著者
Hiroki Teramura Tomonori Sato Kenta Tamura
出版者
Meteorological Society of Japan
雑誌
SOLA (ISSN:13496476)
巻号頁・発行日
vol.15, pp.143-148, 2019 (Released:2019-06-27)
参考文献数
24

This study investigated the impact of land surface heterogeneity on Mesoscale Convective System (MCS) initiations in East Asia, using geostationary satellite data during June–August from 1996 through 2018. The detected MCSs over land exhibited clear diurnal variation with the lowest existence frequency at 10:00 and highest initiation frequency during 12:00-17:00 local time. To quantify land surface heterogeneity, the spatial standard deviation of equivalent Black-Body Temperature (TBB) within a cloud-free 0.35° × 0.35° box (σLSTBB: Land Surface TBB) was computed for 10:00 each day. A comparison of the σLSTBB and MCS databases revealed that the probability of MCS initiations increased with increasing σLSTBB in East Mongolia while the probability was not sensitive to σLSTBB in East China. This indicated that MCSs tend to form over heterogeneous land surface conditions in the semiarid region. We found that the impact of land surface heterogeneity on MCS initiations was highest over flat terrain in East Mongolia, where the convection trigger due to topographically-induced circulation was absent. These results suggest that the impact of land surface heterogeneity on MCS initiations during the warm season varies with climate zones and terrain complexities in East Asia, with strongest impact in semiarid and flat regions.
著者
Akifumi Nishi Hiroyuki Kusaka
出版者
Meteorological Society of Japan
雑誌
SOLA (ISSN:13496476)
巻号頁・発行日
vol.15, pp.160-165, 2019 (Released:2019-08-21)
参考文献数
46
被引用文献数
2

In the present study, we conducted dual-sonde observations and a numerical simulation when the “Karakkaze”, a local wind in Japan, blew. The result showed that the basic features of the Karakkaze coincide closely with the characteristics of convexity wind defined as “strong winds in the leeward region of a convex-shaped mountain range”.Firstly, we investigated the horizontal distribution of surface winds during the Karakkaze event on 24 January 2019. The results showed that the Karakkaze blows in the downwind plain of the convexity of the mountain range.Secondly, we compared the vertical distribution of the winds inside and outside the Karakkaze region, using the results of dual-sonde observations and a numerical simulation. Our results showed that strong winds blew from near ground level to a height of 1.8 km above mean sea level (AMSL) in the Karakkaze region. In contrast, weaker winds were observed and simulated outside the Karakkaze region. The reason of the weaker winds is that a hydraulic jump occurs on the slope of the mountain range and that the area outside the Karakkaze region is located in a more leeward direction than the hydraulic jump. These features closely match the characteristics of convexity winds.
著者
Hossain Mohammed Syedul Hoque Hitoshi Irie Alessandro Damiani Prajjwal Rawat Manish Naja
出版者
Meteorological Society of Japan
雑誌
SOLA (ISSN:13496476)
巻号頁・発行日
vol.14, pp.159-164, 2018 (Released:2018-11-09)
参考文献数
56
被引用文献数
9

Since January 2017 continuous multi-axis differential optical absorption spectroscopy (MAX-DOAS) observations have been performed for the first time at Pantnagar (29.03°N, 79.47°E), a semi-urban site located in the Indo-Gangetic Plain region in India. Here we report the formaldehyde (HCHO), glyoxal (CHOCHO), and nitrogen dioxide (NO2) concentrations for the lowest layer (0-1 km) of the retrieved vertical profiles. The ratio of CHOCHO to HCHO concentrations (RGF), an important tracer indicative of changes in volatile organic compound emissions was estimated. During spring and autumn enhanced concentrations of HCHO and CHOCHO were observed under the influence of biomass burning. The mean RGF for the whole observation period (January–November) in Pantnagar was estimated to be 0.029 ± 0.006. Comparing with similar MAX-DOAS observations in central Thailand and reported literature values, we found that the RGF tends to be < ∼0.04 under the influence of biomass burning and/or anthropogenic emissions.
著者
Van Q. Doan Hiroyuki Kusaka
出版者
Meteorological Society of Japan
雑誌
SOLA (ISSN:13496476)
巻号頁・発行日
vol.15, pp.37-40, 2019 (Released:2019-02-19)
参考文献数
27
被引用文献数
3

