2018 (Released:2018-11-18)

参考文献数

17

被引用文献数

9

---

Effects of obstacle-height variability on mixing length and dispersive stress are investigated by conducting large-eddy simulations of airflows over arrays of roughness obstacles with variable height. We evaluate differences among three simulations of flows over obstacles with no, moderate, and high obstacle-height variability. Within the canopies, effective mixing length shows one local maximum and minimum in the simulation with no obstacle-height variability but two maxima and minima in the simulations with obstacle-height variability. The number of the local maxima and minima corresponds to that of the shear layers seen at the heights of obstacle tops. Enhanced dispersive stress appears within the canopy between the heights of the lower- and higher-obstacle tops in the simulations with obstacle-height variability. Particularly in the simulations with high obstacle-height variability, the magnitude of dispersive stress becomes comparable to that of the Reynolds stress at the height of the lower-obstacle top. These results suggest that actual urban areas with high building-height variability should significantly affect properties of mixing length and dispersive stress.

著者

Tetsuya Takemi Takashi Unuma

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-006, (Released:2020-01-21)

被引用文献数

33

---

This study investigated the environmental factors responsible for the development of heavy rainfall in eastern Japan during the passage of Typhoon Hagibis (2019) by using mesoscale gridded analysis data as well as observed data. Environmental indices for diagnosing stability and moisture conditions were examined. It was found that the whole troposphere is almost saturated and the column total water vapor content is extremely large. In the lower troposphere we identified layers of moist absolutely unstable states with the thickness deeper than 2 km. Such deep moist absolutely unstable layers as well as abundant moisture content and almost saturated troposphere set a high potential for convective development. Under these favorable environmental conditions, the fact that the heights of the absolutely unstable layers' bottom are comparable to the mountain elevations is considered to be favorable for topographic lifting of unstable, moist air, which will trigger and activate strong convection and hence heavy rainfall. In spite of a moderate amount of convective available potential energy and a nearly moist-adiabatic lapse rate, moist absolute instability, abundant moisture, and high humidity jointly play a key role to increase the potential for generating the present heavy rainfalls.

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.125-131, 2019 (Released:2019-05-30)

参考文献数

32

被引用文献数

23

---

This study investigated the impacts of global warming on extreme rainfall produced by a slow-moving typhoon by conducting pseudo-global warming (PGW) experiments. We examined Typhoon Talas (2011) that caused long-lasting heavy rainfall exceeding 2000 mm over the Kii Peninsula. The experiments successfully captured the track and translation speed of the actual typhoon, which enabled to quantitatively assess the climate change impacts. The PGW experiments indicated that the extreme rainfall is intensified in the future climates than in the present climate. Especially, the higher extremes of the accumulated rainfall are projected to be more severe in the future climate scenario. The analysis on the environmental factors showed that the cases with increased precipitable water lead to the increases in rainfall in future climates, despite the stabilized atmospheric conditions. Among the PGW experiments, the most increased amount of rainfall was found not to be produced by the most intensified typhoon.

著者

Tomoro Yanase Tetsuya Takemi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.116-120, 2018 (Released:2018-08-21)

参考文献数

29

被引用文献数

4

---

This study investigates the representation of the diurnal variation of cumulus convection in radiative-convective equilibrium states in an area of 200 km by 200 km without large-scale forcing by using a non-hydrostatic model with sub-kilometer horizontal resolutions. The experiment with the horizontal resolution of 200 m successfully reproduced the diurnal variability of the trimodal characteristics of cumulus convection. We demonstrated that the horizontal resolution dependence largely affects the trimodal structure of clouds and the characteristics of precipitation and its diurnal variation. With the coarse resolution of 1600 m, a signature of convective aggregation appeared and the diurnal variation of convection was not clearly seen. We further examined the mechanisms for the diurnal variation of cumulus convection by focusing on the temporal and vertical variations of radiative and latent heating anomalies. The diurnal variability of the static stability caused by both radiative and latent heating plays a role in characterizing the diurnal variation of the cumulus convection.

著者

Pin-Ying Wu Tetsuya Takemi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2021-024, (Released:2021-06-23)

被引用文献数

1

---

Identical twin experiments with and without topography are conducted with the Weather Research and Forecasting (WRF) model in an idealized framework to investigate the impact of topography on the initial error growth associated with moist convection. A topography is set as a single Gaussian shape mountain with a peak height of about 1000 m. Both experiments show clear diurnal cycles, while moist convection develops earlier and organizes to a larger size in the experiment with topography. To evaluate the initial error growth, a metric referred to as moist difference total energy (MDTE) is proposed to represent the differences between the two simulations in twin experiments. The horizontal spatial distribution, temporal evolution, and horizontal wavenumber space of the MDTE suggest that the error growth is greatly dominated by the different features of convection development between the two experiments. The analysis based on individual cloud areas shows that the convective clouds developing over the mountain have smaller MDTE at the early stage of development.

