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

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 55

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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

石井 隆

出版者

公益社団法人 日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.7, no.12, pp.436-436, 1930-02-25 (Released:2009-02-05)

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

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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

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

Takahiro ITO Hirotada KANEHISA

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.91, no.6, pp.775-788, 2013

被引用文献数

4

---

The initial value problem of vortex Rossby waves (VRWs) is analytically solved in a linearized barotropic system on an <i>f</i> plane. The basic axisymmetric vorticity <span style="text-decoration: overline;"><i>q</i></span> is assumed to be piecewise uniform in the radial direction so that the radial gradient <i>d<span style="text-decoration: overline;"><i>q</i></span>/dr</i> and the disturbance vorticity <i>q</i> are expressed in terms of Dirac delta functions. After Fourier transformation in the azimuthal direction with the wavenumber <i>m</i>, the linearized vorticity equation becomes a system of ordinary differential equations with respect to time; these can be analytically solved to give a closed-form solution with a prescribed initial value.<br> For a monopolar <span style="text-decoration: overline;"><i>q</i></span>, the solution of <i>q</i> starting from the innermost radius exhibits the outward propagation of VRWs. As the outer disturbances are generated, the inner disturbance is diminished. On the other hand, in the case of a solution forced at the innermost radius, the inner disturbance is not diminished, and the outward propagation of VRWs forms a distribution of spiral-shaped disturbance vorticity.<br> For a basic vorticity <span style="text-decoration: overline;"><i>q</i></span> with a moat, and if the radial distribution of <span style="text-decoration: overline;"><i>q</i></span> satisfies a certain additional condition, the solution of <i>q</i> with |<i>m</i>| ≠ 1 grows exponentially or linearly in time as a result of the interaction of counterpropagating VRWs near the moat. Although the solution of <i>q</i> with |<i>m</i>| = 1 cannot grow exponentially for any <span style="text-decoration: overline;"><i>q</i></span>, it can grow as a linear function of time. This linear growth may be regarded as a result of resonance between two internal modes of the system.

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.

著者

Yueqing LI Lian YU Baode CHEN

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.93, no.3, pp.343-358, 2015 (Released:2015-07-10)

参考文献数

33

被引用文献数

3

---

An Observing System Simulation Experiment (OSSE) was conducted to test the rationality and regional representation of the layout of the upper-air observation system over the Tibetan Plateau and neighboring areas and to consider the actual significance of observation stations. The simulations were validated primarily by comparing results from corresponding experiments wherein simulated observations were assimilated into the initial fields or not. The results showed that there were significant differences in prediction for the different layouts. The layout with both existing and planned observation stations was better than the ones with only existing or only planned stations in terms of forecast accuracy, especially around the areas with new observations added. Specifically, for winds, there were large improvements in Xinjiang, Qinghai, Gansu Corridor, Tibet, Yunnan and mid-west and northeast Sichuan. For temperature and relative humidity, the most significant improvement was in Tibet, southwest and east Qinghai, mid-east Sichuan, and mid-north Yunnan. For heights, the major improvements were in Xinjiang, Qinghai, east Tibet, mid-west Sichuan and Yunnan. The results also validated the layout of the observations and indicated the necessity to add planned observations over the Tibetan Plateau and neighboring areas.

著者

Tsuyoshi T. SEKIYAMA Masaru KUNII Mizuo KAJINO Toshiki SHIMBORI

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.93, no.1, pp.49-64, 2015 (Released:2015-03-18)

