著者

村上 多喜雄 松本 淳

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.72, no.5, pp.719-745, 1994-10-25 (Released:2008-01-31)

参考文献数

38

被引用文献数

151 267

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西部北太平洋における夏のモンスーン(WNPM)は、8月中ごろの最盛期には、東南アジアモンスーン(SEAM)と同程度かそれ以上に活発になる。これら2つの夏のモンスーン地域の境界は、OLRが190Wm-2以下になる両モンスーンの上昇域の間にあって、OLRが230Wm-2以上と比較的高く、相対的な好天域である南シナ海にある。主要な下降域は中部北太平洋にあり、そこでは太平洋高気圧の発散域の上層に、熱帯上部対流圏トラフの収束域が位置している。すなわち、29℃を超える世界でもっとも高い海水温域にあるWNPMの中心地域(北緯10-20度、東経130-150度)では、活発な対流活動が生じ、東経110度付近の南シナ海と、西経140度付近の中部北太平洋との間に、顕著な東西循環が起こっている。この東西循環の鉛直構造は、北緯10-20度付近ではバロクリニックで、東経150度以東では下層が偏東風、上層が偏西風となっており、以西ではこの逆となる。WNPMは、北緯10度から20度付近における海水温の東西コントラストと、北緯20-30度付近における、大陸-海洋間の東西の熱的コントラストの複合作用の結果として生じていると考えられる。WNPM域の極側には大きな大陸がないため、南北の熱的コントラストの影響は、二義的なものとなる。一方SEAMは、主に南北の海陸熱的コントラストによって駆動される、南北循環によって生じている。SEAMは10月初め以前に後退するのに対し、WNPMは29℃を超える高海水温が維持されているため、11月初めまで持続する。

著者

Augusto José PEREIRA FILHO Felipe VEMADO Kazuo SAITO Hiromu SEKO José Luis FLORES ROJAS Hugo Abi KARAM

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.96A, pp.247-263, 2018 (Released:2018-05-17)

参考文献数

54

被引用文献数

5

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The Tokyo Metropolitan Area Convection Study (TOMACS) for extreme-weather-resilient cities is a research and development project (RDP) of the World Weather Research Programme (WWRP). TOMACS provided a multiplatform and high spatiotemporal resolution dataset for the present research on three episodes of deep convection in the Tokyo Metropolitan Area (TMA) under its heat island effect and sea breeze circulations. Heavy rainfall episodes of August 26, 2011, and July 23 and August 12, 2013, were simulated with (and without) the tropical town energy budget (T-TEB) model coupled with the advanced regional prediction system (ARPS). The T-TEB/ARPS system used initial and boundary conditions from the Japan Meteorological Agency (JMA) mesoscale analysis data for 24-hour integration runs at 5-km resolution over Japan and at 1-km resolution over TOMACS area. The 1-km resolution hourly rainfall field simulations were verified against the respective automated meteorological data acquisition system (AMeDAS) rain gauge network measurements. Statistics of the Contingency tables were obtained to estimate the critical success index (CSI), probability of detection (POD), and false alarm rate (FAR) as well as the root mean square error (RMSE). The T-TEB/ARPS simulations improved the south and east sea breeze circulations of TMA and its urban heat island effect. The time evolution of CSI scores improved within the advective time scale, whereas dissipation (phase) errors on precipitation RMSE increased with the integration time and were larger than the dispersion (amplitude) errors. The initial and boundary conditions of JMA greatly improved the simulations as compared to the previous ones performed with the outputs of NCEP's global forecast system as indicated by the TOMACS datasets. Thus, the results represent the temporal and spatial evolutions of the atmospheric conditions leading to the development of a deep convection within TOMACS region. Furthermore, TMA is a good testbed to evaluate the urban surface schemes, such as T-TEB in this study.

