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

Faye T. Cruz Hidetaka Sasaki

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.13, pp.13-18, 2017 (Released:2017-01-29)

参考文献数

37

被引用文献数

7

---

This study evaluates the performance of the Non-hydrostatic Regional Climate Model (NHRCM) in simulating the present climate over Southeast Asia to determine its applicability in downscaling climate projections in the region. Simulations from 1989 to 2008 are conducted over the region at 25-km resolution using boundary conditions from the ECMWF ERA-Interim dataset. The topographic effect on rainfall is well represented in NHRCM but can result in wet (dry) biases in the windward (leeward) side of mountains. NHRCM is able to reduce the overestimated rainfall in ERA-Interim, particularly over eastern Philippines and in the Maritime Continent, with improvements in spatial patterns. Both seasonality and daily distribution of rainfall are represented in most regions. On the other hand, there is a tendency to underestimate the number of wet days, especially during the respective wet season of the subregion, and to overestimate daily rainfall intensity. NHRCM also has an overall cold model bias, which reduces the warm bias in ERA-Interim, except for some parts of Indochina during boreal winter and spring. These results indicate the improved representation of present climate in Southeast Asia using NHRCM, and its potential applicability in downscaling climate projections to increase projected climate scenarios for the region.

著者

Masaru Kunii Michiko Otsuka Kazuki Shimoji Hiromu Seko

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.12, pp.209-214, 2016 (Released:2016-08-05)

参考文献数

21

被引用文献数

13

---

Himawari-8, a next-generation geostationary meteorological satellite that has been in operation since July 2015, incorporates significant improvements in resolution, scan frequency, and number of bands, bringing new capabilities to weather forecasting. By taking advantage of the availability of high-frequency data with high spatial resolution, an ensemble Kalman filter implemented with a mesoscale regional model assimilated rapid-scan atmospheric motion vectors (RS-AMVs) from Himawari-8. Data assimilation and ensemble forecast experiments were conducted for a heavy rainfall event that occurred in September 2015 in the Kanto and Tohoku regions of Japan. The results showed that the inclusion of RS-AMVs improved precipitation scores, especially for weak and moderate rainfall. In addition, the subsequent model forecast simulated successfully the band of heavy rainfall. Ensemble-based probabilistic forecasts showed that when RS-AMVs were assimilated, the results captured the occurrence of torrential rainfall with a relatively high probability. The ensemble-based correlation analysis indicated that the strong rainfall was related to advection of moisture at low to mid levels and moisture flux convergence at lower levels. Simulations with a higher resolution model initialized by nested data assimilation showed that the assimilation of frequent RS-AMVs improved the forecast results.

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

1 5

---

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.

著者

Tadahiro HAYASAKA

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.94, no.5, pp.393-414, 2016 (Released:2016-10-31)

参考文献数

111

被引用文献数

9

---

We reviewed the long-term trends and inter-annual variations in the surface shortwave irradiance in China and Japan. Pyranometer observations revealed decreases followed by increases in the shortwave irradiance in China and Japan between the 1960s and 2000s, while obvious long-term trends were not evident in the satellite observations after 1983. In China, surface shortwave irradiance decreased from 1961 until around 1990, but then began to increase. In Japan, on the contrary, the decreasing trend stopped in the 1960s, with little inter-annual variation during the 1970s and 1980s, and an increase began around 1990. The causes of the differences between the shortwave irradiance trends in China and Japan were ascribed to an increase in light-absorbing aerosols in China that began in the 1960s and a decrease in absorbing aerosols in Japan that began in the late 1970s. Absorbing aerosols decrease both direct and diffuse radiation, while non-absorbing aerosols decrease direct radiation but increase diffuse radiation. Although these aerosol influences are generally found under clear sky conditions, absorbing aerosols could have direct effects even under cloudy sky conditions. The trends of surface shortwave irradiance in China and Japan are in line with the so-called global dimming and brightening dimming processes, although the phases of the minimum periods in the two regions slightly differed. An increase in anthropogenic aerosol was responsible for the variation in the shortwave irradiance through the direct radiative effect of aerosol in the polluted area, while indirect radiative effects, i.e., changes in cloud cover due to an increase in cloud condensation nuclei, dominated in pristine areas. The effects of other factors, such as variations in water vapor and natural aerosol levels, appear to be small compared to the effects of cloud and anthropogenic aerosols.

