著者

Yu Matsumoto Minrui Wang Yousuke Sato Takashi Y. Nakajima

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.19, pp.63-69, 2023 (Released:2023-04-15)

参考文献数

38

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This paper shows the CFODD of the regional dependence of cloud growth processes in low-level clouds obtained by the combined use of the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the Aqua satellite and the Cloud Profiling Radar (CPR) on the CloudSat satellite. This enabled the evaluation of the cloud growth process based on the cloud optical thickness (τ) and the effective radius of cloud particle (Re), similar to previous studies that performed statical analysis on low-level clouds over the globe. Our targets were regions in East Asian, Californian, and Peruvian. In all analysis areas, our results showed that the internal structure of clouds changed as Re increased, indicating cloud growth. In the East Asian region, the maximum τ remained relatively constant even when cloud droplet size grew. In contrast, in the regions of Californian and Peruvian, the maximum τ increased with Re during the condensation growth process and then decreased as drizzle particles transformed into rain. It was also found that Re was smaller in the East Asian region unlike in Californian and Peruvian. This indicates that there are more aerosols in the East Asian region, which is consistent with its geographical characteristics.

著者

Peiming Wu Masayuki Hara Hironori Fudeyasu Manabu D. Yamanaka Jun Matsumoto Fadli Syamsudin Reni Sulistyowati Yusuf S. Djajadihardja

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.3, pp.93-96, 2007 (Released:2007-09-13)

参考文献数

10

被引用文献数

38 67

---

Torrential rains that repeatedly occurred over Java Island causing widespread floods in late January and early February 2007 coincided with a strong and persistent trans-equatorial monsoon flow from the Northern Hemisphere. While convections develop frequently over the island’s mountainous areas in the afternoon, convections over the northern plains are active during the night and morning hours. The strong trans-equatorial monsoon flow with an upper southeasterly wind produces a strong low-level vertical shear of wind and dry mid-level environment over the island. These conditions allow the severe convections to occur repeatedly for days and to sustain for an extended period of time. The results suggest that the trans-equatorial monsoon flow plays a principal role in the formation of the repeated torrential rains. The probability of occurrence of a strong and persistent trans-equatorial monsoon flow that causes torrential rains and widespread floods over Java Island is estimated to be once every 5-10 years.

著者

Migyeong Kim Jeong Hoon Cho Sang-Boom Ryoo

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.19, pp.26-32, 2023 (Released:2023-02-18)

参考文献数

22

---

Forecasts of discrete events, such as precipitation, dust storms, and typhoons, can be deterministic, categorical, or probabilistic. Ensemble-based probabilistic predictions generate more consistent forecasts than individual deterministic models. We introduce and evaluate the Ensemble Prediction System of Asian Dust Aerosol Model 3, which generates probability forecasts of Asian dust. Probability forecasts were produced for 300 μgm−3 PM10 mass concentrations, according to the air-quality standards of the Ministry of Environment of South Korea and Korea Meteorological Administration. Crisis-level information was produced to categorize the dust risk level for Asia, using a risk matrix. The model's performance was evaluated using a 2 × 2 contingency table, the Brier skill score, and a reliability diagram. For skill score evaluation via the contingency table, the average hit rate and threat score were 0.46 and 0.34 for the best three sites, Jurihe, Erenhot, and Wulatezhongqi. The Brier skill score was positive for approximately 60% of stations, with the highest (0.410) and lowest (−2.038) values in Erenhot and Yanan, respectively. The reliability diagram revealed overestimated Asian dust frequencies for all stations. Although the stations were located within the same regions, their skill scores differed. Regional characteristics of skill scores should be further investigated in the future.

