著者

VITANOVA Lidia Lazarova KUSAKA Hiroyuki DOAN Van Quang NISHI Akifumi

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.2019-013, (Released:2018-11-16)

被引用文献数

6

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This study investigates the impact of urbanization on surface air temperature and the urban heat island (UHI) for Sendai City. We estimate the impacts of the urbaniza-tion during the 150-year period by comparing the 1850s to the 2000s case. We use the Weather Research and Forecasting (WRF) model with 1-km horizontal resolution and three land-use datasets, one for potential natural vegetation (PNV) data, the other two for realistic land-use data (the 1850s and 2000s). Results from the control simulation (2000s land-use case) are firstly verified against observations. The results show that the WRF model reasonably well reproduces the diurnal variation of the observed surface air temperatures in the 2000s land-use case at six stations in Miyagi prefecture. The model mean biases range from −0.29 to −1.18°C in August (10-year average) and from −0.44 to −1.50°C in February (10-year average). Secondly, the impacts of urbanization on the surface air temperature distribution in and around Sendai City are evaluated. In the 1850s land-use case, the very small urban area of Sendai City results in a negligible UHI. This case gives nearly the same surface air temperatures as experiments using the PNV. Comparing the simulated monthly mean surface air temperatures in the central part of Sendai City between the 1850s and 2000s land-use cases, we find that the monthly mean temperature for February in the 2000s is 1.40°C higher than that in the 1850s, whereas that for August is 1.30°C. Similarly, we find considerable nocturnal (1800–0500 JST) average surface air temperature increases of 2.20°C in February and 2.00°C in August.

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

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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

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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

Kotaro BESSHO Kenji DATE Masahiro HAYASHI Akio IKEDA Takahito IMAI Hidekazu INOUE Yukihiro KUMAGAI Takuya MIYAKAWA Hidehiko MURATA Tomoo OHNO Arata OKUYAMA Ryo OYAMA Yukio SASAKI Yoshio SHIMAZU Kazuki SHIMOJI Yasuhiko SUMIDA Masuo SUZUKI Hidetaka TANIGUCHI Hiroaki TSUCHIYAMA Daisaku UESAWA Hironobu YOKOTA Ryo YOSHIDA

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.94, no.2, pp.151-183, 2016 (Released:2016-04-28)

参考文献数

66

被引用文献数

143 885

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Himawari-8/9—a new generation of Japanese geostationary meteorological satellites-carry state-of-the-art optical sensors with significantly higher radiometric, spectral, and spatial resolution than those previously available in the geostationary orbit. They have 16 observation bands, and their spatial resolution is 0.5 or 1 km for visible and near-infrared bands and 2 km for infrared bands. These advantages, when combined with shortened revisit times (around 10 min for Full Disk and 2.5 min for sectored regions), provide new levels of capacity for the identification and tracking of rapidly changing weather phenomena and for the derivation of quantitative products. For example, fundamental cloud product is retrieved from observation data of Himawari-8 operationally. Based on the fundamental cloud product, Clear Sky Radiance and Atmospheric Motion Vector are processed for numerical weather prediction, and volcanic ash product and Aeolian dust product are created for disaster watching and environmental monitoring. Imageries from the satellites are distributed and disseminated to users via multiple paths, including Internet cloud services and communication satellite services.

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

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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

ITO Takahiro NISHIMOTO Shusuke KANEHISA Hirotada

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.2018-055, (Released:2018-09-07)

被引用文献数

1

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In this study, we show analytically that vortex Rossby waves (VRWs) with azimuthal wavenumber m =1 in a basic axisymmetric vortex can grow exponentially in a quasi-geostrophic system, although they cannot do so in a barotropic system. VRWs grow exponentially if Rayleigh’s condition and Fjørtoft’s condition are satisfied. Satisfying Rayleigh’s condition means that two horizontally aligned VRWs at two different radii propagate (here and hereafter “propagate” refers to propagation relative to the fluid) azimuthally counter to each other. Satisfying Fjørtoft’s condition means that the cyclonic advective angular velocity of the basic vortex is distributed radially so as to enable the VRWs to be phase-locked with each other. Under these conditions, a strong mutual interaction between the VRWs becomes possible, and thus they grow exponentially. In a barotropic system, even if Rayleigh’s condition is satisfied, the azimuthal counter propagation of VRWs with azimuthal wavenumber m =1 is so strong that phase-locking between them cannot occur, and thus they cannot grow exponentially. In a quasi-geostrophic system, however, the upper and lower VRWs of the first baroclinic vertical mode are equal in magnitude and have opposite signs. Because of this baroclinic structure, the azimuthal counter propagation of the horizontally aligned VRWs is suppressed by the vertical interactions between the upper and lower VRWs. Consequently, horizontally aligned VRWs with azimuthal wavenumber m =1 may become phase-locked, and hence they may grow exponentially. By analytically solving the linear problem of VRWs in a quasi-geostrophic system, we show that this is indeed the case.

