著者

Tana Bao Tao Gao Banzragch Nandintsetseg Mei Yong Erdemtu Jin

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.145-150, 2021 (Released:2021-08-27)

参考文献数

42

被引用文献数

13

---

In this study, we investigated the spatiotemporal variations of border-crossing dust events (DEs), including floating, blowing dust, and dust storms between Mongolia (MG) and Inner Mongolia (IM), China using the ground-based observations from 91 synoptic stations across the Mongolian Plateau during 1977-2018. We defined the intensity of DEs (progressive and recessive) depending on the dust impact area (number of stations affected by dust) by dividing them into three categories: DEs, transported dust events (T-DEs), and severe transported dust events (ST-DEs). The results revealed that during 1977-2018, the frequency of DEs in MG was two times higher than in IM. Simultaneously, the frequency of DEs (dominated by dust storms) increased in MG, whereas IM experienced a decrease in DEs (prevalent types of blowing dust). The T-DEs occurred 2.4 times higher than the ST-DEs over Mongolian Plateau. For the border-crossing DEs, transported dust storms were the dominant type. During 1977-1999, approximately 86% of DEs in IM originated from MG; however, this was decreased to 60% in the 2000s (2000-2018). The intensity of the border-crossing DEs originated from MG and the recessive T-DEs increased significantly since the 2000s, which were more significant than the progressive type.

著者

Tetsuro Miyachi Takeshi Enomoto

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.140-144, 2021 (Released:2021-08-20)

参考文献数

14

---

Tropical cyclone track forecast experiments were conducted using the National Centers for Environmental Prediction Global Forecast System with the initial conditions from three numerical weather prediction centers, to distinguish between tropical cyclone track forecast errors attributable to the initial state uncertainty and those attributable to the model imperfection. The average position error was reduced by replacing the initial conditions from the European Centre for Medium-range Weather Forecasts. The northward recurvature of Lupit (2009) was not reproduced with initial conditions from the Japan Meteorological Agency. It was consistent with the preceding study, indicating sensitivity to the initial state. The sensitivity to the model and the initial state was obtained for Parma (2009), as opposed to the conclusion of the previous study, where Parma was discovered to be insensitive to the initial state, and the error was assumed to come from the model difference. Insensitivity to the initial vortex structures in the predicted tracks for Parma indicates that the error in the steering flow formed by the environmental field around tropical cyclone contributes to the northward bias.

著者

Brandon J. Bethel Kelly Dusabe

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2021-028, (Released:2021-08-25)

被引用文献数

1

---

Precipitation in East Africa has the potential to enrich the lives of or bring ruin to millions of people that rely heavily on agriculture. Precipitation itself is in turn reliant on regional and extra-regional factors. The Indian Ocean Dipole (IOD) is such a factor and in this paper, its influence on the short rains that occur from October to December is studied through a quantitative assessment of information flow (IF) between the Dipole Mode Index and stations scattered throughout Burundi, Rwanda, and Uganda. Although it was initially thought that the African Great Lakes would have had an effect on the sensitivity of a given station's precipitation to the IOD, clear patterns on which stations were most sensitive or insensitive to IOD activity could not be properly identified. This is perhaps due to the plethora of atmospheric and topographic factors that contribute to local precipitation and as such, additional research is strongly encouraged to elucidate the reason, if any excluding statistical artifacts, for observed discrepancies.

著者

SATO Takuto KUSAKA Hiroyuki

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2021-047, (Released:2021-04-14)

被引用文献数

1

---

In this study, we compare the accuracy of five representative similarity metrics in extracting sea level pressure (SLP) patterns for accurate weather chart classification: correlation coefficient, Euclidean distance (EUC), S1-score (S1), structural similarity (SSIM), and average hash. We use a large amount of teacher data to statistically evaluate the accuracy of each metric. The evaluation results reveal that S1 and SSIM have the highest accuracy in terms of both average and maximum scores. Their accuracy does not change even when non-ideal data are used as the teacher data. In addition, S1 and SSIM can reproduce the subjective resemblance between two maps better than EUC. However, EUC reproduces the central position of the signal in a sample case. This study can serve as a reference for identifying the most useful similarity metric for the classification of SLP patterns, especially when using non-ideal teacher data.