参考文献数

55

被引用文献数

1 34

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We investigated the horizontal resolution dependence of atmospheric radionuclide (Cs-137) simulations of the Fukushima nuclear accident on March 15, 2011. We used Eulerian and Lagrangian transport models with low- (15-km), medium- (3-km), and high- (500-m) resolutions; both models were driven by the same meteorological analysis that was prepared by our data assimilation system (NHM-LETKF) for each horizontal resolution. This preparation was necessary for the resolution-dependent investigation, excluding any interpolation or averaging of meteorological fields. In the results, the 15-km grid analysis could not reproduce Fukushima’s mountainous topography in detail, and consequently failed to depict a complex wind structure over mountains and valleys. In reality, the Cs-137 plume emitted from the Fukushima Daiichi Nuclear Power Plant (FDNPP) was mostly blocked by Mt. Azuma and other mountains along the Naka-dori valley after crossing over Abukuma Mountains on March 15, 2011. However, the 15-km grid simulations could not represent the blockage of the Cs-137 plume, which unnaturally spread through the Naka-dori valley. In contrast, the 3-km and 500-m grid simulations produced very similar Cs-137 concentrations and depositions, and successfully produced the plume blockage and deposition along the Naka-dori valley. In conclusion, low-resolution (15-km grid or greater) atmospheric models should be avoided for assessing the Fukushima nuclear accident when a regional analysis is needed. Meanwhile, it is reasonable to use 3-km grid models instead of 500-m grid models due to their similarities and the high computational burden of 500-m grid model simulations.

著者

Tomoki NAKAYAMA Hiroyuki SUZUKI Satomi KAGAMITANI Yuka IKEDA Akihiro UCHIYAMA Yutaka MATSUMI

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.93, no.2, pp.285-308, 2015 (Released:2015-05-14)

参考文献数

60

被引用文献数

8 65

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Laboratory experiments were conducted for characterizing the performance of two commercially available instruments employed for the measurement of light absorption and scattering coefficients of aerosols at λ = 405, 532, and 781 nm (using three-wavelength photoacoustic soot spectrometer; PASS-3) as well as at 375 nm (using photoacoustic extinctiometer; PAX) based on photoacoustic spectroscopy and reciprocal nephelometry, respectively. The calibration factors (conversion factors from the readout to real values) associated with scattering measurements, estimated using gaseous molecules, mono-disperse polystyrene latex and ammonium sulfate particles, and/or poly-disperse ammonium sulfate particles, are in good agreement with one another, typically within 5 %, 5 %, and 10 % at 375, 405, and 781 nm, respectively. In contrast, a significant particle size dependency was observed for the calibration factors at 532 nm, which is possibly because of a combination of differences in the polarization states of the lasers relative to the scattering planes and large truncation angle. Considering the estimated effective truncation angle, the typical uncertainties in calibration factors for scattering when measuring non- or weakly light-absorbing particles, with volume-based geometrical diameters of less than 700 nm, were estimated to be 12 %, 7 %, 34 %, and 17 %, at 375, 405, 532, and 781 nm, respectively. The typical uncertainties in the calibration factors for absorption measurements, which were determined using poly-disperse propane soot particles, were estimated to be 6 %, 4 %, 8 %, and 11 %, at 375, 405, 532, and 781 nm, respectively. The calibration factors for absorption determined by the poly-disperse soot particles at 375 and 405 nm were 48 % and 36 % smaller than those by light absorption of NO2 molecules possibly because of NO2 photolysis, although good agreement was observed at 532 nm. These results suggest that the photolysis effect should be taken into account when light absorption by NO2 is used for calibration at 375 and 405 nm.

著者

Hisaki EITO Kazumasa AONASHI

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.87A, pp.425-446, 2009-03-31 (Released:2009-08-07)

参考文献数

34

被引用文献数

7 16

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This paper compares satellite microwave radiometer and ground-based radar observations with the Japan Meteorological Agency nonhydrostatic model (JMA-NHM) simulations, using a bulk microphysical parameterization, for a typical rainfall system associated with the Baiu front around the Okinawa Islands, Japan, on 8 June 2004.  The JMA-NHM correctly replicated the shape, location and intensity of the precipitation associated with the observed rainfall system. Radar reflectivities and microwave brightness temperatures (TBs) were simulated using output from the JMA-NHM simulations. They were then compared with concurrent corresponding observations by the National Institute of Information and Communications Technology (NICT), CRL Okinawa Bistatic Polarimetric Radar (COBRA), and Advanced Microwave Scanning Radiometer for EOS (AMSR-E). Fairly good agreement was obtained between the simulated and observed reflectivities under the melting layer and TBs at low frequency (18.7 GHz), indicating that the JMA-NHM adequately simulated the amount of liquid hydrometeors. However, the intensity of scattering in the simulations was stronger than that in the COBRA observations above the melting layer and the AMSR-E observations at high frequencies (36.5 and 89.0 GHz). This was due to the fact that the JMA-NHM overestimated the amount and size of snow particles as a result of large depositional growth.  The excessive snow contents were reduced by adjusting some of the microphysical processes in the JMANHM: the snowfall speeds were increased and a riming threshold for snow to graupel conversion was changed. These adjustments helped to reduce the amount and size of snow, resulting in further agreement with the COBRA observations. These adjustments also further improved the simulated TBs at high frequencies, especially at 36.5 GHz. However, differences still exist between the simulated and the observed TBs at high frequencies, suggesting that additional adjustment to and improvement of the snow microphysical processes are needed for the application of the model to microwave remote sensing of precipitation.