著者

KUJI Makoto MURASAKI Atsumi HORI Masahiro SHIOBARA Masataka

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.2018-025, (Released:2018-02-05)

被引用文献数

9

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Cloud fractions were observed during research cruises onboard the research vessel (R/V) Shirase between Japan and Antarctica using a whole-sky camera and a ceilometer. The cruises, Japanese Antarctic Research Expeditions (JARE) 55 and 56, took place from November 2013 to April 2014 and November 2014 to April 2015, respectively. Cloud fractions were estimated from the whole-sky camera based on the sky brightness and spectral characteristics, while the ceilometer recorded the cloud occurrence frequency. According to the comparison of daily-averaged cloud fractions from the whole-sky camera with the ceilometer observations over the open ocean between Japan and Antarctica, the correlation coefficients were 0.87 and 0.93 for JARE 55 and 56, respectively. Overall, the results from both observation methods were consistent over the open ocean. Nevertheless, it was necessary to take surface conditions into consideration, particularly for the estimated cloud fractions from the whole-sky camera, because the contrast in brightness and spectral properties between cloudy and clear skies was lower over the sea ice region, owing to the higher surface albedo. Hence, the classification parameter was expressed as a function of sun elevation over the sea ice region in this study. This parameter was determined from part of the data over the sea ice region during JARE 55 and then applied to JARE 56 as well as to remaining data from JARE 55. As a result, the daily-averaged cloud fractions over the sea ice region were approximately 84% and 57% from JARE 55 and 56, respectively. The daily-averaged cloud fractions estimated from the whole-sky camera were also consistent with the ceilometer observations where the correlation coefficients with the sea ice region were 0.93 and 0.96 for JARE 55 and 56, respectively.

著者

Guanghua CHEN Ke WANG

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.96, no.2, pp.97-110, 2018 (Released:2018-03-23)

参考文献数

38

被引用文献数

8

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Although both the tropical cyclone (TC) peak seasons in 2016 and 1998 are in the decaying stage of a super El Niño, TC activities over the western North Pacific (WNP) exhibit vast differences. The TCs in 2016 were greater in number and intensity and had distinct monthly variations in TC activity in contrast to those in 1998. The detailed comparison shows that the warm sea surface temperature anomaly over the WNP in 2016 had higher magnitude and a more eastward extension than that in 1998. In August, coincident with the enhanced Madden–Julian oscillation westerly phase, more TCs clustered within the eastward-extending convective belt caused by the southwesterly surge. The mean longitude of TC genesis in 2016 shifted more eastward, which is favorable for the longer lifetime and greater intensity of the TCs. In terms of the extratropical influences, the cyclonic circulation anomaly associated with the Silk Road Pattern from the middle latitude penetrated southward and split the WNP subtropical high (WNPSH) into two components in August of 2016, thus causing deep-tropospheric southerly steering flows in between and TC northward-prone tracks. During the boreal autumn in 2016, the WNPSH strengthened and stretched westward, producing the robust easterly steering flows that led to successive TCs affecting the coastal areas of East Asia.

著者

Yuhei YAMAMOTO Hirohiko ISHIKAWA Yuichiro OKU Zeyong HU

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.96B, pp.59-76, 2018 (Released:2018-03-16)

参考文献数

53

被引用文献数

28

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This paper presents a method for estimating the land surface temperature (LST) from Himawari-8 data. The Advanced Himawari Imager onboard Himawari-8 has three thermal infrared bands in the spectral range of 10-12.5 μm. We developed a nonlinear three-band algorithm (NTB) that makes the best use of these bands to estimate the LST. The formula of the algorithm includes 10 coefficients. The optimum values of these coefficients were derived using a statistical regression method from the simulated data, as obtained by a radiative transfer model. The simulated data sets correspond to a variety of values of LST, as well as surface emissivity, type and season of temperature and water vapor profiles. Viewing zenith angles (VZAs) from 0° to 60° were considered. For the coefficients obtained in this way, we verified the root-mean-square error (RMSE) in terms of the VZA, LST and precipitable water dependence. We showed that the NTB can accurately estimate the LST with an RMSE less than 0.9 K compared with the nonlinear split-window algorithm developed by Sobrino and Romaguera (2004). Moreover, we evaluated the sensitivities of the LST algorithms to the uncertainties in input data by using the dataset independent of the dataset used to obtain coefficients. Consequently, we showed that the NTB has the highest robustness against the uncertainties in input data. Finally, the stepwise LST retrieval method was constructed. This method includes a simple cloud mask procedure and the land surface emissivity estimation. The LST product was evaluated using in-situ data over the Tibetan Plateau, and the validity was confirmed.