著者

Masamichi Ohba Hiroaki Ueda

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.2, pp.176-179, 2006 (Released:2006-12-26)

参考文献数

16

被引用文献数

15 47

---

Interannual fluctuations of the convective activity around the Philippines are highly correlated with the east-west gradient of SST between the North Indian Ocean (NIO) and the western North Pacific (WNP). We conducted a set of experiments by use of an atmospheric general circulation model (AGCM) to assess the relative importance of the remote (NIO) versus in situ (WNP) SST anomalies in determining the WNP monsoon rainfall as ocean-to-atmosphere feedback. The solutions indicate that both in situ and remote SST anomalies regulate precipitation around the Philippines in the early summer. This result implies that the WNP monsoon rainfall is sensitive to the spatial distribution of the NIO SST anomalies as well as the in situ anomalies. These physical interpretations suggest further increase of the predictability in the WNP monsoon.

著者

謝 尚平 佐伯 なおみ

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.77, no.4, pp.949-968, 1999-08-25 (Released:2008-01-31)

参考文献数

57

被引用文献数

3 57

---

世界最大の砂漠と最大のモンスーン域は共にほぼ同じ緯度のアフリカ・ユーラシア大陸の亜熱帯に存在する。このような降水の東西分布の形成機構を調べるために、大気大循環モデルを用いて理想化した海陸分布の下で実験を行った。特にここではアジア大陸の南岸を北緯17度線に沿って東西真っ直ぐに設定した。山岳がなく、また海面水温と陸面パラメータが東西一様であるにも関わらず、夏期の降水は亜熱帯大陸の東部で多く、西部で少ない。このような降水分布の東西非一様性は夏期の海洋上に現れる高気圧の水蒸気輸送によると考えられる。更に、降水と土壌水分のゆっくりとした相互作用はモンスーン降水帯の北進を遅らせ、土壌水分が十分に増加する前に、太陽放射の強制によって降水帯は南下し、大陸内部まで進入できない。太陽放射を夏の値に固定した実験では、モンスーン降水帯が徐々に北進し、北アフリカ全域をカバーするようになった。モデルのモンスーン降水は6月後半に突然大陸南岸に現れる。このようなモンスーンの急な開始は西進する波動の発達に伴って起きる。春分後、暑い大陸と冷たい海洋間に北向きの温度傾度が大気下層で形成され、時間と共に強化されていく。この下層の南北温度傾度は偏東風シアーとほぼ温度風バランスをしており、背の高い南北モンスーン循環は形成されない。しかし、このような温度風バランスは最終的には傾圧的に不安定になり、湿潤傾圧不安定の爆発的な成長によってモンスーンが始まる。

著者

Akio KITOH Tomoaki OSE Izuru TAKAYABU

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.94A, pp.1-16, 2016 (Released:2016-02-11)

参考文献数

109

被引用文献数

3 32

---

High-resolution downscaling is vital to project climate extremes and their future changes by resolving fine topography reasonably well, which is a key to represent local climatology and impacts of weather extremes. A direct dynamical downscaling with a regional climate model (RCM) embedded within an atmosphere-ocean coupled general circulation model (AOGCM) is commonly used but is subject to systematic biases in their present-day simulations of AOGCM, which may cause unexpected effects on future projections and lead to difficult interpretation of climate change. In a high-resolution atmospheric general circulation model (AGCM)-RCM system, the present-day climate in AGCM is forced by observed sea surface temperature (SST) and sea-ice distribution. Then, the future climate is calculated with the “future” boundary conditions (SST and sea-ice), which are created by adding their future changes projected by AOGCM to the observed present-day values, besides the future radiative forcing. This system is one of methods to minimize the effects of such biases. A Meteorological Research Institute AGCM with 20-km grids is successfully applied to project future changes in weather extremes such as tropical cyclones and rain systems that cause heavy rainfall and strong winds. Regional downscaling with 5-km mesh RCM is then performed over certain area to investigate local extreme rainfall events and their future changes. In this paper, we review various downscaling methods and try to rationalize a use of high-resolution AGCM-RCM system.