著者

Tetsuya Takemi Takashi Unuma

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.15A-011, (Released:2019-08-26)

被引用文献数

25

---

This study documented the environmental properties of precipitation systems that produced the July 2018 Heavy Rainfall event in Japan. The gridded analysis data were used to diagnose the potential for the development of convective systems in terms of thermodynamic environmental indices. Precipitable water vapor was extremely larger than that seen in the climatology of warm-season quasi-stationary convective clusters (QSCCs). Such an extreme moisture content was realized by very humid conditions at the middle-levels. In contrast, temperature lapse rate in a convectively unstable layer was not so significant in comparison to the QSCC climatology. Among the environmental indices, K Index was shown to describe the potential for the rainfall development. Based on the analysis, the roles of moisture content and profile on the convection development were discussed. It was suggested that the middle-level high humidity contributes to the occurrence of the present heavy rainfall by minimizing negative effects of environmental mixing and by decreasing vertical displacements to reach levels of free convection. In regions where heavy rainfall occurred, an automated algorithm detected the development of QSCCs, which were mostly categorized as a linear type.

著者

Tetsuya Takemi Takashi Unuma

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16, pp.30-36, 2020 (Released:2020-02-22)

参考文献数

23

被引用文献数

33

---

This study investigated the environmental factors responsible for the development of heavy rainfall in eastern Japan during the passage of Typhoon Hagibis (2019) by using mesoscale gridded analysis data as well as observed data. Environmental indices for diagnosing stability and moisture conditions were examined. It was found that the whole troposphere is almost saturated and the column total water vapor content is extremely large. In the lower troposphere we identified layers of moist absolutely unstable states with the thickness deeper than 2 km. Such deep moist absolutely unstable layers as well as abundant moisture content and almost saturated troposphere set a high potential for convective development. Under these favorable environmental conditions, the fact that the heights of the absolutely unstable layers' bottom are comparable to the mountain elevations is considered to be favorable for topographic lifting of unstable, moist air, which will trigger and activate strong convection and hence heavy rainfall. In spite of a moderate amount of convective available potential energy and a nearly moist-adiabatic lapse rate, moist absolute instability, abundant moisture, and high humidity jointly play a key role to increase the potential for generating the present heavy rainfalls.

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

---

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

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).

著者

Takashi Unuma Tetsuya Takemi

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.111-115, 2016 (Released:2016-05-06)

参考文献数

27

被引用文献数

1 20

---

A role of environmental shear on the organization mode of warm-season quasi-stationary convective clusters (QSCCs) was statistically investigated by using operational weather radar and radiosonde data from May to October during 2005-2012. With the use of an ellipse-fitting method, the total number of QSCCs whose shape was determined was 2549. It was found that 87% of the QSCCs have an aspect ratio of larger than 1.4, suggesting that the elongated mode is dominant during the warm season in Japan. The elongated QSCCs were mostly oriented southwest–northeast. The analyses of the environmental shear direction with respect to the orientation of the elongated QSCCs showed that the wind shear direction at the lower troposphere is mainly parallel to the orientation of the elongated QSCCs. A comparison between the elongated and the circular QSCCs with the environmental parameters showed that the lower convective instability and stronger intensity of the low-level shear clearly characterize the elongated QSCC environments. A parameter combining convective instability and shear, bulk Richardson number, characterizes the environmental conditions for determining the organization mode of the QSCCs, suggesting that a back-building mechanism should play a role in generating the elongated QSCCs.

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.153-158, 2018 (Released:2018-10-19)

参考文献数

24

被引用文献数

35

---

An extreme, damaging rainfall occurred in northern Kyushu in July 2017. Whether such an extreme rainfall is quantitatively captured by numerical models is a challenging issue. We investigate the influences of terrain representation in simulating a stationary convective system and the resulting heavy rainfall for this case by conducting a series of 167-m-resolution numerical experiments. By employing a high-resolution elevation dataset as well as a double-moment cloud microphysics scheme, the control experiment successfully reproduced the stationary, linear-shaped convective system and the associated heavy rainfall. When the model terrain was created by a coarser-resolution elevation dataset, the 167-m-resolution experiment underestimated the accumulated rainfall, because of discretely developing convection and weaker intensities of the rainfall. These impacts of the terrain representation were confirmed to be robust through conducting another experiments with a different microphysics scheme. The representation of model terrains is critically important in simulating stationary convective systems and quantitatively the resulting heavy rainfall.