著者

Yuhei YAMAMOTO Hirohiko ISHIKAWA

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.96B, pp.43-58, 2018 (Released:2018-03-16)

参考文献数

32

被引用文献数

20

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Land surface emissivity (LSE) in the thermal infrared (TIR) is an essential parameter in the retrieving land surface temperature (LST) from space. This paper describes the LSE maps in three TIR bands (centered at 10.4, 11.2 and 12.4 μm) used for retrieving the LST from Himawari-8. Himawari-8, a next-generation geostationary satellite has high spatial and temporal resolutions compared to previous geostationary satellites. Because of these improvements, the Himawari-8 LST product is expected to contribute to the observation of small-scale environments in high-frequency. In this study, the LSE is estimated by a semi-empirical method, which is a combination of the classification based method and the normalized difference vegetation index (NDVI) thresholds method. The land cover classification information is taken from the Global Land Cover by National Mapping Organizations version3 (GLCNMO 2013). Material emissivities of soil, vegetation and others are taken from the MODIS UCSB emissivity library and the ASTER spectral library. This method basically follows the semi-empirical methods developed by the previous studies, but advanced considerations are added. These considerations are the phenology of vegetation, flooding of paddy fields, snow/ice coverage, and internal reflections (cavity effect) in urban areas. The average cavity effect on LSE in urban canopies is approximately 0.01, but it reaches 0.02 in built-up areas. The sensitivity analysis shows that the total LSE errors for the three bands are less than 0.02. The LSE estimation is especially stable at the vegetation area, where the error is less than 0.01.

著者

Ryo OYAMA Masahiro SAWADA Kazuki SHIMOJI

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.96B, pp.3-26, 2018 (Released:2018-03-16)

参考文献数

56

被引用文献数

9

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The high temporal and spatial resolutions of geostationary satellite observations achieved by recent technological advancements have facilitated the derivation of atmospheric motion vectors (AMVs), even in a tropical cyclone (TC) wherein the winds abruptly change. This study used TCs in the western North Pacific basin to investigate the ability of upper tropospheric AMVs to estimate the TC intensity and structure. We first examined the relationships between the cloud-top wind fields captured by 6-hourly upper tropospheric AMVs derived from images of the Multi-functional Transport Satellite (MTSAT) and the surface maximum sustained wind (MSW) of the Japan Meteorological Agency's best-track data for 44 TCs during 2011-2014. The correlation between the maximum tangential winds of the upper tropospheric AMVs (UMaxWinds) and MSWs was high, approximately 0.73, suggesting that the cyclonic circulation near the cloud top was intensified by the upward transport of absolute angular momentum within the TC inner core. The upper tropospheric AMVs also revealed that the mean radii of UMaxWinds and the maximum radial outflows shifted inward as the TC intensification rate became large, implying that the low-level inflow was strong for TCs undergoing rapid intensification. We further examined the possibility of estimating the MSW using 30-min-interval UMaxWinds derived from Himawari-8 target observations, which have been used to track TCs throughout their lifetimes. A case study considering Typhoon Lionrock (1610) showed that the UMaxWinds captured the changes in the cyclonic circulation near the cloud top within the inner core on a timescale shorter than 1 day. It was apparent that the increase in the UMaxWind was associated with the intensification of the TC warm core and the shrinkage of UMaxWind radius. These results suggest that Himawari-8 AMVs include useful information about TC intensification and related structural changes to support the TC intensity analysis and structure monitoring.