著者

Junya Miyajima Fumiaki Fujibe

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.7, pp.157-160, 2011 (Released:2011-10-14)

参考文献数

6

被引用文献数

5 9

---

Climatological features of the distribution of extreme precipitation in Japan were documented using record values of ten-minute, hourly and daily precipitation for 1994 to 2009. It was found that the distribution of top ten-minute precipitation has a moderate north-south gradient (increasing southward at about 3% per degree in latitude), while ten-minute precipitation of lower ranks (up to 50th to 100th cases at each station) shows a stronger latitude dependence (about 6% per degree) that is comparable to those of hourly and daily precipitations. In addition, extreme precipitation shows local maxima on southern sides of land in western Japan corresponding to orographic enhancement, which is found for all the time scales but is most conspicuous for daily precipitation.

著者

Naoya Takahashi Tadahiro Hayasaka Hajime Okamoto

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.12, pp.91-95, 2016 (Released:2016-04-05)

参考文献数

34

被引用文献数

1

---

We revealed the difference in the ice cloud microphysical properties of high clouds between the western Pacific (WP) and eastern Pacific (EP) regions, based on satellite retrievals. The effective particle radius (re) was analyzed by using active sensors on board the CloudSat and CALIPSO satellites. We focused on ice clouds, defined as clouds with cloud top temperatures of less than 0°C. These ice clouds are classified into five types defined by the cloud optical thickness (COT). Mean cloud top heights of high cloud in WP were higher than those in EP by about 2km. The re of optically thin clouds (0 < COT < 0.3) showed weak temperature dependency over both regions. For optically thick clouds (3 < COT), re increases with temperature (T). In the WP, re at lower temperatures (T < −40°C) is larger than that in the EP, whereas in the EP, re at higher temperatures (T > −40°C) is larger than that in the WP. The difference in re may be caused by differences in moisture convergence and upward motion.

著者

HAYASAKA Tadahiro

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.2016-024, (Released:2016-07-13)

被引用文献数

9

---

We reviewed the long-term trends and inter-annual variations in surface shortwave irradiance in China and Japan. Pyranometer observations indicated a decrease followed by an increase in shortwave irradiance in China and Japan during the period from the 1960s to 2000s, while obvious long-term trends were not found from satellite observations after 1983. In China, surface shortwave irradiance decreased from 1961 to around 1990, but then began to increase. In Japan, on the other hand, the decreasing trend stopped in the 1960s, with little inter-annual variation during the 1970s and 1980s, and an increase that began around 1990. The causes of the difference in shortwave irradiance trends between China and Japan were ascribed to an increase in light-absorbing aerosols in China since the 1960s and a decrease in absorbing aerosols in Japan since the late 1970s. Absorbing aerosols decrease both direct and diffuse radiation, while non-absorbing aerosols decrease direct radiation but increase diffuse radiation. Although these aerosol influences are generally found under clear-sky conditions, absorbing aerosol could have a direct effect even under cloudy-sky conditions. The trends of surface shortwave irradiance in China and Japan are in line with the so-called global dimming and brightening dimming processes, although the phase of the minimum period differed slightly between the two regions. An increase in anthropogenic aerosol was responsible for the variation in shortwave irradiance through the direct radiative effect of aerosol in the polluted area, while an indirect radiative effect, i.e., changes in cloud cover due to an increase in cloud condensation nuclei, dominated in pristine areas. The effect of other factors, such as variations in water vapor and natural aerosol levels, appear to be small compared to the effects of cloud and anthropogenic aerosols.