This study introduces a new multiple-layer urban canopy model (MUCM) combined with a ray-tracing algorithm. In the model, we parameterize the urban morphology as an infinite array of identical three-dimensional buildings separated by roads. Heat exchanges are solved for each urban surface at each vertical layer. The ray-tracing scheme is used to explicitly calculate the view factors as well as both the sunlit and shadow fractions of the urban surfaces during the daytime. As a test, we show that this combined MUCM accurately models observations at Kugahara, Tokyo. Thus, the combined MUCM is a new tool for urban climate modelers to more realistically represent radiative processes on urban surfaces. In particular, it may contribute to our understanding of urban climate in the mega-cities of Asia, which generally have high-rise buildings that are more difficult to model with simpler radiative schemes.
著者
Akifumi Nishi Hiroyuki Kusaka
出版者
Meteorological Society of Japan
雑誌
SOLA (ISSN:13496476)
巻号頁・発行日
vol.15, pp.12-16, 2019 (Released:2019-02-05)
参考文献数
24
被引用文献数
2

This study uses a numerical model to examine how a convex feature and a gap feature in a mountain range affect the leeward wind field. In the “convexity case”, the mountain ridge has a convex feature (viewed from above). In the “gap case”, the mountain ridge has a gap. The results show that both cases have local winds at the surface exceeding 8 m s−1, and both have similar spatial flow-patterns. However, the momentum budgets at the strong-wind regions differ between the cases. In the convexity case, the downdrafts are important in the momentum balance, whereas in the gap case, both the downdrafts and the pressure-gradient force are important. Thus, although their spatial patterns of surface wind are similar to each other, their mechanisms for producing a strong local wind differ.Sensitivity experiments of Frm show that strong-wind appears in both the convexity and gap cases when Frm is between 0.42 and 1.04. In contrast, when Frm is 0.21, strong winds only appear in the gap case because the flow can go around the gap. When Frm exceeds 1.25, strong surface winds appear in the entire leeward plain.
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
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

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
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
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

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
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

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
Yousuke Yamashita Hideharu Akiyoshi Makoto Inoue
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.19B-002, (Released:2023-10-18)

The dynamical response of the southern hemisphere stratosphere to the ocean-surface conditions in 2002 and 2019, when exceptional sudden stratospheric warming (SSW) events occurred, was examined through the chemistry–climate model and experiments with 1,000 ensemble members using the sea-surface temperature (SST) and sea-ice conditions. Planetary waves propagating from the troposphere to the stratosphere in experiments using the ocean-surface conditions in 2002 and 2019 were markedly enhanced compared to those in experiments using climatological ocean conditions, owing to the enhancement of the zonal wavenumber-2 component in August 2002 and the wavenumber-1 component from August to November 2019. The distribution function from the ensemble members of the Antarctic polar-vortex intensity shifted to a weaker side in the 2002 and 2019 experiments relative to that of the climatological ocean conditions. The planetary wave propagation to the stratosphere was more enhanced in 2019 than in 2002 from austral winter to spring. This result is consistent with the weakening of the Antarctic polar-vortex intensity in the 2019 experiment relative to the 2002 experiment. These results suggest that the SSWs in 2002 and 2019 are closely related to the ocean surface conditions in these years through wave propagation in the troposphere and stratosphere.
著者
Takashi Unuma Hiroshi Yamauchi Akihito Umehara Teruyuki Kato
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.2023-020, (Released:2023-06-09)
被引用文献数
1

We investigated the microphysical mechanisms for the enhancement of rainfall in a precipitating system that spawned heavy rainfall over the central part of the Kanto Plain in eastern Japan on 12 July 2022. Optical disdrometer observations confirmed the existence of an equilibrium state in the raindrop size distribution, especially when the precipitation intensity was high (e.g., 20 mm hr−1). As the raindrop size distribution approached equilibrium, raindrop sizes centered around 1.5 mm were observed initially, and then the number concentration of smaller and larger size raindrops increased simultaneously. The raindrop size distribution was closely related to the vertical profile of the parameters of raindrop size distribution that were estimated from polarimetric radar observations. These results suggest that the formation of equilibrium raindrop size distributions is important to produce substantial rainfall in the midlatitude as well as in the tropics.
著者
Naoko Kosaka Yusuke Umemiya Naoto Endou Tsuneko Kura Hiroshi Matsubara Masaki Hisada Akinori Murata Satoshi Mitarai
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.2023-016, (Released:2023-05-22)