著者

Trismidianto Tri Wahyu Hadi Sachinobu Ishida Qoosaku Moteki Atsuyoshi Manda Satoshi Iizuka

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.6-11, 2016 (Released:2016-01-25)

参考文献数

26

被引用文献数

23

---

This study analyzed the oceanic convective systems that induced heavy rainfall over the western coast of Sumatra on 28 October 2007. The convective systems that satisfied the definition of a mesoscale convective complex (MCC), as identified by infrared satellite imagery, developed repeatedly for 16 hours over the Indian Ocean near Sumatra. The MCC developed from midnight on 27 October until the early morning of 28 October, and it was intensified by the land breeze from Sumatra. New convective systems around the decaying MCC were generated during the daytime of 28 October, and they propagated to the western coast of Sumatra in the evening because of a divergent outflow from a cold pool. The combination of the land breeze from Sumatra and cold pool outflows from the decaying MCC was a significant factor in the formation of the convective system that induced strong rainfall up to 46 mm h−1 over the western coast of Sumatra.

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

pp.19B-001, (Released:2023-02-13)

---

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 that 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 August 30, 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

Kai Cao Xiao Tang Lanning Wang Xueshun Chen Qizhong Wu Lei Kong Miaomiao Lu Huangjian Wu Zifa Wang

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.19, pp.16-25, 2023 (Released:2023-02-07)

参考文献数

54

---

From the end of 2019 to the beginning of 2020, Australian bushfires caused by high temperatures and drought significantly impacted the local and global atmosphere. This work uses the global atmospheric chemistry transport model and observations to assess the enormous impact of bushfire emissions on PM2.5 in Australia. During December 2019, the significant increase in biomass-burning emissions led to increases in PM2.5 observations in megacities such as Canberra, Sydney, Newcastle, Brisbane and Melbourne by 845%, 322%, 171%, 141% and 58%, respectively. Numerical simulations reveal that bushfires increased PM2.5 in Australia and in the Southern Hemisphere by 49% and 13%, respectively. Although the aerosols produced by bushfires could not cross the equator at ground level and affect the air quality in the Northern Hemisphere, they were transported to South Asian countries such as Malaysia and India, as well as Papua New Guinea and New Zealand. In addition, they were also injected upward into the stratosphere (approximately 15 km height). Aerosols injected into the stratosphere could be transported to Antarctica and South America, thus completing global transport.

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

Yang Zhao Seok-Woo Son Seung-Yoon Back

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.2023-006, (Released:2023-02-01)

被引用文献数

2

---

On 18-20 July 2021, Henan Province in China experienced a historically rare extreme precipitation event, termed as the “21.7” event. Its synoptic environment was characterized by a large amount of moisture supply by binary typhoons located over the ocean and a potential vorticity intrusion in the upper level. The present study examines the importance of the latter by conducting WRF model experiments. A qualitatively similar rainfall amount to observation is obtained when the zonal wavenumbers 7 and larger is kept above 300 hPa in the initial and lateral boundary conditions. When only the large-scale disturbances with wavenumbers 2-4 are kept, the precipitation is greatly reduced. This result indicates that the upper-level synoptic-scale disturbance, which leads to the development of potential vorticity anomaly and its downward intrusion, has likely played a critical role in the development of this event along with a large amount of moisture transport in the low level.

著者

Migyeong Kim Jeong Hoon Cho Sang-Boom Ryoo

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.2023-004, (Released:2023-01-10)

---

Forecasts of discrete events, such as precipitation, dust storms, and typhoons, can be deterministic, categorical, or probabilistic. Ensemble-based probabilistic predictions generate more consistent forecasts than individual deterministic models. We introduce and evaluate the Ensemble Prediction System of Asian Dust Aerosol Model 3, which generates probability forecasts of Asian dust. Probability forecasts were produced for 300 μ gm−3 PM10 mass concentrations, according to the air-quality standards of the Ministry of Environment of South Korea and Korea Meteorological Administration. Crisis-level information was produced to categorize the dust risk level for Asia, using a risk matrix. The model's performance was evaluated using a 2 × 2 contingency table, the Brier skill score, and a reliability diagram. For skill score evaluation via the contingency table, the average hit rate and threat score were 0.46 and 0.34 for the best three sites, Jurihe, Erenhot, and Wulatezhongqi. The Brier skill score was positive for approximately 60% of stations, with the highest (0.401) and lowest (−2.038) values in Erenhot and Yanan, respectively. The reliability diagram revealed overestimated Asian dust frequencies for all stations. Although the stations were located within the same regions, their skill scores differed. Regional characteristics of skill scores should be further investigated in the future.