著者

KADOYA Toshiki MASUNAGA Hirohiko

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.2018-054, (Released:2018-08-24)

被引用文献数

11

---

A new observational measure, or the morphological index for convective self-aggregation (MICA), is developed to objectively detect the signs of convective self-aggregation on the basis of a simple morphological diagnosis of convective clouds in the satellite imagery. The proposed index is applied to infrared imagery from the Meteosat-7 satellite and is assessed with the sounding-array measurements in the tropics from Cooperative Indian Ocean experiment on Intraseasonal variability in the Year of 2011 (CINDY2011)/Dynamics of the Madden-Julian Oscillation (MJO) (DYNAMO)/Atmospheric Radiation Measurements (ARM) MJO Investigation Experiment (AMIE). The precipitation events during the observational period are first classified by MICA into “aggregation events” and “non-aggregation events”. The large-scale thermodynamics implied from the sounding-array data are then examined with focus on the difference between the two classes. The composite time series show that a drying proceeds over 6-12 hours as precipitation intensifies in the aggregation events. Such a drying is unclear in the non-aggregation events. The moisture budget balance is maintained in very different manners between the two adjacent sounding arrays for the aggregation events, in contrast to the non-aggregation events which lack such apparent asymmetry. These results imply the potential utility of the proposed metrics for future studies in search of convective self-aggregation in the real atmosphere.

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

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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

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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

OTSUKA Michiko SEKO Hiromu SHIMOJI Kazuki YAMASHITA Koji

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.2018-034, (Released:2018-03-23)

被引用文献数

11

---

Rapid scan atmospheric motion vectors (RS-AMV) were derived with an algorithm developed by the Meteorological Satellite Center of the Japan Meteorological Agency (JMA) from Himawari-8 rapid scan imagery over the area around Japan. They were computed every 10 min for seven different channels, namely, the visible channel (VIS), near infrared and infrared channels (IR), three water vapor absorption channels (WV), and CO2 absorption channel (CO2), from image triplets with time intervals of 2.5 min for VIS and 5 min for the other six channels. In June 2016, the amount of data was increased by more than 20 times compared to the number of routinely used AMVs. To exploit these high-resolution data in mesoscale data assimilation for the improvement of short-range forecasts, data verification and assimilation experiments were conducted. The RS-AMVs were of sufficiently good quality for assimilation and consistent overall with winds from JMA’s mesoscale analyses, radiosonde, and wind profiler observations. Errors were slightly larger in WV than in VIS and IR channels. Significant negative biases relative to sonde winds were seen at high levels in VIS, IR, and CO2, while slightly positive biases were noticeable in WV at mid- to high levels. Data assimilation experiments with the JMA’s non-hydrostatic model based Variational Data Assimilation System (JNoVA) on a cold vortex event in June 2016 were conducted using RS-AMVs from seven channels. The wind forecasts improved slightly in early forecast hours before 12 hours in northern Japan, over which the vortex passed during the assimilation period. They also showed small improvement at low levels when averaged over the whole forecast period. The results varied slightly depending on the channels used for assimilation, which might be caused by different error characteristics of RS-AMVs in different channels.

著者

MISUMI Ryohei UJI Yasushi TOBO Yutaka MIURA Kazuhiko UETAKE Jun IWAMOTO Yoko MAESAKA Takeshi IWANAMI Koyuru

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.2018-040, (Released:2018-04-13)

被引用文献数

7

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Continuous observations of cloud droplet size distributions (DSDs) in low-level stratiform clouds have been conducted at a height of 458 m from Tokyo Skytree (a 634-m high broadcasting tower in Tokyo) using a cloud droplet spectrometer. In this report, the characteristics of cloud parameters related to the cloud DSD from June to December 2016 are presented. The mean cloud droplet number concentration (Nc), average diameters, and effective diameters of cloud droplets in non-drizzling clouds were 213 cm-3, 7.3 μm, and 9.5 μm, respectively, which are close to the reported values for continental stratiform clouds. The relationship between the liquid water content (LWC; g m-3), Nc (cm-3) and radar reflectivity (Z; mm6 m-3) was estimated as LWC = 0.17Nc0.50 Z0.45, with a coefficient of determination ( R 2) of 0.93. The observed cloud DSDs were well fitted by a lognormal distribution and the average median diameter of the fitted DSD was 6.6 μm.