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.96, no.1, pp.1-2, 2018 (Released:2018-02-28)

参考文献数

6

著者

Woosub ROH Masaki SATOH

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.96, no.1, pp.55-63, 2018 (Released:2018-02-08)

参考文献数

34

被引用文献数

10

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As an alternative approach to previous multisensor satellite evaluations for cloud system resolving models (CSRMs), a technique for precipitation clouds over the ocean of CSRMs is presented using combined infrared and microwave channels. This method quantitatively analyzes precipitation clouds using cloud-top temperatures and ice scatterings from infrared 11 μm and high frequency microwave (89.0 GHz) brightness temperatures (TBs). The TB threshold at low frequencies (18.7 GHz) is used to identify precipitation regions. This method extends a previous approach based on tropical rainfall measuring mission (TRMM) precipitation radar which uses a narrow coverage, by incorporating a wide passive microwave sensor swath and ice cloud sensitivity.  The numerical results of the non-hydrostatic icosahedral atmospheric model, NICAM, with two cloud microphysics schemes were evaluated over the tropical open ocean using this method. The scattering intensities in both simulations at 89.0 GHz were different due to the parameterizations of the snow and graupel size distributions. A bimodal snow size distribution improved the TB underestimation at 89.0 GHz. These results exhibited similar structures to the joint histograms of cloud-top temperatures and precipitation-top heights generated using the previous method; the frequencies of overestimated scattering intensities in this study and the frequencies of high precipitation-top heights above 12 km in the previous study. It was observed that the change in the snow size distribution in the cloud microphysics scheme can lead to better agreements of simulated TBs at 89.0 GHz. Furthermore, we investigated the impacts of nonspherical snow assumptions using a satellite simulator. The effect of a nonspherical snow shape in the radiative transfer model caused a smaller change in TBs at 89.0 GHz compared to the difference between the TBs of the two simulations without nonspherical assumptions.

著者

Brett T. HOOVER Rolf H. LANGLAND

出版者

(公社)日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.95, no.6, pp.369-389, 2017 (Released:2017-11-14)

参考文献数

22

被引用文献数

3

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This study examines analysis and forecast impacts in the Navy Global Environmental Model (NAVGEM) from direct assimilation of temperature and wind “pseudo-raob” profiles derived from analysis fields of the European Centre for Medium-Range Weather Forecasting-Integrated Forecast System (ECWMF-IFS). The pseudo-raob profiles are provided on eight vertical levels from 250 hPa to 1000 hPa on a 1° × 1° resolution rectilinear grid and are assimilated as synthetic observation data by NAVGEM at 0000 UTC and 1200 UTC for an experimental time period of 48 days. The pseudo-raob observations are assumed in these experiments to have observation errors identical to temperature and wind data provided by conventional radiosonde observations.  In this diagnostic context, the assimilation of pseudo-raob profiles significantly reduces temperature and height biases in the NAVGEM analysis and provides general improvements to forecast skill when verified against both self-analysis and rawinsondes. Reduction of NAVGEM temperature bias is most evident in southern hemisphere high latitudes, where the assimilation of pseudo-raob information mitigates NAVGEM temperature bias and indicates sub-optimal bias correction of radiance data in the NAVGEM Control analysis. Despite the revisiting of assimilated observation information when assimilating pseudo-raobs from the IFS analysis into the NAVGEM analysis, improvement to the NAVGEM analyses and forecasts is both statistically significant and consistent across several verification techniques. This suggests that there are likely small effects from any correlations between pseudo-raob data and the NAVGEM background. The assimilation of pseudo-raob data also reduces the total observation impact in NAVGEM as estimated by the adjoint model, which is an indicator of general improvement to analysis and forecast quality.

