著者

Yuhei Takaya

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15A, pp.55-59, 2019 (Released:2019-08-24)

参考文献数

30

被引用文献数

15

---

The western North Pacific (WNP) exhibited markedly enhanced tropical cyclone (TC, typhoon) activity during the boreal summer (June–August) of 2018; 18 named typhoons were generated and 13 of these approached near Japan, causing serious damage and disruption in the country. During the summer of 2018, warm sea surface temperature persisted over the tropical Northeastern Pacific, which are typical oceanic conditions of a positive phase of the Pacific meridional mode (PMM), while no El Niño condition was observed. The Japan Meteorological Agency seasonal forecast system successfully predicted the enhanced TC activity in the WNP as well as associated seasonal characteristics such as a deep monsoon trough and active convection. Results of sensitivity experiments clearly indicate that the positive phase of the PMM played a major role in establishing the active TC conditions in the WNP during the summer of 2018 and reveal predictable seasonal processes of TC activity (genesis and tracks) during the summer of 2018, when there was no El Niño.

著者

Akiyo Yatagai Kotaro Minami Minami Masuda Naho Sueto

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15A, pp.43-48, 2019 (Released:2019-08-09)

参考文献数

10

被引用文献数

10

---

This study developed a rain-gauge-based hourly precipitation dataset to analyze the heavy precipitation event of July 2018 in Japan (H2018). We modified the APHRODITE algorithm to treat hourly precipitation data, and we detected orographically induced heavy precipitation patterns in western Japan. We compared the heavy precipitation pattern along with moisture transport with that of another disastrous precipitation event in 2014 over Hiroshima (H2014). It is evident that heavy precipitation occurred over a much wider area in Chugoku district during H2018 than in H2014, and extreme precipitation which exceeds 10mm/hr appeared three times in H2018 while at one time in H2014. Atmospheric rivers (ARs) were detected during two distinct episodes of heavy precipitation over Hiroshima, i.e., 19 August 2014 and 6 July 2018. Of the two events, the precipitation amount and the depth (height) of the AR were much greater in the latter. In the mid-troposphere, abundant moisture and high equivalent potential temperatures along the Meiyu frontal system can produce a large area of continuous heavy precipitation. The intensive hourly rainfall dataset developed in this study will be useful for investigations of AR and meso-scale system that affect heavy precipitation and validation of numerical models.

著者

Tomoe Nasuno

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.99-106, 2019 (Released:2019-05-16)

参考文献数

39

被引用文献数

5

---

Transport of moisture over the western Maritime Continent (MC) was examined using global cloud-system-resolving simulations for the Years of the Maritime Continent (YMC) field campaigns in 2015 and 2017, under peak El Niño and moderate La Niña conditions, respectively. We focused on the role of high- and low-frequency variability in the moistening over land and ocean, and their relationship with intraseasonal oscillation (ISO) events.The period-mean profiles indicate moistening by low-frequency upward motion in the deep troposphere and drying (moistening) in the lower (middle and upper) troposphere by high-frequency variability. The advection over ocean was greater in 2017 than in 2015, with the opposite occurring over land with smaller interannual differences. Over ocean, the roles of the high-frequency variability in the ISO life cycle, namely, the lower-to-middle-tropospheric moistening (enhanced upward transport of moisture) during the preconditioning (active) phases of the ISO, were common in both years, while over land, the high-frequency effects were nearly in phase (not correlated) with the ISO in the 2015 (2017) case. These results highlight clear land-ocean contrasts in the sensitivity of local convection to the background state and its link with the ISO life cycle.

著者

Van Q. Doan Van Nguyen Dinh Hiroyuki Kusaka Thanh Cong Ansar Khan Du Van Toan Nguyen Dinh Duc

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.113-118, 2019 (Released:2019-05-30)

参考文献数

32

被引用文献数

5

---

This study revealed great potential and shortcoming of offshore wind energy in Vietnam by numerical simulations with Weather Research and Forecasting (WRF) model at 10-km resolution for 10 years (2006-2015). The greatest energy potential was found in the offshore area of Phu Quy island (Binh Thuan province). The area, alone, can provide the 38.2 GW power generation capacity corresponding to the increasing renewable-energy demand by 2030 planned by the country. There is also a drawback of the wind resource, which is associated with strong multiple-scale temporal variabilities. The seasonal variability associated with monsoon onsets and daily variability associated with the wind diurnal cycles were found ranging 30-50%. Meanwhile, the inter-annual variability could reach up to 10%. These variabilities must be considered when designing wind farms and grids over the region. Additionally, due to the fact that the WRF model performed climatological features of the winds well against the observations, this results indicate that it can be useful tools for wind-power assessment as compared to other reanalysis or QuikSCAT data with coarser spatio-temporal resolutions.