著者

Takeshi Horinouchi Yu Kosaka Hiroshi Nakamigawa Hisashi Nakamura Norihisa Fujikawa Yukari N. Takayabu

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17B, no.Special_Edition, pp.1-8, 2021 (Released:2021-06-01)

参考文献数

30

被引用文献数

14

---

A prolonged heavy rainfall event occurred in Kyushu in early July 2020. Its large-scale environmental factors are investigated with observational and reanalysis data. Seven-day precipitation and moisture flux convergence around Kyushu were the greatest among the last 30 years. This pronounced convergence was maintained by nearly steady moisture influx, and the persistent upper-level trough to the northwest enhanced the ratio of moisture convergence to the influx. The magnitude of instantaneous moisture flux, however, was not particularly large among those along the subtropical jet axis or the Meiyu-Baiu rainband. What made this event unique is the persistence of the moisture flux peak anchored around Kyushu under the influence of the Silk-Road teleconnection. In June 2020, three upper-level troughs, whose easternmost one corresponding to the aforementioned trough, tend to form along the subtropical Asian jet. This wave train was persistent in the month and lasted until mid-July, 2020. Our analysis suggests that, prior to the rainfall event, the Silk-Road teleconnection was intensified through an interaction with a wave train at subpolar latitudes, which involves nonlinear processes including trough cut-off.

著者

Kyohei Yamada Masatoshi Kuribayashi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17A, no.Special_Edition, pp.45-50, 2021 (Released:2021-08-12)

参考文献数

24

被引用文献数

1

---

In October of 2019, Typhoon Hagibis brought abundant rainfall to eastern Japan that caused flooding of the Chikuma River in the northern region of Nagano prefecture. This study simulated the effects of changes in the elevation of the model terrain every 100 or 300 m with a regional meteorological model to understand the cause of the heavy precipitation that accompanied the typhoon in Nagano prefecture and the influence of the heights of mountains on the amount of rainfall. The model reproduced the typhoon track and spatiotemporal distribution of heavy precipitation. Mountains in the northern region of Nagano Prefecture contributed to the heavy precipitation, which increased at an approximately constant rate of 4.4 mm per 100 m increase of elevation. However, the rate of increase was especially large at elevations of 900-1200 m. The correlation of precipitation with topographic height was not as strong in the south as in the north, but the rate of variation was also anomalously high at elevations of 900-1200 m. These elevations roughly corresponded to the level of free convection or to elevations between the level of free convection and the lifted condensation level around the typhoon track.

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

Sachie Kanada Hidenori Aiki Kazuhisa Tsuboki

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17A, no.Special_Edition, pp.38-44, 2021 (Released:2021-07-27)

参考文献数

32

被引用文献数

3

---

Torrential rain associated with Typhoon Hagibis (2019) caused extensive destruction across Japan. To project future changes of the record-breaking rainfall, numerical experiments using a regional 1-km-mesh three-dimensional atmosphere–ocean coupled model were conducted in current (CNTL) and pseudo-global warming (PGW) climates. The water vapor mixing ratio in the lower troposphere increased by 23% in response to a 3.34 K increase in sea surface temperature (SST) in the PGW climate. The abundant moisture supply by the westward winds of the typhoon caused strong precipitation from its rainbands for a long period, resulting in 90% increase in total precipitation in eastern Japan before landfall. However, the strong PGW typhoon caused high SST-cooling. Mean precipitation in eastern Japan during the typhoon passage increased by 22% when the SST-cooling east of Kanto was strengthened from 0.11 K to 0.72 K from the CNTL to PGW simulations; the increase was above 29% when the SST-cooling was lowered. Since Typhoon Hagibis accelerated as it traveled northward, the magnitude of the SST-cooling and weakening of the typhoon were suppressed. Consequently, strong precipitation in the inner-core of the strong PGW typhoon caused 30% increase in precipitation in the areas on the Pacific side of northern Japan.

著者

Mikiko Fujita Tatsuya Fukuda Iwao Ueki Qoosaku Moteki Tomoki Ushiyama Kunio Yoneyama

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16A, no.Special_Edition, pp.19-24, 2020 (Released:2020-11-07)

参考文献数

34

被引用文献数

1 4

---

We report experimental observations of precipitable water vapor (PWV) derived using Global Positioning System/Global Navigation Satellite System (GPS/GNSS) receivers mounted on autonomous surface vehicles (ASVs), which were deployed in the tropical Pacific Ocean from July to September 2018. The GPS atmospheric delay was estimated by precise point positioning and converted to PWV with ASV surface meteorological data. The GPS-PWV was in agreement with the PWV obtained from radiosondes, with a root mean square error of 3.02 mm and a mean difference of 0.16 mm. A similar accuracy was found in a comparison of GPS-PWV with satellite-based microwave measurements. In anticipation of real-time monitoring applications, PWV was also estimated using real-time clock and orbit data. These estimates were in agreement with the post-processing values. High-resolution temporal observations of PWV over the open ocean made possible by ASV technology could greatly improve our understanding of the rapid variations of developing convective systems.