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

50

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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

Ryohei MISUMI Namiko SAKURAI Takeshi MAESAKA Shin-ichi SUZUKI Shingo SHIMIZU Koyuru IWANAMI

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.51-66, 2018 (Released:2018-02-19)

参考文献数

26

被引用文献数

4

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Convective storms are frequently initiated over mountains under weak synoptic forcing conditions. However, the initiation process of such convective storms is not well understood due to a lack of observations, especially the transition process from non-precipitating cumuli to precipitating convective clouds. To investigate the initiation process, we conducted observations around the mountains in the Kanto region, Japan on 18 August 2011 using a 35 GHz (Ka-band) Doppler radar and a pair of digital cameras. The evolution of convective clouds was classified into three stages: convective clouds visible but not detected by the Ka-band radar (stage 0), convective clouds detectable by the Ka-band radar with reflectivity below 15 dBZ (stage 1), and convective clouds accompanied by descending echoes corresponding to precipitation (stage 2). During the transition process from stage 1 to stage 2, weak radar echoes rose to the higher level and reflectivity rapidly increased. This phenomenon suggests that drizzle particles produced in a preexisting convective cloud were lifted by a newly developed updraft, and raindrops were formed rapidly by coalescence of the drizzle particles and cloud droplets. This hypothetical process explains the precipitation echo formation in the lower layer frequently observed in the mountainous area in the Kanto region.

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

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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.

著者

Hirokazu Endo Akio Kitoh Hiroaki Ueda

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.57-63, 2018 (Released:2018-04-28)

参考文献数

39

被引用文献数

33

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Recent studies indicate that the view of a general weakening of the monsoon circulation in a warmer climate cannot be simply applied in the Asian monsoon regions. To understand the Asian summer monsoon response to global warming, idealized multi-model experiments are analyzed. In the coupled model response to increased CO2, monsoon westerlies in the lower troposphere are shifted poleward and slightly strengthened over land including South Asia and East Asia, while the tropical easterly jet in the upper troposphere are broadly weakened. The different circulation responses between the lower and upper troposphere is associated with vertically opposite changes in the meridional temperature gradient (MTG) between the Eurasian continent and the tropical Indian Ocean, with a strengthening (weakening) in the lower (upper) troposphere. Atmospheric model experiments to separate the effects of CO2 radiative forcing and sea surface temperature warming reveal that the strengthened MTG in the lower troposphere is explained by the CO2 forcing. On a global perspective, CO2-induced enhancement of the land–sea thermal contrast and resultant circulation changes are the most influential in the South Asian monsoon. This study emphasizes an important role of the land warming on the Asian monsoon response to global warming.

著者

Stéphane BÉLAIR Sylvie LEROYER Naoko SEINO Lubos SPACEK Vanh SOUVANLASSY Danahé PAQUIN-RICARD

出版者

Meteorological Society of Japan

雑誌

Journal of the Meteorological Society of Japan. Ser. II (ISSN:00261165)

巻号頁・発行日

pp.2018-011, (Released:2017-12-21)

被引用文献数

20

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Heavy precipitation fell over Tokyo in the afternoon of 26 August 2011, leading to flooding and major disruptions for the population, businesses, and authorities. Over 150 mm of precipitation was observed over the city center on that day, with hourly accumulations reaching values as high as 90 mm in late afternoon. Numerical forecasts of this case were performed with a 250-m grid spacing version of the Global Environmental Multi-scale (GEM) model in the context of the Tokyo Metropolitan Area Convection Study (TOMACS). Although initialized only from a global 25-km upper-air analysis, results indicate that GEM is able to produce the intense precipitation over Tokyo at about the right location and time. A sensitivity test in which the urban surface scheme is switched off and replaced with tall grass suggests that the urban environment might have had considerable impact on precipitation intensity, but not on its occurrence or its timing. Based on diagnostics from the GEM integrations, the increased intensity of precipitation seems more related to an enhancement of lateral inflow of low-level moist static energy from Tokyo Bay than to augmented surface fluxes of heat and humidity from the city itself. The existence of low-level bands with locally high values of equivalent potential temperature indicates that the additional moist energy is distributed unevenly through the Tokyo area, an aspect of the simulation which is speculated to have directly contributed to the increase in precipitation intensity over the city.