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

pp.19A-001, (Released:2022-12-28)

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

Kai Cao Xiao Tang Lanning Wang Xueshun Chen Qizhong Wu Lei Kong Miaomiao Lu Huangjian Wu Zifa Wang

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.2023-003, (Released:2022-12-28)

---

From the end of 2019 to the beginning of 2020, Australian bushfires caused by high temperatures and drought significantly impacted the local and global atmosphere. This work uses the global atmospheric chemistry transport model and observations to assess the enormous impact of bushfire emissions on PM2.5 in Australia. During December 2019, the significant increase in biomass-burning emissions led to increases in PM2.5 observations in megacities such as Canberra, Sydney, Newcastle, Brisbane and Melbourne by 845%, 322%, 171%, 141% and 58%, respectively. Numerical simulations reveal that bushfires increased PM2.5 in Australia and in the Southern Hemisphere by 49% and 13%, respectively. Although the aerosols produced by bushfires could not cross the equator at ground level and affect the air quality in the Northern Hemisphere, they were transported to South Asian countries such as Malaysia and India, as well as Papua New Guinea and New Zealand. In addition, they were also injected upward into the stratosphere (approximately 15 km height). Aerosols injected into the stratosphere could be transported to Antarctica and South America, thus completing global transport.

著者

Kazuto Takemura Hitoshi Mukougawa

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.19, pp.1-8, 2023 (Released:2023-01-01)

参考文献数

23

---

This study shows a possible mechanism of abnormal extension of North Pacific subtropical high (NPSH) toward western and eastern Japan observed in late June 2022, when Japan experienced an unprecedented heat wave lasting more than a week. During the period, an upper-tropospheric anticyclonic circulation anomaly amplifies to the east of northern Japan associated with the Silk-Road pattern.  A diagnosis using quasi-geostrophic potential vorticity (QGPV) inversion shows that the lower-level anticyclonic circulation anomalies induced by the upper-level anticyclone are the primary factor in the generation of lower-level negative QGPV anomalies from mainland Japan to its south associated with the anomalous extension of the NPSH. The induced circulation causes the lower-level negative QGPV anomalies by upgradient horizontal advection of the climatological QGPV, which has a strong gradient from mainland Japan to its south associated with the Baiu frontal zone. The proposed mechanism well explains a peculiar vertical structure of the observed anticyclone near Japan.  A sensitivity diagnosis considering the sub-seasonal variation of the climatological lower-tropospheric QGPV distribution during summer indicates that the proposed NPSH extension mechanism toward Japan becomes most efficient from late June to early July, when the Baiu frontal zone is most enhanced near Japan.

著者

Shengning Zhang Yaokun Li

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.254-258, 2022 (Released:2022-12-09)

参考文献数

22

---

The ENSO phenomenon is investigated by building a fractional derivative recharge-discharge model in which the integer derivative is replaced with the left-sided Caputo type fractional derivative. The results suggest that when the highest order fractional derivative is larger than 1 but smaller than or equal to 2, the model exhibits a variation between exponential decay and pure harmonic oscillation. The system will strengthen to an El Niño/La Niña event and then weaken to the neutral state which does not require a zero value. Therefore, there is only a life cycle of an El Niño/La Niña event, rather than the life cycle of a complete ENSO event in the pure harmonic oscillation. When the highest order fractional derivative is larger than 2, the model exhibits an exponential-like amplified oscillation. The system benefits to exhibit the life cycle of strong ENSO events. The fractional derivative recharge-discharge model, in general, extends the integer model and can be applied in studying the complexity in ENSO phenomenon.