著者

Pin-Ying Wu Tetsuya Takemi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.134-139, 2021 (Released:2021-07-30)

参考文献数

22

被引用文献数

1

---

Identical twin experiments with and without topography are conducted with the Weather Research and Forecasting (WRF) model in an idealized framework to investigate the impact of topography on the initial error growth associated with moist convection. A topography is set as a single Gaussian shape mountain with a peak height of about 1000 m. Both experiments show clear diurnal cycles, while moist convection develops earlier and organizes to a larger size in the experiment with topography. To evaluate the initial error growth, a metric referred to as moist difference total energy (MDTE) is proposed to represent the differences between the two simulations in twin experiments. The horizontal spatial distribution, temporal evolution, and horizontal wavenumber space of the MDTE suggest that the error growth is greatly dominated by the different features of convection development between the two experiments. The analysis based on individual cloud areas shows that the convective clouds developing over the mountain have smaller MDTE at the early stage of development.

著者

Yasuko OKADA Tetsuya TAKEMI Hirohiko ISHIKAWA Shoji KUSUNOKI Ryo MIZUTA

出版者

(公社)日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.95, no.4, pp.239-260, 2017 (Released:2017-07-04)

参考文献数

45

被引用文献数

19

---

This study investigates future changes in atmospheric circulation during the Baiu in Japan using 20-km-mesh atmospheric general circulation model (AGCM) simulations for the present-day (1979-2003) and the future (2075-2099) climates under the Representative Concentration Pathways 8.5 scenario. The simulated future climates include the outputs obtained with one control sea surface temperature (SST) and three different SST patterns. The Baiu frontal zone, defined as the meridional gradient of equivalent potential temperature, gradually moves northward during June–July–August in the present-day climate. In the future climate simulations using the control SST, the Baiu frontal zone is projected to stay to the south of Japan in June. Thus, precipitation is projected to increase over this region, while decreasing in the western part of Japan. Future changes in precipitation and atmospheric circulations in June are consistent across all four SST patterns. However, precipitation and atmospheric circulation in July and August in the future climate simulation depends on the SST patterns as follows: in non-El Niño-like SST pattern, the Baiu terminates in late July, similar to that of the present-day climate; a result with an El Niño-like SST pattern shows that sufficient amount moisture is transported to the Japanese islands and leads in a delay of the Baiu termination until August; and in the SST pattern with strong warming in the western North Pacific (WNP), a sufficient amount of moisture is transported to the south of Japan from June until August. The difference in the SST pattern leads to a variation in sea-level pressure in the WNP and affects a variation of the Northern Pacific subtropical high around the Japanese islands in July and August.

著者

Nanami Naka Tetsuya Takemi

出版者

公益社団法人 日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.19A-002, (Released:2023-06-05)

被引用文献数

2

---

Using mesoscale gridded analysis data and radar/raingauge-analyzed precipitation products, this study investigated the environmental conditions for the occurrence of extremely heavy rain events that occurred in northern Kyushu during the warm season in recent years. In all cases, the environmental conditions were not particularly unstable but were almost saturated in the deep layer of the troposphere. The existence of moist absolutely unstable layers (MAULs) was confirmed in and around the rainfall areas. A positive correlation was found between the volume of deep MAULs and the area total rainfall. A large convergence of the water vapor flux is observed in the lower troposphere, which appears to maintain very humid conditions and MAULs. The moisture convergence in the lower troposphere and the presence of deep MAULs is considered to enhance the heavy rainfall in the preceding hours. Humid conditions form deep MAULs that appear to precede the heavy rainfalls.