著者

Hien Xuan Bui Jia-Yuh Yu Hsiao-Wei Liu Chia-Ying Tu Pin-Ging Chiu Huang-Hsiung Hsu

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.119-124, 2019 (Released:2019-05-30)

参考文献数

34

被引用文献数

6

---

While most studies have argued a slower increase of 1-3% K−1 of precipitation globally, others note that this is not necessarily the case from a regional perspective. In this study, we examine the convective structure changes over the equatorial Pacific with highly increased precipitation under global warming using simulations from the High Resolution Atmospheric Model (HiRAM). The moisture budget analysis shows that the precipitation increases must result from a significant enhancement of convection, with a minor modulation from the thermodynamic effect. Two different types of enhanced convection are identified. Over the mean ascending region, precipitation increases are associated with an enhancement of deep convection; while over the mean descending region, the precipitation increases are a result of enhanced shallow convection.

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.149-153, 2019 (Released:2019-07-17)

参考文献数

23

被引用文献数

2

---

This study revealed that the Karakkaze events accompanied by rising temperature are more frequent than those accompanied by dropping temperature. This finding contrasted with the general belief for many years that the Karakkaze is a bora-type local wind. By focusing on the temporal evolution of temperature and wind, we were able to characterize three types of Karakkazes as follows: the surface wind speed and temperature both increase in the morning and then decrease in the afternoon (type Foehn-D); during the night, the temperature increases or stops decreasing, and the surface wind speed increases (type Foehn-N); and in the morning, the temperature decreases or stops increasing, and the surface wind speed increases (type Bora). As a result, we found that among the 238 Karakkazes that we identified, 103 were type Foehn-D events, 56 were type Foehn-N events, and 79 were type Bora events.

著者

Minghao Yang Ruiting Zuo Xin Li Liqiong Wang

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.166-171, 2019 (Released:2019-08-21)

参考文献数

40

被引用文献数

3

---

The Qian atmospheric forcing dataset is used to drive version 4.5 of the Community Land Model (CLM4.5) in off-line simulation tests. Based on the Global Land Evaporation Amsterdam Model (GLEAM) data, we attempt to ameliorate the canopy interception parameterization scheme in CLM4.5 by improving the empirical parameter and the physical structure. Considering that different plant functional types (PFTs) have different capacities to intercept rainfall is denoted as SEN1, and accounting for the influence of wind speed on canopy interception on the basis of SEN1 is denoted as SEN2. SEN1 shows obvious improvement in the simulated evaporation of intercepted water from vegetation canopy (Ec), not only greatly reduces the positive bias of the model to simulate Ec, especially in the equatorial region, but also significantly reduces the root mean square error (RMSE). SEN2 further improves the simulation of Ec by lowering the RMSE and increasing consistency with GLEAM data. In addition, the percentages of Ec over total evapotranspiration in both SEN1 and SEN2 are more reasonable and much closer to GLEAM data than that in CLM4.5.

著者

Jianbo Yang Min Shao Qingeng Wang Xu Yang

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.172-177, 2019 (Released:2019-08-24)

参考文献数

30

---

The relationships between the prediction of near-surface winds and the corresponding time of observations in eastern China were explored using the Advanced Weather Research and Forecasting (WRF) model and the three-dimensional variational (3D-Var) scheme in the gridpoint statistical interpolation (GSI) system. A series of one-month experiments was conducted in January 2018 with different time window configurations from 0.01 to 3.0 h. The relationship between the wind observation time and the model forecast was non-linear. An observational time closer to the initial time in the model usually have greater impact on the prediction of near-surface wind speeds. Observations in the 0.4-0.8 h time window associated with abnormally high with large near-surface wind speeds provide a negative impact. The predictions improved at a much smaller rate when the time window was increased from 0.8 to 3.0 h. No significant difference was seen as the time window increased in wind direction predictions, even with large wind increments. The optimum configuration of the time window in the GSI 3D-Var system for predicting near-surface winds should therefore be 0.2 or 0.4 h. A better understanding of the relationships between the observations and the predictions will help select more effective observations when using the 3D-Var scheme.