著者

Kazuto Takemura Hitoshi Mukougawa

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.2023-001, (Released:2022-11-29)

---

This study shows a possible mechanism of abnormal extension of North Pacific subtropical high (NPSH) toward western and eastern Japan observed in late June 2022, when Japan experienced an unprecedented heat wave lasting more than a week. During the period, an upper-tropospheric anticyclonic circulation anomaly amplifies to the east of northern Japan associated with the Silk-Road pattern.  A diagnosis using quasi-geostrophic potential vorticity (QGPV) inversion shows that the lower-level anticyclonic circulation anomalies induced by the upper-level anticyclone are the primary factor in the generation of lower-level negative QGPV anomalies from mainland Japan to its south associated with the anomalous extension of the NPSH. The induced circulation causes the lower-level negative QGPV anomalies by upgradient horizontal advection of the climatological QGPV, which has a strong gradient from mainland Japan to its south associated with the Baiu frontal zone. The proposed mechanism well explains a peculiar vertical structure of the observed anticyclone near Japan.  A sensitivity diagnosis considering the sub-seasonal variation of the climatological lower-tropospheric QGPV distribution during summer indicates that the proposed NPSH extension mechanism toward Japan becomes most efficient from late June to early July, when the Baiu frontal zone is most enhanced near Japan.

著者

Shengning Zhang Yaokun Li

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.2022-041, (Released:2022-11-11)

---

The ENSO phenomenon is investigated by building a fractional derivative recharge-discharge model in which the integer derivative is replaced with the left-sided Caputo type fractional derivative. The results suggest that when the highest order fractional derivative is larger than 1 but smaller than or equal to 2, the model exhibits a variation between exponential decay and pure harmonic oscillation. The system will strengthen to an El Niño/La Niña event and then weaken to the neutral state which does not require a zero value. Therefore, there is only a life cycle of an El Niño/La Niña event, rather than the life cycle of a complete ENSO event in the pure harmonic oscillation. When the highest order fractional derivative is larger than 2, the model exhibits an exponential-like amplified oscillation. The system benefits to exhibit the life cycle of strong ENSO events. The fractional derivative recharge-discharge model, in general, extends the integer model and can be applied in studying the complexity in ENSO phenomenon.

著者

Fumiaki Fujibe Nobuo Yamazaki Mitsugi Katsuyama Kenji Kobayashi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.1, pp.41-44, 2005 (Released:2005-04-21)

参考文献数

14

被引用文献数

78 86

---

Long-term changes of precipitation intensity were analyzed using a dataset which was recently compiled by the Japan Meteorological Agency (JMA). After some quality check, data of four-hourly, daily, and hourly precipitation at 46, 61, and 8 stations, respectively, were used for the period 1898-2003 on the condition that data for at least 80 years were usable in each month. As the measure of precipitation intensity, ten categories were defined so as to equate the total precipitation amount in each month at each station. The result is characterized by increase of precipitation in high categories, namely intense precipitation, and decrease in low categories. The linear trend for the highest and lowest categories is ±20-30% per century. This feature is found invariably for four-hourly, daily, and hourly precipitation, and qualitatively for all the seasons and regions.

著者

Masahiro Ohashi H. L. Tanaka

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.6A, no.SpecialEdition, pp.1-4, 2010 (Released:2010-03-13)

参考文献数

17

被引用文献数

6 5

---

In this study, we investigate the mechanism of the arctic warming pattern in surface air temperature (SAT) and sea ice concentrations over the last two decades in comparison with global warming since the 1970s.According to the analysis result, it is found that the patterns of SAT and sea ice before 1989 are mostly determined by the Arctic Oscillation (AO) in winter. In contrast, arctic warming patterns after 1989 are characterized by the intensification of the Beaufort High and the reduced sea-ice concentrations in summer induced by the positive ice-albedo feedback.It is concluded that the arctic warming before 1989 especially in winter was explained by the positive trend of the AOI. Moreover the intensified Beaufort High and the drastic decrease of the sea ice concentrations in September after 1989 were associated with the recent negative trend of the AOI. Since the decadal variation of the AO is recognized as the natural variability of the global atmosphere, it is shown that both of decadal variabilities before and after 1989 in the Arctic can be mostly explained by the natural variability of the AO not by the external response due to the human activity.