著者

Hiroki TSUJI Hisanori ITOH Kensuke NAKAJIMA

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.94, no.3, pp.219-236, 2016 (Released:2016-07-02)

参考文献数

29

被引用文献数

15

---

To understand the basic mechanism governing the size evolution of tropical cyclones (TCs), we systematically perform numerical experiments using the primitive equation system on an f-plane. A simplified, TC-like vortex is initially given and an external forcing mimicking cumulus heating is applied to an annular region at a prescribed distance from the vortex center. Moist process and surface friction are excluded for simplification. We focus on the sensitivity of size evolution to the location of the forcing. The vortex size is defined as the radius of 15 m s-1 lowest-level wind speed (R15). The evolution of R15 depends on the forcing location, and its dependence can be understood by considering radial transport of the absolute angular momentum (AAM) at R15 due to the heat-induced secondary circulation (SC), whose structure is governed by the distribution of inertial stability. When the forcing is applied to the outer part of a vortex but still inside R15, where inertial stability is weak, the SC extends to the outside of R15 and carries AAM inward. Thus, R15 increases. Conversely, when the forcing is applied near the center of the vortex, where inertial stability is strong, the SC closes inside R15 and R15 hardly increases. These results indicate that extension of the heat-induced SC to the outside of R15 is important for the evolution of the vortex size. Moreover, the further beyond R15 the SC extends, the more the vortex size increases. This relationship is consistent with the result of the parcel trajectory analysis; the larger the extent of SC, the longer distances the parcels cover, conserving larger AAM. Finally, when the forcing is applied to the outside of R15, smaller AAM is carried outward by the SC on the inward side of the heating location, resulting in the decrease of R15.

著者

Kentaro TAKIDO Oliver C. SAAVEDRA VALERIANO Masahiro RYO Kazuki TANUMA Tomoo USHIO Takuji KUBOTA

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.94, no.2, pp.185-195, 2016 (Released:2016-04-28)

参考文献数

30

被引用文献数

24

---

This study evaluated the accuracy of gauge-adjusted Global Satellite Mapping of Precipitation (GSMaP_Gauge version V5.222.1, hereafter G_Gauge) data in Japan’s Tone River basin during 2006-2009. Specifically, the accuracy of a gauge non-adjusted product, GSMaP Moving Vector with Kalman Filter (GSMaP_MVK, hereafter G_MVK), was also evaluated. Both products were also evaluated against ground observation data from rain gauge-radar combined product Radar-Automated Meteorological Data Acquisition System (Radar-AMeDAS) in terms of temporal and spatial variability. Temporal analyses showed that G_Gauge had better accuracy than G_MVK at sub-daily time scales (1, 3, 6, 9, 12, and 24 h) within any range of precipitation intensity and better detection capabilities of rainfall event. Linear regressions with Radar-AMeDAS showed better performance for G_Gauge than G_MVK at any time scales in terms of Pearson’s correlation coefficient and the slope of regression. At an hourly scale, in particular, Pearson’s correlation coefficient for G_Gauge (0.84) was higher than that for G_MVK (0.72) as well as the slope of linear regression (0.87 and 0.65, respectively). The probability of detection (POD) improved from 0.48 (G_MVK) to 0.70 (G_Gauge) when gauge-adjusted data were used. However, spatial analysis detected that G_Gauge still underestimated the precipitation intensity in high-elevation regions and slightly overestimated it in low elevation regions. The POD and false alarm ratio had a linear relationship with log-transformed elevation data, and the relationships were stronger in the winter seasons than in the summer seasons. At any spatial and temporal scale, the evaluation of these products should consider seasonal changes (especially in winter) and the topographic effects. For further improvements of G_Gauge, we suggest including higher resolution gauge-based network data than the Climate Prediction Center unified gauge-based analysis of global daily precipitation, which is used for G_Gauge.

著者

Rui Ito Tetsuya Takemi Osamu Arakawa

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.12, pp.100-105, 2016 (Released:2016-04-22)

参考文献数

23

被引用文献数

5 38

---

Typhoon Songda (2004), while undergoing an extratropical transition and reintensification over the Sea of Japan, spawned serious damages over forest areas in the northern part of Japan. To clarify influences of anticipated global warming on the typhoon hazard in high-latitude regions, we carried out numerical experiments on Typhoon Songda in a current climate and a pseudo global warming climate and examined the impacts of climate change on the typhoon intensify and windstorms for the region. The typhoon intensity at its maturity becomes stronger in a warming climate, and the typhoon while passing over the Sea of Japan weakens more rapidly in the warming climate. Thus the strong wind over the northern part of Japan in the warming climate also becomes weaker. We examined atmospheric environmental factors in the higher-latitude region: sea surface temperature, vertical shear, and meridional gradient of temperature. It was found that the environmental meridional gradient of temperature at the 500 hPa level is smaller in the warming climate than in the current climate, which indicates that the baroclinicity becomes weak under global warming. The weak baroclinicity makes the typhoon environment unfavorable for the extratropical transition, and therefore, possibly reduces the severity of typhoon wind in northern Japan.