著者

Masaya Nosaka Hiroaki Kawase Hidetaka Sasaki Akihiko Murata

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.107-112, 2019 (Released:2019-05-22)

参考文献数

20

被引用文献数

3

---

High-frequency variations are excluded in the merged satellite and in-situ data global daily sea surface temperature (MGDSST) used in weather forecasting in Japan Meteorological Agency. We investigated the importance of temporal resolution on sea surface temperature (SST) when predicting winter precipitation using the Non-Hydrostatic Regional Climate Model. We used seven-day temporal smoothing to investigate the influence of temporal resolution on prediction. The Gaussian filter was used as spatial smoothing for comparison with the influence of spatial resolution. The influence of the temporal resolution of SST on monthly precipitation is smaller than that of spatial resolution. However, the influence of the temporal resolution on daily precipitation is comparable to that of spatial resolution. The temporal resolution of SST greatly affects precipitation, particularly in December, as the variations in SST are largest compared to the rest of the year. Furthermore, the winter monsoon promotes the effect of SST on winter precipitation. Our experiments using seven-day moving average smoothing indicates that the temporal resolution of the SST on precipitation become about 15 %/K under the winter monsoon.

著者

Kengo Arai Kazuaki Yasunaga

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.80-86, 2019 (Released:2019-04-12)

参考文献数

13

被引用文献数

1

---

This study examines dominant precipitation patterns during winter in the north-central region (Hokuriku District) of Japan, based on empirical orthogonal functions (EOFs) analysis. The pattern of the first leading component is similar to that of the mean precipitation, and the second leading component shows a dipole structure in which positive and negative regions are separated by the coast line. This dipole pattern across the coast line is robust regardless of data stratifications for the EOF calculation. Composites reveal that maritime and inland precipitation is relatively enhanced before and after the passage of a mid-level trough, respectively. In the former case, the temperature is higher and westerly or southwesterly wind prevails, while northwesterly wind dominates in the latter case. It is suggested that interactions between cold air over the land and warm air over the ocean are essentially important to the distinct precipitation patterns; offshore winds wedge the inland cold air under the maritime warm air, and intensifies the precipitation over the ocean. On the other hand, the northwesterly monsoonal flow pushes the maritime warm air onto the inland cold air, and more precipitation is brought about around the mountain range.

著者

Kazuto Takemura Akihiko Shimpo

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.75-79, 2019 (Released:2019-04-06)

参考文献数

20

---

Herein, (i) the remote influence of positive Indian Ocean Dipole (P-IOD) events in enhancing Tibetan High and (ii) its impact on the East Asian climate, from July to September, is analyzed based on composite analysis and linear baroclinic model experiment. In the equatorial Indian Ocean, convective activity enhances over the western part and suppresses over the eastern, which is associated with the zonal contrast of the sea surface temperature anomaly during P-IOD events. A lower-tropospheric clockwise circulation anomaly is evident from the eastern equatorial Indian Ocean where the suppressed convection is seen to the Indochina Peninsula. The streamlines arrive at the seas east of the Philippines, contributing to the enhancement of the monsoon trough. In the upper troposphere, crucial divergence anomaly over a wide area in the western North Pacific and the associated stronger-than-normal northward divergent winds toward East Asia cause strong northward negative-vorticity advection over the northern part of East Asia, contributing to the northeastward extension of the Tibetan High. This circulation anomaly contributes to both the significantly hot conditions in boreal summer and the late-summer heat over East Asia.

著者

Hai Bui Shigeo Yoden Eriko Nishimoto

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.62-67, 2019 (Released:2019-03-21)

参考文献数

15

被引用文献数

4

---

We present a three-dimensional minimal model that produces a self-sustained oscillation reminiscent of the quasi-biennial oscillation (QBO) in a radiative–moist convective quasi-equilibrium state. The computational domain is rectangular (640 km × 160 km) with doubly periodic boundary conditions. After initial transient time, an oscillation with a period of about 300 days emerges in the stratosphere, both in the domain-averaged zonal wind and meridional wind. A synchronization of the zonal and meridional winds is observed and is characterized as an anti-clockwise rotation of a skewed spiral feature with height in the mean horizontal wind vectors. The QBO-like wind oscillations penetrate into the troposphere. Modulation of tropospheric temperature anomalies and precipitation occurs with an irregular period of about 100 days, in which heavy precipitation is associated with positive temperature anomalies. The simulation reveals three types of precipitation patterns: isolated quasi-stationary type clusters, fast-moving back-building type and squall-line type patterns. The quasi-stationary type is newly identified in this three-dimensional model. Intermittent self-organization of convective systems into quasi-stationary type and transition back to the fast-moving back-building type or squall-line type are fundamental characteristics of self-aggregation in the three-dimensional model.