著者

Keita Fujiwara Tetsuya Takemi Nobuhito Mori

出版者

公益社団法人 日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2023-019, (Released:2023-06-03)

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To investigate the effects of global warming on Typhoon Jebi (2018), we performed high-resolution pseudo-global 2-K and 4-K warming simulations with initial time ensembles using a regional atmospheric model. The pseudo-global warming experiments demonstrated the further facilitation of Jebi's development with a higher rise in the temperature. The intensity over the ocean to the south of Japan increased by 8% (20%) in the climate warmed 2-K (4-K) to the current climate. Typhoon Jebi, in the 4-K warming simulations, maintained a robust inner-core characterized by a compact and deep eyewall and well-developed primary and secondary circulations even immediately before landfall, in contrast to the result in the 2-K warming simulations. The sustained robust axisymmetric structure immediately before landfall in the 4-K warming runs was strongly associated with the enhanced ocean warming around Japan, notable moistening of the lower-to-middle troposphere in the vicinity of Typhoon Jebi, and a significant decrease in vertical wind shear under the extremely warmed future climate. The nonlinear responses of Typhoon Jebi to the tropospheric temperature rise are attributable to the drastic changes in the midlatitude's thermodynamic and dynamic environments under climate changes resulting from 2-K to 4-K global warming.

著者

Tetsuya Takemi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.19, pp.ii-iii, 2023 (Released:2023-02-11)

参考文献数

2

---

The Editorial Committee of Scientific Online Letters on the Atmosphere (SOLA) presents the SOLA Award to one or two outstanding papers published each year. We are pleased to announce that the SOLA Award in 2022 will be given to the paper by Dr. Yasumitsu Maejima et al., entitled “Observing system simulation experiments of a rich phased array weather radar network covering Kyushu for the July 2020 heavy rainfall event” (Maejima et al. 2022), and to the paper by Dr. Tomoe Nasuno et al., entitled “Impacts of midlatitude western North Pacific sea surface temperature anomaly on the subseasonal to seasonal tropical cyclone activity: Case study of the 2018 boreal summer” (Nasuno et al. 2022).

著者

Tetsuya Takemi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16, pp.i-ii, 2020 (Released:2020-01-28)

参考文献数

12

---

Scientific Online Letters on the Atmosphere (SOLA) has been a fully Open Access journal under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) License (http://creativecommons.org/ license/by/4.0) since 2018, and has been added in the DOAJ (Directory of Open Access Journals) list. Last year, SOLA has updated the Guide for Authors and renewed its own web site (https://www.metsoc.jp/sola/). In response to the extreme weather events in the summers of 2017 and 2018, SOLA welcomed submissions of paper on the related topics and has published the special edition “Extreme Rainfall Events in 2017 and 2018” as Volume 15A. The published papers cover the large-scale atmospheric and oceanic features of extreme weather in the summer of 2018 (Shimpo et al. 2019; Sekizawa et al. 2019; Takemura et al. 2019; Takaya 2019), the mesoscale environmental properties of the extreme rainfall in July 2018 (Takemi and Unuma 2019), the predictability of extreme weather in the summer of 2018 (Kotsuki et al. 2019; Matsunobu and Matsueda 2019; Kobayashi and Ishikawa 2019), the relationship between a typhoon and the rainfall in July 2018 (Moteki 2019; Enomoto 2019), the use of a gridded precipitation product in investigating extreme rainfalls (Yatagai et al. 2019), and the impacts of global warming on the extreme hot summer in 2018 (Imada et al. 2019). We are growing. SOLA welcomes submission from the international community in meteorology, atmospheric sciences, and the related fields.

著者

Tetsuya Takemi Rui Ito Osamu Arakawa

出版者

Japan Society of Hydrology and Water Resources (JSHWR) / Japanese Association of Groundwater Hydrology (JAGH) / Japanese Association of Hydrological Sciences (JAHS) / Japanese Society of Physical Hydrology (JSPH)

雑誌

Hydrological Research Letters (ISSN:18823416)

巻号頁・発行日

vol.10, no.3, pp.81-87, 2016 (Released:2016-11-12)

参考文献数

23

被引用文献数

7 19

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Typhoon Mireille (1991) caused devastation over Japan. Assessing the impacts of such an extreme typhoon under global warming is an important task to prevent and mitigate future natural disasters. This study investigated the influences of global warming on the strong winds of Typhoon Mireille by conducting pseudo-global warming (PGW) experiments with a regional model. Since significant damages to forest areas occurred in Kyushu and Tohoku, we compared the typhoon impacts in these two regions. It was demonstrated that on average the mean wind speeds induced by Typhoon Mireille become stronger in Kyushu and weaker in Tohoku under the PGW conditions than under the September 1991 conditions. The difference between the two regions in the future is due to the simulated typhoons under PGW being stronger at lower latitudes and weakening more rapidly at higher latitudes. Thus, the impacts of Typhoon Mireille under a warmed climate are considered to be more severe at a lower latitude and weaker at a higher latitude.