著者

Shaoping WANG Yongjian DING Fengqing JIANG Muhammad Naveed ANJUM Mudassar IQBAL

出版者

(公社)日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.95, no.5, pp.287-299, 2017 (Released:2017-09-16)

参考文献数

47

被引用文献数

11

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Northern Xinjiang (NX), China, located at the middle latitude of the Northern Hemisphere, has abundant snowfall and a long period of snow cover. In this study, to assess the impact of climate change in this region and to provide scientific knowledge for the resource management, analyses of the spatial and temporal variations in extreme snowfall events (ESEs) in NX was conducted based on five defined ESE indices: days of heavy snowfall (DHS), maximum 1-day snowfall amount (MASD), maximum 1-event snowfall amount (MASE), the maximum number of consecutive snowfall days (MDSE), and frequency of heavy snowfall events (HSE). To reconstruct the snowfall dataset, the relationship between air temperature and snowfall events was determined, and it was found that the daily minimum air temperature below 0°C is the best indicator to identify snowfall days. ESEs in NX occupied an increasing proportion of snow events, although the number of snowfall days decreased. Consistent increasing trends in all ESE indices were found for the entire NX region, while different changes in these indices were noted between subregions. With highly increasing trends of these ESE indices in most of subregions, the Daxigou–Xiaoquzi and Qitai areas were the hotspots for ESEs. Since these hotspots are likely influenced by airflow from the Arctic Ocean, the changes in the Arctic Ocean and the associated atmospheric circulation resulting from climate change might be the main reasons for the increasing trend of ESEs in NX.

著者

KAMAE Youichi MEI Wei XIE Shang-Ping

出版者

(公社)日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2017-027, (Released:2017-09-07)

被引用文献数

54

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Eddy transport of atmospheric water vapor from the tropics is important for rainfall and related natural disasters in the middle latitudes. Atmospheric rivers (ARs), intense moisture plumes typically associated with extratropical cyclones, often produce heavy precipitation upon encountering topography on the west coasts of mid-latitude North America and Europe. ARs also occur over the northwestern Pacific and sometimes cause floods and landslides over East Asia, but the climatological relationship between ARs and heavy rainfall in this region remains unclear. Here, we evaluate the contribution of ARs to the hydrological cycle over East Asia using high-resolution daily rainfall observations and an atmospheric reanalysis during 1958–2007. Despite their low occurrence, ARs account for 14–44% of total rainfall and 20–90% of extreme heavy-rainfall events during spring, summer and autumn seasons. AR-related extreme rainfall is especially pronounced over western-to-southeastern slopes of terrains over the Korean Peninsula and Japan, owing to strong orographic effects and a stable direction of low-level moisture flows. A strong relationship between warm-season AR heavy rainfall and preceding-winter El Niño is identified since the 1970s, suggesting the potential of predicting heavy-rainfall risk over Korea and Japan at seasonal leads.