著者

Wenkai Li Shuzhen Hu Zongmei Pan Xiaoyun Su Xinyue Luo Yijuan Wang

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.47-51, 2019 (Released:2019-02-28)

参考文献数

45

被引用文献数

2

---

The apparent temperature (APT), or human-perceived temperature, is commonly defined as a function of the surface air temperature (SAT), vapour pressure (or humidity) and wind speed. This paper demonstrates that the APT over China, as revealed by daily station-observed data, has generally increased faster than the SAT during summertime in the past 50 years (1968-2017). The rate of increase in APT was significantly faster than that of SAT in 60.1% of stations, and the difference between the average China-wide APT and SAT was 0.11°C decade−1. This phenomenon is occurring nationwide, but it is more intense over western, north-eastern and eastern coastal China. The more rapid increasing trend in APT indicates that human beings actually experience surplus heat stress under a certain change in SAT, and the increased SAT explains 67.0% of the average APT warming for the country, contributing to the change in the base APT. Apart from the increasing SAT, a decrease in surface wind speed and an increase in surface vapour pressure have also been observed, contributing to 21.6% of the increase in APT and explaining the remaining 11.4%, respectively.

著者

Takumi Honda Shohei Takino Takemasa Miyoshi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.15, pp.7-11, 2019 (Released:2019-01-19)

参考文献数

23

被引用文献数

7

---

Tropical cyclones (TCs) and associated heavy precipitation have large impacts in Japan. This study aims to find how data assimilation (DA) of every-10-minute all-sky Himawari-8 radiances could improve the quantitative precipitation forecast (QPF) for TC cases. As the first step, this study performs a single case study of Typhoon Malakas (2016) using a regional atmospheric model from the Scalable Computing for Advanced Library and Environment (SCALE) coupled with the local ensemble Kalman filter (LETKF). The results show that the all-sky Himawari-8 radiance DA at 6-km resolution improves the representation of Malakas and may provide more accurate deterministic and probabilistic precipitation forecasts if the horizontal localization scale is chosen appropriately.

著者

Chia Rui Ong Hiroaki Miura

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.170-173, 2018 (Released:2018-11-13)

参考文献数

17

被引用文献数

2

---

Empirical formulae of the terminal velocity and shape of a water droplet in microphysics parametrizations are derived from experiments or theoretical works and they are only verified under room temperature and standard atmospheric pressure. A two-phase direct numerical simulation model can be a strong tool to improve those empirical formulae under general conditions. Recently, the global B-spline fitting has been applied and its smooth one dimensional (1D) surface reconstruction of water droplets has enabled stable simulations of falling two dimensional (2D) droplets by the immersed boundary method (IBM). However, an extension of the global reconstruction from 1D to 2D is highly complex and is almost impossible to use in a model. To overcome this limitation, an iterative algorithm is proposed for a local smooth surface reconstruction in this work. One significant advantage is its straightforward extension to 2D surfaces. To test the new method, simulations of an axisymmetric free-oscillating water droplet are compared between the global and local surface reconstructions. A further simulation of a rising air bubble is performed to examine the robustness of the new algorithm for the highly distorted interface. This new method opens a pathway to three dimensional (3D) water droplet simulations by the IBM.

著者

Xinyi Yang Xiaofan Li

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.185-191, 2018 (Released:2018-11-28)

参考文献数

45

被引用文献数

2

---

Four cases of heavy rainfall over Zhejiang, Fujian and Jiangxi during mid-June are simulated by the two-dimensional (2D) cloud-resolving model using the large-scale forcing data derived from the 6-hourly ERA-Interim data set. The simulations are used to conduct budget analysis of precipitation and energetics associated with the development of torrential rainfall. Surface rainfall is dominated by water vapor convergence (QWVF) in water vapor related surface rainfall budget and heat divergence (SHF) in thermally related surface rain budget. The high linear correlation coefficients between water vapor related precipitation efficiency (PEWV) and heat related precipitation efficiency (PEH) stem from the statistical similarities between QWVF and SHF. The diurnal variations of surface rainfall correspond to the upward motions. An energy conversion efficiency is defined as the ratio of perturbation kinetic-energy to convective available potential energy to measure how efficiently the secondary circulations develop under the consumption of the convective available potential energy. The diurnal variations of energy conversion efficiency generally are in phase with the rainfall, indicating importance of interaction between dynamics and water vapor in build-up of rainfall peaks.