著者

FUJIBE Fumiaki

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.2018-021, (Released:2018-01-23)

被引用文献数

1

---

Climatological features of surface air temperature variations on time scales of a few minutes to one hour were examined using one-minute data, spanning a four-year period, from 917 automated stations in Japan. The temperature time series was spectrally analyzed after the application of a Gaussian high-pass filter, and the variances with periods of 64 minutes or less were statistically analyzed as sub-hourly temperature variations. The result obtained shows that daytime temperature variation is observed throughout the country with relatively small regional differences. The amplitudes of daytime temperature variations were larger during spring and summer than those during autumn and winter, and under high temperature and sunny weather than under low temperature, no sunshine, and precipitation. A cross spectral analysis of temperature and wind speed reveals that temperature peaks tend to coincide with or lag behind wind speed minima. The variation is likely to correspond to the convective motion in the mixing layer. On the other hand, the intensity of nighttime temperature variation showed a large amount of scatter among stations, with exceptionally large variations during winter at some stations in northern and eastern Japan. Nighttime temperature variation tends to be in-phase with wind speed variation, with longer periods than daytime temperature variation, and is more intense under low temperature and low wind speed than under high temperature, high wind speed, and precipitation. Stations with large winter nighttime temperature variations tend to be located on a col or a slope, where the surface inversion layer is likely to be easily disturbed by any kind of atmospheric motion.

著者

Tetsuya Kawano Ryuichi Kawamura

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.1-5, 2018 (Released:2018-01-18)

参考文献数

21

被引用文献数

5

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To investigate the influence of the distribution of sea ice in the Sea of Okhotsk on the behavior of a severe snowstorm, which occurred in Hokkaido, Japan, on 2 March 2013 and which was associated with an explosive cyclone, three WRF simulations with realistic, reduced, and enhanced sea ice-cover were carried out. A comparison among these experiments reveals that the extent of the sea ice influenced low-level temperatures and winds to the rear of the cyclone center during the development of the explosive cyclone over the Sea of Okhotsk. Sea ice insulates the ocean from heat exchange with the atmosphere. As a result, when the Okhotsk sea ice extent reaches Hokkaido Island, cold air masses from the north traverse the island without first being heated by the ocean. The consequent temperature reduction produces a low-level higher pressure region to the rear of the cyclone center. As a result, a large geopotential gradient is generated just to the rear of the cyclone center, and low-level winds are intensified within this region. Therefore, the Okhotsk sea ice extent reaching Hokkaido Island plays a significant role in lowering temperatures and intensifying winds in the island.

著者

MURAZAKI Kazuyo TSUJINO Hiroyuki MOTOI Tatsuo KURIHARA Kazuo

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.161-179, 2015

被引用文献数

12

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We performed a 20-year numerical experiment over the period 1985 to 2004 using a high-resolution North Pacific Ocean General Circulation Model (NPOGCM) and a 20 km-resolution regional climate model (RCM20) to clarify the impact of the Kuroshio large meander (LM) on the climate around Japan. The NPOGCM reproduced the two primary quasi-stationary states, straight path (SP), and large meander (LM), although the periods during which each state prevailed differed from those indicated in the observational data. The NPOGCM result also showed that the Kuroshio LM causes a cold sea surface temperature anomaly to the south of the Pacific coast of the central Japan. Using the result as a lower boundary condition, a continuous numerical integration was performed by the RCM20. An 8-year composite analysis of the atmospheric circulations of the RCM20 simulation for the Kuroshio LM and SP showed that, in both winter and summer, substantial decreases in the upward surface turbulent heat flux, the frequency of precipitation, and the frequency of steep horizontal gradients in equivalent potential temperature over the ocean are caused by the cold sea surface temperature anomaly. Similar effects are evident over the land area of Japan, although they are less intense, at most 20-50 % of magnitude over the cold sea surface temperature anomaly area, and limited to the coastal region on the Pacific Ocean side in the central part of the country.

出版者

Meteorological Society of Japan

雑誌

Journal of the Meteorological Society of Japan. Ser. II (ISSN:21869057)

巻号頁・発行日

vol.91, no.6, pp.775-788, 2013 (Released:2014-01-10)

被引用文献数

4