著者

SU Shih-Hao KUO Hung-Chi HSU Li-Huan YANG Yi-Ting

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.90, no.5, pp.721-736, 2012

被引用文献数

57

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We studied the temporal and spatial characteristics of extreme typhoon rainfall in Taiwan using Central Weather Bureau hourly precipitation data from 21 surface stations during the past 51 years (1960-2010). Extreme rainfall is defined as 95th percentile intensity of total rain events, or equivalently, rain events greater than 9 mm hr^-1 which contribute 40% to the total rain amount in Taiwan. It was found that approximately 70% (20%) of extreme rain is in the typhoon season (Mei-Yu) from July to October (from May to June). There are significant variations of typhoon extreme rainfall over the annual and decadal time scales, with larger extreme rainfall values and events in the periods of 1960-1976 and 1994-2010, and less in the 1977-1993 period. The recent 1994-2009 period has the most extreme rainfall and events, as well as, inter-annual variability. In contrast, there are strong inter-annual variations of Mei-Yu extreme rainfall, but no significant decadal variations. The averaged typhoon rain intensity, however, is about the same, being 19 mm hr^-1 in all these three periods. Our analysis indicates that the typhoon extreme rainfall spatial pattern is phased locked with the Central Mountain Range, Taiwan. In general, the amount of extreme rainfall was related to the typhoon translation speed and duration time, but not typhoon intensity. Slower speeds and longer duration time lead to larger extreme rainfall values. Our analysis also indicate that the mean duration time of Taiwan landfall typhoons with northern tracks (tracks north of 23 degrees latitude) is about 3 hours longer than that of southern track typhoons in the last 51 years, and is more likely to produce three times as much extreme rainfall. The interactions of summer or winter monsoons with typhoons are also important factors that may contribute to the extreme rainfall in Taiwan. Examples of extreme rainfall due to typhoon circulation interaction with summer and winter monsoon flows are presented. Monsoon water vapor supply, typhoon slow translation speed, and mesoscale convection due to typhoon-monsoon flow interactions are the key factors in extreme precipitation events.

著者

吉松 隆三郎

出版者

(公社)日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.15, no.4, pp.158-160, 1937-04-05 (Released:2009-02-05)

被引用文献数

3

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Eliminating the so-called universal variations with two independent base lines, we find that earth-currents va_??_ in some manner with the activity of the earthquakes and their after shocks. The relation between the mode of the variation of earth-currents and mechanism of earthquake is not clear at the present time.

著者

Jiangman WANG Chun LI

出版者

(公社)日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.95, no.3, pp.199-211, 2017 (Released:2017-05-27)

参考文献数

28

被引用文献数

10

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The Pacific Decadal Oscillation (PDO) and North Pacific Gyre Oscillation (NPGO) are the two dominant low-frequency modes in the North Pacific. This study focused on the simulation capability of the two leading low-frequency modes in current-coupled models, based on 24 coupled model outputs from the Coupled Model Intercomparison Project Phase 5 (CMIP5). Results showed that most of these models captured the two low-frequency modes, but the air–sea coupling relationship (covariability of the ocean low-frequency modes with the atmospheric forcing modes) captured by CMIP5 models had drastic differences. Four models (CCSM4, CESM-WACCM, MIROC5, and NorESM1-M) not only captured the spatial and temporal characteristics of the PDO and NPGO modes but also simulated their air–sea coupling relationships. Therefore, we selected these four models to examine changes in the PDO and NPGO modes under different global warming scenarios using RCP4.5 and RCP8.5 forcing (RCP: Representative Concentration Pathway). In future RCP scenarios, the spatial patterns of PDO and NPGO showed no obvious changes. However, the dominant periods of the PDO and NPGO modes were shorter, which is consistent with faster oceanic Rossby waves induced by enhanced upper oceanic stratification in the warming scenarios.

著者

Yanfeng ZHAO Donghai WANG Zhaoming LIANG Jianjun XU

出版者

(公社)日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.95, no.2, pp.111-125, 2017 (Released:2017-03-17)

参考文献数

41

被引用文献数

6

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Persistent severe rainfall (PSR) events during the rainy season (April to July) in southern China were studied in terms of the dynamic features of the large-scale circulation. The aim of the study was to understand the formation mechanism and improve forecasting. The circulation field and spatiotemporal distribution of waves at 500 hPa for different types of PSR were analyzed. The results reveal the following: (1) During the pre-flood season (April to June) in southern China, troughs have the same phase in the middle latitudes as those in the high latitudes. The East Asia major trough (3–5 wave numbers) in the middle latitudes strengthens southwards and interacts with the 30°N subtropical high (1–2 wave numbers) from three days prior to the PSR events. (2) During the post-flood season (June to July) in South China, the weather regime transitions occur on five days prior to the PSR events. The 40°N trough (2–4 wave numbers) strengthens southwards and interacts with the subtropical high (1–2 wave numbers). It is also affected by the blocking ridge (3 wave number) in the high latitudes. (3) During the Mei-yu period (June to July) over the Yangtze–Huaihe River basin, the transitions of circulation pattern start three days prior to the PSR events. With the northwest development of the subtropical high, there is a transfer process from long to short waves in terms of energy for the trough at 50°N.