著者

Yoshio Kawatani Takeshi Horinouchi Naoki Sato

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.122-128, 2022 (Released:2022-06-16)

参考文献数

11

被引用文献数

1

---

Climate changes around Japan associated with upper troposphere and stratosphere responses of global warming during December-January-February were investigated using the storyline approach and the Coupled Model Intercomparison Project 5 dataset. Climate change was calculated by subtracting the 1959-1990 mean in historical simulations from the 2068-2099 mean in the Representative Concentration Pathways 8.5. Four storylines in plausible future climates were discussed by considering two remote indices representing tropical amplification (tropical upper tropospheric temperature changes) and stratospheric vortex strength. Stratosphere-troposphere connections in terms of zonal wind responses are most pronounced in the storyline of high tropical amplification with strong stratospheric vortex in which the subtropical jet shifts substantially northward. The multimodel mean displays more (less) precipitation in the northern (southern) parts of Japan, while the storyline of high (low) tropical amplification with strong (weak) stratospheric vortex shows increasing (decreasing) precipitation in most parts of Japan. Projected precipitation changes around Japan depend heavily on the storyline adopted and the degree of global warming in these two storylines. Alternatively, precipitation changes depend mostly on the overall strength of global warming with minor influences from storylines in the case of low (high) tropical amplification with strong (weak) stratospheric vortex.

著者

Yaokun Li Yanyan Kang

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.18, pp.76-80, 2022 (Released:2022-04-25)

参考文献数

23

被引用文献数

2

---

The energy dispersion process of westward propagating Rossby waves in tropical easterlies are investigated in the linear nondivergent barotropic atmosphere. The variations in wave energy and amplitude along energy dispersion paths are calculated by solving the wave action conservation equation. The results suggest that a westward marching ray can form a cycle-like path near the turning latitude that is located in easterlies. Waves with shorter periods propagate between two turning latitudes, which are located in either the easterlies or westerlies and have the largest meridional propagation range. Waves with longer periods propagate between a turning latitude in westerlies and a critical latitude in easterlies. Both wave energy and amplitude can simultaneously increase to their maximum values at the turning latitudes that are located in easterlies. This implies that waves may develop significantly. Wave energy and amplitude do not always have an in-phase variation when the ray moves toward the turning latitude that is located in westerlies. The oscillating ranges of wave energy and amplitude are also limited. In this case, waves may not develop significantly.

著者

Hirokazu Endo Akio Kitoh Ryo Mizuta

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.18, pp.58-64, 2022 (Released:2022-03-29)

参考文献数

38

被引用文献数

1

---

Future changes in extreme precipitation over the western North Pacific and East Asia (WNP-EA) are investigated using a 20 km mesh atmospheric general circulation model (AGCM). Time-slice simulations are performed under low- and high-emission scenarios using different spatial patterns of changes in sea surface temperature. In the WNP-EA region, future changes in the climatological mean of the annual maximum 1 day precipitation total (Rx1d) are characterized by a large meridional variation, where the higher the latitude, the greater the rate of increase in Rx1d, although this pattern is not so clear under the low emission scenario. This feature probably results from a combination of two factors: a greater warming in high latitudes and a decrease in tropical cyclone (TC) frequency in the subtropics. The future changes in Rx1d climatology for the 20 km AGCM show a marked difference in comparison with those of the lower-resolution AGCM and conventional climate models. Part of this discrepancy may come from differences in model resolution through representation of TCs, suggesting that coarse-resolution models may have some systematic bias in future projections of extreme precipitation in the WNP-EA region.