著者

He Gong Mei Huang Zhaosheng Wang

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2021-027, (Released:2021-07-28)

---

The northern Eurasia is a region heavily affected by the Arctic polar vortex (APV). Understanding the vegetation responses to anomalous APV in this region is important for dealing with climate change. In this study, we investigated the impacts and mechanism of the anomalous APV phases on the vegetation dynamics in the northern Eurasia. The larger and smaller APV phases correspond to almost opposite atmospheric circulation patterns which result in opposite vegetation responses. The decreased (increased) solar radiation, the enhanced (weakened) northerly winds, together with the decreased (increased) water vapor divergence, caused the decreasing (increasing) of the air temperature, increasing (decreasing) of the precipitation and soil moisture in the study area during the larger (smaller) APV phase. The response of vegetation growth to the APV depends on climate change and vegetation sensitivity to it. In most parts of the study area, vegetation growth was positively associated with air temperature, and hence, vegetation was suppressed (promoted) during the larger (smaller) APV phase. In the northeast of the Caspian Sea (NCS), vegetation growth was sensitive to precipitation. Therefore, the increased (decreased) soil moisture in summer and autumn were responsible for the promoted (suppressed) vegetation growth during the larger (smaller) APV phase.

著者

Tana Bao Tao Gao Banzragch Nandintsetseg Mei Yong Erdemtu Jin

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2021-026, (Released:2021-07-21)

被引用文献数

13

---

In this study, we investigated the spatiotemporal variations of border-crossing dust events (DEs), including floating, blowing dust, and dust storms between Mongolia (MG) and Inner Mongolia (IM), China using the ground-based observations from 91 synoptic stations across the Mongolian Plateau during 1977-2018. We defined the intensity of DEs (progressive and recessive) depending on the dust impact area (number of stations affected by dust) by dividing them into three categories: DEs, transported dust events (T-DEs), and severe transported dust events (ST-DEs). The results revealed that during 1977-2018, the frequency of DEs in MG was two times higher than in IM. Simultaneously, the frequency of DEs (dominated by dust storms) increased in MG, whereas IM experienced a decrease in DEs (prevalent types of blowing dust). The T-DEs occurred 2.4 times higher than the ST-DEs over Mongolian Plateau. For the border-crossing DEs, transported dust storms were the dominant type. During 1977-1999, approximately 86% of DEs in IM originated from MG; however, this was decreased to 60% in the 2000s (2000-2018). The intensity of the border-crossing DEs originated from MGand the recessive T-DEs increased significantly since the 2000s, which were more significant than the progressive type.

著者

Tetsuro Miyachi Takeshi Enomoto

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2021-025, (Released:2021-07-20)

---

Tropical cyclone track forecast experiments were conducted using the National Centers for Environmental Prediction Global Forecast System with the initial conditions from three numerical weather prediction centers, to distinguish between tropical cyclone track forecast errors attributable to the initial state uncertainty and those attributable to the model imperfection. The average position error was reduced by replacing the initial conditions from the European Centre for Medium-range Weather Forecasts. The northward recurvature of Lupit (2009) was not reproduced with initial conditions from the Japan Meteorological Agency. It was consistent with the preceding study, indicating sensitivity to the initial state. The sensitivity to the model and the initial state was obtained. For Parma (2009), as opposed to the conclusion of the previous study, where Parma was discovered to be insensitive to the initial state, and the error was assumed to come from the model difference. Insensitivity to the initial vortex structures in the predicted tracks for Parma indicates that the error in the steering flow formed by the environmental field around tropical cyclone contributes to the northward bias.

著者

Kyohei Yamada Masatoshi Kuribayashi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.17A-008, (Released:2021-07-15)

被引用文献数

1

---

In October of 2019, Typhoon Hagibis brought abundant rainfall to eastern Japan that caused flooding of the Chikuma River in the northern region of Nagano prefecture. This study simulated the effects of changes in the elevation of the model terrain every 100 or 300 m with a regional meteorological model to understand the cause of the heavy precipitation that accompanied the typhoon in Nagano prefecture and the influence of the heights of mountains on the amount of rainfall. The model reproduced the typhoon track and spatiotemporal distribution of heavy precipitation. Mountains in the northern region of Nagano Prefecture contributed to the heavy precipitation, which increased at an approximately constant rate of 4.4 mm per 100 m increase of elevation. However, the rate of increase was especially large at elevations of 900-1200 m. The correlation of precipitation with topographic height was not as strong in the south as in the north, but the rate of variation was also anomalously high at elevations of 900-1200 m. These elevations roughly corresponded to the level of free convection or to elevations between the level of free convection and the lifted condensation level around the typhoon track.