This paper presents experimental observations to improve typhoon prediction accuracy and to understand interactions between atmosphere and ocean directly under typhoons. Two unmanned surface vehicles (Wave Gliders (WGs)) equipped with interchangeable sensors were sailed toward the path of an approaching Category 5 typhoon (Hinnamnor), which began on 29 August 2022 and subsided on 6 September, reaching a minimum pressure of 920 hPa and a maximum wind speed of 55 m/s (105 knots). Sensors on WGs measured atmospheric pressure, wind speed, atmospheric and seawater temperature, wave height, currents, salinity, and chlorophyll-a concentrations in different parts of the typhoon. These observations made it possible to clarify changes in various phenomena as the typhoon approached and to compare differences in storm characteristics measured by the two WGs. Sea surface pressure in the core of a typhoon is useful as an initial predictor of its intensity. Data assimilation into numerical models and other observations are expected to improve prediction accuracy of typhoon phenomena. Furthermore, simultaneous observations of atmosphere and ocean will also be useful for modeling interactions.
著者
Ken Sawada Naoko Seino Takuya Kawabata Hiromu Seko
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
vol.19B, no.Special_Edition, pp.1-8, 2023 (Released:2023-03-10)
参考文献数
23

Considering urbanization effects on atmospheric states and subsequent precipitation is crucial to improve the accuracy of forecasting localized heavy rainfall around urban areas and to mitigate related disasters. For this purpose, it is effective to use a time development model that can accurately represent city-specific effects, such as urban heat island effect, in the assimilation process, and to assimilate high-frequency/high-density surface observation data that have not been used thus far. Therefore, this study incorporated a forecast model with an urban canopy scheme into an ensemble-based assimilation system and assimilated dense surface data from an Atmospheric Environmental Regional Observation System. Then, we performed analysis-forecast experiments for a heavy rain event in Tokyo metropolitan area on 30 August 2017, to examine the impact of urbanization. Our results showed that the urban scheme and surface observation improved near-surface temperature and moisture fields, thereby contributing to the formation of a clearer convergence line between the easterly and southerly winds where it was observed. Consequently, these improvements resulted in an earlier onset of rainfall and better reproduction of the heavy rainfall distribution.
著者
Masaki Satoh Keisuke Hosotani
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
vol.19A, no.Special_Edition, pp.1-8, 2023 (Released:2023-02-10)
参考文献数
19
被引用文献数
1

A sequence of heavy rainfall events due to quasi-stationary band-shaped precipitation systems, or “senjo-kousuitai“, was observed in the Kyushu region, Japan, from 3 to 8 July 2020. In this study, we investigate two of six indices that have previously been used to determine conditions favorable for senjo-kousuitai, i.e., water vapor flux at the height of 500 m and storm-relative environmental helicity. We examine the relationship between these indices and the occurrence of senjo-kousuitai over the past 20 years using the Japan Meteorological Agency 55-year reanalysis data. We show that the anomaly in wind speeds rather than humidity contributes more to anomalous water vapor flux. The vertical shear of zonal winds and the meridional flow in the lower layer contribute more to the storm-relative environmental helicity. We conducted 20-member ensemble experiments with a 14 km mesh Nonhydrostatic Icosahedral Atmospheric Model (NICAM) for the senjo-kousuitai event. We found that the initial variabilities of the water vapor over the area stretching from the East China Sea to the South China Sea and the wind fields over the western periphery of the North Pacific High are sensitive to the water vapor flux over the senjo-kousuitai area in Kyushu.
著者
Yuta Tamaki Sosuke Okubo Kei Horie
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
vol.18, pp.243-248, 2022 (Released:2022-11-18)
参考文献数
41

We examined forty-five typhoons associated with insurance losses in Japan to explicitly describe typhoon-related variables that explain insurance-loss variations. Multiple regression analysis revealed that the combination of maximum wind speed and translation speed explained more of the variation in insurance-loss size than what the regression model with maximum wind speed alone did. Using maximum wind speed and gale-area radius as explanatory variables also slightly improved the explained variance, but it was less stable than the multiple regression model combining maximum wind speed and translation speed. The translation speed suggested an inland expansion of the strong-wind area associated with wind-speed asymmetry, while considering the exposure led to similar conclusions. Our regression model can be applied to estimate changes in the damage and uncertainty by adjusting the typhoon characteristics under multiple climate-change scenarios.
著者
Takashi Maki Taichu Y. Tanaka Tsuyoshi Koshiro Atsushi Shimizu Tsuyoshi T. Sekiyama Mizuo Kajino Yasunori Kurosaki Toshiya Okuro Naga Oshima
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
vol.18, pp.218-224, 2022 (Released:2022-10-27)
参考文献数
29
被引用文献数
1