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

Lin Chen Lu Wang Tim Li De-Zheng Sun

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.126-131, 2018 (Released:2018-09-12)

参考文献数

55

被引用文献数

11

---

The study presents the contrasting characteristics of cloud-radiative feedbacks to the cold tongue (CT) and warm pool (WP) El Niño (EN). The maximum sea surface temperature anomalies (SSTA) of the CT-EN are located in the far-eastern Pacific. However, the maximum responses of the shortwave- and longwave- cloud-radiative forcing (SWCRF and LWCRF) to the CT-EN warming are centered near the dateline, showing 70° westward shift relative to the maximum SSTA center of CT-WN. In contrast, the maximum responses of the SWCRF and LWCRF to the WP-EN warming show only slight westward shift relative to the maximum SSTA center. The contrasting cloud-radiative feedbacks to the two types of ENs can be traced back to the contrasting precipitation feedbacks, which is associated with the convection threshold. When the warm SSTA of CT-EN occurs in the relatively cold eastern Pacific, the total SST in-situ may not exceed the convection threshold. Therefore, the induced precipitation anomaly would occur towards the warm western Pacific, and the corresponding cloud cover and cloud-radiative feedbacks would exhibit an apparent westward shift. As the warm SSTA of WP-EN occurs in the relatively warm central Pacific, the corresponding responses of the anomalous fields to the WP-EN show only slight westward displacement.

著者

Prabir K. Patra Masayuki Takigawa Shingo Watanabe Naveen Chandra Kentaro Ishijima Yousuke Yamashita

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.91-96, 2018 (Released:2018-07-21)

参考文献数

37

被引用文献数

42

---

The accuracy of chemical tracer simulations by atmospheric general circulation model (AGCM)-based chemistry-transport models (ACTMs) depends on the quality of AGCM transport properties, even when the meteorology is nudged towards the reanalysis fields. Here we show that significant improvements in tracer distribution are achieved when hybrid vertical coordinate is implemented in MIROC4.0 AGCM, compared to its predecessors AGCM5.7b based on sigma coordinate. Only explicitly resolved gravity waves are propagated into the stratosphere in MIROC4-ACTM. The MIROC4-ACTM produces “age-of-air” up to about 5 years in the tropical upper stratosphere (∼1 hPa) and about 6 years in the polar middle stratosphere (∼10 hPa), in agreement with observational estimates. Comparisons of MIROC4-ACTM simulation with observed sulphur hexafluoride (SF6) in the troposphere also show remarkable improvements over the AGCM57b-ACTM simulation. MIROC4-ACTM is characterized by weaker convective mass flux and thus older age of air in the tropical troposphere, relative to AGCM57b-ACTM. The role of convective transport on tracer simulations is depicted using vertical cross-sections of 222Rn (radon) distributions. Both the ACTM versions show similar results when compared with 222Rn measurements at remote sites. All aspects of tracer transport in MIROC4-ACTM is promising for inverse modelling of greenhouse gases sources and sinks at reduced bias.

著者

Fusako Isoda Shinsuke Satoh Tomoo Ushio

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.64-68, 2018 (Released:2018-06-23)

参考文献数

15

被引用文献数

2 6

---

On 26 July 2012, localized rainfall from four isolated convective cells was observed by the Phased Array Weather Radar (PAWR) located in Osaka, Japan. The PAWR can observe fine three-dimensional features of precipitation every 30 seconds. In this paper, we investigated the evolution of localized isolated convective cells using the PAWR data. The first echoes appeared at around 5 km altitude, and light rain (25 dBZ) near the ground started in 3 to 5 minutes after the first echo. Heavy rain (50 dBZ) started in 9 to 15 minutes after the first echo. The lifespan of four convective cells was from 40 to 70 minutes.The reflectivity centroid over 25 dBZ (C25) of the first echo in developing stage descended first and then ascended within the several minutes. The behavior of the first echo motion looked complicated and it is difficult to be explained by the traditional conceptual model. In dissipation stage, the descending C25 was stopped by an alternation of precipitation core.