著者

Takeshi ENOMOTO Shozo YAMANE Wataru OHFUCHI

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.93, no.2, pp.199-213, 2015 (Released:2015-05-14)

参考文献数

31

被引用文献数

8 10

---

Simple methods are formulated using an ensemble forecast to identify the sensitive initial perturbations that grow in a specified region at the verification time. These methods do not require the tangent-linear or adjoint models, but use an ensemble forecast to obtain approximated solutions. Input to the sensitivity calculation can be any ensemble forecast integrated from initial conditions perturbed with the bred vector, singular vector, or ensemble Kalman filter methods. Two formulations are presented here to approximate the adjoint and singular vector methods using an ensemble forecast. The ensemble singular vector sensitivity, which has already been applied in previous studies, is obtained with a single eigenvector calculation. The ensemble adjoint sensitivity only requires an even simpler matrix-vector multiplication. To validate the formulations, ensemble-based sensitivity analysis has been conducted in a few cases. First, the two methods were applied to identify the sensitive initial perturbations that grow in the verification region over Japan in January and August 2003. The first singular vector mode indeed achieves the largest amplitude at the verification time, but that is not necessarily true after the verification time. Both methods can identify the sensitive regions more specifically than the regions with large ensemble spread in cases with a mid-latitude cyclone and with a tropical cyclone. The monthly-mean sensitivity in January 2003 indicates the effect of Rossby waves and synoptic disturbances in upstream sensitive regions over Siberia, Tibet, and a downstream sensitive region in the north-western Pacific; the sensitivity in August 2003 suggests the influence of the Asian summer monsoon. Next, for an August 2002 storm case in Europe, global 20-km resolution simulations were conducted from the initial conditions perturbed by the ensemble singular vector method to compare with the unperturbed simulation. In the perturbed simulation, the cyclone is deeper by a few hPa in its north-east sector with more precipitation north of the Alps more consistently with observations. These results indicate that reasonable sensitive regions can be identified with our methods.

著者

Ryota Ishiyama Hiroshi L. Tanaka

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.120-124, 2021 (Released:2021-06-26)

参考文献数

23

被引用文献数

1

---

In this study, we conducted a domain-integrated vorticity budget analysis to quantitatively understand the developing mechanism of the Arctic Cyclone (AC) in August 2016 (AC16). The results showed that the vorticity enhancement of the AC16 was dominated by the horizontal flux convergence of vorticity at all layers with a maximum near the tropopause. The enhancement near the tropopause was characterized not only by the horizontal supply but also by the vertical transport of vorticity. In the boundary layer within the AC16, the convergence of horizontal winds and the corresponding divergence of vertical winds occurred. In addition, during the merging process, updrafts were dominant in the troposphere due to the structure of the mid-latitude cyclone. These structures caused the upward transport of vorticity to the tropopause, which is considered as an important internal process of the AC16. However, time-averaged vorticity budget during the developing stage indicated that the vertical flux term and the divergence term compensate with each other. As a result, it was concluded that the AC is excited and maintained by the merging of the vortices associated with the migrating mid-latitude cyclone and polar vortex.

著者

Sachie Kanada Hidenori Aiki Kazuhisa Tsuboki

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.17A-007, (Released:2021-06-22)

被引用文献数

3

---

Torrential rain associated with Typhoon Hagibis (2019) caused extensive destruction across Japan. To project future changes of the record-breaking rainfall, numerical experiments using a regional 1-km-mesh three-dimensional atmosphere–ocean coupled model were conducted in current (CNTL) and pseudo-global warming (PGW) climates. The water vapor mixing ratio in the lower troposphere increased by 23% in response to a 3.34 K increase in sea surface temperature (SST) in the PGW climate. The abundant moisture supply by the westward winds of the typhoon caused strong precipitation from its rainbands for a long period, resulting in 90% increase in total precipitation in eastern Japan before landfall. However, the strong PGW typhoon caused high SST-cooling. Mean precipitation in eastern Japan during the typhoon passage increased by 22% when the SST-cooling east of Kanto was strengthened from 0.11 K to 0.72 K from the CNTL to PGW simulations; the increase was above 29% when the SST-cooling was lowered. Since Typhoon Hagibis accelerated as it traveled northward, the magnitude of the SST-cooling and weakening of the typhoon were suppressed. Consequently, strong precipitation in the inner-core of the strong PGW typhoon caused 30% increase in precipitation in the areas on the Pacific side of northern Japan.