Ensemble future climate projections were performed using the Meteorological Research Institute Earth System Model version 2.0 (MRI-ESM2.0) for sand and dust storms (SDS), which have a significant social and climatic impact on East Asia. A replication experiment using MRI-ESM2.0 reproduced the decreasing trend of SDS emissions in the Gobi Desert in the early 21st century. Prediction experiments using MRI-ESM2.0 in Coupled Model Intercomparison Project phase 6 future scenarios indicated no considerable differences in the total amount of SDS emissions in the Gobi Desert for 2015-2100; however, SDS emissions increased with warmer scenarios in spring and autumn. In particular, March in the highest warming scenario (SSP5-8.5) exhibited an annual increase rate of 3.0% in SDS emissions for the years 2015-2100. Friction velocity was highly correlated with SDS emissions, with a correlation of ∼0.6 for all climate scenarios throughout the year. In spring and autumn, snow cover exhibited a low negative correlation with SDS emissions, while ground temperature exhibited a positive correlation. The increase in SDS emissions and subsequent dust transport by midlatitude westerlies in spring and autumn during accelerated warming scenarios could be attributed to the changes in friction velocity and erodibility due to the decrease in snow accumulation.
著者
Chultem Batbold Keiya Yumimoto Sonomdagva Chonokhuu Batdelger Byambaa Batdavaa Avirmed Shuukhaaz Ganbat Naoki Kaneyasu Yutaka Matsumi Teppei J. Yasunari Kenji Taniguchi Noriko Hasebe Keisuke Fukushi Atsushi Matsuki
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
vol.18, pp.225-230, 2022 (Released:2022-10-28)
参考文献数
31
被引用文献数
1

In Mongolia, combined with the dry and windy climate during spring and autumn, the exposed sediment of mine tailings pond becomes an additional source of anthropogenic windblown dust and poses potential threats to the surrounding environment and human health. In this study, we reported on our first attempt to derive the spatiotemporal distribution of dust originating from the tailings pond of the Erdenet mine using a combination of ground-based in-situ measurements and Himawari-8 geostationary satellite remote sensing. Temporal evolution of the dust plume visualized by the RGB imagery corresponded well with the in-situ particle concentration measured on the ground. Under relatively cloud-free conditions, the dust RGB imagery from Himawari-8 clearly showed the spatial extent of the white dust plume originating from the tailings pond, in the range of 2,040-2,748 km2. Therefore, the dust RGB imagery by Himawari-8 is demonstrated to be sensitive enough to resolve the highly localized anthropogenic dust, even from a point source as small as the tailings pond, and is effective in studying susceptible areas subject to associated heavy metal deposition and contamination.
著者
Takehiko Kobori Masayuki Maki Yasushi Fujiyoshi Masato Iguchi Seiji Fukushima
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
vol.18, pp.231-235, 2022 (Released:2022-10-28)
参考文献数
13
被引用文献数
1

We developed a method for estimating the height and growth rate of volcanic eruption columns, at high-temporal resolution, by processing vertical cross-sectional images of areas around the crater obtained with a marine radar tilted on its side. We applied our method to 127 eruptions occurring at Sakurajima (Kagoshima, Japan) from June to December 2019 and successfully estimated the time-series height of the eruption column and its growth rate every 2.5 seconds. In 48 cases, we obtained the maximum height of the eruption column and confirmed that these results were consistent with those estimated using meteorological radar. Although the maximum height estimated with our method tended to be lower than that observed by monitoring cameras, results could be obtained even when observations were difficult due to cloud effects, etc.
著者
Saat Mubarrok Chan Joo Jang
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
vol.18, pp.187-192, 2022 (Released:2022-09-06)
参考文献数
42
被引用文献数
2

Extreme rainfall (ER) in Indonesia frequently leads to floods and landslides, disrupting economic activity and impacting human lives. Here, we investigate ER variability in association with climate teleconnection patterns (CTP) including the El Niño Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), and Madden-Julian Oscillation (MJO), using extreme value analysis based on daily rainfall data from 32 stations for 30 years (1985-2014). By fitting a generalized extreme value distribution, a significant association between the annual maximum rainfall (AMR) and CTP was found in 12 of 32 stations. The sensitivity test of location parameter showed that the AMR-CTP interconnection was spatially inhomogeneous. The positive (negative) significant association of ENSO and IOD to AMR was noticeable in south-western (eastern) Indonesia. Additionally, MJO positive (negative) association was detected at 4 (3) stations mostly located in Sumatra (Java) Island. Furthermore, the return level analysis shows that the 20-year ER intensity waiting time will be shorter and longer when CTP indexes strengthen and weaken, suggesting a potential increase and decrease in the likelihood of future ER occurrences, respectively. These results are relevant for understanding the relationship between ER and CTP that should be considered in the adaptation and mitigation plans to minimize the ER impacts.