著者

Qoosaku Moteki

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.12, pp.60-64, 2016 (Released:2016-02-27)

参考文献数

25

被引用文献数

1 1

---

The eastward propagation processes of the Madden-Julian oscillation (MJO) was examined from a case study of the first MJO generated in late October during CINDY2011. The eastward propagation of the MJO was found to be synchronized with an extratropical cyclone in the Southern Hemisphere. The synchronized propagation of the MJO and the extratrpical cyclone was associated with the ridge and trough pair meridionally extending between 30°S∼15°N. The convection center of the MJO shifted eastward as a result of the westerly winds in the tropics, expanding eastward by the zonal pressure gradient force between the ridge and trough.

著者

Daisuke Takasuka Tomoki Miyakawa Masaki Satoh Hiroaki Miura

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.11, pp.170-176, 2015 (Released:2015-12-21)

参考文献数

42

被引用文献数

3 16

---

The roles of topography on the propagation of the Madden-Julian Oscillation (MJO) are discussed using an aqua-planet of the Nonhydrostatic Icosahedral Atmospheric Model (NICAM) with a 220-km horizontal mesh. Four topographical configurations with different land-sea masks and elevations are tested using a zonally non-uniform fixed-SST distribution. Explicit cloud microphysics is used to obtain MJO-like signals. Broad land cover generally weakens convection because of reduced surface latent heat flux (LHF). Forced lifting because of topography enhances local convection on the upwind side of high topography. It is suggested that the zonal contrasts of LHF are one reason for the delayed eastward propagation of the MJO-like disturbances. When only the eastern portion of the convective envelope is over land where the LHF is small, the LHF becomes rear-heavy, resulting in delayed eastward propagation. As the entire convective envelope proceeds over land, its contrast decreases or even reverses, resulting in faster eastward propagation.

著者

N. A. Phillips

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.35A, pp.262-267, 1957 (Released:2015-02-18)

参考文献数

2

被引用文献数

21

著者

Par J. Saissac

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.35A, pp.144-148, 1957 (Released:2015-02-18)

参考文献数

5

---

Des études sur la diffusion de particules sont effectuées en France depuis 1953 à l’Etablissement d’Etudes et Recherches Météorologiques du Service de la Météologie Nationale. Elles portent sur deux problemes particuliers, celui d’une quantité finie de particules instantanément libérée en un point (cas des flocons de fumée) et celui d’une émission continue de particules, à débit constant, à partir d’un point situé au-dessus du niveau du sol (cas du panache de fumée).  Nous nous proDQSons dans cet article d’exposer l’état actuel de ces études.

著者

Von P. Raethjen

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.35A, pp.160-164, 1957 (Released:2015-02-18)

参考文献数

3

著者

Yuhji KURODA Kunihiko KODERA

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.80, no.4B, pp.973-984, 2002 (Released:2002-10-10)

参考文献数

31

被引用文献数

32 59 42

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Effect of the modulation of the Polar-night jet oscillation (PJO) in winter time by the 11-year solar cycle is examined by the observational data from 1979 to 1999. It is found that zonal wind and the E-P flux anomalies appear commonly in the subtropical upper stratosphere in early winter of both the Northern and Southern Hemispheres as a response to meridional UV heating contrast. These zonal wind anomalies are found to propagate poleward and downward with development as a seasonal march in both hemispheres. Although the length of the record is limited, it is suggested from the available data that the signal due to solar activity appears as the time evolution of the PJO triggered by solar forcing at early winter in both hemispheres. Differences in the signals between the Northern and Southern Hemispheres during late winter are explained in terms of the different characteristics of the PJO in each hemisphere. A significant temperature signal is also found to appear in the Southern Hemisphere in late winter under a solar maximum condition.