著者

Makoto Kondo Yousuke Sato Masaru Inatsu Yuta Katsuyama

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.74-80, 2021 (Released:2021-04-24)

参考文献数

51

被引用文献数

4

---

The performances of bulk microphysical schemes were evaluated through comparisons with observations, including a new volume scanning video disdrometer targeting one of a typical snowfall event in Hokkaido, Japan. For the evaluation, downscaling experiments using three bulk microphysical schemes were conducted: a two-moment bulk scheme, a one-moment bulk scheme, and an improved version of the one-moment bulk scheme coupled with an identical dynamical core. The two-moment scheme successfully simulated the measured relationship between particle size and terminal velocity distribution (PSVD). On the other hand, the one-moment scheme overestimated the graupel frequency, its terminal velocity, and underestimated the particle diameter. The improved version of the one-moment bulk scheme reduced the overestimation of the terminal velocity of hydrometeors, but still overestimated the graupel frequency. We improved the overestimation of terminal velocity and the frequency of graupel in the one-moment scheme by modifying the assumption of the velocity–diameter relationship and the intercept parameter of the size distribution of graupel based on the results of the new disdrometeor. The observation of the new disdrometer would give us hints to improve the microphysics schemes in snowfall cases.

著者

Koichi Watanabe Liu Yang Satoru Nakamura Takuya Otani Kenzaburo Mori

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.109-112, 2021 (Released:2021-05-22)

参考文献数

18

被引用文献数

3

---

Aerosol number concentrations and trace gases (SO2, O3, HCHO, and H2O2) were measured over Imizu City, Toyama Prefecture, Japan on 5 August 2020, from a helicopter. The concentrations of fine particles (0.3-0.5 μm) were high at ground level and at an altitude of approximately 1200 m due to the volcanic plume from Nishinoshima. However, concentrations of aerosol particles were low at an altitude of approximately 2400 m. The volcanic plume did not significantly affect the lower free troposphere. High concentrations of SO2 were also observed. The H2O2 concentrations (0.27-0.56 ppb) were much lower than those during previous observations in the summer (2.0-6.7 ppb) and significantly lower than the SO2 concentrations (1.8-3.3 ppb). The concentrations of HCHO (2.1-2.5 ppb) were higher than those of H2O2. The oxidation of S(IV) to H2SO4 in cloud water might have been suppressed over the studied area.

著者

Masahiro Shiozaki Takeshi Enomoto

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17, pp.103-108, 2021 (Released:2021-05-22)

参考文献数

22

被引用文献数

1

---

La Niña cases that occurred after 1948 are classified into cold and non-cold winters in the Far East to investigate the formation of disparate teleconnection patterns corresponding to the two types and to compare with those during El Niño. According to composite analyses using reanalysis datasets, the North Pacific Oscillation (NPO)/western Pacific (WP) pattern (NPO/WP pattern) and the Pacific-North American (PNA) pattern dominate in the cold and non-cold winters, respectively. As during El Niño, modulations of the local Hadley circulation associated with La Niña play an important role in the formation of the teleconnection patterns. These results indicate that the formation mechanisms of teleconnection patterns during La Niña are the same as those during El Niño but are not simple reverse signals.

著者

WU Ying-Jhang LIOU Yu-Chieng LO Yi-Chuan TAI Sheng-Lun CHANG Shao-Fan SUN Juanzhen

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2021-049, (Released:2021-04-20)

被引用文献数

1

---

The evolution of a heavy rainfall event occurred on 19 August 2014 in northern Taiwan is investigated with observed data and analyses from a newly-developed system named IBM_VDRAS, which is based on a four-dimensional Variational Doppler Radar Assimilation System (VDRAS) with the capability to assimilate radar observations and surface station data over a complex terrain by adopting the Immersed Boundary Method (IBM). This event possesses different precipitating processes and track from those frequently observed in that region. From the surface observations and the high spatiotemporal resolution analysis fields generated by IBM_VDRAS, it is found that the rainfall process started with the initiation of two individual convective cells triggered through the interaction between land-sea breeze and terrain in two different cities (Taoyuan and Taipei). The outflow of one of the convective cells developed in Taoyuan City at an earlier time merged with another convective system which grew in Taipei Basin, and provided favorable conditions to intensify the latter. The enhanced major convective cell moved into the Taipei City metropolitan area and produced 80 mm of precipitation within approximately 2.5 h. The kinematic, thermodynamic, and microphysical fields of the convective cells are analyzed in details to explain the mechanisms which helped to maintain the structure of the rainfall system. Sensitivity experiments of quantitative precipitation forecast (QPF) show that the terrains prevent the location of major rainfall from shifting outside of Taipei Basin. By assimilating surface data, the model can better predict the position of the rainfall.