著者

Takeshi HORINOUCHI

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.92, no.6, pp.519-541, 2014 (Released:2015-01-29)

参考文献数

35

被引用文献数

4 38

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This study provides an overall understanding of the summertime synoptic variability of precipitation and moisture transport at mid-latitude from the eastern coastal region of China to the northwestern Pacific. Using satellite precipitation and reanalysis data, a clear relationship is found between upper tropospheric disturbances (Rossby waves), surface precipitation, and lower tropospheric humidity through July and August. The upper tropospheric disturbances are characterized by the undulation of the 1.5 PVU contours of potential vorticity (PV) on the 350 K isentropic surfaces. Case studies suggest that a precipitation band of several hundred kilometers wide and a thousand to several thousand kilometers long is formed very frequently on the equatorward and low-PV side of the northernmost 1.5 PVU contours, which meander together around 40°N. Lower tropospheric specific humidity is also enhanced there, and it falls sharply to the north of these contours. The synoptic situations associated with it include, but are not limited to, a common situation in which moist convection is enhanced ahead of upper-level troughs. These results are confirmed by a composite analysis over the 12 summers from 2001. A novel method of analyzing the forcing of the quasi-geostrophic potential enstrophy, in which boundary contributions are incorporated, reveals that upper tropospheric disturbances in the area are propagated predominantly from the west along the Asian jet, and that they exert a significant forcing onto near-surface levels, while the upward forcing from near-surface levels to upper tropospheric disturbances is weak. A Q-vector analysis shows that the upwelling associated with the precipitation bands is forced predominantly by confluence. This process is frontogenetic, and surface fronts are often formed therein. The upwelling is enhanced by latent heating. The latitudinal extent of humid air masses is affected not only by this circulation but by low-level flows induced by upper-level disturbances in a cooperative manner.

著者

和達 清夫 益田 クニモ

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.11, no.10, pp.444-454, 1933 (Released:2009-02-05)

参考文献数

6

被引用文献数

3

---

This report is intended to give a complete table of travel times of earthquake waves such as P, S pP, PP, sS, SS, etc. especially taking the depth of focus into account. The calculation for the present table is based upon the results already obtained by us in the previous investigations on both near and distant earthquakes, whose epicente. s lie near the Japanese Islands. (Vol. 10, No.8, p. 460-474 and Vol. 11, No.1, p. 14-28 of this journal). This report is only a summarized one and the full text will be published in the Geophysical Magazine in the near future.

著者

和達 清夫

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.4, no.4, pp.83-86, 1926-07-28 (Released:2009-02-05)

著者

和達 清夫

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.10, no.9, pp.540-551, 1932 (Released:2009-02-05)

参考文献数

6

被引用文献数

1

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The velocity ratio of P and S waves is obtained by many authors to be nearly constant everywhere in the earth's crust. In the present investigatio_??_, is treated this problem by a method of tp-Tp-s diagram which gives the relation between the arrival time of P and duration of (P-S). Examining in many cases of large earthquakes of both shallow and deep origins occurred in our country, the relation is obtained to be approximately linear as is expected, especially in the cases of deep-seated earthquakes. From these investigations, the velocity ratio of P and S waves is obtained as about 1.73 in the upper part, it may be probably the so-called Mohorovicic layer, but its value seems to differ in different localities; while, in the deeper part nearly a constant value of 1.79 is obtained. Thus, using the result we are able to obtain the depth of seismic focus by a simple method, especially in case of deep-seated earthquakes.