著者

Ryuji YOSHIDA Yoshiaki MIYAMOTO Hirofumi TOMITA Yoshiyuki KAJIKAWA

出版者

(公社)日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.95, no.1, pp.35-47, 2017 (Released:2017-03-01)

参考文献数

29

被引用文献数

11

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The environmental conditions for tropical cyclone genesis are examined by numerical experiment. We focus on the case of a non-developing disturbance showed features for tropical cyclone genesis in the Pacific Area Long-term Atmospheric observation for Understanding climate change in 2010 (PALAU2010) observation campaign over the western North Pacific. We clarify the importance of the presence of abundant moisture around the disturbance for continuous convection and demonstrate that the collocation of a mid-level vortex and a low-level vortex, i.e., the persistence of an upright structure of vortices, is important in tropical cyclone genesis. We conduct two numerical experiments using the Weather Research and Forecasting Model Advanced Research WRF model in double nested domains with a horizontal grid space of 27 km and 9 km for the outer domain and the inner domain, respectively. The first experiment is based on reanalysis data (a control experiment) and the second includes increased water vapor content over the northwestern dry area of the disturbance. In the control experiment, the disturbance did not develop into a tropical cyclone in spite of the existence of the mid-level and low-level vortices. In contrast, the sensitivity experiment shows that a tropical cyclone was formed from the disturbance with increased water vapor content. The presence of persistent upright vortices was supported by continuous convection until the genesis of the tropical cyclone.

出版者

(公社)日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.95, no.1, pp.4-5, 2017 (Released:2017-03-01)

参考文献数

5

被引用文献数

1

出版者

(公社)日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.95, no.1, pp.1-2, 2017 (Released:2017-03-01)

参考文献数

8

著者

SUWARMAN Rusmawan ICHIYANAGI Kimpei TANOUE Masahiro YOSHIMURA Kei MORI Shuichi YAMANAKA Manabu D. SYAMSUDIN Fadli BELGAMAN Halda Aditya

出版者

(公社)日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2017-003, (Released:2016-10-31)

被引用文献数

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This study examined the relationship between the El Niño Southern Oscillation (ENSO) and atmospheric water isotopes during the wet season over the Maritime Continent. The model data used were obtained by incorporating stable isotopes into atmospheric general circulation and analytical moisture transport models. These models were used to analyze the climatological variables and rainout processes from various water sources that control isotopic variation. The correlation between the simulated stable isotope ratios and ENSO varied between –0.31 and 0.75 with stronger correlation over most of the Maritime Continent (|r|› 0.36, corresponding to the 95 % significance level) except Java. Generally, during La Niña years, the isotopic ratio in water vapor and precipitation is lighter than during El Niño years by about 2 ‰. It was suggested that anomalous water vapor flux, precipitable water, and precipitation, but not evaporation, are responsible for isotopic variation. Furthermore, it was revealed that water vapor flux is convergent (divergent) during La Niña (El Niño) years, which suggests that the strengthened (weakened) Walker Circulation increases (reduces) precipitation and results in lighter (heavier) atmospheric water isotopes. The relationship between isotopes and precipitation, or the so-called "amount effect," is evident over the most of the Maritime Continent. Analysis of moisture transport suggested that rainout processes control isotopic variation. The increase in the quantity water source, expressed in precipitable water, transported from the north and south Maritime Continent during El Niño years does not result in isotopic depletion attributable to the lack of condensation processes. Moreover, the decrease in the quantity of both water source during La Niña years does not result in isotopic enrichment attributable to intensive rainout. An asymmetric ENSO feature was found in this study, evidenced by the similar contributions of water source from the northern Maritime Continent and the Pacific Ocean during both ENSO phases.